CT Registry
Bronchogenic Carcinoma (CT)
- A malignant neoplasm of the lung arising from the epithelium of the bronchus or bronchiole.
Iodinated Contrast Agents (CT)
U niversally used because they are: - Water soluble - Easy to administer intravascularly - Safe
QA All (CT)
Weekly: - Image Noise - Uniformity Monthly: - Spatial Resolution - Contrast Resolution Semiannually: - Slice Thickness - Laser Light - Linearity
2 Dimensional square (CT)
X= Width Y= Height Z= 3 Dimensional cube or "Voxel"
Which Number is the Pedicle? (CT)
# 1
Pineal Gland (CT)
#3
Which # is the Trapezius Muscle?
#3
CT Tech Chart Master (CT)
*Isocenter:* *Scout:* *SFOV:* *DFOV:* *kVp:* *mAs:* *Slice:* *Pitch:* *WW:* *WL:* *Injection Rate:* *Injection Amount:* *Delay:*
CTA Chest Thoracic Aorta Dissection Chest CT Tech Chart (CT) 65
*Isocenter:* *Scout:* *SFOV:* *DFOV:* *kVp:* *mAs:* *Slice:* *Pitch:* *WW:* *WL:* *Injection Rate:* 4 mL/s *Injection Amount:* 100-125 mL *Monitor:* Ascending Aorta *Delay:* Post threshold delay 3-5 s
Extremity CT Tech Chart (CT) 104
*Isocenter:* *Scout:* *SFOV:* *DFOV:* *kVp:* *mAs:* *Slice:* 0.75 mm *Interval* 0.4 mm *Pitch:* *WW:* *WL:* *Injection Rate:* *Injection Amount:* *Delay:*
L Spine CT Tech Chart (CT) 94
*Isocenter:* *Scout:* *SFOV:* 50 cm *DFOV:* 12-20 cm *kVp:* *mAs:* *Slice:* *Pitch:* *WW:* 2000? *WL:* 200? *Recon:* 1-2 mm
T Spine CT Tech Chart (CT) 94
*Isocenter:* *Scout:* *SFOV:* 50 cm *DFOV:* 12-20 com *kVp:* *mAs:* *Slice:* *Pitch:* *WW:* 2000 *WL:* 200 *Recon:* 1-2 mm?
CTA Abdomen Pelvis CT Tech Chart (CT) 72
*Isocenter:* *Scout:* *SFOV:* *DFOV:* *kVp:* *mAs:* *Slice:* *Pitch:* *WW:* *WL:* *Injection Rate:* *Injection Amount:* 100-150 *Delay:* *Trigger:* 125-150 HUs
Routine Abdomen Pelvis CT Tech Chart (CT) 72
*Isocenter:* Around nipple lineCt *Scout:* Abd only then 2" below axilla or, above diaphragm to Iliac crest *SFOV:* 50 cm *DFOV:* *kVp:* *mAs:* *Slice:* 5 mm *Interval:* 5mm *Pitch:* *WW:* 350-400 *WL:* 40-60
C Cpine CT Tech Chart (CT) 31
*Isocenter:* Mid Neck? *Scout:* Skull base EAM to T2 inferiorly *SFOV:* 50 cm *DFOV:* 12 cm *kVp:* 120-140 *mAs:* 250-250 *Slice:* 2 mm *Pitch:*.75-1.25 *WW:* 300-350 *WL:* 40-50
Routine Neck CT Tech Chart (CT)
*Isocenter:* Mid Neck? *Scout:* Vetrtex of Skull to Mid Chest *SFOV:* 22-25 cm *DFOV:* 50 cm *kVp:* 120 *mAs:* 220 to 400 *Slice:* 2.5 to 3.0 mm *Pitch:* .7 to 1.2 *WW:* 350 - 400 *WL:* 40 *Injection Rate:* 2 to 3 ml/s *Injection Amount:* 75 to 100 ml *Delay:* 35 to 80 seconds
Head CT Tech Chart (CT)
*Isocenter:* OML *Scout:* Vertex of skull to C1 just below skull base *SFOV:* 25 cm *DFOV:* 25 cm *kVp:* 120 *mAs:* 200-600 *Slice:* 5mm *Pitch:* 0.7 - 1.0 *WW* 80 - 100 *WL* 20 - 40 *Injection Rate:*1 ml/s *Injection Amount:* 100 ml *Delay:* 3-4 min
CTA (Angiography) PE Chest CT Tech Chart (CT) 52
*Isocenter:* Top of Shoulders *Scout:* Top of the Shoulders through the Lung bases into upper Abd *SFOV:* 50 cm *DFOV:* Varies. Smallest that includes all Lung and Soft Tissue around the chest *kVp:* 120 *mAs:* 180-250 *Slice:* 2mm *Interval* 2 mm *Additional:* 2 mm w/ 1 mm interval overlap *Pitch:* .7-1.35 ideally less or near 1 *WW/WL* Lungs and Air filled spaces 1500/-600 *WW/WL* Opacified vasculature of Lungs and Aorta 500/60 *Injection Rate:* 4 mL s *Injection Amount:* 75-100 mL followed by 30-50 mL Saline *Monitor:* Main Pulmonary Vein *Trigger:* 90 to 100 HUs *Delay:* Post threshold delay 3-5 s *Recon:* AP, Lat, Oblique Sag MIP of Thoracic Aorta, 3D Aorta
Routine Chest CT Tech Chart (CT) 39
*Isocenter:* Top of the Shoulders *Scout:* Top of the Shoulders through the Lung bases into upper Abd *SFOV:* 50 cm *DFOV:* Varies. Smallest that includes all Lung and Soft Tissue around the chest *kVp:* 120 *mAs:* 180-250 *Slice:* 5 mm *Pitch:* .8-1.35 *WW/WL:* Lungs and air filled spaces 1500/600 *WW/WL:* Mediastinal and Soft Tissue 350/40 *Injection Rate:* 20-30 s *Injection Amount:* 2-3 mL/s *Delay:*
An average CT number value for blood is? (CT)
+45 HU - An average range of CT numbers for blood is +42 to +58. - The CT number of any material is based on many factors, including the beam quality of a particular scanner.
Step and Shoot Method - Axial Scanning, Conventional Scanning, Serial Scanning, or Sequence Scanning (CT)
- (CT) table moves to the desired location and remains stationary while the X-ray tube rotates within the gantry, collecting data. - Will be slight pause between data acquisitions called Interscan Delay. - Result in images that are perpendicular to the "Z" Axis (tabletop) and parallel to every other slice, like slices of sausage
Test Bolus (CT)
- 10-20 mL of contrast is injected and several trial scans are taken to determine the length of time from injection to peak contrast enhancement in a target region - Trial scans are done using very low mAs - Begin from 8 to 15 seconds after the start of the injection - Scan delay is calculated using the formula: Trial scan delay + 2 x image @ peak enhancement + 3 sec See page 161 for an example.
Partial Scan - Half Scans - Segmenting (CT)
- 180 Degree rotation. - Fan Angle - Used to improve Temporal Resolution - Decreased scan time - Decreased patient radiation
Full Scan (CT)
- 360 degree rotation. - Helical
Volume Rendering VR (CT)
- 3D semitransparent representation of the image structure.
Using A CVAD (CT)
- A CVAD is a venous catheter designed to deliver medications and fluids directly into the superior vena cava, inferior vena cava, or right atrium - There are several different kinds of CVADs - Although CVADs are not optimal for contrast administration, in some cases they are the only option available - Make sure it can accept a power injection
Peripherally Inserted Central Catheters (CT)
- A PICC is a long catheter that is inserted through the large veins of the upper arm and advanced so that its tip is located in the lower one third of the SVC. Most PICCs today are power injectable. Check the lines to determine this. - Some PICC lines cannot tolerate the pressure required to inject contrast at the high injection rates typical of CT examinations that use mechanical injectors - In these cases it is recommended that a separate IV be inserted for contrast administration - When no other options exist and the PICC must be used for contrast injection the - injection rate must be slowed - injection should be performed by hand bolus rather than by mechanical injector - Specially designed PICCs (e.g., PowerPICC) can be used for contrast injections with rates up to 6 mm per second - Produced in colors that make the readily distinguishable from the traditional PICC lines. Usually purple and red.
General CT Neck Survey Section Widths
- A contiguous study with section widths ranging from 3 to 6 mm is sufficient for a general survey CT study of the neck.
Modulation Transfer Function MTF (CT)
- A graphical representation of the CT system's capability of passing information through it to the observer
Neoplasm (CT)
- A new and abnormal growth of tissue in some part of the body, especially as a characteristic of cancer.
Suspicion of Stroke Cont'd (Ct)
- A noncontrast CT of the brain is routinely performed to differentiate ischemic stroke from hemorrhagic stroke, to assess the state of cerebral circulation and tissue, and secondarily, to assess the underlying disease - CT brain perfusion provides additional information by allowing qualitative and quantitative evaluation of cerebral perfusion - Perfusion studies are obtained by monitoring the passage of iodinated contrast through the cerebral vasculature - Shows blood flow and transit time
Normal Adult Heart Rate (CT)
- A normal resting heart rate for adults ranges from 60 to 100 beats a minute. - Generally, a lower heart rate at rest implies more efficient heart function and better cardiovascular fitness.
Pulse Oximeter (CT)
- A pulse oximeter is an electronic device used to measure pulse and respiratory status. Placed on a patient's finger, toe, or ear lobe, the pulse oximeter measures blood oxygen levels, which are normally between 95% and 100%.
Urography CTU Study (CT)
- A relatively new imaging examination designed to provide a comprehensive evaluation of the upper and lower urinary tract - Many different protocols exist - Some use a split-bolus injection - These divide the contrast material dose into two bolus injections with a delay of between 2 and 15 minutes between injections - The goal is to image a combined nephrographic-excretory phase
What is Partial Scan? (CT)
- A scan that collects data from 180 degrees tube arc, plus the degree of arc of the fan angle
Aortic Dissection (CT)
- A serious condition in which the inner layer of the aorta, the large blood vessel branching off the heart, tears. - Blood surges through the tear, causing the inner and middle layers of the aorta to separate (dissect).
When an operator reduces the scan field of view for a particular body part, which of the following technical changes occurs? (CT)
- A smaller number of detectors are activated. - The SFOV size is determined by the number of detectors activated along the in-plane (x-, y-) axes during data acquisition.
Difference Between Thrombus, Embolus, Ischemic Stroke, & Myocardial Infarction. (CT)
- A thrombosis is a blood clot. - If the thrombus detaches from its original site, it is referred to as an embolus. - If the embolus occludes a vessel in the brain and disrupts the blood supply, it results in an ischemic stroke. - A myocardial infarction (i.e., heart attack) occurs when the heart does not receive an adequate blood supply.
Adequate Volume of IVCM for SSCT Examination of the Neck in this Figure Is? (CT)
- A total contrast agent volume between 100 and 150 mL is sufficient for imaging the neck. - The precise volume and administration technique vary from one institution to another.
Incidentaloma (CT)
- A tumor (-oma) found by coincidence (incidentally) without clinical symptoms or suspicion.
Lactation & Contrast (CT)
- A very small percentage of the iodinated Contrast given to a mother will be excreted into breast milk and absorbed by the infant - For example, if the maternal dose of contrast is 150 mL, the breast-fed infant will ingest just 0.015 mL Therefore, it is believed to be safe for the mother and infant to continue breast-feeding after receiving Contrast
Localizer Scans (CT)
- AKA Scout - Are poorer image quality
#3 (CT)
- Abdominal Aorta
High Contrast (Detail) Resolution (CT)
- Ability to resolve as separate objects, small, high contrast objects.
MSAD Multiple Scan Average Dose (CT)
- Accounts for the effects of image spacing, or bed index, on patient radiation dose during axial scanning. - MSAD increases when slice thickness is greater than image spacing and decreases when slice thickness is less than the bed index.
Effective Dose (CT)
- Accounts for the type of tissue that the radiation is deposited in. - Different tissues are assigned weighting factors on the basis of their individual radiosensitivities. - Effective dose approximates the relative risk from exposure to low doses of ionizing radiation. - The unit of measurement for effective dose is the sievert (Sv).
#2 (CT)
- Acromion
Aseptic Technique (CT)
- Additional components of the aseptic technique include cleaning the site of venipuncture in a circular motion with alcohol swab before injection. - applying pressure with an alcohol swab to the site after removal of the needle or catheter. ! It is sterile technique that involves establishing a sterile field around the area of an invasive procedure, not necessary for IV.
Components of the Adexal Area of the Uterus (CT)
- Adnexa is used to describe an appendage of an organ. - The ovaries and fallopian tubes constitute the uterine adnexal region.
Epinephrine (CT)
- Adrenalin - An adrenergic drug used as a bronchodilator.
Diphenhydramine (CT)
- Benadryl - used to block the physiologic effects of the body's release of histamine, thus reducing the allergic effect of the contrast material.
Which of the following is considered an equipment induced CT image artifact? (CT)
- Aliasing Artifact - Aliasing is a type of streak artifact caused when an insufficient number of views (data samples) is obtained during data acquisition. - It is typically due to a technical failure of the CT system.
Overbeaming (CT)
- All detectors of the MDCT array must be exposed to x-rays of equal intensity. - The beam must be expanded even further to avoid exposing the detectors to undesirable "penumbra." This process is referred to as ___. - In order to uniformly expose the entire detector array in an MDCT system, the primary beam must be expanded beyond the physical extent of the array in a process known as:
Higher mA settings CT
- Allow shorter scan times - Shorter scan times is critical in reducing image degradation as a result of patient motion
Test Bolus & Bolus Triggering I.E. Timing Bolus (CT)
- Allow the scan to be individualized to the patient - Do not improve patient safety - Major disadvantage of bolus triggering is that the technologist is no longer able to monitor the injection site during the initial seconds of the contrast injection. - Major advantage of bolus triggering is it effectively accommodates for individual differences in circulation time by adjusting the scan delay
CTDI Computed Tomography Dose Index (CT)
- Allows an estimate of the MSAD to be accomplished with a single scan. - The CTDI is what manufacturers report to the U.S. Food and Drug Administration (FDA) and prospective customers regarding the doses typically delivered for their machines. - The CTDI can only be calculated if slices are contiguous, that is, there are no overlapping or gapped slices.
Curved Planar Reformation CPR (CT)
- Allows images to be created along the centerline of tubular organs.
Surface Rendering SR (CT)
- Also called cell shaded surface display SSD. - Creates images display the outline or outside shell of the structure. - In most forms of SR a threshold CT value must be selected. The software will then include or exclude the voxel depending on whether its CT number is above or below the threshold. It uses this information to create an image of the surface of an object. - Is useful for examining tubular structures, such as the inside surfaces of airways, the colon, and blood vessels.
Contrast Media Induced Nephroapathy (CT)
- An acute impairment of renal function that follows the IV administration of contrast material and for which alternative causes have been excluded.
Aortic Aneurysm (CT)
- An aortic aneurysm is an abnormal bulge that occurs in the wall of the major blood vessel (aorta) that carries blood from your heart to your body. - Aortic aneurysms can occur anywhere in your aorta and may be tube-shaped (fusiform) or round (saccular). Abdominal aortic aneurysm: - An abdominal aortic aneurysm occurs along the part of the aorta that passes through the abdomen. Thoracic aortic aneurysm: - A thoracic aortic aneurysm occurs along the part of the aorta that passes through the chest cavity.
Automatic Tube Current Modulation (CT)
- An equipment option that will make changes in tube current (mA) based on the estimated attenuation of the patient at a specific location. - The estimations are derived from scout views done in both the antero-posterior and lateral projections or from the previous slices. - From these views, the mA will be programmed to vary by location along the length of the patient. The exact details of the option vary by manufacturer. ! mA reduction
Single Detector Row Systems SDCT Calculation (CT)
- An examination protocol of the chest calls for contiguous, 4-mm slices to be taken from the level of the sternal notch to the lung base; 60 slices are planned. How much anatomy (in the z direction) will be covered with cross-sectional slices? - 4 mm x 60 = 240 mm
Contrast Washout (CT)
- An imaging characteristic regarding how quickly the iodinated contrast is washed out of the adrenal gland. - It can be used to differentiate adenomas from metastases - relies on physiologic differences in perfusion
Common Sites for IV Injection of CM (CT)
- Antecubital - Basilic - Cephalic - and accessory cephalic veins.
Circle of Willis Make Up Detailed
- Anteriorly formed when the internal carotid artery (ICA) enters the cranial cavity bilaterally and divides into the anterior cerebral artery (ACA) and middle cerebral artery (MCA). - - The anterior cerebral arteries are then united by an anterior communicating (ACOM) artery. - These connections form the anterior half (anterior circulation) of the circle of Willis. - Posteriorly, the basilar artery, formed by the left and right vertebral arteries, branches into a left and right posterior cerebral artery (PCA), forming the posterior circulation. - The PCAs complete the circle of Willis by joining the internal carotid system anteriorly via the posterior communicating (PCOM) arteries.
Abdomen or Pelvis Protocols (CT)
- Appendicitis or diverticulitis - Colonography - Adrenal mass (with delay) - Renal mass - Renal stone - CT urogram - Routine abdomen pelvis - Abdomen pelvis aorta (post-stent, nongated) - Arterial-venous liver - Arterial-venous pancreas - Mesenteric - Enterography
Basic Consent (CT)
- Appropriate for most types of radiologic procedures. "Before the the CT examination, the technologist explains the procedure to the patient and asks them if they agree."
Overlapping Slices with Axial Scanning (CT)
- Are not usually performed due to the increased radiation dose to the patient and lack of additional diagnostic information.
The component of the CT scanner responsible for the mathematical calculations of the image reconstruction process is the?
- Array Processor - The array processor is a specialized component of the CT computer system. - It is capable of performing the massive calculations required for CT image reconstruction. - Reconstructs the projected attenuation raw data into a CT image.
The image in the figure was most likely acquired during which of the following phases of contrast enhancement? (CT)
- Arterial Phase - Dense contrast opacification of the aorta and pulmonary arteries indicates that this image was obtained during the arterial phase, most likely within the first 20 to 30 seconds after bolus injection of contrast material.
Lisfranc Joint (CT)
- Articulation between the tarsals and metatarsals; it can be the site of complex fractures and dislocations of the foot. ! Tarsals & Metatarsals Articulation
Partial Volume Averaging QA (CT)
- Artifact that occurs when a dense object to the edge of the SFOV and is present in some of the views used to create the image.
Artifact (CT)
- Artifacts are defined as anything appearing on the image that is not present in the object scanned. - Artifacts can be: - Physics Based (data acquisition) - Patient Based - Equipment Induced - Artifacts can seriously degrade the quality of CT images, sometimes to the point of rendering them diagnostically unusable
Contrast & Metformin (CT)
- As a precaution, metformin should be temporarily discontinued after Contrast administration; it can be resumed after 2 days 48 hours, assuming kidney function is normal
#6 (CT)
- Ascending Aorta
Steroid Premedication time Frame (CT)
- At least min of 6 hours before contrast administration. - Most common premedication regimen for adult patients calls for three 50 mg doses of Prednisone, beginning 12 hours before the scheduled examination and given every 6 hours. - Often a single dose of 50-mg dose of Diphenhydramine is also given shortly before the examination.
Enteric Precautions (CT)
- Attempt to protect from the spread of infection through direct or indirect contact with fecal matter. Gowns and gloves are common protective devices used for enteric precautions. The use of a surgical mask is not warranted.
#6 (CT)
- Azygos Vein
Cause of Barium Peritonitis (CT)
- Barium leaking into the peritoneal cavity from a perforation of the gastrointestinal tract. - The mortality rate from Barium Peritonitis is significant. - To prevent this a water soluble solution is recommended whenever there is suspicion of a gastrointestinal tract perforation.
Consent (CT)
- Basic Consent - Informed Consent - Implied Consent - Parental Consent
Pregnancy & Contrast (CT)
- Because of concerns about exposing the fetus to ionizing radiation, CT examinations are seldom done during pregnancy - However, in some cases examinations may be vital to the health of the mother - There is no proof that contrast agents present a risk to the fetus - However, there is not enough evidence to be certain they pose no risk
INR International Normalized Ratio (CT)
- Because of the inherent differences in manufactured batches of tissue factor the ___ ___ ___is calculated to standardize PT results. - Compares a patient's PT with a control sample for a more accurate result. ! PT
Why is lead shielding less beneficial in CT than it is in gen- eral radiography? (CT)
- Because of the narrow collimation used in CT, not much radiation is scattered to regions outside the selected scan area. - Because the x-ray beam does not typically scatter great distances in CT, shielding in not nearly as effective in reducing the radiation dose to the patient as it is in general radiography. - However, shielding in CT is not without benefit and is particularly useful in demonstrating to the patient (or the patient's family) that everything possible is being done to minimize the risks from radiation exposure.
Lead Shield Above & Below Patients During Helical (C)
- Because of the rotational nature of the x-ray tube, a patient receives exposure from all sides during a CT examination. Therefore, lead shielding should be placed above and below the patient.
Coumadin/Warfin (CT)
- Belongs to the class of medications called anticoagulants - These drugs, used to treat a variety of health conditions include stroke, inhibit coagulation.
Constant mAs (CT)
- The mA setting in coordination with the scan time (seconds) gives the constant mAs for a CT acquisition.
Metoprolol (CT)
- Beta blocker - It can treat high blood pressure, chest pain (angina), and heart failure. - This may lower the risk of death after a heart attack. - Common brands: Lopressor, Toprol
The electronic combination of signals from adjacent detectors to form a CT image is called? (CT) a. binning b. interpolation c. z-filtering d. partial volume averaging
- Binning - Binning refers to the electronic combination of signal from adjacent detectors to form a reconstructed slice that is thicker than the individual detector width. For example, transmission data from four adjacent 1.25- mm detectors is combined to produce a CT section 5.0 mm thick.
#6 (CT)
- Bladder
BUN Blood Urea Nitrogen (CT)
- Blood urea nitrogen (BUN) and creatinine level are laboratory values used to indicate renal function. These values may be examined individually or in ratio form, as follows: - Normal BUN values in adults range from 7 to 25 mg/dL. Range may vary depending on laboratory testing reference. By itself, BUN is not a sufficient indicator of renal insufficiency. - Normal creatinine levels range from 0.5 to 1.5 mg/dL. Range may also vary with lab reference. An elevated creatinine value (>1.5 mg/dL) may not always indicate renal function compromise, because this value can vary widely with different populations. Recent changes in a patient's creatinine level are thought to be more informative as a renal function indicator. - The BUN/creatinine ratio may also be used to evaluate renal function. Normal BUN/creatinine ratio is approximately 6:1 to 22:1, and this reference is laboratory-specific.
Body Temperature Vital Signs (CT)
- Body temperature is taken by placing the thermometer in the mouth, the ear (using a tympanic infrared thermometer), the axilla, or the rectum - In the CT department, the thermometer is most often an electronic, battery-operated device with disposable protective sheaths - Normal range of oral temperature is 36.0°C-38.0°C or 96.8°F to 100.4°F - 97.7° to 99.5° F (6.5° to 37.5° C) Mosby
General Phases of Tissue Enhancement (CT)
- Bolus phase (arterial phase) - Nonequilibrium phase - Equilibrium phase
Iodinated Agents for Oral Administration (CT)
- Both HOCM and LOCM are positive agents that can be diluted and administered orally - Dosages are similar to those used with barium sulfate - HOCM is used for most situations because it is less expensive and provides equivalent gastrointestinal opacification - LOCM has advantages in selective cases
Contrast & Pulmonary Effects (CT)
- CM may cause Bronchospasm Pulmonary arterial hypertension Pulmonary edema - Patients at increased risk are those with a history of pulmonary hypertension, bronchial asthma, or heart failure - The use of LOCM significantly reduces the risk
Advantage of CO2 over room air in CT Colonography (CT)
- CO2 induces less spastic response of the bowel wall and is therefore better tolerated by most patients. - Both CO2 and Room Air provide very high negative contrast Both are safe and produce only slight post procedure discomfort, but C)2 tends to be better tolerated by patients.
Intrathecal Administration of CM (CT)
- CT examinations are performed after myelography to enhance or clarify findings - A delay of 1 to 3 hours between the intrathecal injection and scanning is recommended to allow the CM to dilute - CM that is too dense may mask intradural structures - With some contrast solutions waiting 1-3 hours is not necessary; they can be scanned right after injection - Use IV contrast when looking for infection, mass, vascular anatomy or other vascular anomalies
Mechanical Injectors (CT)
- CT injectors may have a single head for affixing the syringe or they may accommodate two syringes - Include a programmable pressure limit - Contrast is administered at the selected rate(s), unless the pressure reaches the maximum psi set - Safety precautions must be strictly adhered to - Prevent contrast extravasation - Prevent air embolism
CT Contrast Discriminator (CT)
- CT is an excellent low contrast discriminator and can differentiate an object with contrast variation as low as 5%
Intracranial Hemorrhage ICH (CT)
- CT is the most frequently used initial examination for imaging ICH - The appearance of ICH will change with the passage of time - As a general rule ICH will appear: * Hyperdense to normal brain tissue for the first 3 days * Hyperdense center surrounded by concentric areas of hyperdense and hypodense tissue from 4 to 10 days * Isodense center surrounded by areas of hypodense tissue from 11 days to 6 months * Hypodense to normal tissue after 6 months - Although most patients with an ICH are seen through the ED where images are reviewed by radiologists and reported on quickly, some patients, particularly those with less acute presentations (e.g., headache) may arrive in the CT department as outpatients - In these situations, the technologist can play a vital role by bringing the scan to the radiologist's attention so that these patients receive prompt medical attention
Type of Radiation Dose Measurement Used When Scanner Manufacturers Report to the FDA and Prospective Clients the Doses Typically Delivered for Their Machine? (CT)
- CTDI Computed Tomography Dose Index
CTDIw (CT)
- CTDIw is calculated from measurements made with dosimeters positioned at the center and periphery of a phantom and accounts for the variance in dose distribution due to the effects of /beam hardening./ - Is calculated by summing 2=3 of the exposure recorded at the periphery of the field with 1=3 of the centrally recorded radiation dose.
Slice Incrementation (CT)
- Can be changed Retrospectively - Retro Recon - Less than 1 will have overlap ex. 5, 1.25, .625
Stochastic (CT)
- Certain harmful effects of exposure to diagnostic x-rays, such as cancer formation and genetic mutations, are said to be random, or stochastic, in nature.
Contrast Intrathecal (CT)
- Certain iodinated contrast agents can be injected into the intrathecal space surrounding the spinal cord - Seldom is the contrast agent injected while the patient is in the CT department - Patients are frequently sent to the CT department for a postmyelogram CT, while the contrast agent is still in the intrathecal space - Keep the patient's head elevated - Roll the patient before scanning to mix the Contrast
Raw Data is necessary for? (CT)
- Changing the Display Field - Pixel size Decreases - Spatial resolution Increases
Clearance (CT)
- Clearance refers to the ability of the kidney to remove a substance from the blood - Iodinated agents are not metabolized and are excreted by the body nearly exclusively by the kidneys - The half-life in patients with normal renal function is approximately 2 hours
#1 (CT)
- Common Carotid Artery
T Wave (CT)
- Complete cardiac diastole
CTA's Angiography Study (CT)
- Concentrates contrast in arteries so that they show very bright - Bolus phase of enhancement - Can be done using a test bolus or by manual start - In both methods timing is critical - Rapid, high-resolution scans are taken while contrast is in the arterial enhancement phase - Goals are to * Accurately measure stenosis of the carotid and vertebral arteries and their branches * Evaluate the circle of Willis for completeness using 3D reformation * Detect other vascular lesions
Determining Scanner Generation (CT)
- Configuration of X-Ray tube & Detectors
During CT x-ray exposure, the product of the selected mA setting and the scan time is called the: a. effective mAs b. peak mAs c. absorbed mAs d. constant mAs
- Constant mAs - The mA setting in coordination with the scan time (seconds) gives the constant mAs for a CT acquisition.
The bolus duration of any IV contrast agent administration can be calculated as the product of injection flow rate and?
- Contrast Agent Volume
Pharmacokinetic Factors Controlling Contrast Enhancement (CT)
- Contrast characteristics (concentration, osmolality, viscosity) - Contrast volume - Contrast flow rate - Contrast flow duration - Scan delay time - Total scan time
Contrast High & Low (CT)
- Contrast is the difference between light and dark in an image. - High contrast images will have bright highlights and dark shadows, bold colours, and show texture in the subject. - Low contrast images will have a narrow range of tones and might therefore feel flat or dull.
The Anatomic Plane of the Image in the Figure is? (CT)
- Coronal Plane - The image is a multiplanar reformation (MPR) of the right shoulder in the coronal plane. This perspective demonstrates the relationship between the humeral head and the glenoid fossa (4).
Kidney Enhancement Phases (CT)
- Corticomedullary phase, 30 to 70 s after contrast material bolus - Nephrogram phase, 100 to 120 s after contrast material bolus - Excretory phase, 3 minutes after contrast material bolus
CIN Risk Factors (CT)
- Creatinine clearance less than 25 mL/min or l - History of diabetes mellitus - History of recent administration of iodinated contrast agent - Anticipated large volume of Contrast - History of congestive heart failure
Weekly QA (CT)
- Cross Field Uniformity - Image Noise
D-dimer (CT)
- D-dimer testing is utilized for the diagnosis of deep vein thrombosis (DVT) and pulmonary embolism. - Although nonspecific, the presence of elevated amounts of D-dimer in the bloodstream may indicate recently degraded blood clots. - If the D-dimer value is elevated, additional testing such as CT angiography of the pulmonary arteries may be indicated
Pixel Size (CT)
- Decrease in Pixel size (smaller pixel) :then: Increased (better) Spatial Resolution - Increase in Pixel size (larger pixel) :then: Decreased (worse) Spatial Resolution
Cyanosis (CT)
- Defined as a bluish discoloration, especially of the skin and mucous membranes, due to excessive concentration of deoxyhemoglobin in the blood caused by deoxygenation.
Contrast Delayed Reactions (CT)
- Defined as reactions that occur between 1 hour and 1 week after Contrast injection - Data on delayed reactions are difficult to accurately collect - Skin reactions account for the majority of true late reactions Red spots or bumps, weltlike swelling, hives - Salivary gland swelling (or iodide "mumps") - Patient receiving interleukin-2 may reexperience the side effects of that medication after receiving Contrast
#5 (CT)
- Descending Colon
Pitch (CT)
- Describes the table movement during a Helical Scan Acquisition. - Travel distance of the CT scan table per 360 rotation of the X-ray tube, divided by the X- ray beam collimation width. - When table feed and beam collimation are identical = pitch is 1; When table feed is less than the beam collimation = pitch is less than 1 and overlap occurs. - The increase in pitch is like pulling a spring, the rings get wider. + Pitch = Increased Interpolation + Pitch = Decreased Patient Dose + Pitch = Decreased Image Quality
Window Level - Brightness (CT)
- Designates the center or midpoint of the range of Ct numbers - Determines how BRIGHT the image appears - Low WL = Brighter - High WL = Darker
Properties of Ionic Contrast Medium (CT)
- The molecules in ionic solution dissociate to form ions in water.
Reconstruction Algorithm (CT)
- Determine how data are filtered in the reconstruction process. - Different Filters use different Algorithms. i.e. smoothing, and bone/detail filters - The appropriate reconstruction algorithm depends on which parts of data should be enhanced or suppressed to optimize the image for diagnosis.
Adrenal Glands Study (CT)
- Determining whether an adrenal mass is benign or malignant is accomplished by assessing its attenuation values and by evaluating the degree of contrast material that is washed out of the mass on delayed imaging - Specialized adrenal imaging protocols attempt to characterize lesions of the adrenal gland - The goals of imaging are to reduce the number of unnecessary biopsies, the number of follow-up studies needed for an accurate diagnosis, and the cost of care
Contrast Used to Utilize During Gastrointestinal Tract CT? (CT)
- Diatrizoate Meglumine (Gastrografin) - Effervescent Agents - Iopamidol (Isovue) ! Effervescent agents may be used to ensure proper gastric distention. Intravenous contrast agents are used to opacify blood vessels and are helpful in anatomic differentiation and evaluation of mass vascularity. Tablets which are designed to dissolve in water, and release carbon dioxide.
Enhancement Washout Tecnique for CT Characterization of Adrenal Masses (CT)
- Differentiation between a metastatic lesion and a benign adenoma of the adrenal can be accomplished by calculating the percentage of enhancement washout after a 10- to 15-minute delay. - Pre-contrast, portal venous phase, and delayed acquisitions are obtained. - On delayed post-contrast imaging, metastatic lesions of the adrenal gland remain enhanced longer than adrenal adenomas.
Dyspena (CT)
- Difficult or labored breathing
Ex. of Contrast Resolution Challenge
- Distinguishing between white and gray matter of the brain
Contrast & Dialysis (CT)
- Do not give Contrast to dialysis patients in whom it is hoped that the dialysis is temporary - Contrast may be given to patients on dialysis with end-stage renal failure - Patients on dialysis who undergo contrast-enhanced CT may continue their routine dialysis schedule ! A dialysis catheter should never be used for contrast media administration
Methods of Contrast Delivery (CT)
- Drip infusion Contrast is allowed to drip in during a period of several minutes Scanning begins after most, or all, of the contrast is in Can be used for routine brain scans, but not appropriate for other examinations because all images are obtained in the equilibrium phase - Bolus Rapid injection of contrast, either by hand or mechanical injector
Cerebral blood flow (CBF) (CT)
- During CT Perfusion Studies, the Quantity of Blood in mL that Moves Through 100 g of Tissue each Minute is Termed? Normal CBF range in gray matter: 50 to 60 mL/100 g/min.
Phases of Injection Enhancement (CT)
- Early arterial phase - immediately after bolustracking - Late arterial phase - 15-20 sec after bolustracking. - Hepatic or late portal venous phase - 50-60 sec after bolustracking - Nephrogenic phase - 80 sec after bolustracking - Delayed phase - 6-10 minutes after bolustracking
Automated Injection Triggering Methods are Used to? (CT)
- Effectively accommodate for individual differences in circulation time by adjusting the contrast Scan Delay. ! Scan Delay
Endoluminal imaging (CT)
- Endoluminal imaging is a form of VR designed to reveal the inside of the lumen of a structure. - The technique is also called virtual endoscopy, virtual bronchoscopy, and virtual colonoscopy.
Using an Established Indwelling Venous Catheter (CT)
- Evaluate the site for appropriateness for contrast injection - Verify the patency of the line with a saline flush - Turn off existing medication only long enough to complete the injection - Once the injection is completed, flush the line with saline and restart medications at the identical preexamination rate
Laboratory Values Hematic (CT)
- Examinations of a more interventional nature (e.g., biopsy and fluid drainage) carry the risk of excessive bleeding - Prothrombin time (PT), partial thromboplastin time (PTT), and platelet count provide information about the blood's coagulation ability. Typical normal ranges are - PT: 11 to 14 sec - PTT: 25 to 35 sec - Platelet count: 150,000 to 400,000 mm^3
Contrast Enhancement Phase best showing TCC Transitional Cell Carcinoma? (CT)
- Excretory phase - Excretory phase acquisitions after a delay of 3 to 15 minutes demonstrate the urinary tract while it is opacified with a contrast agent. Transitional cell lesions of the urothelium appear as filling defects within the bladder, ureters, and/or renal pelvis.
#6 (CT)
- Falx cerebri.
Volume Rendering VR (CT)
- Favored 3D imaging technique. - An advantage of the VR technique is that all voxels contribute to the image. This allows VR images to display multiple tissues and show their relationship to one another.
Which of the following mathematical reconstruction methods is used by most modern CT scanners? (CT) a. back-projection b. iterative methods c. Fourier transform d. filtered back-projection
- Filtered Back Projection - The filtered back-projection, or convolution, method of image reconstruction is used by most modern CT scanners. Synonyms: - Convolution - Filtered Back Projection
Bed Index (CT)
- Image spacing - MSAD Multiple Scan Average Dose increases when slice thickness is greater than image spacing and decreases when slice thickness is less than the bed index.
Nonequilibrium Phase - Venous Phase (CT)
- Follows the Bolus Phase - Arterial Phase - Begins immediatley after 1 min - Attenuation difference of 10 to 30 HU AVID - Contrast agent is still brighter in the arteries than in the perenchyma of organs, but now the venous structures are also opacified - Contrast is still in arteries, but also in veins - Commonly called the "_____ ______" - Most Non-angiographic body images are acquired while contrast is in this phase Portal venous phase 65-80 s Hepatic venous phase 75-85 s
Contrast Volume, Flow Duration, Flow Rate (CT)
- For a constant volume and concentration of contrast, as flow rate is increased, there is a decrease in the time to peak enhancement - Hence, scan delay must be adjusted according to flow rate - Increasing the flow rate shortens the duration of the injection
Reduction of Patient Dose per Anatomy (CT)
- For all patients, regardless of age or sex indication, the CT protocol should be optimized according to size or weight.
Adverse Reactions to Contrast, Preventative Measures (CT)
- For patients identified as being at increased risk of adverse reaction to Contrast, options include - Perform examination without Contrast - Use LOCM - Pretreatment with steroids (or steroids + Benadryl)
Liver Study (CT)
- For routine abdominal CT or as part of a chest, abdomen, and pelvic study, the liver is most often scanned just once, during the portal venous phase - For some indications, scanning in more than one enhancement phase may be of diagnostic benefit - Hyperenhancing tumors may be better visualized with dual-phase imaging
Luminal Imaging (CT)
- Form of volume rendering designed to reveal the inside of the lumen of a structure.
Multiphasic Imaging (CT)
- Frequently used for the pancreas, liver, and kidney for specialized studies, as well as in many abdominal CTA protocols
CT images of the chest should be acquired with the patient ? (CT)
- Full Inspiration
#1 (CT)
- Genu of the corpus callosum
#3 (CT)
- Glenoid Process
Systole (CT)
- Heart contracts and pumps blood OUT of the heart.
Diastole (CT)
- Heart relaxes and fills with blood.
A benign, highly vascular mass commonly found in the liver.
- Hemangioma
Contrast Osmolality High Osmolality Contrast Medium HOCM (CT)
- High-osmolality agents (HOCM) may have as much as 7 times the osmolality of blood - Ionic agents that dissociate into charged particles (ions) in solution. - Also called Hyperosmolar - Ionic contrast media are salts consisting of sodium and/or meglumine. Brands: Iothalamate meglumine and diatrizoate sodium are commonly known by the brand names Conray and HYPAQUE, respectively. - Pg 53
The average density of a mass within the kidney measures -75 Hounsfield units (HU). The mass is most likely a? (CT)
- Hydrocele - The density of the mass in question indicates that it consists of fatty tissue. - A lipoma is a benign mass consisting of fat cells. - An angiomyolipoma, a common benign mass found in the kidney, consists of muscle cells, blood vessels, and fat. The average CT value range for fat is: -50 to -100 Hounsfield units.
Following the IV administration of iodinated contrast media, a tumor that exhibits a greater density than the surrounding parenchyma is characterized as? (CT)
- Hypervascular - Upon IV contrast enhancement, a tumor may be described as hypovascular if it is lower in density than the surrounding organ parenchyma or hypervascular if it is higher in density.
Mediastinal Lymphadenopathy Visualization Requires? (CT)
- IV Injection of iodinated contrast agent during a CT of the chest to visualize. - Contrast enhancement greatly improves demonstration of lymphadenopathy within the chest in comparison with other mediastinal structures.
Vascular Access (CT)
- IV catheter (Standard indwelling peripheral catheter) - Central venous access devices (CVAD) Lumens are by collar bone. - Peripherally inserted central catheters (PICC) Lumens are on upper arm - Ports that are under the skin Generally used for cancer patients
Preventing CIN (CT)
- Identify patients at high risk - Patients with diabetes mellitus or other risk factors should have a recent SeCr - Use LOCM or IOCM - Ensure adequate patient hydration - Minimize Contrast volume - Allow at least 48 hours between procedures requiring Contrast - Discontinue other nephrotoxic medications before the procedure
QA Weekly (CT)
- Image Noise - Cross Field Uniformity
Motion QA (CT)
- Image artifact displays a streaking apperance.
Image Center (CT)
- Image coordinates allow the operator to specify the area within the SFOV that will be displayed on the image - Some manufacturers use x and y preceding the number to designate the direction of the coordinates - Some manufacturers precede the number by R (right), L (left), A (anterior), P (posterior), S (superior), and I (inferior) - Often referred to as RAS coordinates - The image center can only be adjusted using the Raw data
Bolus Phase - Arterial Phase (CT)
- Immediately follows bolus injection - Attenuation difference of 30 or more HUs between in Aorta and Inferior Vena Cava - Arterial structers are filled with contrast - Commonly called the "----- -----" - Contrast media has not yet filled the venous structures Early arterial phase 15-25 s Late arterial phase 35-45 s Hepatic arterial phase 17-25 s Late hepatic arterial phase 40-55 s
Reason to use Thinner Slices (CT)
- Improve Spatial Resolution - Decrease Volume Averaging - Better Detail
Estimate the radiation dose for one CT examination versus the dose for one chest radiograph: a. One CT examination is less than or equal to one chest radiograph. b. One CT examination is greater than one chest radio- graph, but less than 100 chest radiographs. c. One CT examination is equal to from 100 to 250 chest radiographs. d. One CT examination is equal to or greater than 500
- In a 2004 study, researchers asked pateints, ED physicians, and radiologists to esti- mate the radiation dose for one CT examination versus the dose for one chest radiograph. The results from that study demonstrated the lack of awareness regarding the radiation dose associated with CT examinations. None of the estimates given by the patients were in the accurate range. Twenty- two percent of ED physicians surveyed reported dose estimates in the accurate range. Most surpris- ing, only 13% of radiologists surveyed reported dose estimates in the accurate range. In all groups, the majority of participants underestimated the dose from CT examinations.
ECG Gating/Cardiac Gating (CT)
- In addition to pharmacologic heart rate control, a technique called cardiac gating attempts to use only those images acquired during periods of the lowest cardiac motion. - Most often this point is during end-diastole, but may also be at end-systole.24,25 In other words, just before or just after the left ventricle is fully contracted.
Creatinine Level Limit for CM (CT)
- In general the normal range is 0.6 to 1.7 mg/dl - Radiologists are typically consulted whenever the creatinine is 2.0 mg/dl or greater.
Contrast & Gastrointestinal (CT)
- In the GI tract, Contrast is essential to distinguish loops of bowel from cyst, abscess, or neoplasm - Oral Contrast is used for most CT studies of the abdomen and pelvis - Rectal administration of Contrast is useful for some indications - The most common definition classifies GI agents as positive or negative depending on the density of the material relative to the wall of the GI tract - By this definition, water is considered a negative agent - Less commonly, oral Contrast is classified in accordance to its HU - Positive agents have positive HU values - Negative agents have negative HU values - Water is considered a neutral agent
Idiosyncratic Reactions (CT)
- Include all other reactions (other than chemotoxic) - Reactions are largely unpredictable - Often occur 1 hour after administration of contrast - Are not related to dose - Not a true allergic reaction since there are no antibodies produced, but still labeled as an "Allergic Reaction" ex. Nausea, vomiting, altered taste (metallic), perspiration, warmth, flushing, anxiety
CIN Risk factors (CT)
- Include pre-existing renal function compromise, dehydration, diabetes, myeloma, advanced age, and cardiovascular disease.
Scan Parameters (CT)
- Include: mA, Scan Time, Slice Thickness, Field of View, Scan Algorithm, kVp. - Helical, pitch is also a Parameter.
Decreasing Pitch (CT)
- Increases patient dose
ROI on a Structure with a Standard Deviation of 0 (CT)
- Indicates that every pixel within the ROI has the same Hounsfield value - Therefore the object must very Homogeneous
#1 (CT)
- Inferior Oblique Muscle
Implied Consent (CT)
- Inferred from signs or actions
Adenomas, Differentiating Benign from Malignant Lesions (CT)
- Intracellular lipid (fat) content - Contrast material washout, Washout can only be evaluated if delayed images are acquired
Intrathecal Injections (CT)
- Intrathecal injections of iodinated contrast material are used in the CT evaluation of the lumbar spine. - This type of injection introduces contrast material directly into the /subarachnoid space/, which is located between the arachnoid and pia mater. - The subarachnoid space contains the cerebrospinal fluid.
Contrast Media-Induced Nephropathy (CT)
- Intravascular Contrast affect kidney function - In most cases the effects are confined to a short period of kidney dysfunction that does not produce symptoms and generally goes undetected - In some cases CM can result in significant nephrotoxic effects, particularly in patients considered at high risk for nephropathy
Adverse Effects of Contrast (CT)
- Iodinated Contrast is one of the most widely used of all medications - They are also one of the safest - Fatal reactions are extremely rare in both HOCM and LOCM Estimated at 0.001% - Although rare, adverse reactions sometimes occur - It is impossible to predict which patient will have an adverse reaction to IV-administered Contrast - Therefore, CT staff must be trained to respond quickly - The term "contrast reaction" is used in a variety of different ways in relation to the effects of iodinated Contrast - In some instances, it describes all undesired effects including the many subjective effects (e.g., heat, metallic taste) - In other instances, it describes the less common, more serious side effects that may require treatment or even be life threatening - Chemotoxic & Idiosyncratic Reactions
CT Arthrography Injection Site (CT)
- Iodinated water-soluble radiopaque contrast media (RCM) are injected directly into the joint space of interest during CT arthrography.
Ionicity (CT)
- Ionic agents contain molecules that will form ions in solution - Nonionic agents contain molecules that do not disassociate - Although most nonionic contrast agents also have low osmolality, the terms are not synonymous
Ionic Contrast Medium (CT)
- Ionic contrast media are salts consisting of sodium and/or meglumine. ex. - iothalamate meglumine
ATCM Automatic Tube Current Modulation (CT)
- Is a form of automatic exposure control for a CT system. - It manages patient radiation dose on the basis of the size, density, and overall attenuation of the part being examined. ! Pt Dose
PT Prothrombin Time (CT)
- Is a measure of blood coagulation. - The normal range for PT is approximately 12 to 15 seconds - is measured in the lab after the addition of a protein called tissue factor to a patient's blood sample
Stroke (t-PA) Tissue Plasminogen Activator 9Ct)
- Is a protein involved in the breakdown of blood clots. It is a serine protease (EC 3.4.21.68) found on endothelial cells, the cells that line the blood vessels. - As an enzyme, it catalyzes the conversion of plasminogen to plasmin, the major enzyme responsible for clot breakdown. - Because it works on the clotting system, tPA (such as alteplase, reteplase, and tenecteplase) is used in clinical medicine to treat embolic or thrombotic stroke. - Use is contraindicated in hemorrhagic stroke and head trauma. The antidote for tPA in case of toxicity is aminocaproic acid.
Fully Automated Segmentation (CT)
- Is a software feature that attempts to remove unwanted data automatically.
PTT Partial Thromboplastin Time (CT)
- Is an additional lab value used to detect abnormalities in blood clotting Normal range for clotting time is generally 25 to 35 seconds
Embolus (CT)
- Is moving until it reaches a narrowing in the vessel - Most emboli arise from thrombi - Sometimes consists of fat, air bubbles, and other formations
Increasing Magnification (CT)
- Is not the same as changing display field size - Magnification only uses image data and not raw data, so Pixel size is NOT affected - Magnification allows for more accurate marker placement for measurements
Automatic Tube Current Modulation (CT)
- Is software that automatically adjusts the tube current based on the estimated attenuation of the patient at a specific location.
Thrombus (CT)
- Is static - Some thrombi do not become emboli - Consists of blood components Source:
Lambert-Beer law Formula (CT)
- Is the mathematical relationship between the primary beam, the object thickness (density), and the radiation measured by each detector in the calculation of the linear attenuation coefficient.
Steatosis
- Is the process describing the abnormal retention of lipids within a cell. - It reflects an impairment of the normal processes of synthesis and elimination of triglyceride fat. - Excess lipid accumulates in vesicles that displace the cytoplasm. - Aka Fatty Liver Disease
Iodine Concentration (CT)
- Is the property of iodine concentration media that is responsible for its capacity to increase a structures ability to attenuate the X-Ray beam.
Noise (CT)
- Is the undesirable fluctuation of pixel values in an image of a homogeneous material (such as water) - Usually caused by mAs being too low, as too high mAs will not affect image quality - Using wider slice thickness results in the reduction of noise, as it results in a greater number of detected photons
Percentage of Overlap of Reconstructed Sections to See Improvement in the Quality of MPR Images? (CT)
- It is widely recommended that volumetrically acquired CT sections be reconstructed with the use of at least a 50% overlap to improve the quality of 3D and MPR images. ! 50%
Kerma (CT)
- Kerma may be used to describe absorbed dose. - Air kerma is the amount of radiation absorbed in a quantity of air.
Left Coronary Artery Branch (CT)
- LM Left main - LAD Left Anterior Descending - LCX Left Circumflex
#4
- Lamina
#4 (CT)
- Large Colon
Which of the following is used to archive a Hard Copy of a CT image? (CT)
- Laser Film - Storage on film is considered to be a hard copy. ! The digital storage of CT images on PACS, CD-ROM, MOD, and so on, is referred to as soft copy.
Equilibrium Phase - Delayed Phase (CT)
- Last phase of tissue enhancement - Follows the Nonequilibrium Phase - Venous Phase - Can begin as soon as 2 min after bolus phase - Attenuation difference between the Aorta and the Inferior Vena Cava of less than 10 HU - In this phase contrast media is largely emptied from the arteries, is greatly diluted in the veins , and has soaked the organ parenchyma - In this phase, interstitial concentrations of contrast material equilibrate and decline at an equal rate Early delayed hepatic phase (i.e., vascular equilibrium) 3-5 min Late delayed hepatic phase (i.e., parenchymal equilibrium) 10-15 min
#3 (CT)
- Left Primary Bronchus
#2 (CT)
- Left Pulmonary Artery
#4 (CT)
- Levator Scapulae Muscle.
Aortic Branches (CT)
- Right to Left 1. Brachiocephalic a. (Right) *Splits - Branches to Right Subclavian (Right) - Right Common Carotid (Middle) 2. Left Common Carotid a. (Middle) 3. Left Subclavian a. (Left)
The graph in the figure is used to evaluate which of the following components of CT image quality? (CT) a. in-plane spatial resolution b. longitudinal spatial resolution c. temporal resolution d. contrast resolution
- Longitudinal Spatial Resolution - The longitudinal spatial resolution is usually qualified by the extent of broadening that occurs to the slice sensitivity profile (SSP) during volumetric acquisition. - The section width (slice) for a volumetric acquisition may be graphically represented as a slice sensitivity profile (SSP).
Compared With Conventional Radiography, Computed Tomography Produces Diagnostic Images with Better? (CT) a. low-contrast resolution b. spatial resolution c. minute detail d. patient radiation dose reduction
- Low Contrast Resolution - Computed tomography has better low-contrast resolution over conventional radiography. - The CT system is extremely sensitive to small changes in tissue density and also removes the problem of superimposition, both leading to greater contrast resolution. ! CT = Better Low Contrast; Other Modalities = better Spatial resolution
Which of the Following Reformation Techniques Best Describes the Image in the Figure?
- MPR - Demonstrating the same density and contrast as a conventional helically acquired axial image, the coronal display in the figure is a standard MPR image. - Multiplanar reformation (MPR) describes the process of displaying CT images in a different orientation from the one used in the original reconstruction process. - The reformatted image is 1 voxel thick, with the pixels facing the viewer each representing the average attenuation occurring within the represented voxels.
3D software Segmentation Techniques
- Manual - Semiautomatic - Automatic
A CT image is formed in part by projecting back all of the attenuation values recorded during data acquisition onto a? (CT)
- Matrix - The back-projection method of image reconstruction involves the acquisition of attenuation values, which are then projected back onto a matrix for subsequent display.
Slice Thickness Accuracy Test QA (CT)
- Max variation for slice > 5mm = +/- 1 mm - Max variation for slice < 5mm = +/- 0.5mm
Fatty Infiltrate (CT)
- Measurements from a CT image of the abdomen show the liver density is 35 HU whereas the density of the spleen is 65 HU. Which is a likely diagnosis?
Which of the following would be the most common cause of the artifact in the figure?
- Metallic Dental Fillings
Lossless Compression (CT)
- Method of image compression in which the image that is then decompressed is an exact replica of the original.
Lossy Compression (CT)
- Method that introduces compression artifacts because not all data are restored; used to transmit images that do not need to be of diagnostic quality. - This is sometimes referred to as "conversational" quality
When one is viewing a minimum intensity projection (min-IP) image, each pixel represents? (CT)
- Min-IP images display the minimum pixel value along each ray to the viewer. - As the viewer faces a min-IP image, each pixel represents the minimum attenuation that occurs in the associated voxel. - Min-IP reformations are used primarily during the evaluation of the biliary tree, colon, lungs, and trachea.
Misregistration
- Misregistration is an artifact that occurs when a patient suspends respiration at different depths during consecutive scans. - It results in the loss of anatomic information.
Contrast Resolution QA (CT)
- Monthly
Spatial Resolution QA (CT)
- Monthly
Morison's Pouch (CT)
- Morison's pouch is the common name for the hepatorenal recess, which is indicated by number 7 in the figure. - This space between the liver and right kidney is a common location for the abnormal collection of fluid known as ascites.
Kidney Study (CT)
- Most examinations use IV contrast - Unenhanced CT of the kidneys and ureters is generally reserved to demonstrate calcification and calculi that may be obscured by contrast material
Coronary Circulation (CT)
- Movement of blood through the tissues of the heart. - Supplies nutrients, oxygen & frees waste products.
R-R Cycle in Diastole on an ECG (CT)
- The least heart motion occurs at approximately 55% to 75% of the R-R interval, typically corresponding to the point of mid-diastole.
Which of the following best describes the shape of the x-ray beam utilized in MDCT? a. pencil beam b. fan-shaped c. electron beam d. cone-shaped
- Multislice CT (MSCT) utilizes a cone-shaped beam that is incident upon an expanded array of detectors. - The detector array consists of multiple rows along the z-axis and requires a cone-shaped beam to measure incident radiation.
Complete CT Study of the Orbits
- Narrow sections (1-3 mm) are required in both the axial and coronal planes to properly demonstrate the orbits. - Isotropic MDCT acquisition may provide multiplanar reformation images of sufficient quality to preclude the need for an additional scan in a second plane.
Contrast & Thyroid Storm (CT)
- No effect on patients with normal thyroid function - Insignificant effect on patients with hypothyroidism - When given to patients with hyperthyroidism Contrast may precipitate thyroid storm - This is a severe, life-threatening condition resulting when thyroid hormone reaches a dangerously high level
Uniformity (CT)
- Noise is measured by obtaining the standard deviation (SD) of the CT numbers within a region of interest (ROI). - Uniformity refers to the ability of the scanner to yield the same CT number regardless of the location of an ROI within a homogeneous object - Like noise, uniformity is most commonly measured using a water phantom - Placing several ROIs within the phantom, it is hoped that each will possess the same measurement - If fluctuations exist at different regions within the phantom (e.g., if a ring around the perimeter measures differently from the center), then a problem with the system's cross-field uniformity can be diagnosed - For noise measurements, the standard deviation of an ROI in a water phantom should not exceed 10 - For uniformity measurements, there should be no more than a ±2 HU variation from an ROI placed at the center of the water phantom to those placed at the periphery
Urinary Tract Calculi Study (CT)
- Non Contrast study - Protocols use a helical scan mode from the top of the kidneys to the base of the bladder and a slice thickness of 3 mm or less - The greatest drawback to NCHCT for the diagnosis of renal stones is the relatively high radiation dose, particularly to the gonads - This is of particular concern because many patients who have stone disease are young and have a tendency to experience repeat stone formation
NCHCT (CT)
- Non-Contrast Helical Computerized Tomography
Difference between ionic and non-ionic contrast? (CT)
- Non-ionic contrast media have a lower osmolality than ionic media.
Dynamic Scanning (CT)
- Nonincremental scanning - Repeating data acquisitions in the same location - Used to watch how a structure fills with an iodinated contrast agent
Liver HU (CT)
- Normal CT attenuation of the unenhanced liver is between 38 and 70 HU - In healthy subjects the liver is at least 10 HU greater than the spleen - Fatty infiltrates (HU of liver at least 10 HU< of spleen) and cavernous hemangioma are two common findings in the liver
Normal Range for Oxygen O2 Saturation (CT)
- Normal range of O2 saturation as measured by a pulse oximeter is between 95% and 100%. - Saturation levels below 95% may indicate respiratory insufficiency.
Nosocomial Infection (CT)
- Nosocomial infections may be commonly referred to as health care-associated infections. -They occur within the first 48 hours of a patient's stay in a health care facility.
Respiration Vital Signs (CT)
- Number of breaths a person takes per minute - Typically measured when the patient is at rest - Commonly accepted normal ranges are - Adults: 14 to 20 - Adolescent youth: 18 to 22 - Children: 22 to 28 - Infants: 30 or greater
Artifact QA (CT)
- Object seen on the image that is not present in the object scanned.
Single Detector Row Systems SDCT (CT)
- Older systems. - Fan Beam. - One rotation = Single Slice - Calculating the area of patient anatomy to be covered: Simple process of multiplying the slice increment selected by the number of slices acquired
Contrast Clearance (CT)
- Once injected all types of iodinated contrast media undergo very rapid distribution throughout the entire extracellular space - They are not metabolized and are excreted by the body nearly exclusively by the kidneys - Patients with normal renal function half of dose is eliminated from the body in approx 2 hours
Stochastic Effect (CT)
- One that has no threshold dose but increases in probability with increasing dose.
#2 (CT)
- Optic Nerve
Coronary Artery Origin
- Originates at the "Base" or ascending portion of the Aorta
Affects Patent Dose (CT)
- Overlapping of Slices - Pitch - mAs - kVp
# 3 (CT)
- Pancreas
Partial Volume Averaging (CT)
- Parameter most responsible for _____ is Slice Thickness - add more jg
3 Types of Artifact Classification (CT)
- Patient Based - Physics Based - Equipment Based
Patient and Equipment Factors Affecting Contrast (CT)
- Patient factors: Cardiac output, Weight - Equipment factors: Scanner speed, Primarily determined by the number of detector rows
Respiration Abdomen Pelvis (CT)
- Patients are asked to suspend respiration during image acquisition to reduce movement and decrease artifact
Coice Between Ionic & Non Ionic CM Should be Based On (CT)
- Patients may be assigned to a higher-risk group for an adverse reaction to iodinated contrast material on the basis of several factors, including: - previous allergic history - physical condition. Patients considered to be at high risk for adverse reactions should be administered: - non-ionic contrast material - Iso-osmolar contrast material is an alternative choice that may also reduce the risk of adverse reactions. ! Ionic = Bad w/ this kind of patient ! Non Ionic = Good w/ this kind of patent
General Rule Regarding the Administration of IV CM to Patients Receiving Dialysis (CT)
- Patients on dialysis who still have residual kidney function should not be given CM - Only patients with end stage renal failure.
#4 (CT)
- Pectoralis Minor Muscle
Neck Study (CT)
- Performed supine with neck slightly extended - Most often done in helical mode - IV contrast is used, unless contraindicated. Split-bolus injection technique is used by some institutions - The goal is to allow sufficient time after contrast administration for mucosa, lymph nodes, and pathologic tissue to enhance, yet acquire images while the vasculature remains opacified - 1st injection - wait 2 min - 2nd injection - wait 25 sec - Angle gantry to hard palate - Scan from mid orbit to clavicular heads
Contrast Osmolality Isomolar Osmolality Contrast Medium IOCM (CT)
- Pg 53 - Isosmolar agents (IOCM) have the same osmolality as blood
Contrast Osmolality Low Osmolality Contrast Medium LOCM (CT)
- Pg 53 - Low-osmolality agents (LOCM) have roughly twice the osmolality of blood ex. - Iodixanol (Visipaque) is an example of a non-ionic isoosmolar contrast agent. - Iohexol (Omnipaque), iopamidol (Isovue), and ioversol (Optiray)
Pleural Effusion (CT)
- Pleural effusions are commonly seen in the posterior portion of the lung field on images obtained with the patient in a supine position on the CT table. - Differentiation between pleural effusion and pleural thickening is made when region of interest (ROI) measurements reveal fluid with density readings at or slightly above zero. ex +/- 5.0 HU's - Pleural effusion may be caused by multiple pathologic processes, including infection, neoplasm, and congestive heart failure.
# 2 (CT)
- Portal Vein
The Liver has a Dual Blood Supply and Receives 75% of its blood from the?
- Portal Vein - Remaining 25% from the hepatic artery.
Positive Contrast Agent (CT)
- Possess a higher density than surrounding structures Barium, iodine
Negative Contrast Agent (CT)
- Possess a lower density than surrounding structures Air, CO2
PE Most Reliable Visual Sign (CT)
- Presence of a low-density filling defect projecting into the vessel lumen, outlined by contrast material.
Blood Pressure (CT)
- Pressure exerted by circulating blood on the walls of the vessels - The systolic pressure is the peak pressure in the arteries, and Occurs near the beginning of the cardiac cycle - The diastolic arterial pressure is the lowest pressure Occurs at the resting phase of the cardiac cycle - Although there is a wide variation, a typical value for a resting, healthy adult is 120 mm Hg systolic and 80 mm Hg diastolic - Systolic blood pressure indicates the pressure within arteries during cardiac contraction and should be less than 120 mm Hg. - Diastolic pressure is measured during relaxation of the heart and should be less than 80 mm Hg.
Risk Factors for Idiosyncratic Reactions (CT)
- Previous reaction - Asthma - A history of allergy to food, drugs, or other substances - Seafood allergy poses no particular risk Seafood allergy results from hypersensitivity to a protein within the seafood and has no association with iodine
Air and Carbon Dioxide as Contrast (CT)
- Produces very high negative contrast - Administered rectally - Particularly useful in CT colonography - Both room air and CO2 provide reliable colonic distention - CO2 is better tolerated by most patients
Head Study (CT)
- Program slices so that they are parallel to the supraorbital meatal line to reduce radiation exposure to the lens of the eye - Some protocols call for images to be taken in the direct coronal plane Can be accomplished either with the patient lying supine or prone which will require a change in orientation - Because of the dense bone of the skull beam-hardening artifacts are often seen in images of the posterior fossa - Thin slices can help to reduce these artifacts - Routine head studies are most often done using the step-and-shoot method (i.e., axial mode) - Helical mode is primarily used for studies that require 3D reformations or for CT angiography (e.g., circle of Willis studies) - Because of the small difference in attenuation between the gray matter and white matter, narrow window widths are used to demonstrate the brain
Primary Responsibility of Computed Tomography in Combined PET-CT is to? (CT)
- Provide precise anatomic location of tumor activity. - Positron emission tomography (PET) provides a map of normal and abnormal tissue function. - It offers excellent sensitivity for malignancy but suffers from an inability to accurately localize tumor activity. - Fusion of PET with CT provides such precise anatomic localization. Non Responsibilities: - Reduction of patient dose - Improvement in radiopharmaceutical uptake
Perspective Volume Rendering (CT)
- Provides one a viewpoint of being within the lumen of the object, similar to an endoscopic view. - Also referred to as immersive rendering, this type of 3D reconstruction is commonly used during CT colonography and CT bronchography.
The measurement of CT system performance through quality testing procedures and evaluation of the test results is referred to as: (CT)
- Quality assurance refers to the measurement of the scanner's performance through quality testing procedures and evaluation of the test results. - ! (Quality control) refers to the implementation of corrective actions to improve any identified performance inadequacies of the CT system found through quality assurance procedures.
Right Coronary Artery Branch (CT)
- RCA Right Main Artery * Controls both Nodes
Can be Used W/ Image Data (CT)
- ROI - Annotation - Measurements
Fan Beam (CT)
- Radiation emitted from older Single Detector Row Systems.
Dynamic CT studies involve rapid bolus contrast administration followed by immediate data acquisition with which paramters? (CT)
- Rapidly scanned sections with short interscan delays.
#1 (CT)
- Rectus Abdominis Muscle.
Reducing mAs while holding kVp constant (CT)
- Reduces patient radiation dose.
Advantages of using a Saline Flush Immeditley Following Contrast Administration (CT)
- Reduction in required contrast agent dose - Reduction in the incidence of CIN - Reduction of streaking artifact from dense contrast agent in the vasculature
Uniformity QA (CT)
- Refers to the ability of the scanner to yield the same CT number regardless of the location of a ROI in a homogeneous object.
Manual Segmentation (CT)
- Refers to the process by which a user identifies and selects data to be saved or removed.
Cardiac Cycle (CT)
- Refers to the series of blood flow- related events that occur from the beginning of one heartbeat to that of the next. - It is the frequency of the cardiac cycle that determines the patient's heart rate. - Diastole refers to relaxation of heart muscle - Systole refers to contraction of the heart muscle.
Multiplanar (CT)
- Reformation that is done to show anatomy in various planes.
Renal Colic (CT)
- Renal Stones - CT Abdomen w/out
Informed Consent (CT)
- Required for procedures of a more invasive nature, such as image guided biopsies. - The administration of intravascular contrast material is invasive in nature and requires the informed consent of the patient.
Documentation of IV Contrast Administartion (CT)
- Required on all patients and should include name of the agent, dose, flow rate and injection site.
Parental Consent (CT)
- Requirement that minors have at least 1 parent sign.
Longitudinal Resolution. (CT)
- Resolution in the z direction
Chemotoxic Reactions (CT)
- Result from the physicochemical properties of contrast media, the dose, and speed of the injection - Contrast media-induced nephropathy - Effects on thyroid function - Pulmonary effects - Pheochromocytoma - Central nervous system effects - Delayed reactions
Retrospective ECG Gating/Cardiac Gating (CT)
- Retrospective gating methods acquire images throughout the cardiac cycle while the patient's ECG is recorded. Images are later reconstructed to create image sets at any desired phase of the cardiac cycle.
Most Blood Supplied to Coronary Arteries (CT)
- Returned to the Right Atrium via the Coronary Sinus
Preferred IV Site and Gauge (CT)
- Right Antecubital Vein - 18 Gauge
Right Atrium in Position to Right Ventricle (CT)
- Right Atrium is posterior to Right Ventricle
Fourth-generation CT scanners use a __________tube-detector configuration. (CT)
- Rotate Stationary - operate with a rotating x-ray tube and a stationary ring of detectors. - Some fourth-generation scanners also use a rotating x-ray tube with a nutating detector ring.
Neurologic Protocols (CT)
- Routine head - Skull base (posterior fossa) - Temporal bones - Sinus screen - Trauma facial bones - Orbits - Sella turcica - Brain perfusion - CTA - circle of Willis - CTA - circle of Willis/carotid - CTV - cranial venography - Soft tissue neck - Cervical spine - Thoracic spine - Lumbar spine - CTA - spine
Hydrocortisone/Corticosteroid (CT)
- SOLU-CORTEF is a brand name for hydrocortisone,which is a type of corticosteroid. - This drug, or other types of corticosteroids, may be used during the treatment of anaphylactoid reactions to iodinated contrast materials.
SSCT & MSCT (CT)
- SSCT Single Slice CT - MSCT Multi Slice CT - The primary difference between single-slice CT SSCT and MSCT hardware is in the design of the detector arrays
Multiplanar Reformations
- Saggital - Coronal - Oblique
CTA Head and Neck Carotids and Circle of Willis Study (CT)
- Scan from Aortic Arch to just above frontal sinus - Use aproximately C4 level for ROI - Some institutions use aortic arch
CTA Head Circle of Willis only (CT)
- Scan from base of skull to just above frontal sinus - Some institutions scan from C2 to just above frontal sinus - Use aproximately C4 level for ROI - Some institutions use C2 or aortic arch
Scan Size to Recon Size
- Scan in 5mm - Recon in 1.25mm
Over Scan (CT)
- Scans over 360 degrees. 400 degree rotation. 4th Generation technology.
Preliminary Image (CT)
- Scout - Topogram - Scanogram
Maximum Intensity Projection MIP (CT)
- Selects only the highest value voxels from the data set for display.
Minimum Intensity Projection MinIP (CT)
- Selects the minimum value voxels for display.
Laser Light QA (CT)
- Semi Annually Twice a Year
Linearity QA (CT)
- Semi Annually Twice a Year
Slice Thickness QA (CT)
- Semi Annually Twice a Year
#3 (CT)
- Seminal Vesicles
Laboratory Values Renal (CT)
- Serum creatinine and blood urea nitrogen (BUN) provide information about a patient's kidney function - Usually today Creatinine and eGFR are used - eGFR - estimated Glomerular Filtration Rate Important if the patient is a candidate for iodinated contrast media - Reference ranges are typically provided by the laboratory, but as a general guide, normal ranges are - Serum creatinine: 0.6-1.7 mg/dL - BUN: 7-25 mg/dL * Other sources say 5-20 mg/dl - eGFR >60
Contraindications to Administration of Iodinated Contrast Material (CT)
- Several factors may be regarded as contraindications to administration of iodinated contrast material, including known allergy to iodine, prior severe reaction, and renal insufficiency. * Multiple myeloma and diabetes, although not absolute contraindications to IV administration of iodinated contrast agents, do require attention to the patient's hydration level to limit renal complications.
Techs & Physicist (CT)
- Share responsibilities for performing and documenting Quality Control Tests.
Multiplanar Reformation MPR (CT)
- Shows anatomy in various planes. - Are 2 Dimensional in nature. - On most scanners MPR's can be created either at the operators console or at a separate workstation. - Can be created in coronal, sagittal, or oblique planes. - Multiplanar reformation (MPR) describes the process of displaying CT images in a different orientation from the one used in the original reconstruction process. - The reformatted image is 1 voxel thick, with the pixels facing the viewer each representing the average attenuation occurring within the represented voxels.
#2 (CT)
- Sigmoid Colon
Attenuation Values of Simple Cysts (CT)
- Simple cysts contain primarily water and therefore exhibit CT numbers ranging from approximately 0 (or slightly below) to +20 Hounsfield units.
Multidetector Row Systems MDCT (CT)
- Single rotation can produce multiple slices, therefore provides longer and faster "Z" axis coverage per gantry rotation. - Cone Beam - Used for either Axial or Helical acquisitions
QA Semi Annually (CT)
- Slice Thickness - Laser Light - Linearity
Semi Annual/Twice a Year QA (CT)
- Slice Thickness - Laser Light - Linearity
Vacuum Phenomenon (CT)
- Small amounts of gas may appear in the areas of degenerated intervertebral discs. - The accumulation of gases such as nitrogen occurs as a by-product of the physical breakdown of the disc material.
IV Gauges Size (CT)
- Smaller the gauge number, the wider around, and has larger the hole. - 24 gauge is wider around, and has a larger hole than a 16 gauge.
3 Methods of Reducing Beam Hardening (CT)
- Software - Filters - Correct SFOV
Water as Contrast (CT)
- Sometimes used in place of a positive agent - It does not obscure mucosal surface - Transits rapidly - Distends the bowel poorly
Monthy QA (CT)
- Spatial Resolution - Contrast Resolution
QA Monthly (CT)
- Spatial Resolution - Contrast Resolution
Two main features are assessed to measure image quality (CT)
- Spatial Resolution - Contrast Resolution
IV's to avoid in CT (CT)
- Straight needle - Butterfly needle - Huber needle ! Straight & Butterfly needle usually cause contrast extravasation.
# 6 (CT)
- Superior Mesenteric Artery
#3 (CT)
- Superior Rectus Muscle
#1 (CT)
- Superior Vena Cava
The mediastinum includes which of the following anatomic structures? (CT)
- Superior Vena Cava - Ascending Aorta - two lungs - heart - great blood vessels - thymus - portions of the trachea and esophagus.
During contrast-enhanced CT examinations of the chest, streaking artifact may obscure portions ofthe superior mediastinum because of dense concentrations of iodine in the? (CT)
- Superior Vena Cava - There is often significant artifact within the mediastinum from high concentrations of iodine in the superior vena cava. - This artifact may be alleviated by administering a bolus of a contrast agent with reduced iodine concentration, which is achieved by diluting a full-strength contrast agent with saline.
Technique Required at the Site of IV Injection of ICM (CT)
- Surgical Asepsis - Insertion of any intravenous line requires the use of sterile technique to prevent microorganisms from entering the bloodstream.
Reason to Scan to Adrenal Glands on Routine Chest (CT)
- Suspected lung cancer
Pitch Formula (CT) 16 Slice Scanner, 0.5mm Slice Thickness, Table Movement of 12mm per rotation?
- Table / (Scanner x Thickness) = Pitch - Ta / (Ss x Th) = P 12 / (16x.05)= 1.5
8 cGy Single Slice, Entire Exam 40 Contiguous Slices for Abdomen Study. What is the Dose? (CT)
- Tails account for 25-40% of radiation dose 8 x .25 = 2 8 x .40 = 3.2 So at 8cGy dose is around 10 to 11.2 cGy
How Rapidly Data is Acquired (CT)
- Temporal Resolution
Triple Rule Out MDCT Protocol for Chest Pain (CT)
- The "triple rule-out" MDCT procedure is a comprehensive evaluation of the chest for cardiac and noncardiac pain. The single acquisition consists of: - Coronary CTA for coronary artery disease - CTA of the aorta for aneurysm - CTA of the pulmonary arteries for embolism. ! Does not include HRCTc
Agaston Score (CT)
- The Agatston scoring system quantifies the volume and density of calcium within the coronary arteries. ! Calcium in the Coronary Arteries
CTDIvol (CT)
- The CTDIvol is now the preferred expression of radiation dose in CT dosimetry. - The CTDIvol is a measure of exposure per slice and is independent of scan length. fm. CTDIvol = CTDIw/pitch
Interscan Delay (CT)
- The Slight pause between data acquisitions with the step and shoot, Axial method - Table movement between slices - Z Axis
Abdominal Aorta Bifurcation (CT)
- The abdominal aorta descends to the level of the fourth lumbar vertebra (L4), where it bifurcates into the left and right common iliac arteries.
Contrast Resolution (CT)
- The ability to differentiate on an image a structure that varies only slightly in density from all its surroundings - Ability to differentiate between objects with very similar densities as their background. - Factors that affect Contrast Resolution: Pixel Size, & Slice Thickness also affect contrast resolution but for different reasons. Also mAs, Patient Size, Subject Contrast, and Inherent Contrast of the object scanned contribute.
Spatial Resolution (CT)
- The ability to resolve as separate objects small, high contrast objects, such as contrast filled vessels, tiny bones, or a calcified nodule - Represents the ability to discriminate objects of varying density, a small distance apart, against a uniform background - Describes the degree of blurring in an image - The number of line pairs visible per unit length - Factors that affect contrast resolution: Pixel Size, Slice Thickness, Focal Spot Size, Reconstruction Algorithm, and Pitch - Decrease in Pixel Size (smaller), then Increase in Spatial Resolution
Asepsis (CT)
- The absence of bacteria, viruses, and other microorganisms. - The exclusion of bacteria and other microorganisms, typically during surgery.
Primary Disadvantage of Axial Scanning (CT)
- The accumulative effect of the interscan delay adds to the time total time of the procedure. - Also Axial data have more limitations regarding reconstruction options than that of data in helical scanning.
Contrast Administration Tecniques for General CT Survey of the Abdomen
- The administration of an oral contrast agent is subject to specific departmental protocol considerations. Correct Choice: - Generally, 400 to 600 mL of oral contrast administered 45 to 90 minutes prior to the exam should opacify the small bowel. - An additional dose of contrast agent (250 mL) immediately before the exam should ensure gastric opacification. Wrong Choice: Administration of contrast agents via enema is indicated for evaluation of the distal large bowel.
Pulse Vital Signs (CT)
- The alternate expansion and recoil of an artery - The patient's blood pressure can impact the ease of palpability of a pulse - Average adult 60 to 100 beats per minute - Athletic adult 45 to 60 beats per minute - Children 95 to 110 beats per minute - Infants 100 to 160 beats per minute
Linear Attenuation Coefficients (CT)
- The amount of the x-ray beam that is scattered or absorbed per unit thickness of the absorber is expressed by the linear attenuation coefficient, represented by the Greek letter μ.
Array Processor (CT)
- The array processor is a specialized component of the CT computer system. - It is capable of performing the massive calculations required for CT image reconstruction - Reconstructs the projected attenuation raw data into a CT image.
Arterial Phase of Hepatic Contrast Enhancement (CT)
- The arterial phase is the period of peak arterial enhancement typically occurring at 25 to 35 seconds after the initiation of contrast agent administration. - During this phase, hypervascular tumors or tumors supplied by the hepatic artery undergo maximal enhancement.
Vital Signs (CT)
- The best early indicators of a problem are a change in vital signs - Body temperature - Pulse - Respiration - Blood pressure
Bolus Phase Characteristics (CT)
- The bolus phase/atrial phase which immediately follows IV bolus injection. - Characterized by a dynamic attenuation difference between the Aorta and the IVC.
Ionic and Non Ionic (CT)
- The classification Ionic & Nonionic refers to whether the molecules of the solution form ions in a water solution. - Although many nonionic contrast agents are also low osmolality, that is not true of all nonionic agents.
Osmolality (CT)
- The concentration of a solution expressed as the total number of solute particles per kilogram. - Particles in solution per unit of liquid/water - Measured in milliosmoles per kilogram (mOsm/kg) of water - Osmolality of blood plasma is approximately 290 mOsm/kg water - Most brands of contrast medium have a greater osmolality than blood plasma, therefore most contrast agents are said to be Hyperosmolar, or Hypertonic solutions.
Which of the following is used to archive a Soft Copy of a CT image? (CT)
- The digital storage of CT images on PACS, CD-ROM, MOD, and so on, is referred to as soft copy. ! Storage on Film/Laser Film is considered to be a hard copy.
R - R Interval (CT)
- The distance between one cardiac cycle to the next
R-R Interval (CT)
- The distance between two R waves represents one complete cardiac cycle and is sometimes referred to as the R-R interval. Hence, a scan that covers the entire heartbeat (a continuous acquisition) might be referred to as covering 100% of the R-R interval.
Bifurcation Level of Carotids (CT)
- The division of the common carotid artery into internal and external carotid arteries; it occurs at the level of the superior border of the thyroid cartilages (vertebral level C4), The carotid body and sinus occur in relation to the carotid bifurcation.
Uncoupling Effect (CT)
- The dose is not related to the image. - The same result can be achieved by using too much technique, and unneeded patient dose.
DLP Dose Length Product (CT)
- The dose length product (DLP) is the total patient dose over a given scan acquisition length (z) and can be illustrated as the product of CTDIvol and scan length. The DLP is expressed in units of milligrays per centimeter (mGy-cm). fm. DLP = CTDIvol × scan length
Edge Gradient Artifact (CT)
- The edge gradient effect results in streak artifact or shading (both light and dark) arising from irregularly shaped objects that have a pronounced difference in density from surrounding structures - A common clinical example is artifacts that result when barium and air lie adjacent to each other in the stomach - Using Neutral Contrast Agent, Water, VoLumen, low HU number all can eliminate streak artifact
Extravasation - Infiltration (CT)
- The escape of contrast material from a needle or blood vessel into the subcutaneous tissues
Sinus Last to Fully Develop (CT)
- The frontal sinuses are absent at birth and do not usually fully develop until after puberty. - The ethmoidal, maxillary, and sphenoidal sinuses begin to develop during gestation. ! Frontal
Which Best Describes this Type of Image (CT)
- The image is a multiplanar reformation (MPR) image through the orbit in the oblique sagittal plane.
Contrast Effects & Central Nervous System (CT)
- The intravascular administration of Contrast has been shown to provoke seizures in patients who have diseases that disrupt the blood-brain barrier - The risk of seizure can be substantially reduced by a one-time oral dose of 5 to 10 mg of diazepam, 30 minutes before Contrast administration - Seizures that occur can also be controlled with diazepam
Gerota's Fascia (CT)
- The kidneys are located in the retro peritoneum and are bound by a band of fibrous connective tissue called Gerota's fascia. - The kidneys are located in a portion of the retroperitoneum known as Gerota's space. They are held in place by fibrous connective tissue commonly referred to as Gerota's fascia. ! Gerota's fascia
Barium Sulfate Solutions (CT)
- The most commonly used are positive agents that contain a 1% to 3% barium sulfate suspension - In general, the higher the dose, the better the bowel opacification - For most examinations a minimum of 500 mL of dilute barium sulfate is given 45 minutes to 2 hours before scanning - An additional 200 mL is given just before scanning to fill the stomach and small bowel - Low HU oral barium sulfate suspension (VoLumen) resembles water on CT images - Just 0.1% barium sulfate solution - Measures from 15 to 30 HU on an image - Advantages of low HU oral contrast - Improved bowel distention (compared with water) - Faster transit than standard CT barium solutions - More effective visualization of both the bowel wall and the mucosa - Contraindicated when perforation of the gastrointestinal tract is suspected - Barium leaking into the peritoneal cavity is referred to as barium peritonitis - Fewer complications from aspiration appear to occur with barium sulfate compared with high-osmolality iodinated agents (e.g., Hypaque)
Normal Renal Function Levels (CT)
- The normal range for creatinine level is 0.5 to 1.5 mg/dL. - The normal range for BUN levels is 7 to 25 mg/dL.
Pancreas Study (CT)
- The pancreas is typically located between T12 and L2 - Water or low-attenuation oral contrast agents are preferred because dense contrast may obscure small stones - When initial scans fail to differentiate the margins of the pancreas from the duodenum, the patient is often given additional oral contrast material and slices are obtained with the patient in the right decubitus position
Complete Cardiac Diastole (CT)
- The period of atrial and ventricular relaxation after heart contraction. - The T wave of an ECG corresponds to cardiac diastole.
CT dose uniformity (CT)
- The peripheral dose, or skin dose, of a body scan can be two to three times higher than the central dose. - As the scan field and patient size increase, the x-ray beam must travel a greater distance and penetrate more tissue to arrive at the center. - The greater distance and increased thickness of the absorber provide more opportunity for the beam to be attenuated. - Hence, the uniformity of the dose decreases as the scan field of view and patient thickness increase. - Therefore, body scans are less uniform than head scans.
Aspirin for Heart Attack (CT)
- The platelets help form a plug that seals the opening in your blood vessel to stop bleeding. - Then, a blood clot can quickly form and block the artery. - This prevents blood flow to the heart and causes a heart attack. - Aspirin therapy reduces the clumping action of platelets, possibly preventing a heart attack.
Clustering (CT)
- The practice of grouping more than one Axial Scan in a single breath.
Low Contrast/ High Contrast & Radiation Dose (CT)
- The price that is paid for the excellent low-contrast resolution seen on CT images is a relatively high radiation dose. ! Low Contrast = High Dose
The prone position may be used for a post-myelogram CT examination of the lumbar spine in an effort to? (CT)
- The prone position during a post-myelogram CT study of the lumbar spine reduces pooling or layering of the intrathecal contrast material. ! reduce metrizamide pooling
Which of the following statements regarding predetector collimation of the CT x-ray beam is true? (CT) a. Predetector collimation reduces patient radiation dose. b. Predetector collimation reduces production of scatter c. Predetector collimation determines the SFOV d. Predetector collimation removes scatter before it reaches the detectors.
- The purposes of pre-detector or post-patient collimation are to remove scatter radiation and to shape the portion of the beam that is incident on each detector. ! Scatter removal before detectors
Photon Flux / Fluence Rate
- The rate at which a quantity of radiation (photon fluence) passes through a unit area over unit time is termed the photon flux.
CTA of the Renal Arteries Should be Performed Using a Section of? (CT)
- The renal arteries are small structures that are optimally visualized with MDCTsection widths of 1.25 mm or less. ! 1.25 mm or less
The retroperitoneum contains which of the follow-ing anatomic structures? (CT)
- The retroperitoneum is the space located between the peritoneum and the posterior abdominal wall. It contains: the duodenum, pancreas, adrenal glands, kidneys, ureters, and bladder.
Comparing the efficiency of scintillation vs. gas ionization detectors (CT)
- The scintillation detector has a higher capture efficiency.
Reformation (CT)
- uses IMAGE data. - The term "reformation" is used when image data are assembled to produce images in different planes, or to produce three-dimensional (3D) images
Using a standard 512 matrix for all studies, which contains the largest pixels? (CT) a. An image of the pituitary; DFOV = 16; slice thickness = 2 mm b. An image of the knee; DFOV = 20; slice thickness = 1 mm c. A scan of the neck; DFOV = 30; slice thickness = 3 mm d. A scan of the abdomen; DFOV = 44; slice thickness = 5 mm
- The slice thickness is irrelevant in determining pixel size. - Pixel size can be calculated by dividing the DFOV by the matrix size. - Therefore, the pixel size of choice (a) is 0.31mm; choice (b) is 0.39mm; choice (c) is 0.59 mm; and choice (d) is 0.86 mm. - Slice thickness does not impact pixel size, only voxel size. 44/5=0.86
Stroke (CT)
- The sudden death of brain cells due to lack of oxygen, caused by blockage of blood flow or rupture of an artery to the brain. - Sudden loss of speech, weakness, or paralysis of one side of the body can be symptoms. - Abbreviated CVA. Also known as cerebrovascular accident.
The mathematical manipulations required duringthe reconstruction of a CT image are accomplishedusing a(n)? (CT)
- The terms algorithm, kernel, and mathematical filter function may all be used interchangeably in describing the mathematical process used for the complex calculations required during CT image reconstruction. Synonyms: - algorithm, kernel, and mathematical filter function
Urinary Tract Calculi Kidney Stones (CT)
- The terms kidney stones, renal stones, renal calculi, nephrolithiasis, and urolithiasis are often used interchangeably - There are four basic types of urinary stones; all can be seen on noncontrast helical CT (NCHCT) - More than 99% of stones, including those that are radiolucent on plain film radiography, will be seen on NCHCT
Viscosity (CT)
- The thickness or friction of a fluid as it flows - The brand, temperature, and concentration of the CM affect its viscosity - May affect the injectability of intravascular agents through small-bore needles and IV catheters
Reconstructed Slice Thickness (CT) ex. On a MDCT system that produces four 1mm slices per rotation, could the slices be divided to produce 16 0.25 mm slices?
- The thinnest images that can be reconstructed for a data set are often predetermined by the slice thickness used for the data acquisition - Images can be added together to create thicker slices for viewing, but in many instances data cannot be divided to produce thinner slices - It is never possible to create an image that is thinner than the size of the individual detector cell
The Third Ventricle of teh Brain Communicates With the Fourth Ventricle Through teh? (CT)
- The third and fourth ventricles communicate through the cerebral aqueduct, which is commonly referred to as the aqueduct of Sylvius. ! Cerebral Aqueduct
Acute Appendicitis (CT)
- The variable position of the appendix is important because it contributes to the diverse clinical presentation of acute appendicitis - This variation in positioning also makes the appendix more challenging to locate on cross-sectional images - Appendicitis protocols vary widely and use different combinations of oral, rectal, IV, or no contrast material - The techniques vary most in their rate of providing an alternative diagnosis when the appendix is found to be normal
Advantage of using higher concentration ≥ 350 mg iodine/mL agents.
- They deliver the same amount of iodine at a lower flow rate.
Advantage of Using Higher Concentration ≥350mg iodine/mL agents (CT)
- They deliver the same amount of iodine at a lower flow rate. - Higher concentration agents are particularly well suited when multislice scanners are used and the duration is quite short.
Abnormalities of the Middle Ear may be best demonstrated with CT Utilizing? (CT)
- Thin sections are required to properly assess abnormalities of the minute structures of the inner ear. - The thinnest sections possible provide maximum detail. ex. Sections 1 to 2 mm
Focused Thin Section Axial CT Through Just the Region of the Vocal Cords Should Extend? (CT)
- Thin-section (0.5-2.0 mm) helical acquisition - Specific to the larynx should extend from just above the hyoid bone inferiorly through the cricoid cartilage. ! hyoid bone inferiorly through the cricoid cartilage
18 Gauge IV Green (CT)
- This size allows you to do most tasks that the 16 gauge can, but it large and more painful to the patient. Some of the common uses include administering blood, pushing fluids rapidly, etc. You can use this for CT PE Protocols or other testing that requires large IV sizes.
16 Gauge IV Gray (CT)
- This size is mostly used in the ICU or surgery areas. This large size enables many different procedures to be performed, such as blood administration, rapid fluid administration, and so forth.
24 Gauge IV Yellow (CT)
- This size is used for pediatrics and is usually only used as a last resort as an IV in the adult population.
22 Gauge IV Blue (CT)
- This small size is good for when patient's won't need an IV long and aren't critically ill. You usually can't administer blood* due to it's small size, however, some hospital protocols allow for 22 G usage if necessary.
Gantry Angulation of 0, 30, 45, & 60 degrees for the knee to show? (CT)
- This technique allows for visualization of the relationship between the patella and the femur as the knee is increasingly flexed. - The patellofemoral congruence, or the position of the patella within the patellar surface of the femur, may be measured at each point of flexion. - Any medial or lateral displacement of the patella may indicate an abnormality of the patellofemoral joint. ! Patellofemoral joint
Reconstruction (CT)
- uses RAW data - raw data are manipulated to create pixels that are then used to create an image
Image Reconstructions (CT)
- when Raw Data is manipulated to create pixels that are then used to create an image.
Which of the following protocols would provide the best image quality for a 3D disarticulation study of the hip? a. 10 mm x 15 mm sections, standard algorithm b. 10 mm x 10 mm sections, bone algorithm c. 1.5 mm x 1.0 mm sections, bone algorithm d. 5 mm x 7 mm sections, standard algorithm
- Three-dimensional studies are best performed with the use of narrow sections acquired with no spacing or, preferably, an overlap. - A detail (bone) algorithm is used for optimal demonstration of bony structures.
Scan Time (CT)
- Time it takes for the Gantry to make a complete 360 rotation.
Suspicion of Stroke (CT)
- Tissue plasminogen activator (t-PA) Tissue plasminogen activator, is a pharmacologic treatment for acute ischemic stroke (blood clot) - To be effective t-PA must be administered within 3 hours of the first signs of stroke - This means that the stroke victim must be transported to the hospital, diagnosed, and administered the t-PA treatment before the 3-hour window has expired - ICH (bleed) contraindicates t-PA therapy
ECG-pulsed tube current modulation (CT)
- To address concern about the radiation dose from retrospective ECG gating methods manufacturers have developed methods that automatically decrease the tube current during the systolic phase of the ECG tracing.
The Most Common Indication for CT-Guided Percutaneous Biopsy? (CT)
- To confirm the malignancy of a mass.
Raw Data w/ MPR
- To create a reformation, source images must posses the same DFOV, Image Center, Gantry Tilt, and they must be contiguous. - If the RAW DATA is available, NEW SOURCE IMAGES cane be created that posses the same DFOV, Image Center, and contiguation. - Reformations can be made from images with variable slice thickness. - NOTHING can be done retrospective about GANTRY TILT!
Beam Hardening (CT)
- To summarize here, as an x-ray beam passes through an object, lower-energy photons are preferentially absorbed, creating a "harder" beam - Individual rays are hardened to differing degrees, and this variation cannot be adjusted for by the reconstruction algorithm - The degree of beam hardening is dependent on the composition of the part examined and the extent the beam must travel through various tissues - 2 types of Bean Hardening Artifact - Cupping (periphery of image being lighter) - Dark bands or streaks between dense objects in the image - 3 Feature to Combat Beam Hardening - Filtration - Calibration correction - Beam Hardening correction software - Filtering the beam by a metallic material such as aluminum filters out the lower-energy components of the beam before they pass through the patient - Raising the kVp will increase the average photon energy of the beam, therefore reducing beam hardening to some extent. - The best strategy available to the operator to avoid beam hardening is to select the appropriate SFOV to ensure the correct filtration, calibration, and beam-hardening correction software is used
Complete CT examinations of the chest for investi-gation of bronchogenic carcinoma should include sections from the? (CT)
- Top of the apices through the liver - Complete CT examination of the chest for bronchogenic carcinoma consists of an acquisition from the apices through the liver. The adrenal gland and liver are common sites for metastatic disease in patients with primary lung neoplasm. - Scanning may be done in a caudocranial direction to ensure maximum contrast enhancement of the liver and adrenals when indicated. ! bronchogenic carcinoma
Intubation (CT)
- Tracheal intubation, usually simply referred to as intubation, is the placement of a flexible plastic tube into the trachea (windpipe) to maintain an open airway or to serve as a conduit through which to administer certain drugs.
Distinguishing Adjacent Tissues (CT)
- Two tissues must differ by at least 10 hounsfield units to be visibly different on a CT scan - An oral or IV administration of a contrast agent is often used to create a temporary, artificial density difference between objects
Cardiac CT Images
- Typically reconstructed from data acquired during the diastolic phase. - Patients with slower heart rates exhibit longer diastolic phases, which yield higher-quality cardiac CT exams
3D Rendering (CT)
- Unlike 2D displays, 3D techniques manipulate CT values to display an image; the original CT value is not included. - Because rendering is time consuming, the software is usually available on independent consoles so the operators console remains available for scanning patients.
#4 (CT)
- Ureterovesical Junction (UVJ) ! The uretrovesical junction is located where the ureter meets the bladder.
CTV Venography Study (CT)
- Used for the depiction of venous anatomy - Use a scan delay of 30 sec for 16 slice, 45 sec for 64 slice
Platelet Count (CT)
- Used to assess the patient's clotting ability. Normal platelet count is 140,000 to 440,000 per mm3 (or mL) of blood
Ileus (CT)
- Used to describe an area of intestine that has lost normal contractile motion, resulting in obstruction. ! loss contractile motion, obstruction
Reformats (CT)
- Used when the image data are assembled to produce images in different planes - or to produce 3D images.
Bolus Triggering (CT)
- Uses the contrast bolus itself to initiate the scan - A series of low-radiation scans monitor the progress of the contrast bolus - Once adequate enhancement is seen the table moves to the starting level and scanning begins - Depending on scanner it might start automatically based on a threshold or the tech might need to start it - A drawback is that a technologist cannot stay with the patient to monitor the injection site See page 163 for an example
Point of Lowest Cardiac Motion (CT)
- Usually at the end of Diastole
VR Volume Rendering (CT)
- VR is a 3D semitransparent representation of the imaged structure - An advantage of VR compared with other 3D techniques is that all voxels contribute to the image - This allows VR images to display multiple tissues and show their relationships to one another - VR has become the favored 3D imaging technique. An advantage of VR is that all voxels contribute to the image, allowing the image to display multiple tissues and show their relationship to one another - Each voxel is assigned an opacity value based on its Hounsfield units - This opacity value determines the degree to which it will contribute, along with other voxels along the same line, to the final image - Unlike other 3D techniques, with VR no information is ignored or discarded; every voxel contributes to the final image
What postprocessing technique created the image of the heart in Figure 24-3? a. MinIP b. MIP c. Volumerendering d. Endoluminal imaging
- VR is a 3D semitransparent representation of the imaged structure. It has become the favored 3D image technique because all voxels contribute to the image.
Hand Bolus (CT)
- Variable flow rate because of syringe size, contrast viscosity, IV catheter size, and operator strength - Results in inconsistent images that are not readily reproducible - Primarily used when injecting into standard PICC and tunneled or non-tunneled central venous catheters
CT study done for the screening, detection, or exclusion pulmonary nodules or infiltrates are typically done
- W/out contrast - IV contrast administration is not neces- sary for all thoracic indications because the struc- tures of the thorax possess high intrinsic natural contrast.
Cross Field Uniformity QA (CT)
- Weekly
Image Noise QA (CT)
- Weekly
Thrombus vs Embolus (CT)
- When a blood clot forms in a blood vessel it is a thrombus. - If, on the other hand, this clot travels further into the body, it is an embolus.
Anatomic Landmarks and Zeroing Out (CT)
- When a patient is positioned on the table an anatomic landmark is recorded - The table readout is set to zero - This is called referencing the table - Could be called zeroing by techs - Commonly used landmarks are the sternal notch, xiphoid, and iliac crest
Coronary Artery Bypass Graft Surgery CABG
- When there is a disease of the Left Main Coronary Artery - disease of three or more vessels - or if non surgical management has failed
Stair Step Artifact (CT)
- When voxels are not isotropic
Non-Tunneled and Tunneled CVCs (CT)
- Whenever possible, avoid using these CVCs by starting a standard peripheral IV line - When they are used for contrast administration follow your institution policy - Are they capable of a power injection? - Never use a dialysis CVC for contrast injection Examples - port that is under the skin - Port that has the lumens hanging outside the skin but line that tunnels under the skin and into the vein
Negative HU (CT)
- Will appear black
Soft Tissue Window Appearance of Thorax (CT)
- With the lung fields black, the bony structures white, and the mediastinum and muscles gray
Which Window Setting was used to Display the Image in the Figure? (CT)
- With the lung fields black, the bony structures white, and the mediastinum and muscles gray, the image in the figure is displayed in a soft tissue window. Window Settings would prob be around: WL +50, WW 400
Which of the following types of gas is commonly used for gas ionization CT detectors? (CT)
- Xenon Gas - Because of its high atomic number and relative stability, xenon gas is commonly used in gas ionization CT detectors.
20 Gauge IV Pink (CT)
- You may be able to push blood* through this size if you can't use an 18 gauge, but always check your employer's protocol. This size is better for patients with smaller veins.
The mathematical process that allows MDCT images to be reconstructed at any point along the acquired volume is commonly referred to as? (CT)
- Z Filtering - Multiple-detector row CT systems utilize the process called z-filtering during image reconstruction. - Z-filtering allows for thin sections to be reconstructed at any point along the acquired z-axis volume. - This interpolation technique utilizes multiple complimentary rays beyond those immediately above and below the particular slice plane. ! Wrong: a. iteration b. filtered back-projection c. Fourier reconstruction
Occlusion (CT)
- a blockage in a canal, vessel, or passage of the body; the state of being closed
Creatinine
- a compound formed in protein metabolism and present in much living tissue. - It is involved in the supply of energy for muscular contraction. - Its main role is to facilitate recycling of adenosine triphosphate (ATP), the energy currency of the cell, primarily in muscle and brain tissue. - This is achieved by recycling adenosine diphosphate (ADP) to ATP via donation of phosphate groups. - Creatine also acts as a pH buffer in tissues.
Infarct
- a small localized area of dead tissue resulting from failure of blood supply.
CIN Contrast-induced nephropathy (CT)
- an acute impairment of renal function that occurs after the intravascular administration of contrast material (for which alternative causes have been excluded) Presentation: - Progressive rise in SeCr serum creatinine within 24 hours of Contrast administration - Typically nonoliguric (excrete more than 500 ml a day)
Antecubital Space (CT)
- anterior recess of the elbow. - It contains the basilic vein medially and the cephalic vein laterally. - Both veins are common sites for the IV administration of iodinated contrast media.
Prospective ECG Gating/Cardiac Gating (CT)
- attempts to identify the areas of lowest cardiac motion and acquire images only in those portions of the cardiac cycle. These methods use a signal, usually derived from the R wave of the patients ECG, to trigger image acquisition. - Prospective ECG gating, also known as sequential or cine-mode scanning, seeks to identify the areas of lowest cardiac motion and acquire images only in those portions of the cardiac cycle, which minimizes radiation exposure.
A region of interest (ROI) measurement place dover a portion of a CT image provides which of the following? (CT)
- average CT number (HU) - The region of interest (ROI) measurement provides a quantitative analysis of the Hounsfield values of a specific anatomic area. - System software calculates the average CT number in HUs within the defined ROI. - The average ROI measurement provides information regarding tissue characteristics that may be helpful for clinical diagnosis.
Slice Thickness Accuracy (CT)
- for slices 5mm or greater then no more than +/- 1mm variance - for slices 5mm or less then no more than +/- 0.5mm variance.
Angiocatheters (CT)
- higher-gauge needles are preferred for administration of a contrast agent with the use of a power injector. - The stability of an angiocatheter maintains proper placement within the vein while withstanding the high pressure applied by the power injector.
Urticaria
- hives - common adverse reaction to iodinated intravenous contrast material.
Parenteral Administration (CT)
- involves the injection of medication into the body. Administration include: - intramuscular - intravenous - intradermal - subcutaneous. ! Injection
ILD Interstitial lung disease & DPLD diffuse parenchymal lung disease
- is a group of lung diseases affecting the interstitium (the tissue and space around the air sacs of the lungs). - It concerns alveolar epithelium, pulmonary capillary endothelium, basement membrane, perivascular and perilymphatic tissues.
GFR Glomerular Filtration Rate (CT)
- is a more accurate measure of renal function. GFR is an approximation of creatinine clearance or the rate by which creatinine is filtered from the blood stream. GFR is calculated using the patient's measured serum creatinine level and takes into account the patient's age, sex, and race. The normal range of GFR is 70 +/- 14 mL/min/m2 for men and 60 +/- 10 mL/min/m2 for women
mediastinal lymphadenopathy
- is an enlargement of the Mediastinal lymph nodes. Causes: Tuberculosis Sarcoidosis lung cancer/oesophageal cancer lymphangitis carcinomatosa Cystic fibrosis Histoplasmosis Acute lymphoblastic leukemia Coccidioidomycosis Lymphoma Whipple's disease Goodpasture syndrome hypersensitive pneumonitis
Parenchyma
- is the functional parts of an organ in the body. This is in contrast to the stroma, which refers to the structural tissue of organs, namely, the connective tissues.
Stroke Penumbra (CT)
- is the ischemic, yet still viable tissue immediately surrounding the infarct core. It can be described as the region of ischemic brain parenchyma where cerebral blood volume (CBV) is compromised but still higher than 2.5 mL per 100 g of tissue.
kV & mA
- kV is the voltage potential between the tube cathode and anode - mA ultimately controls the filament current and, thus the temperature of the cathode filament
Serum Creatinine (CT)
- lthough it has significant limitations, measuring SeCr is a fast and inexpensive way to assess renal function - A normal range is approximately .6 to 1.6 - This range varies by institution
Accurate demonstration of (bronchiectasis, pneumonia, mediastinal lymphadenopathy, a pulmonary nodule) would most likely require the intravenous injection of an iodinated contrast medium during a CT study of the chest? (CT)
- mediastinal lymphadenopathy
Mild Adverse Reactions to Iodinated Contrast Material (CT)
- nausea, vomiting, mild urticaria, and a warm, flushed sensation. !Dyspnea is a moderate reaction, whereas pulmonary edema and shock are severe reactions to contrast media.
Implied Consent (CT)
- occurs when a patient is in need of immediate medical services but is unconscious or physically unable to consent to treatment. The assumption is made that the patient would consent if able.
Image Multiplanar Reformats MPR (CT)
- only use Image Data to generate images in a plane or orientation - different form the prospective images. - Source Images must have same DFOV, Image Center, Gantry Tilt, No Gaps - Better w/ Thinner Slices - Trans, Coronal, Sag, Oblique antonym - Reconstructions use Raw Data
Axial CT sections of the lumbar spine for intervertebral disk evaluation should be acquired with the plane of imaging? (CT)
- parallel to the plane of the intervertebral disk spaces.
CTA of the Neck Usually For? (CT)
- primarily to evaluate the carotid arteries.
STEMI ST elevation myocardial infarction (CT)
- refers to a particular pattern on an EKG heart tracing and "myocardial infarction" - medical term for a heart attack
claudication
- refers to the condition of intermittent cramping pain in the legs due to poor circulation.
Transdermal
- relating to or denoting the application of a medicine or drug through the skin, typically by using an adhesive patch, so that it is absorbed slowly into the body.
Vagal
- relating to the vagus nerve.
Simple cysts of the kidney have average attenuation values in the range of? (CT)
0 to +20 Hounsfield units
The material within the ROI measurement in the figure has a linear attenuation coefficient of? (CT) a. 0.0007 b. 0.185 c. 0.206 d. 0.530
0.2.06 - At the range of photon energies employed during most CT examinations, water exhibits an approximate attenuation coefficient value of 0.206
Filament sizes for modern CT x-ray tubes range between? (CT)
0.5 and 1.2 mm - Modern CT system x-ray tubes utilize dual-filament systems with focal spot sizes ranging between 0.5 and Modern CT system x-ray tubes utilize dual-filament systems with focal spot sizes ranging between 0.5 and 1.2 mm in diameter.
An MDCT image is reconstructed using a 512^2 matrix and a DFOV of 38 cm. If the detector collimation is set to a section width of 1.25 mm, what is the volume of each voxel? (CT)
0.69 mm^3 - The linear dimension of the pixel must first be calculated by dividing the DFOV, in mm, by the matrix (380 mm ÷ 512 = 0.74 mm) . - This linear pixel dimension is squared to yield the pixel area in mm^2 (0.74 x 0.74 = 0.55 mm^2). - The volume of the voxel may be calculated by multiplying the pixel area by the section width 0.55mm^2 x 1.25mm = 0.69 mm^3.
Pedicle
1
common carotid artery
1
genu of the corpus callosum
1
rectus abdominis muscle
1
superior vena cava
1
Liver HU Image (CT)
1 = 64 HU 2 = 136 HU
Which of the following would serve to increase spatial resolution of a CT exam using a large focal spot size, 5-mm sections, and a 512^2 matrix? (CT) 1. change to small focal spot size 2. acquire 2.5-mm sections 3. reconstruct images in a 320^2 matrix
1 and 2 only - The spatial resolution of a CT examination can be improved with the use of small focal spots, narrow sections, and large matrices.
Which of the following are NOT commonly used on today's commercially available CT scanners? 1. xenon detectors 2. fourth-generation technology 3. continuous rotation technology a. 1 only b. 1 and 2 c. 2 and 3 d. 1, 2 and 3
1&2
Which of the following statements is TRUE? 1. kV is the voltage potential between the tube cathode and anode while mA ultimately controls the filament current and, thus the temperature of the cathode filament 2. kV controls the energy level of the x-ray photons and mA controls the nubmer of x-ray photons emitted from the tube 3. althought the kV and the mA affect the operaton of the CT x-ray tube, the two parameters have no bearing on the image quality a. 1 only b. 2 only c. 1 and 2 d. 2 and 3
1&2
Which of the following are included as basic types of iodinated contrast media? 1. iothalamate 2. diatrizoate 3. metrizoate)
1, 2 &3
The data acquisition system (DAS) of a CT scanner is responsible for? 1. measuring transmitted intensity 2. conversion of the transmission data into a digital signal 3. sending the digital information to the computer for processing
1, 2, & 3 The DAS of a CT scanner consists of: - detector array - analog-to-digital convertor - transmission device used to send the converted digital information to the computer for image reconstruction.
The intrathecal administration of an iodinated con-trast agent in the patient in the figure would allowfor greater visualization of the:? (CT) 1. spinal cord 2. nerve roots 3. anulus fibrosis
1, 2, and 3 - Intrathecal administration of an iodinated contrast agent allows for greater visualization of the spinal cord and nerve roots after its introduction into the subarachnoid space.
Which of the following is TRUE regarding solid state detectors? 1. x-ray photons cause the detectors to generate a flash of light 2. they are the detector type used on most CT scanners today 3. they can be used in both third-generation and fourth-generation CT systems a. 1 only b. 2 only c. 3 only d. 1, 2 and 3
1,2&3
X-ray photons are produced by a fast-moving electron: 1. colliding with an atomic nucleus 2. passing close to an atomic nucleus 3. colliding with an electron within an atom and ejecting it
1,2&3
Pathology (CT)
1. : the study of the essential nature of diseases and especially of the structural and functional changes produced by them studied plant pathology 2 : something abnormal: a : the structural and functional deviations from the normal that constitute disease or characterize a particular disease the pathology of pneumonia
Pathway of Blood (CT)
1. Blood enters the right atrium from the superior and inferior venae cavae, and the coronary sinus. 2. From right atrium, it goes through the tricuspid valve to the right ventricle. 3. From the right ventricle, it goes through the pulmonary semilunar valves to the pulmonary trunk. 4. From the pulmonary trunk it moves into the right and left pulmonary arteries to the lungs. 5. From the lungs, oxygenated blood is returned to the heart through the pulmonary veins. 6. From the pulmonary veins, blood flows into the left atrium. 7. From the left atrium, blood flows through the bicuspid (mitral) valve into the left ventricle. 8. From the left ventricle, it goes through the aortic semilunar valves into the ascending aorta. 9. Blood is distributed to the rest of the body (systemic circulation) from the aorta.
Components of a Comprehensive CT Stroke Management Protocol (CT)
1. Pre contrast sequence of the brain 2. CTA of the brain & carotids 3. CT perfusion CTP of the brain - Found typically in the emergency setting, a comprehensive acute stroke CT imaging protocol begins with a pre-contrast sequence to evaluate for hemorrhage. - After the IV administration of an iodinated contrast agent, a CTA acquisition is performed through the carotid vessels and brain. - CTP is then performed to evaluate potential cerebral perfusion defects secondary to stroke.
Data Acquisition Process
1. Xray tube 2. Fan x-ray Beam 3. Beam shaping filters and Collimators 4. Patient 5. Detector Array 6. Electrical Signal ADC 7. Digital Data 8 Computer for image reconstruction and display
Cardiac Cycle Stages PQRST (CT)
1. a. Atrial systole: • Contraction of the left and right atria. • Corresponds to the onset of the P wave of the ECG. 2. Ventricular systole: • Contraction of the left and right ventricles. • Beginning of the QRS complex on the ECG. 3. Complete cardiac diastole: • Period of relaxation after heart contraction. • Consists of ventricular diastole and atrial diastole. • Corresponds to the T wave of the ECG.
Which of the following protocols should provide the best image quality for a three dimentional disarticulation study of the hip? 1. 10x15mmsections/standard algorithm 2. 10x10mm sec/bone algorithm 3. 1.5x1.0 mm sects/bone algorithm 4. 5x7mm sec/standard algorithm
1.5x1.0 mm sects/bone algorithm
How many grams of iodine will be delivered when 100 mL of an agent with 320 mg of iodine/mL is injected? (CT)
100 mL x 320 mg of iodine/mL = 32,000 mg of iodine = 32 g of iodine
The lifetime risk of an eventual cancer-related death as a result of pediatric CT is approximately 1 in? (CT)
1000 - The latency time for cancer induction at the dose ranges used in CT is 10 to 30 years. - However, because of their younger age, children have more time to express a cancer, and more time to undergo more CT examinations, than do adults. - In addition, because of their youth they have more rapidly dividing cells, which are more radiosensitive.
Gauges (CT)
16 = Larger - anything between 25 = Smaller ! Smaller the number larger the lumen ! The viscosity of contrast material necessitates the use of a relatively large-bore needle.
Acromion
2
Internal Capsule
2
Left Pulmonary Artery
2
sigmoid colon
2
During the use of CT fluoroscopy for guided interven-tional procedures, which of the following technicalconsiderations may be used to reduce occupationalradiation exposure? (CT) 1. increased kVp 2. lead shielding 3. use of a needle holder
2 and 3 only
In a single-slice CT (SSCT) system, which of the following technical parameters may be adjusted retrospectively? (CT) 1. section width 2. section increment 3. reconstruction algorithm
2 and 3 only - Single-slice helical geometry allows for volumetric data acquisition. - The reconstruction of CT sections at any point along the scanned volume is possible. - The section width must be the same, however, and is controlled by the collimation (slice thickness) chosen prior to data acquisition. - The advancement of multislice CT (MSCT) allows for retrospective reconstruction of sections at varying thicknesses. ! MDCT can adjust Slice thickness retrospectivley, not SSCT
Which of the following technical adjustments maybe employed to improve the temporal resolution of an MDCT system? (CT) 1. decrease in section width 2. image segmentation 3. physiologic gating
2 and 3 only Reductions in: can be used to reduce the effects of involuntary motion. - scan time (gantry rotation), - image segmentation - physiologic gating - Technical adjustments to improve the temporal resolution of the CT system may help reduce involuntary motion artifacts.
Which of the following technical factors is/are involved in the determination of section width for MDCT images? (CT) 1. scan field of view (SFOV) 2. beam collimation 3. detector configuration
2 and 3 only - The thickness of the reconstructed section is controlled primarily by the detector configuration in an MDCT system. - Beam collimation also exerts an indirect effect on section width by controlling the portion of the detector array exposed to transmitted radiation. ! SFOV does not affect section width
Which of the following is not a category of isolation technique? 1. enteric precautions 2. gram-negative isolation 3. contact isolation 4. strict isolation)
2 only
Range of Serum Iodine Concentration for adequate Tissue Opacification during Contrast Enhanced CT (CT)
2 to 8 mg/mL - The serum iodine concentration is a measure of the amount of iodine within the bloodstream. - The specific dose depends on the patient's age, weight, and renal function, as well as on the clinical indication for the CT procedure. - The specific criteria of intravenous contrast administration must always be directed by a physician.
Which of the following is used to remove image blurring during the back-projection method of CT image reconstruction? 1. z-filtering 2. convolution kernel 3. Feldkamp-Davis-Kress (FDK) algorithma.
2. convolution kernel - During CT image reconstruction using the back-projection method, the data are manipulated with a convolution kernel or algorithm to remove image unsharpness (blurring). - This method is called the filtered back-projection.
CM Pediatric Dose Calculation (CT)
2m/kg fm: 2* Ptkg = Dose ex. patient weight is 18 kg 2*18= 36 mL of CM
Pineal Gland
3
abdominal aorta
3
glenoid process
3
left primary bronchus
3
levator scapulae muscle
3
seminal vesicles
3
spinous process
3
trapezius muscle
3
Helical Scanning - Spiral, Volumetric, Continuous Acquisition (CT)
3 Basic qualities = Continuing rotating X-ray tube, Constant X-ray output, uninterrupted table movement. Advantages = Optimization of Iodinated Contrast Agent Administration, reduction of respiratory misregistartion, reduction of motion artifacts from organs such as heart. Produces a block of data, not separate slices like with axial. Produces slices that are at a slight tilt, similar to the rungs in a spring. Increased slice angle requires more interpolation.
After initiation of rapid bolus administration of iodinated contrast material, the pancreatic phase of contrast enhancement occurs at approximately? (CT)
35 to 45 seconds - The pancreatic phase of contrast enhancement is a delayed arterial phase occurring approximately 35 to 45 seconds after the start of contrast agent administration, assuming an adequate volume injected at a rate of 3 mL/sec or greater.
A complete CT study of the orbits should include? (CT)
3x3mm axial and coronal sections
Lamina
4
ureterovesical junction (UVJ)
4
The maximum beam collimation for an MDCT system with a detector array of 64 detectors, each 0.625 mm wide, is? (CT)
40 mm - At a maximum, the MSCT cone beam may be collimated to a dimension equal to the entire multirow detector array. In the example, the total dimension of the detector array along the z-axis is 40 mm, or 64 x 0.625 mm. ! Multiply Detector # by Detectors Width 64 x 0.625 mm
WW Problem (CT) The selected window width is 400 The selected window level is 50 Which HUs are displayed on the image as shades of gray?
400/2 = 200 -200 + 50 = -150 200 + 50 = 250 -Divide WW by 2 - Subtract that answer positive and negative from WL So: -150 to 250
descending colon
5
What Matrix Size was used to reconstruct an image with the display characteristics DFOV 25 cm and pixel area 0.25 mm^2? (CT)
512 x 512 pixels - The matrix size used to reconstruct an image can be calculated by dividing the display field of view (DFOV) by the pixel dimension. - A pixel whose area is 0.25 mm^2 has a linear dimension of 0.5 mm. - Dividing the DFOV of 250 mm by the pixel dimension 0.5 mm gives a matrix size of approximately 512 x 512 pixels. Matrix Size Fm: Square Root of Pixel Divided by DFOV .5/250=500
Ascending Aorta
6
Bladder
6
Falx Cerebri
6
After initiation of rapid bolus administration of an iodinated contrast agent, the portal venous phase of hepatic contrast enhancement occurs at approximately? (CT)
60 to 70 seconds - The portal (or hepatic) venous phase is the period of peak hepatic parenchymal enhancement, when contrast material redistributes from the blood into the extravascular spaces. - It occurs at approximately 60 to 70 seconds after the initiation of rapid bolus contrast agent administration. ! portal venous phase 60 to 70 seconds
Power output for a modern MDCT x-ray tube hasan approximate range of? (CT)
60-100 kW - The power output of modern MDCT systems is vendorspecific, within a typical range of 60 to 100 kilowatts (kW).
Normal Adult Diastolic Range (CT)
60-90 mm Hg
Nephrographic Contrast Phase Time (CT)
80-130 s
High-density contrast agents, such as barium sulfate, are referred to as? a. positive agents. b. negative agents. c. neutral agents. d. ionic agents.
Answer—a. A positive agent creates image contrast because it has a higher density than surrounding tissues. Iodine and barium sulfate are examples of positive agents.
What is the pitch in the following scenario: 64 detector channels used, 0.625-mm slice thickness, table movement of 55 mm per rotation? a. 1 b. 1.375 c. 1.5 d. 2
Answer—b. 55/(64 × 0.625) 55/40 = 1.375 ! Table/(Detector x ST)
What is the likely cause of the artifact in Figure 24-5? a. Patientmotion b. Patient arms in the SFOV c. Metallicobject d. Not enough data collected (undersampling)
Answer—b. The most likely cause of the streak artifact is from the patient's arms positioned down by his or her sides for scanning. This can be inferred, even without the scout image to confirm, by examining the streaks, which appear to have their origins outside, on either side, of the displayed image. This type of artifact is broadly categorized as out-of-field artifacts.
Circle of Willis Make Up Simple
Anterior: ICA Internal Carotid Artery ACA Anterior Cerebral Artery MCA Middle Cerebral Artery ACOM Anterior Communicating Artery Posterior: VA Vertebral Arteries BA Basilar Artery PCA Posterior Cerebral Artery PCOM Posterior Communicating Arteries
An average range for activated PTT is: a. 10-12 seconds b. 17-21 seconds c. 25-35 seconds d. 43-55 seconds
C 25-35 seconds - The partial thromboplastin time (PTT) is a laboratory measure of blood coagulation. - This value is used for screening of patients for invasive procedures. - Because of individual laboratory practices, the average range may fluctuate slightly.
The proper scan field of view (SFOV) for a CT of the abdomen of a patient who measures 42 cm is? (CT)
Choice: - Large 48 cm - The SFOV chosen must be larger than the width of the patient in order to eliminate out-of-field artifacts. - Some CT scanners may have limited choices for SFOV values. - Other common terminology includes full- or half-field, and body-cal and head-cal.
A total volume of 125 mL of an iodinated contrast agent is administered intravenously via automatic injector in 50 seconds. The flow rate for this injection is: a. 0.75 mL/sec b. 1.25 mL/sec c. 1.75 mL/sec d. 2.5 mL/sec
D - The flow rate may be calculated by dividing the total contrast volume by the time of the injection. - In this example, the total contrast volume is 125 mL and the time for the injection is 50 seconds. - The flow rate programmed for this injection would be 125/50, or 2.5 mL per second. Formula: Contrast Volume/Injection Time
Documenting Contrast Administration (CT)
Documentation of IV contrast administration is a legal necessity and should include: - The name of the agent - The dose (volume and concentration) - The flow rate(s) - The injection site - Any adverse effects and their treatment
Spine Study (CT)
For: - Evaluation of bony abnormalities - Post arthrogram to evaluate stenosis - When patients cannot tolerate MRI - Proper localization is essential in scanning the spine All studies should include both AP and lateral scouts - Visualization of intradural structures is improved by the intrathecal administration of CM - Scan from vertebra below to vertebra above area of interest
Image Accuracy - Image Fidelity (CT)
Image Usefulness.
2
Internal Capsule
Carotids
Internal Carotids Supply Blood -Frontal - Temporal - Parietal External Carotids Supply Blood - Face - Neck
Non Ionic Contrast Media (CT)
Non-ionic contrast media include: - iopamidol (Isovue) - iohexol (Omnipaque) - iopromide (Ultravist).
Full Body Circulation Pathway Shortcut - Left Side Systemic/Arterial Circulation - Away from Heart (CT)
Oxygenated Blood PV *LA* BiMi V. *LV* ASL V. AA Body
PQRST Complex
P = Atrial Systole T = Diastole
Specific Contrast Phases (CT)
Parenchymal pancreatic phase 40-60 s Enteric phase 40-50 s Corticomedullary phase 30-70 s Nephrographic phase 80-130 s Excretory phase 3-15 min Systemic venous phase (inferior vena cava) 3 min
Pediatric & Adult Contrast Dose (CT)
Pediatric dose - Most often based on the weight of the infant or child - The most common formula is: 2 mL/kg Adult dose - Typically, a uniform dose for each protocol However, weight-based dosing for adults has advantages
Renal Dysfunction (CT)
Renal failure: - The inability of the kidneys to maintain homeostasis, resulting in the accumulation of nitrogenous wastes Renal insufficiency: - Renal function is abnormal but capable of sustaining essential bodily functions Nephropathy: - Denotes any condition or disease affecting the kidneys Sometimes used synonymously with renal impairment
Renal Function (CT)
Renal function can be estimated using: - Glomerular filtration rate (GFR) - Effective renal plasma flow (ERPF) - Serum creatinine (SeCr) as an index of GFR - Blood urea nitrogen (BUN) - GFR and ERPF are cumbersome, therefore SeCR is widely used - Also eGFR is used (estimated glomerular filtration rate)
RAO Abdomen
Right lateral decubitus position shows - differentiate the pancreatic head and the duodenum.
Full Body Circulation Pathway Shortcut - Right side Pulmonary/Venous Circulation - To Heart (CT)
SVC *RA* Tri V. *RV* PSL V. PA Lungs Oxygenated Blood
#3 (CT)
Spinous Process
Which Pelvic Bones Combine to Make up the Acetabulum? (CT)
The acetabulum is a cup-shaped cavity that holds the head of the femur, forming the hip joint. composed portions: - ilium - ischium - pubis
Allergy History for CM (CT)
The technologist and/or radiologist should always ask the patient about: - allergic history - current renal function status - history of cardiac illness (high blood pressure, congestive heart failure, and so on) prior to administration of any contrast material.
CT head study for Subdural Hematoma (CT)
_ No IV contrast - Because of their increase in CT number, subdural hematomas may be well visualized without the IV administration of an iodinated contrast agent.
A CT system measures the average linear attenuation coefficient of a voxel of tissue to be 0.008. The linear attenuation coefficient of water for this scanner equals 0.181. The CT number assigned to the pixel representing this voxel of tissue equals: a. -956 HU b. -173 HU c. +44 HU d. +1044 HU
a. -956 HU - The CT number of a pixel may be calculated by subtracting the linear attenuation coefficient of water from the linear attenuation coefficient of the tissue within the voxel (0.008 - 0.181 = -0.173). - This number is divided by the linear attenuation coefficient of water (-0.173 / 1.81 = -0.956). - The quotient is multiplied by a contrast factor of 1000 to yield the value of the pixel in Hounsfield units.
A standard CT image reconstructed on a 512^2 matrix has a digital size of approximately: a. 0.5 MB b. 3.0 MB c. 5.0 MB d. 10.0 MB
a. 0.5 MB - Each CT image reconstructed on a 512^2 matrix is approximately 0.5 megabytes (MB) in digital size.
Filament sizes for modern CT x-ray tubes range between: a. 0.5 and 1.2 mm b. 2.0 and 3.0 mm c. 5.5 and 7.8 mm d. 25.0 and 31.5 mm
a. 0.5 and 1.2 mm - Modern CT system x-ray tubes utilize dual-filament systems with focal spot sizes ranging between 0.5 and 1.2 mm in diameter.
An MDCT image is reconstructed using a 5122 matrix and a DFOV of 38 cm. If the detector collimation is set to a section width of 1.25 mm, what is the volume of each voxel? a. 0.69 mm3 b. 0.93 mm3 c. 1.26 mm3 d. 1.68 mm3
a. 0.69 mm^3 - The linear dimension of the pixel must first be calculated by dividing the DFOV, in mm, by the matrix(380 mm / 512 = 0.74 mm) . This linear pixel dimension is squared to yield the pixel area in mm^2 (0.74 x 0.74 = 0.55 mm^2). The volume of the voxel may be calculated by multiplying the pixel area by the section width 0.55mm^2 x 1.25mm = 0.69 mm^3).
Which region of interest (ROI) on the figure demonstrates the greatest amount of image noise? a. 1 b. 2 c. 3 d. impossible to determine from the information provided
a. 1 - The image noise is equal to the standard deviation of pixel values within an ROI measurement of the image. - ROI number 1 on the figure demonstrates the highest value for standard deviation (SD=2.87).
Components of the aseptic technique utilized for the IV administration of contrast agents include: 1. thorough hand washing between patients 2. wearing of disposable gloves 3. establishment of a sterile field around the site a. 1 and 2 only b. 1 and 3 only c. 2 and 3 only d. 1, 2, and 3
a. 1 and 2 only - Additional components of the aseptic technique include cleaning the site of venipuncture in a circular motion with alcohol swab before injection, and applying pres-sure with an alcohol swab to the site after removal of the needle or catheter. - It is sterile technique that involves establishing a sterile field around the area of an invasive procedure.
This HRCT image of the chest was most likely acquired with a section width of: a. 1 mm b. 5 mm c. 7 mm d. 10 mm
a. 1 mm - HRCT acquisitions of the chest should be performed with thin sections, within the range of 1 to 2 mm.
CTDIw is a weighted index that approximates radiation dose on the basis of the variations that occur across the field of view because of: 1. beam hardening 2. detector configuration 3. pitch a. 1 only b. 1 and 2 only c. 2 and 3 only d. 1, 2, and 3
a. 1 only - As the beam traverses the patient, beam hardening alters the penetrability of the beam and affects the absorption across the field of view. - The CTDIw is calculated by summing 2/3 of the exposure recorded at the peripheryof the field with 1/3 of the centrally recorded radiation dose. This weighting yields a more accurate dose approximation.
A primary responsibility of computed tomography in combined PET-CT is to: 1. provide precise anatomic location of tumor activity 2. reduce patient radiation dose 3. improve radiopharmaceutical uptake a. 1 only b. 1 and 3 only c. 2 and 3 only d. 1, 2, and 3
a. 1 only - Positron emission tomography (PET) provides a map of normal and abnormal tissue function. - It offers excellent sensitivity for malignancy but suffers from an inability to accurately localize tumor activity. - Fusion of PET with CT provides such precise anatomic localization. ! CT role is better for tumor detection
Direct contraindications to the administration of iodinated contrast material include: 1. prior life-threatening reaction to iodinated contrast material 2. multiple myeloma 3. diabetes a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
a. 1 only - Several factors may be regarded as contraindications to administration of iodinated contrast material, including known allergy to iodine, prior severe reaction, and renal insufficiency. - Multiple myeloma and diabetes, although not absolute contraindications to IV administration of iodinated contrast agents, do require attention to the patient's hydration level to limit renal complications.
Which of the following is/are severe adverse reaction( s) to iodinated intravenous contrast media? 1. anaphylaxis 2. urticaria 3. vomiting a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
a. 1 only - Severe reactions to iodinated contrast material include anaphylaxis, shock, cardiac arrest, and death. - Urticaria and vomiting may be considered mild or moderate reactions, depending on their severity.
Abnormalities of the middle and inner ear may be best demonstrated with CT utilizing __________ sections. a. 1- to 2-mm b. 3- to 4-mm c. 5-mm d. 10-mm
a. 1- to 2-mm - Thin sections are required to properly assess abnormalities of the minute structures of the inner ear. The thin-nest sections possible provide maximum detail.
CTA of the renal arteries should be performed using a section width of: a. 1.25 mm or less b. 2-3 mm c. 3-5 mm d. 5-7 mm
a. 1.25 mm or less
When one is assessing an MTF graph such as the figure, the limiting resolution is determined at a point where the signal frequency corresponding to a particular object has reached: a. 10% b. 20% c. 50% d. 100%
a. 10% - The limiting resolution of a particular CT scan is determined at a point on the graph where the signal frequency corresponding to a particular object has reached 10%. - When the MTF is lower that 10% (0.1), the object is no longer resolved. ! 10% or .1 on the graph
During CT scanning of the head, the gantry should be angled: a. 15 degrees above the infraorbital-meatal line (IOML) b. 10 degrees below the IOML c. 0 degrees d. 20 degrees above the skull base
a. 15 degrees above the infraorbital-meatal line (IOML) - Routine CT scanning of the head should be performed with the gantry angled 15 degrees above the infraorbitalmeatal line. - This angle produces axial sections of the brain while limiting beam-hardening artifacts and direct orbital exposure.
An enema is indicated prior to a CT examination of the pelvis to administer positive contrast material into the large bowel. Which of the following dosages would be sufficient to opacify the recto sigmoid region? a. 150-250 mL b. 300-500 mL c. 500-750 mL d. 900-1100 mL
a. 150-250 mL - Positive contrast material can be administered into the large bowel via enema to achieve thorough opacification. - A dosage of 150 to 250 mL should be sufficient to opacify the rectos igmoid region. - Doses of 300 to 500 mL may be necessary to opacify the large bowel inits entirety. ! Small Bowel = 150 to 250 ml: Large Bowel 300 to 500 ml
Which of the following sizes of butterfly needles allows for the most rapid administration of iodinated intravenous contrast media? a. 19 gauge b. 21 gauge c. 23 gauge d. 25 gauge
a. 19 gauge - Larger-lumen (lower-gauge) needles allow for more rapid intravenous administration of contrast media. - The lumen is considerably larger in a 19-gauge needle than in a 25-gauge needle. - The viscosity of contrast material necessitates the use of a relatively large-bore needle.
Which of the following is used to remove image blurring during the back-projection method of CT image reconstruction? 1. z-filtering 2. convolution kernel 3. Feldkamp-Davis-Kress (FDK) algorithm a. 2 only b. 3 only c. 1 and 2 only d. 2 and 3 only
a. 2 only - During CT image reconstruction using the back-projection method, the data are manipulated with a convolution kernel or algorithm to remove image unsharpness (blurring). - This method is called the filtered back-projection.
The range of serum iodine concentration for adequate tissue opacification during contrast-enhanced CT examinations is: a. 2-8 mg/mL b. 12-20 mg/mL c. 30-42 mg/mL d. 75-105 mg/mL
a. 2-8 mg/mL - The serum iodine concentration is a measure of the amount of iodine within the bloodstream. - The specific dose depends on the patient's age, weight, and renal function, as well as on the clinical indication for the CT procedure. - The specific criteria of intravenous contrast administration must always be directed by a physician.
The section thickness that would demonstrate the greatest detail of the paranasal sinuses is: a. 3 mm b. 5 mm c. 7 mm d. 10 mm
a. 3 mm - The section thickness of a CT scan directly affects the detail and spatial resolution of the image. - Narrow section widths result in greater detail for imaging of small anatomic parts such as the sinuses.
Which of the following is the preferred range for patient heart rate for optimal cardiac CT studies? a. 65-75 bpm b. 75-85 bpm c. 85-95 bpm d. > 100 bpm
a. 65-75 bpm - Patients with slower heart rates exhibit longer diastolic phases,which yield higher-quality cardiac CT exams. - The preferred heart rate for optimal imaging on most MSCT systems is 65 beats per minute (bpm). - Newer systems at the 64-slice level and beyond are capable of acquiring adequate cardiac CT images at higher heartrates.
Which of the following display field of view (DFOV) values was most likely used to display the image? a. 9.6 cm b. 18.0 cm c. 25.6 cm d. 51.2 cm
a. 9.6 cm
A patient is being seen in the emergency department for acute respiratory distress. Pulmonary emboli are suspected and a CT is ordered. A review of the patient's history reveals that he is allergic to shellfish. What action should be taken? a. A CT examination using a pulmonary embolism protocol is done. b. A CT examination of the chest, without contrast enhancement, is done. c. The CT examination is cancelled; most likely it will be replaced by a nuclear medicine V/Q examination. d. The patient is given steroids and the CT examination is delayed for 6 hours.
a. A CT examination using a pulmonary embolism protocol is done. - Allergy to foods that contain iodine (e.g., seafood) does not increase the risk of intravenous contrast medium reactions. - Seafood allergy results from hypersensitivity to a protein within the sea- food and has no association with iodine. - Assuming the history does not reveal any contraindications to iodine, the examination should proceed as ordered.
A specialized CT examination involving the administration of an enteral contrast agent directly into the small bowel via nasogastric tube is called: a. CT enteroclysis b. CT colonography c. CT enterography d. CT colonoscopy
a. CT enteroclysis - CT enteroclysisis a specialized evaluation of the small bowel whereby a nasogastric catheter is placed into the duodenum under fluoroscopic guidance. 1.5 to 2.0 L of enteral contrast agent is administered directly into the small intestine for maximal opacification. - Non-IVcontrast, thin-section (0.6-1.25 mm) CT images areacquired through the abdomen and pelvis.
Delayed post-contrast acquisition of the lower extremities following a CTA of the pulmonary arteries is termed: a. CT venography b. CT perfusion c. femoral CTA d. iliac CTA
a. CT venography - Shortly after a CTPA study, CT venography (CTV) of the lower extremities for the identification of deep vein thrombosis (DVT) may also be performed. - After the CTPA acquisition, a delay of 2 to 3 minutes is employed, and an acquisition is made from the iliac crest to the ankles.
The radiation dose index calculation that takes into account the variations in absorption across the field of view due to beam hardening is termed: a. CTDIw b. CTDI100 c. CTDIvol d. MSAD
a. CTDIw - CTDIw is calculated from measurements made with dosimeters positioned at the center and periphery of a phantom and accounts for the variance in dose distribution due to the effects of beam hardening.
Refer to Figure 24-15. Name the structure indicated by arrow #5. a. Cuneiform bone (medial or 1st) b. Cuboid bone c. Calcaneus d. Metatarsal bone
a. Cuneiform bone (medial or 1st)
Refer to Figure 24-7. Name the structure indicated by arrows RAD #2 and #5. a. Falx cerebri b. Pericallosal arteries c. Vermis of cerebellum d. Central sulcus
a. Falx cerebri
Refer to Figure 24-10. Name the structure indicated by arrow #4. a. Head of pancreas b. Tail of pancreas c. Duodenum d. Left renal artery
a. Head of pancreas
CT numbers are usually provided in the form of: a. Hounsfield units b. EMI numbers c. Cormacks d. m
a. Hounsfield units - The CT number is a relative value based on the attenuation that occurs within a voxel of tissue. The Hounsfield unit is used for this value.
Number 3 on the figure corresponds to which of the following? a. left posterior cerebral artery b. left middle cerebral artery c. left anterior cerebral artery d. left posterior communicating artery
a. left posterior cerebral artery
Refer to Figure 24-8. Name the structure indicated by arrow #6. a. Lateral semicircular canal b. Round window c. Eustachian tube d. Vestibular aqueduct
a. Lateral semicircular canal
Refer to Figure 24-12. Name the structure indicated by arrow #3. a. Left common iliac vein b. Left common iliac artery c. Celiac trunk d. Azygos vein
a. Left common iliac vein
Refer to Figure 24-8. Name the structure indicated by arrow #2. a. Malleus b. Stapes c. Trigeminal nerve branches d. Sella turcica
a. Malleus
The abdominal space indicated by number 7 in the figure is commonly referred to as: a. Morison's pouch b. cul-de-sac c. splenorenal recess d. subphrenic space
a. Morison's pouch - Morison's pouch is the common name for the hepatorenal recess, which is indicated by number 7 in the figure.This space between the liver and right kidney is a common location for the abnormal collection of fluid known as ascites.
Which of the following reformation techniques best describes the image in the figure? a. Multiplanar reformation (MPR) b. Volume-rendered 3D c. Maximum intensity projection (MIP) d. Minimum intensity projection (min-IP)
a. Multiplanar reformation (MPR)
Which of the following portions of the electrocardiogram (ECG) corresponds to the period of atrial systole? a. P wave b. QRS complex c. alpha wave d. T wave
a. P wave - Atrial systole refers to the contraction of the left and right atria. - The onset of the P wave on an ECG corresponds to atrial systole.
Refer to Figure 24-10. Name the structure indicated by arrow #3. a. Portal vein b. Inferior vena cava c. Superior mesenteric artery d. Hepatic artery
a. Portal vein
Refer to Figure 24-9. Name the structure indicated by arrow #4. a. Pulmonary trunk b. Descending aorta c. Left atrium d. Superior vena cava
a. Pulmonary trunk
Refer to Figure 24-12. Name the structure indicated by RAD arrow #2. a. Right common iliac vein b. Right common iliac artery c. Rightovary d. Iliacus muscle
a. Right common iliac vein
The benign mass of the eighth cranial nerve known as a vestibular schwannoma may also be termed a(n): a. acoustic neuroma b. hypoglossal adenoma c. olfactory neuroblastoma d. optic nerve glioma
a. acoustic neuroma - The eighth cranial nerve is the vestibulocochlear nerve responsible for both hearing and balance. - Vestibular schwannoma may also be referred to asacoustic neu-roma. - This type of mass most often involves the vestibular portion of the nerve bundle, with deleterious effects on balance and equilibrium.
Why is it necessary to apply a filter function to an attenuation profile to create a CT image? (CT) a. To minimize streaks b. To increase the signal-to-noise ratio c. To eliminate ring artifacts d. To reduce radiation exposure to the patient
a. To minimize streaks - Streaks are inherent in the back-projection process; therefore, it is essential to apply a mathematical filtering process before back projection. ! Filter Function aka Back Projection for Streaks
The use of a saline flush after the injection of the iodinated contrast is recommended for CTA pulmonary studies. Why? a. To reduce or eliminate beam-hardening artifacts from dense contrast media within the superior vena cava that may obscure small emboli in adjacent vessels b. To hydrate the patient and reduce the risk of contrast- induced nephropathy c. So that additional images can be acquired with a negative contrast agent d. To flush any emboli out of the patient's pulmonary arteries
a. To reduce or eliminate beam-hardening artifacts from dense contrast media within the superior vena cava that may obscure small emboli in adjacent vessels.
Refer to Figure 24-14. Name the structure indicated by arrow #3. a. Trachea b. Piriformrecess c. Laryngealvestibule d. Pharynx
a. Trachea
Compare 100 mL of Ultravist (iopromide) 300 with 100 mL of Ultravist (iopromide) 370: a. Ultravist 370 has a higher viscosity. b. Ultravist 370 contains fewer grams of iodine. c. Ultravist 370 is a better choice if the IV catheter is a 22 to 24 gauge. d. Ultravist 370 has a lower osmolality
a. Ultravist 370 has a higher viscosity. - Both the viscosities and the osmolalities of contrast agents classified as nonionic/low osmolality will rise slightly with the concentration. - Because higher-concentration agents are more viscous they may not flow through small-gauge IV catheters as easily as lower-concentration agents. - One hundred milliliters of a 300 concentration agent will contain 30 grams of iodine, whereas 100 mL of a 370 concentration agent will contain 37 grams of iodine.
Spatial resolution can be calculated from the analysis of the spread of information within the system using the modulation transfer function. What is a simpler and more direct way to measure spatial resolution? (CT) a. Using a line/pairs phantom b. Using a water phantom c. Using the readout from the scanner's display d. Calculating it from the radiation dose delivered
a. Using a line/pairs phantom - A typical line/pairs phantom contains groups of lead strips having different strip width and spacing. - In each group, the lead width is equal to the lead spacing. - The spatial resolution is given as the maximum number of visible line pairs (lead strip and space) per millimeter.
Refer to Figure 24-8. Name the structure indicated by arrow #5. a. Vestibule b. Facial canal c. Cochlea d. Internal carotid artery canal
a. Vestibule
Which of the following window settings was most likely used to display the image in the figure? a. WL -300, WW 1000 b. WL -50, WW 50 c. WL +50, WW 150 d. WL +400, WW 3000
a. WL -300, WW 1000 A wide window setting (WL-300,WW 1000) may be used to properly demonstrate the small soft tissue vocal structures from the surrounding air-filled endolarynx.
A circular ROI is defined and placed on the image, and the resultant measurement is 3HU. The standard deviation is 0. It can be surmised that a. all of the pixels within the region have identical values. b. the area measured is composed of a variety of very different tissue types. c. the area is likely a calcified nodule. d. the patient is obese.
a. all of the pixels within the region have identical values. - The standard deviation indicates the amount of CT number variance within the ROI.
The Stanford type A dissecting aneurysm affects which portion of the aorta? a. ascending thoracic b. descending thoracic c. abdominal d. bifurcation
a. ascending thoracic - Stanford type A dissecting aneurysms affect the ascending aorta. Stanford type B dissecting aneurysms affect the descending aorta. ! Stanford A = Ascending Aorta, Stanford B = Descending Aorta
Airway imaging is routinely performed? a. at both inspiration and expiration. b. using a wide slice thickness (≥8 mm). c. using a low-contrast (i.e., soft) algorithm. d. using a representative technique in which only about 10% of the airway is imaged
a. at both inspiration and expiration. - CT imaging of the airways is most often performed in a helical mode, using thin sections and an overlapping z axis image reconstruction of 50% so that images can be postprocessed. - Airway imag- ing is routinely performed at both inspiration and expiration.
CT images of the chest should be acquired with the patient: a. at full inspiration b. breathing quietly c. at full expiration d. breathing normally
a. at full inspiration - Patient inspiration provides optimal chest expansion and allows for better demonstration of anatomic structures. ! Breath in, Breath out, Breath In
The fraction of a beam of x-rays that is absorbed or scattered per unit thickness of the absorber is referred to as the a. attenuation coefficient. b. contrast transfer function. c. spatial resolution. d. modulation transfer function.
a. attenuation coefficient. - The attenuation coefficient is a number derived from a specific strength beam as it travels through a specific substance. - For example, with a CT scanner that is operating in the typical range of 120kVp, the linear attenuation coefficient for water is approximately 0.18cm−1. - This means that when the beam passes through 1.0 cm of water, about 18% of the photons are either absorbed or scattered.
Which of the following is considered in the calculation of the MSAD for an axial (step-and-shoot) CT examination? a. bed index b. gantry rotation time c. mA setting d. pitch
a. bed index - MSAD (multiple scan average dose)accounts for the effects of image spacing, or bed index, on patient radiation dose during axial scanning. - MSAD increases when slice thickness is greater than image spacing and decreases when slice thickness is less than the bed index.
The electronic combination of signals from adjacent detectors to form a CT image is called: a. binning b. interpolation c. z-filtering d. partial volume averaging
a. binning - Binning refers to the electronic combination of signal from adjacent detectors to form a reconstructed slice that is thicker than the individual detector width. - For example, transmission data from four adjacent 1.25-mm detectors is combined to produce a CT section 5.0 mm thick.
The smallest unit of information used in the binary language of computers is the: a. bit b. chip c. base d. byte
a. bit - The bit is the smallest unit of information within the binary system. - Its name is derived from the term "binary digit" and can appear as either a number 1 or 0.A sequence of eight bits constitutes a byte.
At an MTF of 20%, which reconstruction algorithm will demonstrate the greatest number of line pairs per centimeter (lp/cm)? a. bone b. standard c. smooth d. impossible to determine from the information provided
a. bone - According to the MTF diagram, the bone algorithm has a resolution of approximately 12 lp/cm. - The standard algorithm and smooth algorithm are approximately 10 and 7 lp/cm, respectively.
Which of the following pathologic processes may be considered an interstitial disease of the lungs? a. bronchiectasis b. mediastinal lymphadenopathy c. pulmonary metastasis d. bronchogenic carcinoma
a. bronchiectasis - Interstitial diseases of the lungs are usually diffuse pathologicprocesses involving the interstitium, or frame-work, of the lungs. - Examples of interstitial diseases arebronchiectasis, emphysema, asbestosis, and sarcoidosis.
Number 1 on the figure corresponds to which of the following? a. capitate b. lunate c. hamate d. scaphoid
a. capitate
The process of applying a mathematical filter to remove blurring from the reconstructed CT image is termed: a. convolution b. interpolation c. iteration d. z-filtration
a. convolution - The process known as convolution is applied to reduce image unsharpness. - An algorithm, or convolution kernel, acts as a mathematical filter, modifying the ray sum data and removing the unwanted blurring effect of the back-projection. ! Convolution Mathematics / Unsharpness
Which of the following best describes the type of image displayed in the figure? a. coronal maximum intensity projection (MIP) b. direct coronal acquisition c. coronal multiplanar reformation (MPR) d. coronal minimum intensity projection (min-IP)
a. coronal maximum intensity projection (MIP) - Maximum intensity projection (MIP) images are a routine component of CTA examinations of the chest. - This CTA of the pulmonary arteries (CTPA) demonstrates the well-opacified pulmonary vasculature in coronal thick-slab format. - From the perspective of the viewer, each pixel displays the maximum attenuation value contained within the thickness of the slab.
The anatomic plane of the image in the figure can be best described as the: a. coronal plane b. sagittal plane c. axial plane d. oblique axial plane
a. coronal plane
The anatomic plane of the image in the figure can be best described as the: a. coronal plane b. sagittal plane c. axial plane d. oblique axial plane
a. coronal plane - The image in the figure is a multiplanar reformation (MPR) of the wrist in the coronal plane. - MPR images are particularly helpful for trauma indications, such as fracture of the distal radius, labeled number 3 on the figure.
Quality control measurements to test the accuracy of the CT scanner's calibration should be performed: a. daily b. weekly c. monthly d. annually
a. daily - It is important that the calibration of a CT scanner be checked daily by the operator. - CT units should be calibrated with their reference CT number for water at approximately zero. The CT number for air should be at approximately -1000.
6b.
a. descending aorta b. azygos vein c. inferior vena cava d. brachiocephalic artery
As related to the cardiac cycle, the term ____________ refers to the relaxation of heart muscle. a. diastole b. equilibrium c. systole d. a-fib
a. diastole - Diastole refers to the relaxation of heart muscle. - It is the period of the cardiac cycle that occurs between successive contractions of the heart muscle, which are known as systole.
The contrast resolution of a CT scanner is NOT related to which of the following? a. focal spot size b. section width c. reconstruction algorithm d. signal-to-noise ratio
a. focal spot size - The contrast resolution of a CT scanner depends on several factors, including section width, algorithm selection, detector sensitivity, and noise. - The focal spot size is a geometric factor that influences the spatial resolution of a CT scanner. ! Focal Spot Size / Spatial Resolution
Which of the following paranasal sinuses is usually the last to fully develop? a. frontal b. ethmoidal c. sphenoidal d. maxillary
a. frontal - The frontal sinuses are absent at birth and do not usually fully develop until after puberty. - The ethmoidal,maxillary, and sphenoidal sinuses begin to develop during gestation.
Which of the following would be considered the best method to reduce respiratory motion on the CT image? a. good patient-technologist communication b. reduced scan times c. immobilization devices d. glucagon administration
a. good patient-technologist communication - Thorough communication between the technologist and the patient is vital in ensuring superior exam quality. - If the patient has been informed of the exam process, his/her anxiety may be reduced and cooperation improved. - During all CT procedures, the patient must be instructed to hold still in an effort to reduce motion artifact on the CT images.
Following the IV administration of iodinated contrast media, a tumor that exhibits a greater density than the surrounding parenchyma is characterized as: a. hypervascular b. isovascular c. hypovascular d. cavernous
a. hypervascular - Upon IV contrast enhancement, a tumor may be described as hypovascular if it is lower in density than the surrounding organ parenchyma or hypervascular if it is higher in density.
During a complete CT scan of the pelvis, sections should be obtained from the: a. iliac crests to the pubic symphysis b. kidneys through the bladder c. bottom of the kidneys to the pubic symphysis d. iliac crests to the lesser trochanter
a. iliac crests to the pubic symphysis - Complete CT scans of the pelvis should include from the iliac crests to the pubic symphysis. - This scan range maybe extended if clinically warranted. - Scan parameters(i.e., slice thickness, incrementation) can be adjusted to correlate with the patient's clinical history.
1c.
a. inferior rectus muscle b. optic chiasm c. inferior oblique muscle d. levator palpebrae superioris
Where is the high-frequency generator often located in a modern CT scanner? a. inside the gantry b. just outside the scan room c. beneath the CT table d. inside the operator's console
a. inside the gantry - The high-frequency generator used to produce the three-phase power used in modern CT scanners is located inside the gantry. - It may be positioned in a corner of the gantry or fixed to the rotating tube assembly.
An anatomic trait that can help to differentiate an adenoma from a malignant adrenal mass on CT scans is its a. intracellular lipid content. b. calcium content. c. location. d. iron content.
a. intracellular lipid content. - Although both adenomas and metastatic lesions enhance rapidly, because of differences in their intracellular lipid content, metastatic lesions retain the contrast longer.
Which of the following is considered one of the isoosmolar contrast media (IOCM)? a. iodixanol b. iopamidol c. iohexol d. ioversol
a. iodixanol - Iodixanol (Visipaque) is an example of a non-ionic iso-osmolar contrast agent. ! Iohexol (Omnipaque), iopami-dol (Isovue), and ioversol (Optiray) are all nonionic low-osmolar contrast media (LOCM).
During CT arthrography, iodinated contrast media is injected directly into the: a. joint space b. intrathecal space c. subarachnoid space d. venous bloodstream
a. joint space - Iodinated water-soluble radiopaque contrast media(RCM) are injected directly into the joint space of inter-est during CT arthrography.
Which of the following is used to archive a hard copy of a CT image? a. laser film b. PACS c. CD-ROM d. LAN
a. laser film - Storage on film is considered to be a hard copy. - The dig-ital storage of CT images on PACS, CD-ROM, MOD,and so on, is referred to as soft copy.
Number 2 on the figure corresponds to which of the following? a. left ovary b. bladder c. sigmoid colon d. uterus
a. left ovary
Which of the following terms is used to describe a fibroid tumor of the uterus? a. leiomyoma b. cystic teratoma c. endometriosis d. corpus luteum
a. leiomyoma - Aleiomyomais a benign mass of smooth muscle. It commonly occurs in the uterus and is readily identified on CT examination as a bulky, nonspecific uterine enlargement.
The term used to describe the relationship between the linear attenuation coefficient of an object and the calculated CT numbers is: a. linearity b. mottle c. quantum noise d. spatial resolution
a. linearity - Linearity describes the relationship between the CT number and actual linear attenuation coefficients of an object. - It is used to measure the accuracy of a CT scanner.
he relative accuracy between calculated CT numbers and their respective linear attenuation coefficients is referred to as? (CT) a. linearity b. calibration c. uniformity d. contrast resolution
a. linearity - The relative accuracy between calculated CT numbers and their respective linear attenuation coefficients is termed linearity. - Calibration and routine vendor maintenance procedures work to establish and maintain CT system linearity.
The relative accuracy between calculated CT numbers and their respective linear attenuation coefficients is referred to as: a. linearity b. calibration c. uniformity d. contrast resolution
a. linearity - The relative accuracy between calculated CT numbers and their respective linear attenuation coefficients is termed linearity. - Calibration and routine vendor maintenance procedures work to establish and maintain CT system linearity.
Which of the following statements is FALSE regarding the collection of CT data? a. long scan times are more desirable because they average out motion artifacts b. the reconstruction process used to create the image occurs in the array processor c. to collect the complete set of CT data, x-rays must be passed through the body at many different angles d. the detectors measure x-rays which completely penetrate the patient
a. long scan times are more desirable because they average out motion artifacts
Compared with conventional radiography, computed tomography produces diagnostic images with better: a. low-contrast resolution b. spatial resolution c. minute detail d. patient radiation dose reduction
a. low-contrast resolution - Computed tomography has better low-contrast resolution over conventional radiography. - The CT system is extremely sensitive to small changes in tissue density and also removes the problem of superimposition, both leading to greater contrast resolution.
The presence of noise on an image degrades its quality, particularly its? (CT) a. low-contrast resolution. b. longitudinal resolution. c. spatial resolution. d. temporal resolution.
a. low-contrast resolution. - We can recognize noise as the grainy appearance or "salt-and-pepper" look on an image. - Contrast resolution involves differentiating an object from its very similar density background. - - Because the difference between object and background is small, noise plays an important role in low-contrast resolution. ! Noise Degrades Low Contrast resolution
What two factors define the quantity of the x-ray energy? (CT) a. mA and scan time b. kVp and heat capacity c. reconstruction algorithm and heat dissipation d. DFOV and x, y coordinates
a. mA and scan time - The product of the mA and scan time is known as mAs, or tube current. - It determines the amount of x-ray photons. - The kVp determines the quality (or average photon energy) of the x-ray beam. - Neither DFOV nor reconstruction algorithm have any affect on the x-ray beam; rather they control how the raw data are back projected to create an image.
2b.
a. medial rectus muscle b. optic nerve c. lateral rectus muscle d. superior oblique muscle
The reduction in number of infectious organisms without a complete elimination is termed: a. medical asepsis b. sterilization c. surgical asepsis d. immunization
a. medical asepsis - Medical asepsis is the reduction in number of infectious agents without the complete elimination of the organisms. - It is accomplished through the use of soap, water,and many other types of disinfectant materials.
Which of the following would be the most common cause of the artifact in the figure? a. metallic dental fillings b. partial volume averaging c. beam hardening d. detector malfunction
a. metallic dental fillings - Metallic dental fillings often cause a streak artifact dur-ingCT examinations of the head.
Number 6 on the figure corresponds to which of the following? a. navicular b. cuboid c. calcaneus d. talus
a. navicular
Automatic tube current modulation (ATCM) software is used in current MDCT systems to control: a. patient radiation dose b. cardiac motion c. timing of the contrast agent bolus d. tissue perfusion assessment
a. patient radiation dose - Automatic tube current modulation (ATCM) programs adjust the mA throughout an acquisition to reduce patient radiation dose to a minimum. - ATCM automatically alters the applied mA on the basis of a predetermined noise index that is acceptable for appropriate image quality.
4b.
a. pectoralis major b. pectoralis minor c. intercostal d. serratus posterior superior
The International Normalized Ratio (INR) is calculated to standardize which of the following laboratory values? a. prothrombin time (PT) b. partial thromboplastin time (PTT) c. blood urea nitrogen (BUN) d. glomerular filtration rate (GFR)
a. prothrombin time (PT) - Because of the inherent differences in manufactured batches of tissue factor, the International Normalized Ratio (INR) is calculated to standardize PT results. - The INR compares a patient's PT with a control sample for a more accurate result.
Number 6 on the figure corresponds to which of the following? a. psoas muscle b. omentum c. piriformis muscle d. erector spinae muscle
a. psoas muscle
Number 5 on the figure corresponds to which of the following? a. right brachiocephalic vein b. left subclavian artery c. left brachiocephalic vein d. brachiocephalic artery
a. right brachiocephalic vein
Number 5 on the figure corresponds to which of the following? a. right internal jugular vein b. right external carotid artery c. right internal carotid artery d. right external jugular vein
a. right internal jugular vein
Number 3 on the figure corresponds to which of the following? a. right ureter b. inferior vena cava c. renal calculi d. right renal artery
a. right ureter
Patients with metastasis to the brain are at greater risk for _____ after the administration of an IV contrast agent. a. seizures b. contrast-induced nephropathy c. anaphylactoid reaction d. pulmonary effects, such as broncho spasm
a. seizures - The use of iodinated contrast media has been shown to provoke seizures in patients who have diseases that disrupt the blood-brain barrier. - In these patients, the risk of seizure can be reduced by a one-time oral dose of diazepam, 30 minutes before contrast administration. - Seizures that occur can also be controlled with diazepam.
The full width at half maximum (FWHM) of a CT scanner is used to describe: a. spatial resolution b. contrast resolution c. noise d. calibration accuracy
a. spatial resolution - The spatial resolution of a CT scanner can be measured by studying the amount of blurring that occurs around a point within the CT image. - Known as the point spread function (PSF), this image unsharpness may be graphically represented. - The spatial resolution can then be quantified by measuring the graph at half its maximum value. - This measurement, called the full width at half-maximum (FWHM), is used to illustrate the spatial resolution of a CT scanner. ! Full width at half maximum (FWHM): Spatial Resolution
Increasing the kilovoltage results in an increase in the? (RAD)(CT) a. speed of the electrons as they travel from filament to anode. b. number of electrons that "boil off" of the filament. c. speed of electrons as they travel from the anode through the patient. d. rate at which the system can rid itself of by-product heat.
a. speed of the electrons as they travel from filament to anode. - Electrons "boil off" of the heated filament and are propelled across to strike the anode, where they disarrange the target material to produce x-ray photons. - The x-ray photons (not electrons) then travel from the anode to the patient. - Increasing the kilovoltage increases the speed at which they travel. - Ultimately, this results in a higher photon energy of the resultant x-ray beams.
The degenerative pathologic process involving the forward slipping of an upper vertebral body over a lower vertebral body is called: a. spondylolisthesis b. spondylolysis c. herniated nucleus pulposus d. spinal stenosis
a. spondylolisthesis - Spondylolisthesis refers to the forward "slipping" of an upper vertebral body over the lower as a result of degenerative changes of the facet joints.
Late effects of radiation, such as genetic mutations, may occur with even small doses of radiation and are termed: a. stochastic b. somatic c. nonstochastic d. chronic
a. stochastic - A stochastic,or random, effect of radiation exposure is one having no threshold dose. - Common examples of stochastic radiation effects are genetic mutations and cancer.
An intrathecal injection prior to a CT examination of the lumber spine places iodinated contrast material directly into the: a. subarachnoid space b. dura mater c. vertebral foramen d. subdural space
a. subarachnoid space - Intrathecal injections of iodinated contrast material are used in the CT evaluation of the lumbar spine. - This type of injection introduces contrast material directly into the subarachnoid space, which is located between the arachnoid and pia mater. - The subarachnoid space contains the cerebrospinal fluid.
Which of the following medications may be administered to dilate the coronary vasculature prior to a cardiac CT examination? a. sublingual nitroglycerine b. a b-adrenergic receptor blocking agent (b-blocker) c. atropine d. albuterol
a. sublingual nitroglycerine - If not contraindicated, sublingual nitroglycerine may be administered just prior to the cardiac multislice CT(MSCT) study to cause dilation of the coronary vessels, improving their visualization. - Please consult the refer-ring physician and/or department protocol for further information regarding pharmaceutical administration for cardiac CT procedures.
Number 2 on the figure corresponds to which of the following? a. superior mesenteric vein b. superior mesenteric artery c. renal artery d. portal vein
a. superior mesenteric vein
3a.
a. superior rectus muscle b. lateral rectus muscle c. medial rectus muscle d. inferior rectus muscle
The Lisfranc joint is the articulation between the: a. tarsals and metatarsals b. tarsals and lower leg c. metatarsals and phalanges d. metatarsals and tarsals
a. tarsals and metatarsals - The Lisfranc joint is the articulation between the tarsals and metatarsals; it can be the site of complex fractures and dislocations of the foot.
Number 3 on the figure corresponds to which of the following? a. caudate nucleus b. thalamus c. third ventricle d. pineal gland
b. thalamus
Segmenting the data acquisition process into separate components of smaller rotation angles may improve which of the following components of CT image quality? a. temporal resolution b. longitudinal spatial resolution c. contrast resolution d. in-plane spatial resolution
a. temporal resolution - The controlling factors of the temporal resolution of a CT system are the gantry rotation speed and reconstruction method. - Temporal resolution can be improved by segmenting the data acquisition process into separate components of smaller rotation angles. - Single-segmentor half-scan acquisitions reconstruct data obtained from half of the rotation time. - For example, this type of segmentation would yield a 250-msec temporal resolution from a 0.5-sec gantry rotation time.
During a CT examination of a female pelvis for a suspected malignancy, ascites may be present in an area posterior to the uterus and ovaries known as: a. the cul-de-sac b. Morison's pouch c. the space of Retzius d. the prevesical compartment
a. the cul-de-sac - Thecul-de-sacis the area posterior to the uterus and ovaries in the female patient. - It is a common site forascites in the patient with pelvic pathology.
The process in CT by which different tissue attenuations are averaged to produce one less accurate pixel reading is called? (CT) a. the partial volume effect. b. beam hardening. c. photon deprivation. d. ring artifacts.
a. the partial volume effect. - The partial volume effect occurs when more than one type of tissue is contained within a voxel.
A patient's blood pressure is measured as 140/70 mm Hg. The number 140 represents: a. the pressure within the arterial vessels during contraction of the heart b. the pressure exerted on the chambers of the heart while it is relaxed c. the pressure within the arterial vessels while the heart is relaxed d. the pressure exerted on the chambers of the heart during a contraction
a. the pressure within the arterial vessels during contraction of the heart - The top number of a blood pressure measurement is the systolic pressure. - This is a measure of the pressure exerted on the arterial walls during a contraction of the heart.
During CT examinations, the patient's body should be shielded above and below because of: a. the rotational nature of the x-ray tube b. extremely high kVp techniques c. lack of filtration of the CT beam d. reduced collimation of the CT beam
a. the rotational nature of the x-ray tube - Because of the rotational nature of the x-ray tube, a patient receives exposure from all sides during a CT examination. - Therefore, lead shielding should be placed above and below the patient.
The type of MSCT detector array that contains multiple rows of detector elements, each of the same length, is called a(n): a. uniform matrix array b. adaptive array c. hybrid array d. stationary array
a. uniform matrix array - A uniform matrix array consists of multiple detectors in the longitudinal direction, each with the same dimensions.
Number 1 on the figure corresponds to which of the following? a. ureteropelvic junction b. ureterovesical junction c. ureterocalyceal junction d. ureteropyramidal junction
a. ureteropelvic junction
Number 3 on the figure corresponds to which of the following? a. vestibule b. semicircular canal c. cochlea d. incus
a. vestibule
Which of the following types of gas is commonly used for gas ionization CT detectors? a. xenon b. cadmium tungstate c. helium d. nitrogen
a. xenon - Because of its high atomic number and relative stability ,xenon gas is commonly used in gas ionization CT detectors.
Changing the slice incrementation is also referred to as a. z axis reconstruction or changing the reconstruction interval. b. dynamic or cine scanning. c. changing the zoom, target, or display field-of-view. d. electron beam or fifth-generation CT.
a. z axis reconstruction or changing the reconstruction interval. - Changing the slice incrementation is only possible with helical CT data.
A CT system measures the average linear attenuation coefficient of a voxel of tissue to be 0.008. The linear attenuation coefficient of water for this scanner equals 0.181. The CT number assigned to the pixel representing this voxel of tissue equals? (CT) a.-956 HU b.-173 HU c.+44 HU d.+1044 HU
a.-956 HU
mm to cm (Ct)
add a 0 ex. 38 cm is 380 mm ex. 380 mm is 38 cm
Simple cysts of the kidney have average attenuation values in the range of: a. -40 to 0 Hounsfield units b. 0 to +20 Hounsfield units c. +30 to +50 Hounsfield units d. above +60 Hounsfield units
b. 0 to +20 Hounsfield units - Simple cysts contain primarily water and therefore exhibit CT numbers ranging from approximately 0 (or slightly below) to +20 Hounsfield units.
Which of the following is/are (a) component(s) of the adnexal area of the uterus? 1. ovaries 2. fallopian tubes 3. vagina a. 1 only b. 1 and 2 only c. 2 and 3 only d. 1, 2, and 3
b. 1 and 2 only - Adnexa is used to describe an appendage of an organ. - The ovaries and fallopian tubes constitute the uterineadnexal region.
Compared with single-slice CT (SSCT), patient radiation dose during a multidetector CT study may be higher because of: 1. use of a cone beam of radiation 2. acquisitions at thinner section widths 3. higher-powered x-ray tubes a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
b. 1 and 2 only - Dose can be considerably higher with MSCT owing to a decrease in the focal spot-detector distance, the use of a cone beam instead of a more z-axis-collimated fan beam, an increase in number of imaging phases enabled by shorter scan times, and the acquisition of thinner sections for improvement of 3D and MPR images.
The intrathecal administration of an iodinated contrast agent in the patient in the figure would allow for greater visualization of the: 1. spinal cord 2. nerve roots 3. anulus fibrosis a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
b. 1 and 2 only - Intrathecal administration of an iodinated contrast agent allows for greater visualization of the spinal cord and nerve roots after its introduction into the subarachnoid space.
Which of the following would serve to reduce the image artifact present in the figure? (1) increase in filtration (2) increase in kVp (3) increase in section width a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
b. 1 and 2 only - Streaking edge gradient artifacts may be reduced with increases in the beam's average photon energy. - Increases in kVp and filtration would accomplish this. - This type of artifact may also be reduced with a decrease in reconstructed section width, which helps minimize the edge gradient effect. - A decrease in partial volume averaging may lessen the streaking that is apparent from edge gradient inconsistencies.
Which of the following contrast agent administration techniques should be used for a general CT survey of the abdomen? 1. 400-600 mL oral contrast agent 45-90 minutes prior to the exam 2. 250 mL oral contrast agent immediately before the exam 3. 700-900 mL contrast agent administered as an enema immediately before the exam a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
b. 1 and 2 only - The administration of an oral contrast agent is subject to specific departmental protocol considerations. Generally, 400 to 600 mL of oral contrast administered 45 to 90 minutes prior to the exam should opacify the small bowel. - An additional dose of contrast agent (250 mL) immediately before the exam should ensure gastric opacification. ! Administration of contrast agents via enema is indicated for evaluation of the distal large bowel.
Which of the following would serve to increase spatial resolution of a CT exam using a large focal spot size, 5-mm sections, and a 512^2 matrix? 1. change to small focal spot size 2. acquire 2.5-mm sections 3. reconstruct images in a 320^2 matrix a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
b. 1 and 2 only - The spatial resolution of a CT examination can be improved with the use of small focal spots, narrow sections, and large matrices.
The enhancement washout technique for CT characterization of adrenal masses includes: 1. thin-section pre-contrast acquisition through the adrenals 2. arterial phase post-contrast acquisition through the adrenals 3. 10- to 15-minute delayed post-contrast acquisition through the adrenals a. 1 and 2 only b. 1 and 3 only c. 2 and 3 only d. 1, 2, and 3
b. 1 and 3 only - Differentiation between a metastatic lesion and a benign adenoma of the adrenal can be accomplished by calculating the percentage of enhancement washout after a 10- to 15-minute delay. - Precontrast, portal venous phase, and delayed acquisitions are obtained. - On delayed post-contrast imaging, metastatic lesions of the adrenal gland remain enhanced longer than adrenal adenomas.
During a general CT examination of the abdomen, an intravenous contrast agent is indicated and is administered with the aid of an automatic injector. Which of the following ranges of flow rate should be used? a. 0.2-1.0 mL/sec b. 1.0-3.0 mL/sec c. 4.0-6.0 mL/sec d. 7.0-10.0 mL/sec
b. 1.0-3.0 mL/sec - The flowrate range 1.0 to 3.0mL/sec should be sufficient to provide the enhancement necessary for proper evaluation of the abdomen. This is a general range that may be adjusted to meet the needs of the exam at the discretion of the physician and medical personnel involved for each patient.
Which of the following is the correct angle of insertion for placing a butterfly needle into a vein for intravenous administration of a contrast agent? a. 5 degrees b. 15 degrees c. 45 degrees d. 60 degrees
b. 15 degrees
A 16-slice MSCT system utilizes an adaptive array of 24 detectors, each ranging in size from 0.625 to 1.25 mm. What is the maximum number of sections the system can acquire with each rotation of the gantry? a. 8 b. 16 c. 32 d. 64
b. 16 - The number of data channels controls the number of sections the scanner can simultaneously acquire with each gantry rotation. - A 16-slice system possesses 16 data channels and is capable of acquiring 16 images per gantry rotation. - The configuration of the detector array with regard to the size of individual detector elements controls the possible section widths for each reconstructed CT image.
After initiation of rapid bolus administration of an iodinated contrast agent, the arterial phase of hepatic contrast enhancement occurs at approximately: a. 15-20 seconds b. 25-35 seconds c. 60-70 seconds d. 120-180 seconds
b. 25-35 seconds - The arterial phase is the period of peak arterial enhance-ment typically occurring at 25 to 35 seconds after the initiation of contrast agent administration. - During this phase, hypervascular tumors or tumors supplied by the hepatic artery undergo maximal enhancement.
Retrospective ECG gating utilizes which of the following portions of the cardiac cycle for image reconstruction? 1. atrial systole 2. ventricular systole 3. cardiac diastole a. 2 only b. 3 only c. 1 and 2 only d. 2 and 3 only
b. 3 only - Complete cardiac diastole is the period of relaxation after heart contraction. - Diastoleis the portion of the cardiac cycle when coronary artery motion is the slowest and cardiac motion is at its lowest. - For evaluation of the coronary arteries, the MDCT system utilizes only the diastolic portion of the acquisition in the reconstruction process.
The size of the CT image displayed on a computer monitor can be enlarged by increasing the: 1. DFOV 2. SFOV 3. image magnification a. 1 only b. 3 only c. 1 and 2 only d. 1 and 3 only
b. 3 only - Increasing the display field of view (DFOV) for are constructed CT image decreases its displayed size. - Electronically magnifying the image on the display system results in a larger displayed image but has no effect on pixel or voxel dimension.
Which of the following may be considered a low osmolar contrast medium? 1. iothalamate meglumine 2. diatrizoate sodium 3. iohexol a. 1 only b. 3 only c. 1 and 2 only d. 1, 2, and 3
b. 3 only - Low osmolar contrast media(LOCM)are non-ionic agents that do not dissociate into charged particles(ions) in solution. - Examples of LOCM are iohexol (Omnipaque), iopamidol (Isovue), and ioversol (Optiray).
For a single-slice CT (SSCT) system, which of the following statements regarding pre-patient collimation is true? 1. An increase in pre-patient collimation increases patient radiation dose. 2. Pre-patient collimation is used to focus radiation through the section of interest. 3. Pre-patient collimation directly controls slice thickness. a. 2 only b. 3 only c. 1 and 2 only d. 2 and 3 only
b. 3 only - Pre-patient collimation influences the slice thickness by reducing the size of the primary beam. - This is accomplished with the use of lead shutters that absorb the outer margins of the primary beam. - Increases in pre-patient collimation diminish patient radiation dose by reducing the number of x-ray photons that reach the patient. ! Pre Patient Collimation cleans up the beam before it is focused through the patient. That is why I believe #2 is inaccurate.
Risk factors for contrast-induced nephrotoxicity (CIN) include: 1. pheochromocytoma 2. allergy to shellfish 3. dehydration a. 2 only b. 3 only c. 1 and 2 only d. 1, 2, and 3
b. 3 only - Risk factors for contrast-induced nephrotoxicity (CIN) include pre-existing renal function compromise, dehydration, diabetes, myeloma, advanced age, and cardio-vascular disease.
After initiation of rapid bolus administration of iodinated contrast material, the pancreatic phase of contrast enhancement occurs at approximately: a. 15-25 seconds b. 35-45 seconds c. 60-70 seconds d. 120-180 seconds
b. 35-45 seconds -
On an unenhanced abdominal CT, what is the range of CT attenuation values of a normal liver? a. −10HU to 30HU b. 38HU to 70HU c. 85HU to 132HU d. 147HU to 165HU
b. 38HU to 70HU - The normal CT attenuation of the liver in unenhanced studies varies among individuals and ranges from 38 to 70HU.
The image in the figure was most likely displayed with the use of which of the following window widths? (CT) a. 70 b. 400 c. 1300 d. 3800
b. 400 - The width of a window used to display a CT image of the abdomen should be within the range of 350 to 600 HU. - This range allows for excellent visualization of the soft tissue structures.
The image in the figure was most likely displayed with the use of which of the following window widths? a. 70 b. 400 c. 1300 d. 3800
b. 400 - The width of a window used to display a CT image ofthe abdomen should be within the range of 350 to 600 HU. - This range allows for excellent visualization of the soft tissue structures.
Which number on the figure corresponds to the anterior horn of the lateral ventricle? a. 1 b. 5 c. 3 d. 2
b. 5
A normal range for diastolic blood pressure in an adult is: a. 40-60 mm Hg b. 60-90 mm Hg c. 80-120 mm Hg d. 95-140 mm Hg
b. 60-90 mm Hg - The normal range for diastolic blood pressure in adults is 60-90 mm Hg. Diastolic pressure is the measurement of blood pressure at its lowest point, in between contractions of the heart.
The average photon energy of the primary beam of a CT scanner operating at a tube potential of 120 kVp is approximately: a. 50 keV b. 70 keV c. 100 keV d. 120 keV
b. 70 keV - The average photon energy of the primary beam used in CT is approximately 70 keV. - The average photon energy of any radiographic primary beam is typically 30% to 40% of the applied kilovoltage. - The average photon energy of the CT beam is increased through beam filtration.
Number 5 on the figure corresponds to which of the following? a. capitate b. lunate c. hamate d. scaphoid
b. lunate
When imaging the heart, particularly when the structures of interest are small, such as the coronary arteries, a regular heart rate of less than ____ is important. a. 50bpm b. 70bpm c. 90bpm d. 110bpm
b. 70bpm - Motion artifact can be a problem when the patient's heart rate is greater than 70bpm, or if the heart rate is irregular. - When imaging larger cardiac structures, heart rate is less of an issue, although a slower, regular heart rate is still preferred.
How is a cursor measurement different than obtaining a region of interest measurement? (CT) a. A cursor measurement provides only the standard deviation, whereas an ROI provides an HU measurement. b. A cursor measurement is the HU measurement for a single pixel, whereas an ROI is the average HU for all pixels within the ROI. c. A cursor measurement uses raw data, whereas an ROI uses image data. d. A cursor measurement shows what mAs was used to create the image, whereas an ROI obtains both mAs and kVp settings.
b. A cursor measurement is the HU measurement for a single pixel, whereas an ROI is the average HU for all pixels within the ROI. - Both a cursor measurement and an ROI obtain an HU measurement. - Because the ROI is the average HU for all the pixels within the region, the standard deviation can also be calculated. - Both a cursor measurement and an ROI use image data. Neither indicates what scan parameters were used for data acquisition.
What technique is often used to differentiate the margins of the pancreas from the duodenum? a. Water-soluble contrast medium administered by enema b. Acquire scans while the patient is a right decubitus postion c. Unenhanced imaging; no oral or intravenous contrast is used d. Scan approximately 2 hours after the patient ingests 600 mL of a barium sulfate oral contrast medium
b. Acquire scans while the patient is a right decubitus postion - When initial scans fail to differentiate the margins of the pancreas from the duodenum, the patient is often given additional oral contrast material and additional slices are obtained with the patient lying in a right decubitus position.
Refer to Figure 24-9. Name the structure indicated by arrow #3. a. Right atrium b. Ascending aorta c. Right ventricle d. Superior vena cava
b. Ascending aorta
Refer to Figure 24-15. Name the structure indicated by arrow #1. a. Talus b. Calcaneus c. Navicularbone d. Distal fibula (lateral malleolus)
b. Calcaneus
Refer to Figure 24-7. Name the structure indicated by arrow RAD #3. a. Putamen b. Caudate nucleus c. Thalamus d. Pons, medulla oblongata
b. Caudate nucleus
What can be done to reduce streak artifacts such as those seen in Figure 24-13? a. Increase the kVp b. Contrast administration is immediately followed by a saline solution bolus. c. Begin scanning 45-seconds after contrast media is seen in the monitoring slice. d. Lift the patient's arms over his or her head.
b. Contrast administration is immediately followed by a saline solution bolus. - A "saline chaser" reduces streak artifacts over the superior vena cava that result from dense contrast material. - Although increasing the scan delay (choice c) would reduce the streak artifact by allowing the contrast to dilute, the examination would be degraded.
What plane is the MPR depicted by Figure 24-6? (CT) a. Sagittal b. Coronal c. Oblique d. Curved
b. Coronal
Refer to Figure 24-15. Name the structure indicated by arrow #3. a. Talus b. Cuneiform (interomedial or 2nd) c. Navicular bone d. Metatarsal bone
b. Cuneiform (interomedial or 2nd)
Refer to Figure 24-10. Name the structure indicated by arrow #2. a. Hepatic flexure of colon b. Duodenum c. Gastroesophageal junction d. Body of stomach
b. Duodenum
Refer to Figure 24-8. Name the structure indicated by arrow #3. a. Mastoid antrum b. Epitympanic recess c. Internal auditory canal d. Vestibule
b. Epitympanic recess
Refer to Figure 24-8. Name the structure indicated by arrow #1. a. Mastoid air cells b. Incus c. Stapes d. Cochlea
b. Incus
In a CT system, what is the function of the generator? (CT) a. It produces an electric current of very high amperage and transmits it to the filament. b. It produces high voltage and transmits it to the x-ray tube. c. It samples the detectors thousands of times per second. d. It dissipates the heat built up during x-ray production.
b. It produces high voltage and transmits it to the x-ray tube. - The generator produces high voltage and transmits it to the x-ray tube. - This high voltage propels the electrons from the x-ray tube filament to the anode. ! High amperage is not necessary for the production of x-rays.
The adult spinal cord ends at what vertebral level? a. T11-T12 b. L1-L2 c. L3-L4 d. superior portion of the coccyx
b. L1-L2 - The spinal cord extends to the lower margin of the first or upper margin of the second lumbar vertebra. - At this level it tapers to a point known as the conus medullaris.
Refer to Figure 24-12. Name the structure indicated by arrow #4. a. Left common iliac vein b. Left common iliac artery c. Celiac trunk d. Azygos vein
b. Left common iliac artery
Which of the following statements is true regarding the relationship between multiple scan average dose (MSAD) and image spacing during axial (step-and shoot) scanning? a. MSAD decreases with overlapping scans. b. MSAD increases with overlapping scans. c. MSAD increases with noncontiguous scans. d. MSAD equals the product of image spacing and pitch.
b. MSAD increases with overlapping scans. - During axial scanning, overlapping scans increase the patient radiation dose, whereas gaps between slices decrease the dose.
Which of the following abbreviations is used to identify a computerized network that stores, retrieves, communicates, and displays digital medical images? a. WORM b. PACS c. DICOM d. HIPAA
b. PACS - Picture archival and communications systems (PACSs) are computerized networks charged with the responsibility of storing, retrieving, distributing, and displaying CT and other digital medical images.
A CT image is displayed in a window with a level of 0 and a width of 500. Which of the following statements is correct? a. Pixels with values between 0 HU and 500 HU will appear white. b. Pixels with values between -250 HU and +250 HU will be assigned shades of gray. c. Pixels with values greater than +500 HU will be black. d. Pixels with values less than 0 HU will appear white.
b. Pixels with values between -250 HU and +250 HU will be assigned shades of gray. - The width of a window determines the range of pixel values that will be assigned shades of gray around a given level. - In this example, all pixels within the range of -250 to +250 HU will be assigned shades of gray. - Pixels below -250 HU will appear black, and pixels above +250 HU will appear white.
Which of the following is NOT an advantage of using helical CT for the diagnosis of PE? a. It is cost effective. b. Quality images are produced even if the patient is uncooperative c. It is often helpful in establishing an alternative diagnosis in the absence of PE. d. It is less invasive than pulmonary angiography.
b. Quality images are produced even if the patient is uncooperative - Overt patient motion will create artifacts that can greatly degrade image quality. - It is unlikely that a diagnostic examination can be produced in a patient unable to lie still for the length of time required to complete the test. - Although newer scanners can often complete the arterial phase acquisition in just seconds, the patient must be able to lie still for that short time.
Why is it more common practice to manipulate the mAs, rather than the kVp, for a CT examination? (CT) a. Changing the mAs does not affect the radiation dose to the patient. b. Scanners offer more mA options and the effect of mAs on image quality is more predictable. c. Tube cooling is not affected by adjusting the mAs set- tings. d. Changing the mAs will not affect the quality of the images.
b. Scanners offer more mA options and the effect of mAs on image quality is more predictable.
The trachea bifurcates at the level of a. C6 to C7. b. T4 to T5. c. T7 to T8. d. T10 to T11.
b. T4 to T5.
Which of the following statements comparing the efficiency of scintillation and gas ionization detectors is correct? a. Both have approximately the same capture efficiency. b. The scintillation detector has a higher capture efficiency. c. Unlike the scintillation detector, the gas ionization detector has a problem with afterglow. d. Gas ionization detectors have a higher conversion efficiency.
b. The scintillation detector has a higher capture efficiency. - Because of its solid nature, the scintillation detector interacts with a higher percentage of incident x-ray photons, giving it a better capture efficiency.
For single-slice CT (SSCT) systems, which of the following statements regarding retrospective image reconstruction is FALSE? a. The algorithm, matrix size, and DFOV may all be changed. b. The slice thickness and SFOV may be changed. c. Scan (raw) data must be available. d. Retrospective image reconstruction may be used to adjust the center of the image.
b. The slice thickness and SFOV may be changed. - Retrospective reconstruction uses scan or "raw" data tochangethe matrix, DFOV, center, and/or algorithm used for a CT image. - The slice thickness and SFOV are specifically used for data acquisition and cannot be altered retrospectively with a single-slice CT (SSCT) system. - The advent of multislice CT (MSCT) technology has made retrospective adjustments in section width possible. - The scan field of view (SFOV) remains an item that may not be altered retrospectively.
Which is a true statement regarding Figure 24-11? a. The gallbladder is absent. b. The spleen is absent. c. The patient has breast implants. d. The patient had a Whipple procedure.
b. The spleen is absent. - The gallbladder is present in the expected location adjacent to the liver. - A Whipple procedure consists of removal of the gallbladder (along with the distal portion of the stomach, the distal portion of the common bile duct, the head of the pancreas, the duodenum, and the proximal jejunum). - The high-density objects on the anterior chest wall are breast shields, intended to reduce radiation to the breast.
Refer to Figure 24-14. Name the structure indicated by arrow #2. a. Hyoidbone b. Thyroidcartilage c. Mandible d. Cricoid cartilage
b. Thyroidcartilage
Refer to Figure 24-12. Name the structure indicated by arrow #5. a. Nucleus pulposus b. Vertebral canal with spinal cord c. Transverse ligament d. Intervertebral foramen
b. Vertebral canal with spinal cord
In which of the following situations would an LOCM be beneficial when delivered orally? a. When a patient is unable to drink the full dose of oral contrast b. When oral contrast is needed for neonatal CT examinations c. When patients are older than 70 years of age d. When patients have a hiatal hernia
b. When oral contrast is needed for neonatal CT examinations - In most situations, HOCM (e.g., Hypaque) is used for oral administration because it is less expensive than LOCM (e.g., Omnipaque) and provides equivalent gastrointestinal opacification. - However, in some cases LOCM has advantages. If aspirated, LOCM causes less pulmonary edema than HOCM. - In newborns, researchers have noted a reduction in complications when LOCM is used compared with barium sulfate or HOCM. - Barium sulfate is preferred when a patient is unable to drink the full dose of oral contrast This is because in small amounts barium sulfate tends to cling to the intestinal wall, providing at least a small amount of visible contrast. - In comparison, the bowel usually absorbs a small quantity of water-soluble oral contrast.
Effective slice-thickness blooming is? (CT) a. the process in CT by which different tissue attenuations are averaged to produce one less accurate pixel reading. b. a disadvantage often associated with the interpolation of helical data. c. an improvement to image resolution associated with helical scans. d. the trend toward selecting a wider slice thickness to improve spatial resolution.
b. a disadvantage often associated with the interpolation of helical data. - Interpolation methods used with helical data can result in a scan that is wider than that selected by the operator. This is referred to as slice thickness blooming or degradation of the slice sensitivity profile.
Interpolation, as it is used in CT, is? (CT) a. a statistical measure of the spread or dispersion of a set of data; it is the positive square root of the variance. b. a mathematical method to estimate a missing value by taking an average of known values at neighboring points. c. the method used to convert the electric signal to a digital format. d. the method used to convert light levels into an electric current.
b. a mathematical method to estimate a missing value by taking an average of known values at neighboring points. - This method is used in helical scanning. - The system takes the slanted helical data and estimates what its appearance would be if the slices were taken axially, with each slice parallel to the plane of the table. - The greater the slant (i.e., the higher the pitch), the more interpolation is required. - Choice (a) is the definition for standard deviation.
Which of the following terms is used to describe a set of rules for solving a mathematical problem? a. reconstruction b. algorithm c. function d. array
b. algorithm - Analgorithm may be defined as a set of rules or steps used to solve a mathematical problem. - The programs used by the CT computer to reconstruct the image are often referred to as algorithms.
Before a CT image can be reconstructed by a computer, the transmission signal produced by the detectors must be converted into numerical information by a(n): a. kernel b. analog-to-digital converter (ADC) c. array processor d. digital-to-analog converter (DAC)
b. analog-to-digital converter (ADC) - The analog-to-digital converter is responsible for transforming the analog signal from the detectors into a digital form that may be used by the computer. - Analog information is based on a scale, whereas digital information is in numerical form.
Number 2 on the figure corresponds to which of the following? a. left mainstem bronchus b. anterior segment of left upper lobe bronchus c. posterior segment of left upper lobe bronchus d. anterior segment of left lower lobe bronchus
b. anterior segment of left upper lobe bronchus
The component of the CT computer system responsible for the data processing of image reconstruction is the: a. pipeline memory b. array processor c. hard disk drive d. RAM microprocessor
b. array processor - The primary data processing component of the CT system is the array processor. It is responsible for receiving scan data from the host computer, performing all of themajor processing of the CT image, and returning thereconstructed image to the storage memory of the hostcomputer.
The image in the figure was most likely acquired during which of the following phases of contrast enhancement? a. pre-contrast b. arterial phase c. venous phase d. delayed phase
b. arterial phase - Dense contrast opacification of the aorta and pulmonary arteries indicates that this image was obtained during the arterial phase, most likely within the first 20 to 30 seconds after bolus injection of contrast material.
Coronary artery calcium (CAC) quantitation by MDCT exam is used primarily to assess: a. aortic aneurysm b. atherosclerotic disease c. coronary artery stenosis d. ejection fraction
b. atherosclerotic disease - The primary clinical indication for MDCT coronaryartery calcium (CAC) quantitation is the assessment ofatherosclerotic disease. The presence of coronary arterycalcium (CAC) is a specific indicator of atheroscleroticdisease.
During data acquisition, a CT system may continuously adjust the mA relative to the measured image noise for a method of dose reduction referred to as? (CT) a. iterative reconstruction b. automatic tube current modulation c. attenuation correction d. Nyquist sampling
b. automatic tube current modulation - Automatic tube current modulation (ATCM) programs adjust the mA throughout an acquisition to reduce patient radiation dose to a minimum. - ATCM automatically alters the applied mA on the basis of a predetermined noise index that is acceptable for appropriate image quality.
During data acquisition, a CT system may continuously adjust the mA relative to the measured image noise for a method of dose reduction referred to as: a. iterative reconstruction b. automatic tube current modulation c. attenuation correction d. Nyquist sampling
b. automatic tube current modulation - Because of its solid nature, the scintillation detector interacts with a higher percentage of incident x-ray photons, giving it a better capture efficiency.
Which of the following type(s) of oral contrast material could cause peritonitis if leakage from the digestive tract occurs from perforation? a. iopamidol (Gastrografin) b. barium sulfate c. diatrizoate (Hypaque) d. effervescent granules
b. barium sulfate - Barium sulfate is not water soluble and is not easily absorbed by the body. - If it leaks out of the digestive tract because of perforation, this agent may cause peritonitis.
Number 5 on the figure corresponds to which of the following? a. left ovary b. bladder c. sigmoid colon d. uterus
b. bladder
An enterovesical fistula is an abnormal communication between the bowel and the: a. uterus b. bladder c. vagina d. umbilicus
b. bladder - An enterovesical fistula is an abnormal communication between the bowel and the bladder. - It typically results from inflammatory processes of the colon such as diverticulitis.
Which of the following terms is used to describe the intravenous injection of medication or contrast agent in one complete dose over a short time? a. infusion b. bolus c. IV drip d. Infus-A-Port
b. bolus - A bolus injection is one in which the entire volume of medication or contrast agent is administered at once over a short period.
Which of the following intravenous contrast agent administration methods provides the greatest overall plasma iodine concentration? a. drip infusion b. bolus technique c. biphasic technique d. CT portography
b. bolus technique - A bolus administration of contrast agent requires the entire volume of material to be injected over the shortest possible time. - Accomplished by hand or with the use of an automatic injector, bolus administration provides the maximum plasma iodine concentration and subsequent tissue enhancement.
During CT perfusion studies, the quantity of blood (in mL) that moves through 100 g of tissue each minute is termed the: a. mean transit time (MTT) b. cerebral blood flow (CBF) c. cerebral blood volume (CBV) d. percentage washout value (PWV)
b. cerebral blood flow (CBF) - Cerebral blood flow (CBF) describes the quantity of blood (in mL) that moves through 100 g of brain tissue each minute. - Normal CBF range in gray matter is 50 to 60 mL/100 g/min.
The acquisition of a series of CT images at a single anatomic location over a set period is referred to as: a. ultrafast CT b. cine CT c. conventional CT d. temporal CT
b. cine CT - Cine CT acquisition involves multiple axial scans obtained at a single anatomic level over a predetermined period. - Clinical applications of cine CT acquisition include contrast bolus tracking, dynamic imaging of physiologic processes such as respiration, swallowing,and the cardiac cycle as well as for CT perfusion studies.
The condition of intermittent cramping pain in the legs due to poor circulation is called: a. varices b. claudication c. stenosis d. thrombosis
b. claudication - Claudication refers to the condition of intermittent cramping pain in the legs due to poor circulation.
Which of the following is NOT a part of the CT tube? a. tungsten target b. collimator c. rotating anode d. filament
b. collimator
Which of the following is NOT a part of the CT tube? a. tungsten target b. collimator c. rotating anode d. filament
b. collimator
The pituitary gland is best demonstrated during CT in which of the following imaging planes? a. axial b. coronal c. sagittal d. transaxial
b. coronal - The pituitary and other structures involving the sella tur-cica are usually imaged in the coronal plane with CT. - The coronal plane provides the best visualization of the pituitary gland with regard to its position within the sella turcica and involves less partial volume averaging of the pituitary with surrounding structures than scans obtained in the axial plane.
The data for this reformatted image of the abdomen was most likely acquired in which of the following renal enhancement phases? a. pre-contrast b. corticomedullary c. nephrographic d. excretory
b. corticomedullary - Beginning 30 to 40 seconds after the initiation of contrast agent administration, the corticomedullary phase demon-strates optimal enhancement of the renal cortex with maxi-mum differentiation of the cortex from the renal medulla.
Which of the following laboratory values is the most dependable measure of renal function? a. BUN b. creatinine c. PT d. PTT
b. creatinine - Serum creatinine levels are the most accurate and dependable laboratory measures of renal function. - The blood urea nitrogen (BUN) level may be affected by many variables and is not a suitable test of renal function by itself. - BUN levels are usually evaluated in con-junction with creatinine levels for a more accurate measurement of renal function.
Number 4 on the figure corresponds to which of the following? a. navicular b. cuboid c. calcaneus d. talus
b. cuboid
CT is commonly referred to as all of the following names EXCEPT: a. computerized axial tomography b. digital subtraction angiography c. CAT-scan d. Computed tomography
b. digital subtraction angiography
A narrow window width is best for? (CT) a. displaying the aerated lungs. b. displaying the white and gray matter of the brain. c. suppressing noise on an image. d. reducing the appearance of streak artifact.
b. displaying the white and gray matter of the brain. - Tissues types with similar densities, such as the white and gray matter of the brain, should be displayed in a narrow window width. - Wider window settings are used to suppress image noise and to reduce the appearance of streak artifact. - Wider window widths encompass greater anatomic diversity (such as aerated lung), but subtle density discrimination is lost.
Which of the following radiation dose indices is a measure of the total radiation exposure for an entire series of CT images? a. CTDI100 b. dose length product (DLP) c. CTDIvol d. multiple scan average dose (MSAD)
b. dose length product (DLP) - The CTDIvol is a measure of dose to each slice along a helically acquired volume. The dose length product (DLP) is calculated by multiplying the CTDI vol by the total scan length.
CT examinations of the abdomen are often performed in the position on the figure to demonstrate the relationship between the: a. ureters and renal collecting systems b. duodenum and pancreatic head c. large and small colon d. liver and gallbladder
b. duodenum and pancreatic head - The right lateral decubitus position is often used to differentiate the pancreatic head and the duodenum.
Number 1 on the figure corresponds to which of the following? a. sphenoid sinus b. ethmoid sinus c. frontal sinus d. maxillary sinus
b. ethmoid sinus
A set of ROIs, one placed within the liver and one placed within the spleen, is often used to document? a. splenomegaly. b. fatty infiltrate of the liver. c. sickle cell disease. d. lymphoma.
b. fatty infiltrate of the liver. - Fatty infiltration reduces the CT attenuation of the involved liver. - With fatty infiltration, the liver is at least 10HU lower than that of the spleen.
The area of the anode where the electrons strike and the x-ray beam is produced is the? (CT) a. filament. b. focal spot. c. generator. d. detector.
b. focal spot. - The focal spot is also called the anode target.
Number 1 on the figure corresponds to which of the following? a. trachea b. piriform sinus c. aryepiglottic fold d. vocal cord
b. piriform sinus
Areas of a CT image that contain abrupt changes in tissue density are electronically represented by which of the following? a. positive CT numbers b. high spatial frequencies c. negative CT numbers d. low spatial frequencies
b. high spatial frequencies - The contrast of a CT image is controlled by the spatial frequencies of the tissue(s) within the section. - Tissues of differing densities are represented electronically by different spatial frequencies. - Adjacent tissues that greatly differ in density are represented by high spatial frequencies.
Temporal resolution refers to? (CT) a. the spatial resolution measurable in images of the temporal bone. b. how rapidly the data are acquired by the CT system. c. the ability to differentiate between objects with very similar densities as their backgrounds. d. the level of noise apparent on an image.
b. how rapidly the data are acquired by the CT system. - In the context of image quality the word "temporal" refers to the characteristic of being limited by time and relates to a scanner's data acquisition speed. - The temporal resolution of a system is typically reported in milliseconds.
Which of the following terms describes the appearance of an acute subdural hematoma on a CT image of the brain? a. radiolucent b. hyperdense c. hypodense d. isodense
b. hyperdense - Subdural hematomas are collections of blood that occur throughout the subdural space after traumatic injury to the head. - An acute subdural hematoma is one that has manifested clinically during the first 24 hours after the injury. - During this stage, the hematoma appears hyper-dense compared with normal brain tissue because of the initial clotting that has occurred and the concentration of hemoglobin in fresh blood.
In-plane resolution refers to the resolution? (CT) a. resulting from helical data. b. in the xy direction. c. in the z direction. d. related to the slice thickness.
b. in the xy direction. - Resolution in the xy direction is called in- plane resolution. - The in-plane resolution is affected by pixel size, which is affected by the DFOV. - Resolution in the z direction is called longitudinal resolution. - This is affected largely by slice thickness and (in helical scans) pitch.
The average photon energy of the CT x-ray beam can be increased by: a. increasing mAs b. increasing filtration c. increasing collimation d. all of the above
b. increasing filtration - Increases in filtration cause a greater amount of low-energy x-ray photons to be absorbed, thereby increasing the average photon energy of the beam. - Higher mAs values increase the intensity of the beam but do not affect average photon energy.
The difference among the bolus phase, the nonequilibrium phase, and the equilibrium phase of contrast enhancement is primarily determined by the? a. brand of iodinated contrast agent that is used. b. injection rate and scan delay. c. type of pathologic disease present. d. film processing time.
b. injection rate and scan delay.
The mathematical technique that involves the estimation of an unknown value from values on either side of it is known as: a. filtering b. interpolation c. convolution d. summation
b. interpolation - Interpolationis a mathematical technique used in the reconstruction process of the spiral CT image. - It involves the estimation of an unknown value from information above and below it.
Which of the following is a parenteral route of medication administration? a. sublingual b. intramuscular c. transdermal d. oral
b. intramuscular - Parenteral administration involves the injection of medication into the body. - Common routes of parental medication administration include intramuscular, intravenous, intradermal, and subcutaneous. ! Transdermal is relating to or denoting the application of a medicine or drug through the skin, typically by using an adhesive patch, so that it is absorbed slowly into the body.
Which of the following is considered one of the ionic radiopaque contrast media (RCM)? a. iohexol b. iothalamate meglumine c. iopamidol d. ioversol
b. iothalamate meglumine - Ionic contrast media are salts consisting of sodium and/ormeglumine.
Voxels with equal dimensions along the x-, y-, and z-axes are referred to as: a. prospective b. isotropic c. retrospective d. anisotropic
b. isotropic - Isotropic is used to describe voxels with equal dimensions along the x-, y- and z-axes. - The ability to acquire an isotropic data set is a distinct advantage of MDCT.
The amount of x-ray energy absorbed in a quantity of air is termed: a. dose profile b. kerma c. becquerel d. MSAD
b. kerma - Kerma may be used to describe absorbed dose. - Airkerma is the amount of radiation absorbed in a quantity of air
Number 2 on the figure corresponds to which of the following? a. left posterior cerebral artery b. left middle cerebral artery c. left anterior cerebral artery d. left posterior communicating artery
b. left middle cerebral artery
Number 2 on the figure corresponds to which of the following? a. right brachiocephalic vein b. left subclavian artery c. left brachiocephalic vein d. brachiocephalic artery
b. left subclavian artery
The average density of a mass within the kidney measures -75 Hounsfield units (HU). The mass is most likely a: a. cyst b. lipoma c. stone d. hydrocele
b. lipoma - The density of the mass in question indicates that it consists of fatty tissue. - Alipomais a benign mass consisting of fat cells. Anangiomyolipoma, a common benign mass found in the kidney, consists of muscle cells, blood vessels, and fat. - The average CT value range for fat is50 to100 Hounsfield units.
The graph in the figure is used to evaluate which of the following components of CT image quality? a. in-plane spatial resolution b. longitudinal spatial resolution c. temporal resolution d. contrast resolution
b. longitudinal spatial resolution - The longitudinal spatial resolution is usually qualified by the extent of broadening that occurs to the slice sensitivity profile (SSP) during volumetric acquisition. - The section width (slice) for a volumetric acquisition may be graphically represented as a slice sensitivity profile (SSP).
The phantom in Figure 24-4 features a series of cylinders with different diameters, all at 0.6% (6HU) difference from the background material. This phantom is used to measure a. slice thickness accuracy. b. low-contrastresolution. c. high-contrastresolution. d. CT number accuracy.
b. low-contrastresolution.
Which combination of factors is likely to result in the lowest RAD radiation dose to the patient? a. mAs = 180; kVp = 140; pitch = 0.8; 2-mm slice thickness b. mAs = 200; kVp = 120; pitch = 1.8; 5-mm slice thickness c. mAs = 280; kVp = 120; pitch = 1.5; 2-mm slice thickness d. mAs = 300; kVp = 120; pitch = 1.0; 5-mm slice thickness
b. mAs = 200; kVp = 120; pitch = 1.8; 5-mm slice thickness - In general, increasing radiation dose results from increasing mAs, increasing kVp, decreasing pitch, and decreasing slice thickness. - Although choice (a) includes the lowest mAs, it is more than offset by the increased kVp and decreases in pitch and slice thickness.
The loss of anatomic information between contiguous sections due to inconsistent patient breathing is called: a. cupping artifact b. misregistration c. overshoot artifact d. out-of-field artifact
b. misregistration - Misregistration is an artifact that occurs when a patient suspends respiration at different depths during consecutive scans. - It results in the loss of anatomic information.
The fluctuation of CT numbers in an image of uniform, homogeneous material may occur because of? (CT) a. linearity b. noise c. aliasing d. partial volume effect
b. noise - Noise appears on the CT image as an inaccuracy in CT number. - The noise of a CT scanner may be measured by scanning a homogeneous object such as a water phantom. - Fluctuations in CT number from pixel to pixel indicate the presence of noise. ! Noise = Inaccuracy in CT#s
The fluctuation of CT numbers in an image of uniform, homogeneous material may occur because of: a. linearity b. noise c. aliasing d. partial volume effect
b. noise - Noise appears on the CT image as an inaccuracy in CT number. - The noise of a CT scanner may be measured by scanning a homogeneous object such as a water phantom. - Fluctuations in CT number from pixel to pixel indicate the presence of noise.
A(n) ________ contrast material may be described as one that does not dissociate into charged particles in solution. a. neutral b. non-ionic c. osmolar d. ionic
b. non-ionic - Non-ionic contrast materials do not dissociate into charged particle (ions) when placed in solution.Ioniccontrast materials are salts that form independent parti-cles in aqueous solutions.
Check answer? Radiation exposure and its potentially harmful effects have a relationship that is termed ________ in nature. a. stochastic b. nonstochastic c. negligible d. somatic
b. nonstochastic - Certain harmful effects of exposure to diagnostic x-rays, such as cancer formation and genetic mutations, are said to be random, or stochastic, in nature. A stochastic effect is one that has no threshold dose but increases in probability with increasing dose.
A(n) _________ infection is one that a patient acquires during a stay in a health care institution. a. blood-borne b. nosocomial c. iatrogenic d. staphylococcal
b. nosocomial - Nosocomial infections may be commonly referred to as health care-associated infections. - They occur within the first 48 hours of a patient's stay in a health care facility.
Reformatted CT image planes that lie perpendicular to the original plane of acquisition may be described as: a. oblique b. orthogonal c. obtuse d. orthographic
b. orthogonal - Orthogonal planes are at right angles to each other. - Orthogonal reformations are perpendicular to the original plane of data acquisition.
Used in determining the biologic effect of iodinated contrast media, the term __________ refers to the number of ions formed when a substance dissociates in solution. a. solubility b. osmolality c. concentration d. iodination
b. osmolality - Osmolality or osmotic concentration is the number of ions or particles formed when a substance (solute) dissociates in a given solution. - It is described as the number of particles in solution per kg of water.
The artifact present on the lateral borders of the image in the figure most likely represents which of the following? a. edge gradient b. out-of-field artifact c. tube arcing d. beam hardening
b. out-of-field artifact - The artifact present in the figure most likely represents an out-of-field artifact. - This relatively large patient was incorrectly positioned, and a portion of the anatomy lies outside the scanned field of view. - This improperly centered anatomy interferes with the reference detectors, thus causing a streak artifact near the unscanned area.
In order to uniformly expose the entire detector array in an MDCT system, the primary beam must be expanded beyond the physical extent of the array in a process known as: a. interpolation b. overbeaming c. photon flux d. back-projection
b. overbeaming - All detectors of the MDCT array must be exposed to x-rays of equal intensity. - The beam must be expanded even further to avoid exposing the detectors to undesirable"penumbra." - This process is referred to as overbeaming
Number 7 on the figure corresponds to which of the following? a. duodenum b. pancreatic head c. jejunum d. gallbladder
b. pancreatic head
Axial CT images of the knee may be acquired in four separate series with gantry angulations of 0, 30, 45, and 60 degrees in order to demonstrate the: a. tibial plateau b. patellofemoral joint c. medial and lateral menisci d. anterior cruciate ligament
b. patellofemoral joint - This technique allows for visualization of the relationship between the patella and the femur as the knee is increasingly flexed. - The patellofemoral congruence, or the position of the patella within the patellar surface of the femur, may be measured at each point of flexion. - Any medial or lateral displacement of the patella may indicate an abnormality of the patellofemoral joint.
The rate at which a quantity of x-radiation emitted from a CT tube passes through a unit area over a unit of time is called the: a. effective mAs b. photon flux c. constant mAs d. photon fluence
b. photon flux - The rate at which a quantity of radiation (photon fluence) passes through a unit area over unit time is termed the photon flux. - It may also be referred to as the fluence rate.
Pixels representing tissues with average attenuation coefficients greater than that of water have which of the following types of values? a. extremely small b. positive c. negative d. low contrast
b. positive - When calculated by a formula comparing the attenuation coefficient of tissue with that of water, materials whose coefficients are greater than that of water are assigned positive CT numbers.
Which of the following is NOT a component of the "triple rule-out" MDCT protocol for patients complaining of chest pain? a. CTA of the pulmonary arteries b. prone HRCT of the lungs c. CTA of the aorta d. coronary CTA
b. prone HRCT of the lungs - The"triple rule-out" MDCT procedure is a comprehensive evaluation of the chest for cardiac and noncardiac pain. - The single acquisition consists of a coronary CTA for coronary artery disease, a CTA of the aorta for aneurysm, and a CTA of the pulmonary arteries for embolism.
Number 2 on the figure corresponds to which of the following? a. aortic arch b. pulmonary trunk c. superior vena cava d. left anterior descending artery
b. pulmonary trunk
The process of using raw data to create a new image after the initial image has been generated is typically referred to as? (CT) a. prospective reconstruction. b. reformatting. c. retrospective reconstruction. d. step-and-shoot scanning.
b. retrospective reconstruction. - Prospective reconstruction is that which occurs automatically with scanning. - Reformatting includes only image data. - Step-and-shoot scanning is also called axial scanning and refers to a nonhelical scan process in which the table movement is stopped during each scan acquisition.
Number 1 on the figure corresponds to which of the following? a. right brachiocephalic artery b. right pulmonary artery c. right pericardiacophrenic artery d. right subclavian artery
b. right pulmonary artery
A CT examination of the lumbar spine reveals a herniated disc at the level of L2-L3. Which of the following reformation planes would best demonstrate posterior compression of the disc material onto the spinal cord? a. coronal b. sagittal c. axial d. oblique
b. sagittal - A sagittally reformatted image would demonstrate the relationship of the disc material as it protrudes posteriorly into the spinal cord.
Complex fractures of the wrist are most common in which of the following carpal bones? a. hamate b. scaphoid c. capitate d. triquetrum
b. scaphoid - The wrist's scaphoid bone (navicular) is a common location for complex fracture.
Which of the following is NOT commonly used as a CT scintillation detector material? a. ceramic rare earth b. silver halide c. bismuth germanate d. cadmium tungstate
b. silver halide - CT does not employ silver halide crystal as a detector material.
Which of the following is NOT commonly used asa CT scintillation detector material? (CT) a. ceramic rare earth b. silver halide c. bismuth germanate d. cadmium tungstate
b. silver halide - CT does not employ silver halide crystal as a detector material.
Number 4 on the figure corresponds to which of the following? a. descending colon b. spleen c. adrenal gland d. renal vein
b. spleen
Diffuse fatty infiltration of the hepatic parenchyma may be referred to as: a. chromatosis b. steatosis c. cirrhosis d. lipomatosis
b. steatosis - Fatty liver disease, or hepatic steatosis, is a condition in which large quantities of fats (lipids) are retained within the liver. - Whereas normal liver parenchyma exhibits attenuation values approximately 10 HU higher than those of the spleen, the liver with steatosis has attenuation values at least 10 HU below those of the spleen.
Number 5 on the figure corresponds to which of the following? a. transverse colon b. stomach c. duodenum d. hepatic flexure
b. stomach
Which of the following is the common term for the artifact present on the image in the figure? a. aliasing b. streaking c. edge gradient d. tube arcing
b. streaking - The presence of metal within the patient causes a streak artifact on the image. - The artifact occurs when the dense metal absorbs a large amount of the radiation, interfering with the signal produced.
Which of the following is the common term for the artifact present on the image in the figure? a. aliasing b. streaking c. edge gradient d. tube arcing
b. streaking - The presence of metal within the patient causes a streak artifact on the image. - The artifact occurs when the dense metal absorbs a large amount of the radiation, interfering with the signal produced.
Number 6 in the figure corresponds to which of the following? a. superior mesenteric vein b. superior mesenteric artery c. gastric artery d. right renal vein
b. superior mesenteric artery ! Looks like a circle as apposed to the portal vein which is ob longed and transverse
Number 5 on the figure corresponds to which of the following? a. optic nerve b. superior ophthalmic vein c. oculomotor nerve d. superior oblique muscle
b. superior ophthalmic vein
During CT examination of the chest, the administration of a saline flush following the bolus injection of iodinated IV contrast media helps alleviate artifact from dense contrast in the: a. ascending aorta b. superior vena cava c. descending aorta d. inferior vena cava
b. superior vena cava - The use of a saline flush reduces artifact from dense contrast in the superior vena cava. - The streaking artifact can hamper visualization of the upper mediastinum and surrounding lung tissue.
During contrast-enhanced CT examinations of the chest, streaking artifact may obscure portions of the superior mediastinum because of dense concentrations of iodine in the: a. descending aorta b. superior vena cava c. ascending aorta d. pulmonary arteries
b. superior vena cava - There is often significant artifact within the mediastinum from high concentrations of iodine in the superior vena cava. - This artifact may be alleviated by administering a bolus of a contrast agent with reduced iodine concentration, which is achieved by diluting a full-strength contrast agent with saline.
When one is viewing a multiplanar reformation (MPR) image, each pixel represents: a. the maximum attentuation occurring within the voxel b. the average attenuation occurring within the voxel c. the minimum attenuation occurring within the voxel d. all attenuation occurring within the voxel above a set threshold value
b. the average attenuation occurring within the voxel - A standard MPR image is 1 voxel thick, with the pixels facing the viewer each representing the average attenuation occurring within the represented voxels.
What control does the operator have over the x-rays in a CT exam? a. the temperature and color of the x-rays can be tuned b. the energy level and the quantity of x-rays can be selected c. the volume and tone of the x-rays can be dialed d. the phase and frequency of the x-ray can be adjusted
b. the energy level and the quantity of x-rays can be selected
Effective dose is a relative radiation dose measurement term that accounts for the: a. beam pitch b. tissue radiosensitivity c. detector pitch d. collimation
b. tissue radiosensitivity - Effective dose accounts for the type of tissue that the radiation is deposited in. - Different tissues are assigned weighting factors on the basis of their individual radio sensitivities.
Number 5 on the figure corresponds to which of the following? a. right common iliac vein b. ureter c. right common iliac vein d. inferior mesenteric vein
b. ureter
Non-contrast CT of the urinary tract is a valuable tool in the investigation of: a. transitional cell carcinoma (TCC) b. urinary tract lithiasis c. renal artery stenosis d. ureteral duplication
b. urinary tract lithiasis - Lithiasisrefers to the presence of stones. Unenhanced helical CT of the urinary tract has become the standard for the investigation of urinary tract lithiasis.
The accumulation of gas within a degenerating intervertebral disc is called the: a. aeration effect b. vacuum phenomenon c. oxygen saturation point d. carbonization sign
b. vacuum phenomenon - Small amounts of gas may appear in the areas of degen-eratedintervertebral discs. - The accumulation of gases such as nitrogen occurs as a by-product of the physical breakdown of the disc material.
Which of the following is the most common sign of GI pathology on CT images? a. fluid collection b. wall thickening c. air distention d. dense fecal matter
b. wall thickening - The most important identifying sign of GI pathology on CT examination is wall thickening. - The ability to evaluate the gastric and bowel walls is a crucial component of the successful CT evaluation of the GI system. - Distention and opacification with oral media, coupled with contrast enhancement through IV administration, offer the best demonstration of the GI wall.
An average CT number value for bone is: a. +100 HU b. +500 HU c. +1000 HU d. +3000 HU
c. +1000 HU - An average CT number value for bone is approximately +1000 HU. - This may vary widely with the density of the particular bone in question and with the beam quality of the CT scanner.
An average CT number value for blood is: a. -20 HU b. +10 HU c. +45 HU d. +100 HU
c. +45 HU - An average range of CT numbers for blood is +42 to +58. - The CT number of any material is based on many factors, including the beam quality of a particular scanner.
The image in the figure was most likely displayed in a window with a level of: a. -150 b. 0 c. +50 d. +400
c. +50 - The level chosen for a given window setting should correspond to the average density value of the tissue(s) of interest. - Areas of soft tissue, such as the brain, are often displayed at window levels of approximately +50 HU. ! Add Image
The material within the ROI measurement in the figure has a linear attenuation coefficient of: a. 0.0007 b. 0.185 c. 0.206 d. 0.530
c. 0.206 - At the range of photon energies employed during most CT examinations, water exhibits an approximate attenuation coefficient value of 0.206.
Which of the following sets of values would be considered normal levels for creatinine and BUN, respectively? a. 3.1 mg/dL; 1.2 mg/dL b. 1.2 mg/dL; 14 mg/dL c. 0.7 mg/dL; 39 mg/dL d. 5.2 mg/dL; 12 mg/dL
c. 0.7 mg/dL; 39 mg/dL - The normal range for creatinine level is 0.5 to 1.5 mg/dL. - The normal range for BUN levels is 7 to 25 mg/dL. - Creatinine and BUN are laboratory measurements that may be used to evaluate the renal function of a patient scheduled to undergo a CT examination that involves intravenous administration of an iodinated contrast agent. ! C= 0.5 to 1.5, B= 7 to 25
Which number on the figure corresponds to the superior mesenteric vein? a. 3 b. 5 c. 1 d. 2
c. 1
The mediastinum includes which of the following anatomic structures? 1. superior vena cava 2. stomach 3. ascending aorta a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
c. 1 and 3 only - The mediastinum is a potential space located between the two lungs. - It contains the heart, great blood vessels,thymus, and portions of the trachea and esophagus.
Which of the following angio catheter sizes may be safely used for the automated power injection of iodinated contrast agents at flow rates higher than 3 mL/sec? 1. 18-gauge 2. 20-gauge 3. 22-gauge a. 1 only b. 3 only c. 1 and 2 only d. 1, 2, and 3
c. 1 and 2 only - 22-gauge angio catheters are sufficient for flow rates up to 3 mL/sec. - 20-gauge or larger angio catheters should be utilized whenever flow rates exceed 3 mL/sec.
Which of the following may be considered one of the high-osmolar contrast media (HOCM)? 1. iothalamate meglumine 2. diatrizoate sodium 3. iohexol a. 1 only b. 3 only c. 1 and 2 only d. 1, 2, and 3
c. 1 and 2 only - High-osmolar contrast media (HOCM) are ionic agents that dissociate into charged particles (ions) in solution.Ionic contrast media are salts consisting of sodium and/or meglumine. - Iothalamate meglumine and diatrizoate sodium are commonly known by the brand names Conray and HYPAQUE, respectively.
Risk factors for contrast-induced nephrotoxicity (CIN) include: 1. diabetes 2. advanced age 3. hematuria a. 1 only b. 3 only c. 1 and 2 only d. 1, 2, and 3
c. 1 and 2 only - Risk factors for contrast-induced nephrotoxicity (CIN) include pre-existing compromise of renal function, dehydration, diabetes, myeloma, advanced age, and cardio vascular disease.
Which of the following may be included as part of a routine preparation for a general contrast-enhanced CT examination of the abdomen and pelvis? 1. instructing the patient to take nothing by mouth (NPO) for 4 hours prior to exam 2. 1200 mL of oral contrast agent administered 90 minutes prior to exam 3. having the patient drink 4 liters of polyethylene glycol (PEG) 24 hours prior to exam a. 1 only b. 2 only c. 1 and 2 only d. 1 and 3 only
c. 1 and 2 only - Routine preparations for general studies of the abdomen and pelvis include the administration of an oral contrast agent for opacification of the GI tract. - Patients are typically instructed to refrain from eating or drinking anything else for up to 6 hours prior to the exam. ! Polyethylene glycol (PEG) is used for bowel cleansing prior to a colonoscopy and may have certain applications for CT preparation limited to CT colonography.
Which of the following pharmaceuticals may be administered prior to a cardiac CT procedure in an effort to improve visualization of the coronary vessels? 1. b-blocker 2. nitroglycerin 3. metformin a. 1 only b. 2 only c. 1 and 2 only d. 1, 2, and 3
c. 1 and 2 only b-Adrenergic receptor blocking agents (b-blockers) maybe used to reduce a patient's heart rate, and sublingual nitroglycerin may be administered to cause dilation of the coronary vessels. - The use of these pharmaceuticals may improve the overall visualization of the coronary vessels during a cardiac CT examination. - Please consult the physician and/or department protocol for further information regarding pharmaceutical administration for cardiac CT procedures.
Proper immobilization during a CT procedure may involve the use of: 1. soft, hook-and-loop (e.g., Velcro) immobilization straps 2. adhesive medical tape 3. good patient communication a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
c. 1 and 3 only - CT manufacturers routinely supply comfortable, non adhesive straps and cushions to help maintain motion-free patient positioning. - Adhesive tape should not be routinely used because of the abrasive effects of tape removal. - Good patient communication is a key immobilization technique. - Proper instructions for remaining still, suspending respiration, not swallowing, and soon, help ensure patient cooperation and yield higher-quality CT examinations.
Collimation of the CT x-ray beam occurs: 1. at the x-ray tube, regulating slice thickness 2. just beyond the patient, focusing off-axis transmitted radiation 3. before the detectors, limiting the amount of scatter radiation absorbed a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
c. 1 and 3 only - Collimation of the x-ray beam in CT is accomplished by both pre-patient and pre-detector collimators, or detectors. - The pre-patient detectors restrict the field size, directly influencing the reconstructed section thickness. - The pre-detector or post-patient detectors absorb scatter radiation before it contributes to the signal produced by the detector array. ! X-Ray Tube, Pre Detector
Which of the following medications may be administered to a patient who is having a severe anaphylactoid reaction to iodinated contrast material? 1. epinephrine 2. atropine 3. diphenhydramine a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
c. 1 and 3 only - Epinephrine (Adrenalin) is an adrenergic drug used as a bronchodilator. - Diphenhydramine (Benadryl) may be used to block the physiologic effects of the body's release of histamine, thus reducing the allergic effect of the contrast material. - Atropine should be used only to combat bradycardia during a vagal reaction to contrast material.
The choice between ionic and non-ionic contrast media should be based on: 1. the allergic history of the patient 2. the cost of the contrast material 3. the age and physical condition of the patient a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
c. 1 and 3 only - Patients may be assigned to a higher-risk group for an adverse reaction to iodinated contrast material on the basis of several factors, including previous allergic history and physical condition. - Patients considered to beat high risk for adverse reactions should be administered non-ionic contrast material. - Iso osmolar contrast mate-rial is an alternative choice that may also reduce the risk of adverse reactions.
During a spiral or helical CT examination, the scanner acquires data: 1. continuously as the patient travels through the gantry 2. one section at a time 3. in the form of a complete volumetric data set a. 1 only b. 2 only c. 1 and 3 only d. 2 and 3 only
c. 1 and 3 only - Spiral/helical CT examinations are obtained with the scanner continuously acquiring data as the patient travels through the gantry. - The data acquired are volumetric, containing all of the attenuation information for a given area of anatomy.
Vascular components of the brain's blood supply known as the circle of Willis include the: 1. internal carotid arteries 2. basilar artery 3. anterior communicating artery a. 2 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
c. 1 and 3 only - The circle of Willis is composed of the anterior cerebral, anterior communicating, internal carotid, posterior cerebral, and posterior communicating arteries. - The basilar artery is an important vessel supplying blood to the brain, but it is not part of the circle of Willis
Which of the following laboratory measurements can be used to evaluate the renal function of a patient? 1. BUN 2. PTT 3. creatinine a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
c. 1 and 3 only - The laboratory measurements BUN (blood urea nitrogen) and serum creatinine (a component of urine) can be used to indicate the status of a patient's renal function.
The injection rate of an automatic injector is set at 1.5 mL/sec. What is the injection time for a contrast agent volume of 150 mL? a. 60 seconds b. 90 seconds c. 100 seconds d. 120 seconds
c. 100 seconds - The total injection time may be calculated by dividing the contrast agent volume by the flow rate. - In this example, the flow rate is 1.5 mL/sec, for a total of 150 mL. - The time required for this injection would be 100 seconds.
An adequate volume of intravenous contrast agent for the SSCT examination of the neck in this figure would be: a. 25 mL b. 50 mL c. 125 mL d. 225 mL
c. 125 mL - A total contrast agent volume between 100 and 150 mL is sufficient for imaging the neck. - The precise volume and administration technique vary from one institution to another.
The limiting resolution of the bone algorithm in the figure is: a. 6.1 lp/cm b. 9.5 lp/cm c. 14.6 lp/cm d. 15.5 lp/cm
c. 14.6 lp/cm - The limiting resolution of a particular CT scan is deter-mined at a point on the graph where the signal frequency corresponding to a particular object has reached 10% (MTF = 0.1).
A first-generation CT scanner consists of an x-ray tube and two detectors that translate across the patient's head while rotating in 1-degree increments for a total of: a. 45 degrees b. 90 degrees c. 180 degrees d. 360 degrees
c. 180 degrees - First-generation CT scanners were based on a translate-rotate principle. - The x-ray tube and detectors would translate across the patient's head and then rotate 1 degree. - This process would repeat in a semicircular fashion, for 180 degrees around the patient's head. ! Translate Rotate
Which number on the figure corresponds to the zygomatic bone? a. 3 b. 1 c. 2 d. 6
c. 2
In a single-slice CT (SSCT) system, which of the following technical parameters may be adjusted retrospectively? 1. section width 2. section increment 3. reconstruction algorithm a. 2 only b. 1 and 2 only c. 2 and 3 only d. 1, 2, and 3
c. 2 and 3 only - Single-slice helical geometry allows for volumetric data acquisition. - The reconstruction of CT sections at any point along the scanned volume is possible. - The section width must be the same, however, and is controlled by the collimation (slice thickness) chosen prior to data acquisition. - The advancement of multislice CT (MSCT)allows for retrospective reconstruction of sections at varying thicknesses.
Which of the following is considered an analytic form of image reconstruction? 1. iterative technique 2. Fourier reconstruction 3. filtered back-projection a. 1 only b. 1 and 2 only c. 2 and 3 only d. 1, 2, and 3
c. 2 and 3 only - The analytic methods of CT image reconstruction include the filtered back-projection and the Fourier transform method. - These techniques are called analytic because they utilize precise formulas for image reconstruction.
Vital components of a CT urogram (CT-IVP) protocol include: 1. administration of 1200 to 1500 mL of a positive oral contrast agent 90 minutes prior to examination 2. thin-section excretory phase imaging of the entire urinary tract 3. volume-rendered 3D and maximum intensity projection (MIP) imaging of the urinary tract a. 2 only b. 1 and 2 only c. 2 and 3 only d. 1, 2, and 3
c. 2 and 3 only - Water is the preferred oral contrast material for CT urograms, because its use avoids the interference seen with denser materials when one is producing volume-rendered and MIP images. - Additional protocol considerations include pre-contrast acquisition of the urinary tract and post-contrast nephrographic phase imaging. - Excretory phase imaging occurs after a delay of 5 to 15 minutes and may be aided by the IV drip administration of approximately 250 mL of normal (0.9%) saline to improve urinary tract opacification.
A common formula used to calculate the maximum dosage of intravenous iodinated contrast material used in any CT examination is: a. 5 mg per kg of body weight b. 5 mL per lb of body weight c. 2 mL per kg of body weight d. 1 mL per lb of body weight
c. 2 mL per kg of body weight - Dosage calculations for intravenous contrast agent administration should adhere to the general guiding principle of injecting the smallest quantity of contrast agent possible to meet the technical requirements of the examination. - The maximum dose for any procedure should not exceed 2 mL per kg of body weight. ! Should not exceed 2 ml per kg
For routine CT of the chest, abdomen, or pelvis, the range of suggested IV contrast flow rates is a. 0.2 mL/s to 0.5 mL/s. b. 1.0 mL/s to 2.0 mL/s. c. 2.0 mL/s to 4.0 mL/s. d. 6 mL/s to 12 mL/s.
c. 2.0 mL/s to 4.0 mL/s.
Which of the following sets of section width and spacing would be most suitable for a general survey CT of the neck? a. 0.75 mm thick every 0.75 mm b. 3 mm thick every 5 mm c. 3 mm thick every 3 mm d. 10 mm thick every 10 mm
c. 3 mm thick every 3 mm - A contiguous study with section widths ranging from 3 to 6 mm is sufficient for a general survey CT study of the neck.
Which of the following does NOT affect the quantity of x-rays that completely penetrates the patient? 1. the distance that the x-ray photons must travel on their course throught the patient's body 2. the molecular composition of the tissues through which the x-ray photons pass 3. the type of detector material used a. 1 only b. 2 only c. 3 only d. 1, 2 and 3
c. 3 only
Which of the following acquisitions may be characterized as contiguous? a. 2.5-mm sections reconstructed every 1.25 mm b. 5.0-mm sections reconstructed every 7.5 mm c. 3.75-mm sections reconstructed every 3.75 mm d. 20-second cine acquisition with 1.25-mm sections
c. 3.75-mm sections reconstructed every 3.75 mm - Contiguous images are those acquired with equal section thickness and interval. - For example, 3.75-mm sections reconstructed every 3.75 mm completely cover a given volume of tissue with no unmeasured tissue.
Which number on the figure corresponds to the septum pellucidum? a. 2 b. 3 c. 4 d. 5
c. 4
Which number on the figure corresponds to the left common carotid artery? a. 1 b. 6 c. 4 d. 3
c. 4
At what percentage of overlap should CT sections be reconstructed to improve the quality of multiplanar reformation (MPR) images? a. 10% b. 25% c. 50% d. 100%
c. 50% - It is widely recommended that volumetrically acquired CT sections be reconstructed with the use of at least a 50% overlap to improve the quality of 3D and MPR images.
On an ECG of the complete cardiac cycle, at which portion of the R-R interval is the heart muscle in diastole? a. 10%-20% b. 35%-50% c. 55%-75% d. 85%-95%
c. 55%-75% - The least heart motion occurs at approximately 55% to 75% f the R-R interval, typically corresponding to the point of mid-diastole.
An acquisition is made on a 64-slice MSCT system in which each detector element has a z-axis dimension of 0.625 mm. With a selected beam width of 40 mm and the beam pitch set at 1.50, how much will the table move with each rotation of the gantry? a. 20 mm b. 40 mm c. 60 mm d. 80 mm
c. 60 mm - The beam pitch for a given acquisition is equal to the table feed per rotation divided by the total collimation. - The total collimation for this acquisition is equal to the total number of sections (detectors) multiplied by the detector dimension, or 64x0.625 mm. - The table feed per rotation can be calculated as the product of the total collimation and the beam pitch, or 40 mmx1.5, and equals 60 mm for the example provided. 64x0.625 = 40 40x1.5 = 60mm
After initiation of rapid bolus administration of an iodinated contrast agent, the portal venous phase of hepatic contrast enhancement occurs at approximately: a. 15-20 seconds b. 25-35 seconds c. 60-70 seconds d. 120-180 seconds
c. 60-70 seconds - The portal (or hepatic) venous phase is the period of peak hepatic parenchymal enhancement, when contrast material redistributes from the blood into the extravascular spaces. - It occurs at approximately 60 to 70 seconds after the initiation of rapid bolus contrast agent administration.
The normal range of glomerular filtration rate (GFR) for men is: a. 50 +- 14 mL/min/m2 b. 60 +- 10 mL/min/m2 c. 70 +- 14 mL/min/m2 d. 80 +- 10 mL/min/m2
c. 70 +- 14 mL/min/m2 - Normal range of GFR is: 70 +- 14mL/min/m^2 for men 60 +- 10 mL/min/m^2 for women.
After initiation of rapid bolus administration of an iodinated contrast agent, the nephrographic phase of renal contrast enhancement occurs at approximately: a. 20-25 seconds b. 30-40 seconds c. 70-90 seconds d. 3-5 minutes
c. 70-90 seconds - The nephrographic phase occurs between 70 and 90 seconds after the start of injection. - Enhancement of the renal cortex and medulla reaches equilibrium, providing optimal sensitivity for parenchymal lesions.
Fresh blood in the brain, as in the case of a recentonset subdural hematoma, will measure approximately a. −80HU. b. 20HU. c. 70HU. d. 150HU.
c. 70HU. - The appearance of an intracranial hemorrhage (ICH) will change with the passage of time, as red blood cells begin to deteriorate outside the vasculature. - As a general rule ICH will appear hyperdense to normal brain tissue for approximately 3 days, after which it will gradually decrease in density.
To scan in the nephrographic phase of contrast enhancement, scans should be acquired approximately ____ after a bolus contrast injection. a. 15 to 25 seconds b. 30 to 70 seconds c. 80 to 130 seconds d. 3 to 15 minutes
c. 80 to 130 seconds - The nephrogram phase occurs when the contrast media reaches the kidneys.
What type of filter accentuates the difference between neighboring pixels to enhance spatial resolution? (CT) a. A bow-tie filter b. A smoothing algorithm c. A bone algorithm d. A soft-tissue algorithm
c. A bone algorithm - This type of filtering is applied to scan data before back projection occurs. - Many different filters are available that use different algorithms depending on which part of the data must be enhanced or suppressed. - Bone (or high-contrast algorithms) accentuate the difference between neighboring pixels to optimize spatial resolution, but must make sacrifices in low-contrast resolution. - These filters are most often used when there are great extremes of tissue density and when optimal low- contrast resolution is not necessary. ! Bone Algorithm aka High Contrast
In scanning the abdomen, what can be done if the patient is unable to take fluids by mouth? a. The volume of intravenous contrast material is increased by 25% to compensate for the lack of oral contrast medium. b. 600mL of dilute water-soluble agent is administered by enema. c. A nasogastric tube may be inserted for the administration of an oral contrast agent. d. A small volume of dilute water-soluble contrast agent can be administered by an inhaler.
c. A nasogastric tube may be inserted for the administration of an oral contrast agent.
Refer to Figure 24-15. Name the structure indicated by arrow #2. a. Talus b. Cuneiform (lateral or 1st) c. Cuboid bone d. Metatarsal bone
c. Cuboid bone
Which system component coverts the projection attenuation data into the proper digital form for the array processor? a. detector b. photodiode c. analog-to-digital converter d. host computer
c. analog-to-digital converter
In patients with suspected PE, CT venography is sometimes performed to assess for venous thrombosis within the pelvis and lower extremities. How is this accomplished? a. A single helical scan is obtained in the cranial-to-caudal direction extending from the lung apices to the knees while contrast is in the bolus phase (20 to 30 seconds after IV contrast injection). b. A second scan series is obtained in the nonequilibrium phase (approximately 45 seconds after IV contrast injec- tion) from the iliac crest through the knees. c. A second scan series is obtained in a delayed venous phase (approximately 180 seconds after IV contrast injection) from the iliac crest through the knees. d. A second scan series is obtained after most of the con- trast has washed out of the venous structures (8 to 12 minutes after IV contrast injection) from the iliac crest through the knees.
c. A second scan series is obtained in a delayed venous phase (approximately 180 seconds after IV contrast injection) from the iliac crest through the knees. ! venous thrombosis within the pelvis and lower extremities = 180 sec
When an operator reduces the scan field of view for a particular body part, which of the following technical changes occurs? a. The displayed image appears larger. b. Spatial resolution increases. c. A smaller number of detectors are activated. d. The displayed image appears smaller.
c. A smaller number of detectors are activated. - The SFOV size is determined by the number of detectors activated along the in-plane (x-, y-) axes during data acquisition.
The volume and density of calcium measured in the coronary arteries on MDCT examination are quantified with use of a value called the: a. Euler constant b. Hounsfield number c. Agatston score d. Lambert-Beer value
c. Agatston score - The Agatston scoring system quantifies the volume and density of calcium within the coronary arteries.
Refer to Figure 24-10. Name the structure indicated by RAD arrow #1. a. Portal vein b. Inferior vena cava c. Aorta d. Left renal artery
c. Aorta
Which of the following CT studies of the head is typically performed without a contrast agent? a. CT angiogram for circle of Willis b. coronal scan to rule out (R/O) pituitary tumor c. CT of brain to R/O subdural hematoma d. CT of brain to R/O metastatic disease
c. CT of brain to R/O subdural hematoma - Because of their increase in CT number, subdural hematomas may be well visualized without the IV administration of an iodinated contrast agent.
The dosimetry index used to approximate the radiation dose for CT sections acquired during a helical scan is called the: a. CTDIW b. effective dose c. CTDIvol d. equivalent dose
c. CTDIvol - CTDI vol is used to approximate the dose from a helical scan. It corresponds to the axially acquired CTDIw divided by the helical pitch. - Whereas CTDIw approximates dose along the x- and y-axes of the acquired CT image, CTDIvol also includes dose along the z-axis of the scan acquisition. - As pitch increases, the dose per section, or CTDIvol, decreases.
Refer to Figure 24-8. Name the structure indicated by arrow #4. a. Tympanicsinus b. Internal jugular vein c. Cochlea d. Facial nerve
c. Cochlea
What two factors control the slice thickness of an MDCT scanner? (CT) a. Gantry rotation time and mAs setting b. Table speed and kVp setting c. Collimation of the x-ray beam and width of the detectors in the z axis d. Reconstruction algorithm and detector material
c. Collimation of the x-ray beam and width of the detectors in the z axis - MDCT systems modify many of the rules established with SDCT. MDCT contains multiple parallel rows of detector elements that can be combined in various ways to yield slices with different section thicknesses. - In SDCT slice thickness was controlled exclusively by the degree of physical collimation. -- But in MDCT slice thickness is also affected by the width of the detectors in the z axis.
Which is an example of an offline archiving device? (CT) a. Hard drive b. Optical jukebox c. Compact disks d. RAID
c. Compact disks - Offline storage refers to data that is kept in a location not immediately accessible and requires manual intervention to use. - Offline storage can be time consuming because it requires personnel to locate the appropriate disc, and then load it into the reader.
Which type of artifact is only present on images produced from MDCT systems? (CT) a. Edge gradient b. Aliasing c. Cone-beam d. Tube arcing
c. Cone-beam - As the number of detector channels increases, a wider collimation is required and the x-ray beam becomes cone-shaped, rather than fan-shaped. - This can result in cone-beam artifacts, which are more pronounced for the outer detector rows. - The larger the cone beam (i.e., more detector channels), the more pronounced the effect.
Which of the following parameters will produce near- isotropic voxels? (CT) a. DFOV = 12; slice thickness = 1 mm b. DFOV = 25; slice thickness = 5 mm c. DFOV = 35; slice thickness = 0.625 mm d. DFOV = 44; slice thickness = 2 mm
c. DFOV = 35; slice thickness = 0.625 mm - An isotropic voxel is a cube, measuring the same in the x, y, and z directions. - The pixel size is the xy size (because pixels are square). - The pixel size for the four choices are (a) 0.23, (b) 0.49, (c) 0.68, and (d) 0.86. \ - For the voxel to be near-isotropic, the pixel size must be close to that of the slice thickness (the z direction).
Refer to Figure 24-9. Name the structure indicated by arrow RAD #5. a. Bronchus intermedius b. Azygos vein c. Esophagus d. Right crus of diaphragm
c. Esophagus
A bolus injection of 125mL of an iodinated contrast media with a concentration of 320mg of iodine/mL is adminis- tered to a 150-pound patient, but because of an unexpected equipment malfunction scan data could not be acquired. The decision must be made as to whether the patient should be moved to a functioning scanner within the department and the contrast injection repeated. What information will be par- ticularly important for the radiologist making the decision? a. The amount of radiation the patient received from the failed attempt b. The patient's history of allergy to any food or medication c. Evidence of renal impairment or dehydration d. The brand of the contrast media being used
c. Evidence of renal impairment or dehydration - Most institutions set guidelines as to the upper limit of contrast media that can routinely be given (typically 64 grams of iodine). - However, the guidelines are typically quite cautious, and specific circumstances (such as equipment malfunction) may necessitate exceeding the limit. - A radiologist will determine whether the guidelines can safely be exceeded by considering individual factors, such as a patient's level of hydration and renal function. - Several studies have shown a direct correlation between the volume of contrast administered and the risk of contrast-induced nephropathy.
In scanning the brain, using which one of the following reference lines reduces the radiation exposure to the lens of the eye? a. Canthomeatalline b. Orbital meatal line c. Glabellomeatalline d. Infraorbital meatal line
c. Glabellomeatalline - The glabellomeatal line is the imaginary reference line that runs approximately 15° cephalad from the orbital meatal line. The glabella is the surface of the frontal bone lying between the eyebrows.
Refer to Figure 24-14. Name the structure indicated by arrow #5. a. Pericallosal arteries b. Thyroidgland c. Jugular vein c. Lingualartery
c. Jugular vein
Refer to Figure 24-7. Name the structure indicated by arrow #1. a. Corpus callosum b. Caudate nucleus c. Lateral ventricle d. External capsule
c. Lateral ventricle
What type of 3D display is depicted in Figure 24-2? (CT) a. Volumerendering b. Surfacerendering c. MIP d. MinIP
c. MIP - The MIP maximum-intensity projection examines each voxel along a line from the viewer's eye through the data set and selects only the voxel with the highest value for inclusion in the displayed image. - - This method tends to display bone and contrast-filled structures; lower-attenuation structures are not well visualized.
A CT image is displayed in a window with a level of +200 and a width of 1000. Which of the following statements is correct? a. Pixels with values between +200 HU and -1000 HU will appear white. b. Pixels with values greater than +200 HU will appear black. c. Pixels with values between -300 HU and +700 HU will be assigned shades of gray. d. Pixels with values between -1200 HU and +1200 HU will be assigned shades of gray.
c. Pixels with values between -300 HU and +700 HU will be assigned shades of gray. - The width of a window determines the range of pixel values that will be assigned a shade of gray around a given level. - In this example, all pixels within the range of -300 to +700 HU will be assigned shades of gray. - Pixels below -300 HU will appear black, and pixels above +700 HU will appear white. !This calculation is performed by dividing the width in half (1000/2 = 500) and subtracting and adding this value to the level (+200 HU + 500 = +700 HU) (+200 HU - 500 = -300 HU).
A CT image is displayed in a window with a levelof +200 and a width of 1000. Which of the fol-lowing statements is correct? a. Pixels with values between +200 HU and -1000 HU will appear white. b. Pixels with values greater than +200 HU will appear black. c. Pixels with values between -300 HU and +700HU will be assigned shades of gray. d. Pixels with values between -1200 HU and -1200 HU will be assigned shades of gray
c. Pixels with values between -300 HU and +700HU will be assigned shades of gray.
Refer to Figure 24-10. Name the structure indicated by arrow #6. a. Rectus abdominis muscle b. Diaphragm c. Psoasmuscle d. Erector spinae muscle
c. Psoasmuscle
Prospective ECG gating methods for imaging the heart use a signal, usually derived from the ____ of the patient's ECG, to trigger image acquisition. a. ST segment b. PR segment c. R wave d. T wave
c. R wave
What scan parameter determines how the raw data are filtered in the reconstruction process? (CT) a. Window width b. Window level c. Reconstruction algorithm d. kVp
c. Reconstruction algorithm - It is important to differentiate reconstruction algorithms from setting a window width and level. - Changing the window setting merely changes how the image is viewed. - Changing the reconstruction algorithm will change the way the raw data are manipulated to reconstruct the image.
Refer to Figure 24-9. Name the structure indicated by arrow #1. a. Leftatrium b. Aorticarch c. Right pulmonary artery d. Right brachiocephalic vein
c. Right pulmonary artery
How does object size and scan field diameter affect radiation dose to the patient? (CT) a. Scan field diameter has no effect; it is the display field diameter that has an impact on dose. b. Changing from a small scan field, such as that used for a head scan, to a large scan field, such as that used for a body scan, will have a negligible effect on the radiation dose. It could either reduce or increase the dose slightly, depending on the patient factors. c. Smaller objects, which are scanned with a small scan field, always absorb a much higher dose than do larger objects, which are scanned with a large scan field. d. Smaller objects, which are scanned with a small scan field, always absorb a much lower dose than do larger objects, which are scanned with a large scan field.
c. Smaller objects, which are scanned with a small scan field, always absorb a much higher dose than do larger objects, which are scanned with a large scan field. - Holding all technical factors constant, smaller objects always absorb a higher dose by a factor of at least two. - This effect is primarily attributed to the fact that total exposure is made up of both entrance radiation and exit radiation. - For smaller patients, the patient has less tissue to attenuate the beam, which results in a much more uniform dose distribution. - Conversely, for a larger patient the exit radiation is much less intense owing to its attenuation through more tissue.
Number 2 on the figure corresponds to which of the following? a. hepatic vein b. suprarenal lymph node c. adrenal gland d. common bile duct
c. adrenal gland
On the basis of the information provided on the graph in the figure, which of the following statements is true? a. The limiting resolution in section A is less than that in section B. b. The signal-to-noise ratio (SNR) of section A is greater than that of section B. c. The effective width of section B is greater than that of section A. d. Section B is isotropic in dimension.
c. The effective width of section B is greater than that of section A. - The section width (slice) for a volumetric acquisition maybe graphically displayed as a slice sensitivity profile (SSP). - The effective section width is defined as the full-width at half-maximum (FWHM) of the SSP. - The full-width at half-maximum is labeled in the figure as C. At this point of the graph, the section width of B is wider than that of A.
On the basis of the information provided on the graph in the figure, which of the following statements is true? (CT) a. The limiting resolution in section A is less than that in section B. b. The signal-to-noise ratio (SNR) of section A is greater than that of section B. c. The effective width of section B is greater than that of section A. d. Section B is isotropic in dimension.
c. The effective width of section B is greater than that of section A. - The section width (slice) for a volumetric acquisition may be graphically displayed as a slice sensitivity profile (SSP). - The effective section width is defined as the full-width at half-maximum (FWHM) of the SSP. - The full-width at half-maximum is labeled in the figure as C. - At this point of the graph, the section width of B is wider than that of A.
Which of the following window settings was used to display the image in the figure? a. WL -400, WW 1500 b. WL 0, WW 150 c. WL +50, WW 400 d. WL +275, WW 2500
c. WL +50, WW 400 - With the lung fields black, the bony structures white, and the mediastinum and muscles gray, the image in the figure is displayed in a soft tissue window.
Writable CD and DVD media are optical disks that may be described as? a. read-only b. lossy c. WORM d. lossless
c. WORM - Write-once, read-many (WORM) describes certain CD and DVD media capable of storing data only once. - The stored images can be read multiple times, but once recorded on, the media may not be reused. ! WORM = 1 Write only
Writable CD and DVD media are optical disks that may be described as: a. read-only b. lossy c. WORM d. lossless
c. WORM - Write-once, read-many (WORM)describes certain CD and DVD media capable of storing data only once. - The stored images can be read multiple times, but once recorded on, the media may not be reused.
Accurate demonstration of __________ would most likely require the intravenous injection of an iodinated contrast agent during a CT study of the chest. a. pneumonia b. asbestosis c. a dissecting aortic aneurysm d. a solitary pulmonary nodule
c. a dissecting aortic aneurysm - Intravenous administration of an iodinated contrastagent is vital to making an accurate diagnosis of a dissecting aortic aneurysm. - The contrast agent helps out-line the wall of the aorta and improves visualization of any division within it. - Because of differences in blood flow, CT numbers within the actual lumen of the aorta are different from those in the dissected portion.
The firm, outer portion of each intervertebral disc is called the: a. nucleus pulposus b. nucleus prepositus c. anulus fibrosus d. anulus stapedius
c. anulus fibrosus
Number 1 on the figure corresponds to which of the following? a. right atrium b. pulmonary trunk c. ascending aorta d. right ventricle
c. ascending aorta
The imaging plane that is parallel to the foot's plantar surface is called the: a. coronal plane b. sagittal plane c. axial plane d. oblique axial plane
c. axial plane - The axial plane is parallel to the foot's plantar surface. - The oblique axial plane is parallel to the metatarsals,approximately 20 to 30 degrees caudal from the direct axial plane.
The differences in Hounsfield value exhibited in the ROIs measured on this CT image of a water filled phantom are most likely due to the phenomenon referred to as: a. partial volume averaging b. noise c. beam hardening d. detector drift
c. beam hardening - Beam hardening occurs as low-energy x-ray photons are absorbed while the beam passes through the patient. - The average photon energy of the beam increases along the path and may result in a loss of system uniformity.
A CT angiogram of the neck is performed primarily for the evaluation of the: a. carotid veins b. jugular veins c. carotid arteries d. coronary arteries
c. carotid arteries - CTA of the neck is used primarily to evaluate the carotid arteries.
Prior to a CT colonography, the patient may undergo a process of bowel cleansing termed: a. purgation b. hydration c. catharsis d. fasting
c. catharsis - describesthe process of bowel cleansing that isrequired to improve the exam quality of CT colonography. - A combination of restricted diet and bowel cleansing with polyethylene glycol (PEG) or magnesium citrateis used to achieve catharsis.
The third ventricle of the brain communicates with the fourth ventricle through the: a. anterior commissure b. septum pellucidum c. cerebral aqueduct d. fornix
c. cerebral aqueduct - The third and fourth ventricles communicate through the cerebral aqueduct, which is commonly referred to as the aqueduct of Sylvius.
Number 2 corresponds to which of the following? a. carotid canal b. incus c. cochlea d. vestibule
c. cochlea
The most common indication for CT-guided percutaneous biopsy is the: a. identification of foreign bodies b. quantification of bone mineral density c. confirmation of a malignancy d. measurement of tissue perfusion
c. confirmation of a malignancy - The most common indication for CT-guided percutaneous biopsy is to confirm the malignancy of a mass.
The CT "window" controls the ____________ of the CT image as it appears to the viewer. a. density and detail b. spatial and contrast resolution c. contrast and brightness d. attenuation coefficient and Hounsfield value
c. contrast and brightness - The operator may control the contrast and brightness of the CT image by adjusting the "window" setting. - As a form of gray-scale mapping, the window determines the pixels assigned shades of gray on the basis of their CT numbers.
The use of flow-control mechanical pressure injectors are recommended for CT studies of the chest, abdomen, and pelvis because a. there is a reduced risk of extravasation of the contrast media into the soft tissues. b. side effects such as heat and nausea are reduced. c. contrast media dose and timing can be easily regulated and reproduced in subsequent studies. d. the risk of air embolus is eliminated.
c. contrast media dose and timing can be easily regulated and reproduced in subsequent studies. - The use of mechanical injection systems in CT produces the best results. - However, precautions must be taken to prevent contrast media extravasation and care must be taken in the preparation and connection of the injector and cannula to avoid the risk of large air emboli.
The potentially serious decline in renal function following the IV administration of contrast material is called: a. anaphylaxis b. bronchospasm c. contrast-induced nephrotoxicity (CIN) d. urticaria
c. contrast-induced nephrotoxicity (CIN) - Contrast-induced nephrotoxicity (CIN) is a potentially serious delayed effect of contrast agent administration. - It is a considerable decline in renal function that canoccur after a patient receives an IV contrast agent. - CIN is typically marked by an increase in serum creatinine concentration in comparison with a baseline measurement obtained prior to contrast agent administration.
Reduction of the type of artifact seen in the figure on a coronal MDCT view of the sinuses may be accomplished through: a. an increase in the mA b. a decrease in the kVp c. coronal MPR images built from an axial acquisition d. a reduction in the scan field of view (SFOV)
c. coronal MPR images built from an axial acquisition - An isotropic axial acquisition of the paranasal sinuses from the hard palate superiorly through the frontal sinus avoids artifact from dental fillings while providing excellent multiplanar reformations (MPRs) in any plane. - Direct coronal acquisition may not be required because the detail provided by the reformatted images is usually sufficient.This technique also aids in reducing patient radiation dose.
Reduction of the type of artifact seen in the figure on a coronal MDCT view of the sinuses may be accomplished through? (CT) a. an increase in the mA b. a decrease in the kVp c. coronal MPR images built from an axial acquisition d. a reduction in the scan field of view (SFOV)
c. coronal MPR images built from an axial acquisition - An isotropic axial acquisition of the paranasal sinuses from the hard palate superiorly through the frontal sinus avoids artifact from dental fillings while providing excellent multiplanar reformations (MPRs) in any plane. - Direct coronal acquisition may not be required because the detail provided by the reformatted images is usually sufficient. This technique also aids in reducing patient radiation dose.
Image data can be used for? (CT) a. changing the display field size. b. changing the reconstruction algorithm. c. creating multiplanar reformations. d. creating overlapping slices from helical data.
c. creating multiplanar reformations. - Multiplanar reformation software stack up images, and then slice the stacked whole in a plane specified by the operator. - These can be created from image data, providing the images possess the same display field size, center, and gantry tilt and the slices are contiguous. - Changes to the display field size, the reconstruction algorithm, or the slice increment must be done using raw data.
Which of the following technical changes would serve to decrease patient radiation dose during a CT examination? a. increase in matrix size b. change from soft tissue to bone algorithm c. decrease of tube rotation from 360 to 180 degrees d. decrease in DFOV
c. decrease of tube rotation from 360 to 180 degrees - Many CT scanners allow the technologist to reduce the total rotation of the x-ray tube, thus reducing the scan time and subsequent patient radiation dose. - This type of partial scan, commonly referred to as a "half-scan"or segmenting, is most often used to improve the temporal resolution of the acquisition. ! Half Scan/Segmentation = Improves Temporal Resolution
Which of the following is not an advantage of an automatic power injector over the manual bolus method of intravenous contrast agent administration? a. uniform contrast enhancement throughout the exam b. consistent contrast agent administration for all patients c. decreased risk of contrast-induced nephrotoxicity (CIN) d. shorter injection times
c. decreased risk of contrast-induced nephrotoxicity (CIN) - The use of automatic injectors does not decrease the risk of CIN in comparison with the manual bolus technique. - Automatic injectors do offer shorter injection times, more consistent administration, and greater enhancement.
Which of the following artifacts is evident on the image in the figure? a. blooming b. aliasing c. edge gradient effect d. ring artifact
c. edge gradient effect - The edge gradient effect occurs when the CT x-ray beam passes through areas of abrupt changes in density that are represented by high spatial frequencies. - This type of streak artifact commonly occurs at the interface of dense bone and soft tissue in anatomic areas such as the brain.
The quantity of absorbed radiation dose based on the radiosensitivity of a particular tissue type is called: a. stochastic dose b. kerma c. effective dose d. CTDI
c. effective dose - Effective dose accounts for the type of tissue that the radiation is deposited in. - Different tissues are assigned weighting factors on the basis of their individual radio-sensitivities. - Effective dose approximates the relative risk from exposure to low doses of ionizing radiation. - The unit of measurement for effective dose is the sievert (Sv).
In the binary number system, a byte is a series of __________ bits of information. a. two b. four c. eight d. sixteen
c. eight - A byte is a series of eight bits. Bits and bytes are part of the binary language used by computers to process information.
Which of the following types of isolation techniques protects against infection transmitted through fecal material? a. acid-fast bacillus isolation b. contact isolation c. enteric precautions d. drainage-secretion precautions
c. enteric precautions - Enteric precautions attempt to protect from the spread of infection through direct or indirect contact with fecal matter. Gowns and gloves are common protective devices used for enteric precautions. The use of a surgical mask is not warranted.
Which of the following is used as the IV-administered radio pharmaceutical during a PET-CT fusion examination? a. technetium Tc 99m b. iodine I 131 c. fludeoxyglucose F 18 (FDG) d. strontium chloride Sr 89
c. fludeoxyglucose F 18 (FDG) - Positron emission tomography (PET) is a functional nuclear medicine study utilizing fluorodeoxyglucose F 18(FDG) as a radiopharmaceutical.
Number 4 on the figure corresponds to which of the following? a. third ventricle b. quadrigeminal cistern c. fourth ventricle d. sagittal sinus
c. fourth ventricle
A focused, thin-section axial CT acquisition through just the region of the vocal cords should extend: a. from the external auditory meatus inferiorly to the mandible b. from the hard palate inferiorly to the hyoid bone c. from just above the hyoid bone inferiorly through the cricoid cartilage d. from the cricoid cartilage inferiorly through sternoclavicular joint
c. from just above the hyoid bone inferiorly through the cricoid cartilage - Thin-section (0.5-2.0 mm) helical acquisition specific to the larynx should extend from just above the hyoid bone inferiorly through the cricoid cartilage.
The display function that creates a bar graph to show how frequently a range of CT numbers occurs within a specified ROI is called a a. gray scale. b. localizer image. c. histogram. d. beam attenuation chart.
c. histogram.
Urticaria is which of the following? a. severe nausea with associated vomiting b. urinary tract infection c. hives d. bronchospasm
c. hives - Urticaria is a common adverse reaction to iodinated intravenous contrast material. - Characterized by the presence of wheals or localized skin eruptions, it is commonly referred to as "hives."
Because of its inherent iodine concentration, the thyroid gland appears __________ on CT images. a. hypodense b. isodense c. hyperdense d. mottled
c. hyperdense - In comparison with the surrounding soft tissues, the thyroid gland is hyperdense on CT because it naturally contains iodine. - This density increases further with administration of an iodinated contrast agent.
Bowel obstruction due to loss of normal contractile motion in an area of intestine is termed: a. dyspepsia b. intussusception c. ileus d. adhesion
c. ileus - Ileus is used to describe an area of intestine that has lost normal contractile motion, resulting in obstruction.
If all other technical factors remain constant, which of the following would serve to decrease patient radiation dose during a helical SSCT examination? a. decreased scan field of view (SFOV) b. decreased filtration c. increased pitch d. increased matrix size
c. increased pitch - With an SSCT system, pitch equals the ratio of the table speed with the section thickness. - As the detector pitch is increased, the patient translates through the gantry at a greater rate relative to each rotation of the x-ray tube,resulting in the acquisition of a given volume of anatomy with fewer tube-detector rotations and shorter scan times. - Increases in pitch therefore allow for reduced patient radiation dose while covering the necessary anatomic area.
Often evaluated during body CTA examinations, the branches of the celiac axis are the: 1. left gastric artery 2. common hepatic artery 3. splenic artery a. 1 only b. 3 only c. 2 and 3 only d. 1, 2, and 3
d. 1, 2, and 3 - The branches of the celiac axis are the left gastric artery,common hepatic artery, and splenic artery.
The mathematical technique allowing the reconstruction of motion-free images from helically acquired CT data is called: a. convolution b. radon transformation c. interpolation d. Fourier reconstruction
c. interpolation - Interpolation is the mathematical process whereby data from tube rotations just above and just below a given slice position are used for image reconstruction. - Interpolation allows for the reconstruction of a thin, motion-free image from a volumetric data set acquired from a moving patient.
Which of the following is a non-ionic contrast material? a. iodamide b. iothalamate c. iohexol d. diatrizoate
c. iohexol Non-ionic contrast media include: - iopamidol (Isovue) - iohexol(Omnipaque) - iopromide (Ultravist).
Which of the following devices is used to measure the patient dose from a CT examination? a. Geiger counter b. proportional counter c. ionization chamber d. film badge
c. ionization chamber An ionization chamber is a device used to accurately measure radiation exposure. - Radiation causes ionization within the chamber, which is measured by an electrode. - The amount of charged particles is proportional to the radiation exposure. - The ionization chamber is an extremely accurate device that is used to quantify radiation exposure from a CT scan.
The still viable ischemic cerebral tissue that surrounds the infarct core in a patient with an acute stroke is termed the: a. thrombolytic zone b. hemorrhage focus c. ischemic penumbra d. stroke volume
c. ischemic penumbra - Penumbraisthe ischemic, yet still viable tissue immediately surrounding the infarct core. - It can be described as the region of ischemic brain parenchyma where cerebral blood volume (CBV) is compromised but still higher than 2.5 mL per 100 g of tissue.
Which of the following factors does not affect the dimensions of a voxel? a. slice thickness b. matrix size c. kernel d. display field of view
c. kernel - The dimensions of a voxel are determined by multiplying the pixel dimensions by the slice thickness. - The dimensions of a pixel are directly controlled by the matrix size and the field of view. ! Dimensions of a Voxel: Pixel Dimensions x ST ! Controlled by Matrix Size & Field of View
The retroperitoneum contains which of the following anatomic structures? a. spleen b. ovaries c. kidneys d. stomach
c. kidneys - The retroperitoneum is the space located between the peritoneum and the posterior abdominal wall. - It contains the duodenum, pancreas, adrenal glands, kidneys,ureters, and bladder.
Number 6 on the figure corresponds to which of the following? a. optic nerve b. medial rectus muscle c. lateral rectus muscle d. oculomotor nerve
c. lateral rectus muscle
Number 1 on the figure corresponds to which of the following? a. right brachiocephalic vein b. left subclavian artery c. left brachiocephalic vein d. brachiocephalic artery
c. left brachiocephalic vein
Number 4 on the figure corresponds to which of the following? a. left common iliac artery b. right common iliac artery c. left common iliac vein d. right common iliac artery
c. left common iliac vein
Number 2 on the figure corresponds to which of the following? a. left internal jugular vein b. left external carotid artery c. left internal carotid artery d. left external jugular vein
c. left internal carotid artery
It is imperative that all scans be completed before the equilibrium phase of contrast enhancement in studies of the a. brain. b. urinary tract. c. liver. d. postsurgical lumbar disk.
c. liver.
High-resolution computed tomography (HRCT) is most commonly used for the evaluation of the: a. pancreas b. brain c. lungs d. pelvis
c. lungs - High-resolution CT is a specialized technique using narrow section widths and a high-resolution algorithm for image reconstruction. - It is used to maximize detail of high spatial frequency tissue, such as the lungs and bony structures.
Which of the following technical factors has a direct effect on patient dose? a. matrix size b. algorithm c. mAs d. window level
c. mAs - With no consideration of image quality, reductions in mA and/or scan time (seconds) are direct methods of decreasing patient dose during a CT exam.
A CT image is formed in part by projecting back all of the attenuation values recorded during data acquisition onto a: a. pixel b. voxel c. matrix d. reformat
c. matrix - The back-projection method of image reconstruction involves the acquisition of attenuation values, which are then projected back onto a matrix for subsequent display.
Number 9 on the figure corresponds to which of the following? a. ethmoid sinus b. nasal concha c. maxillary sinus d. sphenoid sinu
c. maxillary sinus
Accurate demonstration of __________ would most likely require the intravenous injection of an iodinated contrast agent during a CT study of the chest. a. bronchiectasis b. pneumonia c. mediastinal lymphadenopathy d. pulmonary nodule
c. mediastinal lymphadenopathy
The thick, layered portion of the peritoneum responsible for attaching portions of the intestines to the bowel wall is called the: a. Gerota fascia b. falciform ligament c. mesentery d. ligamentum teres
c. mesentery - The mesentery is a double fold of the peritoneum that attaches the jejunum and ileum of the small bowel to the abdominal wall.
During which of the following IV contrast phases does the bladder wall enhance? a. early arterial b. corticomedullary c. nephrographic d. excretory
c. nephrographic - Nephrographic (70-90 sec) imaging provides enhancement of the bladder wall, which is used to evaluate the extent of tumor infiltration.
Complete cardiac diastole corresponds to which portion of the cardiac cycle on an electrocardiogram (ECG)? a. P wave b. QRS complex c. Alpha wave d. T wave
d. T wave - Complete cardiac diastole is the period of atrial and ventricular relaxation after heart contraction. - - The T wave of an ECG corresponds to cardiac diastole.
Bow-tie filters are employed in a CT x-ray system to reduce: a. image noise b. low spatial frequency signal c. patient radiation dose d. high spatial frequency signal
c. patient radiation dose - Bow-tie filters, which are thicker at the ends than in the middle, help shape the beam to reduce patient radiation exposure. - Because most body parts are circular or cylindrical,less radiation is necessary at the periphery than in the center. - Bow-tie filters reduce beam intensity toward the outer margins, resulting in a reduction in patient radiation dose.
The circle shown on the image in the figure is used to: a. magnify a portion of the image b. localize an area for percutaneous biopsy c. perform an ROI measurement d. produce an MPR image
c. perform an ROI measurement - Region of interest (ROI) measurements may be made by superimposing a cursor over an area and instructing the computer to average the CT numbers included within the region.
Which of the following 3D imaging techniques is utilized to provide "fly-through" images during CT colonography? a. orthographic volume rendering b. shaded surface display (SSD) c. perspective volume rendering d. minimum intensity projection (min-IP)
c. perspective volume rendering - Perspective volume rendering provides one a view point of being within the lumen of the object, similar to an endoscopic view. - Also referred to as immersive rendering, this type of 3D reconstruction is commonly used during CT colonography and CT bronchography.
Which of the following is a solid-state device used to record the light flashes given off by a scintillation crystal? a. photomultiplier tube b. anode c. photodiode d. input phosphor
c. photodiode - Scintillation crystals are used in cooperation with photodiodes in a scintillation-type CT detector. The photodiodeis a solid-state device that absorbs the light flashes given off by the crystal. - The photodiode then emits an electrical signal in response to this light.
Number 2 in the figure corresponds to which of the following? a. inferior vena cava b. common bile duct c. portal vein d. superior mesenteric vein
c. portal vein
The liver has a dual blood supply and receives 75% of its blood from the: a. hepatic artery b. superior mesenteric artery c. portal vein d. superior mesenteric vein
c. portal vein - The liver has a dual blood supply, receiving 75% of its supply from the portal vein and the remaining 25%from the hepatic artery.
Which of the following techniques may be employed to reduce patient radiation dose during a cardiac CT examination? a. retrospective ECG gating b. z-axis interpolation c. prospective ECG gating d. multisegment reconstruction
c. prospective ECG gating - During MSCT cardiac studies, prospective gating can be used to reduce patient radiation dose. - In this technique, ECG-triggered tube current modulation allows for pulses of x-ray energy to be used rather than continuous exposure. - Both retrospective ECG gating and multi segment reconstruction require constant radiation exposure throughout multiple heartbeats.
The areas of image quality degradation indicated by number 3 on the figure are an example of: a. aliasing artifact b. windmill artifact c. pulsation artifact d. beam-hardening artifact
c. pulsation artifact - Pulsation artifacts are unique to cardiac imaging and CTA procedures of the mediastinum. - They appear as a type of stair-step artifact and result from the diastolic heart motion occurring during relatively long exposure times. - Improving the temporal resolution of the scanand ECG gating are methods employed to reduce pulsation artifact.
The measurement of CT system performance through quality testing procedures and evaluation of the test results is referred to as: a. calibration b. uniformity c. quality assurance d. linearity
c. quality assurance - Quality assurance refers to the measurement of the scanner's performance through quality testing procedures and evaluation of the test results. - Quality control refers to the implementation of corrective actions to improve any identified performance inadequacies of the CT system found through quality assurance procedures.
A detector's dynamic range is? a. time that is required for the signal from the detector to return to zero b. number of photons absorbed by the detector. c. ratio of the maximum signal measured to the minimum signal the detector can measure. d. amount of afterglow exhibited.
c. ratio of the maximum signal measured to the minimum signal the detector can measure. - Choice (a) is the response time of the detector. - Choice (b) is the detector absorption efficiency. - Choice (d) refers to the brief, persistent flash of scintillation that occurred with older detector materials.
The prone position may be used for a post myelogram CT examination of the lumbar spine in an effort to: a. reduce the lordotic curve b. decrease patient gonadal radiation dose c. reduce metrizamide pooling d. increase the lordotic curve
c. reduce metrizamide pooling - The prone position during a post-myelogram CT study of the lumbar spine reduces pooling or layering of the intrathecal contrast material.
Automatic tube current modulation (ATCM) is employed by an MDCT system for the purpose of: a. z-axis interpolation b. improving 3D and MPR image quality c. reducing patient radiation dose d. freezing heart motion during cardiac CT
c. reducing patient radiation dose - ATCM is a form of automatic exposure control for a CT system. - It manages patient radiation dose on the basis of the size, density, and overall attenuation of the part being examined.
Number 6 on the figure corresponds to which of the following? a. renal cortex b. renal pelvis c. renal calyx d. renal pyramid
c. renal calyx
Following the intrathecal injection of an iodinated contrast agent for a post-myelography CT study of the lumbar spine, the patient should be instructed to: a. take a cleansing enema b. resume normal activity c. rest for 8-24 hours with the head slightly elevated d. rest for 8-24 hours in the Trendelenburg position
c. rest for 8-24 hours with the head slightly elevated - In an effort to reduce the possibility of headaches after a CT examination involving an intrathecal injection of contrast material, the patient should rest for 8 to 24 hours with the head slightly elevated (35-45 degrees).
Which of the following technical maneuvers may be used to remove unwanted pulsation artifacts from cardiac motion during a CTA of the chest for pulmonary embolism? a. automated bolus tracking b. automatic tube current modulation c. retrospective ECG gating d. saline flush
c. retrospective ECG gating - Electrocardiographic (ECG) gating can be utilized to eliminate pulsation artifacts due to cardiac motion during the study. - Retrospective gating involves scanning throughout the entire cardiac cycle. - Only data from specific user-determined portions of the ECG waveform are reconstructed into images.
The best method for targeting the sacrum in the figure for detailed examination would be to: a. magnify the image 2x b. re-scan the patient using a small SFOV c. retrospectively reconstruct the image using a small DFOV d. decrease the matrix dimension
c. retrospectively reconstruct the image using a small DFOV - Portions of the CT image may be enlarged on the display screen by either of two methods. - The image may be magnified to offer the viewer a closer, enlarged look at a specific area. - A CT image may also be "targeted" through a decrease in the display field of view (DFOV) size. - A targeted image places the area of interest over the entire display matrix, providing greater resolution and more detail than a magnified image.
Fourth-generation CT scanners use a __________ tube-detector configuration. a. rotate-translate b. electron beam-stationary c. rotate-stationary d. rotate-rotate
c. rotate-stationary - Fourth-generation CT scanners operate with a rotating x-ray tube and a stationary ring of detectors. - Some fourth-generation scanners also use a rotating x-ray tube with a nutating detector ring. ! 4th Gen = Rotate, Stationary
Which of the following best describes the type of image displayed in the figure? a. sagittal maximum intensity projection (MIP) b. direct sagittal acquisition c. sagittal multiplanar reformation (MPR) d. volume-rendered 3D
c. sagittal multiplanar reformation (MPR)
The part of the CT system referred to as the DAS Data-acquisition system is responsible for? (CT) a. converting the light emitted from the detector to an electric current. b. projecting the data from the attenuation profile onto a matrix. c. sampling each of the detector cells many times per second. d. converting digitized data to shades of gray to be displayed.
c. sampling each of the detector cells many times per second. - Choice (a) is the response time of the detector. - Choice (b) is the detector absorption efficiency. - Choice (d) refers to the brief, persistent flash of scintillation that occurred with older detector materials.
In an effort to reduce patient radiation dose, the technical factors of the applied CT protocol should be optimized on the basis of: a. age b. sex c. size or weight d. physical condition
c. size or weight - For all patients, regardless of age or sex indication, the CT protocol should be optimized according to size or weight.
The continuous gantry rotation required by helical CT acquisition is made possible by the application of: a. electromagnetic bushings b. titanium bearings c. slip-rings d. oil-cooled couplings
c. slip-rings - Eliminating the need for cables, slip-ring technology allows for continuous gantry rotation by utilizing a system of contact brushes that supply electricity to power the system, enabling the passage of transmission data to the computer system.
The most common site of organ injury due to blunt abdominal trauma is the: a. liver b. kidney c. spleen d. pancreas
c. spleen - The spleen is the most common site of organ injury due to blunt abdominal trauma. - Hematoma, hemorrhage, andlaceration are typical signs of traumatic splenic injury.
Pitch is a parameter that is commonly used in helical CT to describe? a. the number of detectors in the z axis. b. tube heat capacity. c. table speed. d. different types of interpolation methods.
c. table speed. - Pitch is most commonly defined as the travel distance of the CT scan table per 360° rotation of the x-ray tube, divided by the x-ray beam width. - In the case of MDCT, the beam width can be determined by multiplying the number of slices by slice thickness.
When one is viewing a minimum intensity projection (min-IP) image, each pixel represents: a. the maximum attentuation occurring within the voxel b. the average attenuation occurring within the voxel c. the minimum attenuation occurring within the voxel d. all attenuation occurring within the voxel above a set threshold value
c. the minimum attenuation occurring within the voxel - Min-IP images display the minimum pixel value along each ray to the viewer. - As the viewer faces a min-IP image, each pixel represents the minimum attenuation that occurs in the associated voxel. - Min-IP reformations are used primarily during the evaluation of the biliary tree, colon, lungs, and trachea.
The acronym CTDI is used to describe which of the following? a. a specialized CT imaging technique used to measure bone mineral density b. a quality control test that measures the accuracy of the laser lighting system c. the radiation dose to the patient during a CT scan d. a high-speed CT scanner used for cardiac imaging
c. the radiation dose to the patient during a CT scan - The CT dose index (CTDI) is used to quantify the radiation dose received by the patient during a CT scan. - It involves the use of an ionization chamber to accurately measure radiation exposure for a given set of technical factors.
MSCT systems typically employ which of the following detector geometries? a. first-generation b. second-generation c. third-generation d. fourth -generation
c. third-generation - All MSCT systems utilize third-generation geometry and solid-state scintillation detectors.
The information included during the 3D reconstruction of a CT scan is controlled by the: a. algorithm b. window setting c. threshold setting d. gray-scale map
c. threshold setting - The threshold setting is used to include and exclude information during the 3D reconstruction of a CT scan. - For example, a high threshold (+150 HU) may be set to produce a 3D model of a bony structure. This threshold eliminates any density value below +150 HU from the data set. - The reconstructed 3D model would include only bone tissue or any other substance with a Hounsfield value above +150.
Number 2 on the figure corresponds to which of the following? a. hyoid bone b. cricoid cartilage c. thyroid cartilage d. mandible
c. thyroid cartilage -
Complete CT examinations of the chest for investigation of bronchogenic carcinoma should include sections from the: a. mandible through the liver b. apices to the diaphragm c. top of the apices through the liver d. clavicles through the adrenals
c. top of the apices through the liver - Complete CT examination of the chest for bronchogenic carcinoma consists of an acquisition from the apices through the liver. - The adrenal gland and liver are common sites for metastatic disease in patients with primary lung neoplasm. - Scanning may be done in a caudo cranial direction to ensure maximum contrast enhancement of the liver and adrenals when indicated.
First-generation CT scanners used a method of data acquisition based on a __________ principle. a. multiplanar b. rotation-only c. translate-rotate d. transaxial
c. translate-rotate - The first-generation CT scanner acquired data through a process based on the principle of tube translation and rotation around the patient's head.
First-generation CT scanners used a methodof data acquisition based on a __________principle. a. multiplanar b. rotation-only c. translate-rotate d. transaxial
c. translate-rotate - The first-generation CT scanner acquired data through a process based on the principle of tube translation and rotation around the patient's head.
Number 2 on the figure corresponds to which of the following? a. superior facet b. pedicle c. transverse process d. lamina
c. transverse process
In general, the pancreas is located between the areas of the? a. fifth and eighth thoracic vertebrae. b. ninth and eleventh thoracic vertebrae. c. twelfth thoracic vertebra and the second lumbar vertebra. d. second and fourth lumbar vertebrae.
c. twelfth thoracic vertebra and the second lumbar vertebra. ! Pancrease = T12 - L2
The epithelial lining of the urinary tract is called the: a. omentum b. haustrum c. urothelium d. pyelocalyx
c. urothelium - The urothelium lines most of the urinary tract, including the renal pelvis, ureters, and bladder. - The transitional portion of the urothelium can be the site of transitional cell carcinoma (TCC), a common malignancy of the bladder, ureters, and kidneys.
Which of the following MDCT examinations may include endobrachial views? a. virtual colonoscopy b. HRCT of the lungs c. virtual bronchoscopy d. CTA of the aorta
c. virtual bronchoscopy - CT bronchography is a three-dimensional examination of the tracheo bronchial tree. - It may include detailed endobrachial views, on which the viewer has the perspective of flying through the trachea and bronchi, as in conventional bronchoscopy. - These specialized 3D reconstructions are commonly referred to as virtual bronchoscopy
The density measurement performed in the figure yielded an average CT number of zero. This area consists of: a. fat b. blood c. water d. air
c. water
Which of the following sets of technical factors would yield an isotropic data set when an MDCT image is reconstructed using a 512^2 matrix? (CT) a. 5.0-mm sections, 17-cm DFOV b. 3.0-mm sections, 25-cm DFOV c. 1.25-mm sections, 48-cm DFOV d. 0.625-mm sections, 32-cm DFOV
d. 0.625-mm sections, 32-cm DFOV - Thin-section reconstruction using the smallest display field of view (DFOV) possible results in the smallest pixel and voxel dimensions. - Voxels with equal dimensions along the x-, y- and z-axes are described as isotropic ! Thinnest Section
Which of the following sets of technical factors would yield an isotropic data set when an MDCT image is reconstructed using a 5122 matrix? a. 5.0-mm sections, 17-cm DFOV b. 3.0-mm sections, 25-cm DFOV c. 1.25-mm sections, 48-cm DFOV d. 0.625-mm sections, 32-cm DFOV
d. 0.625-mm sections, 32-cm DFOV - Thin-section reconstruction using the smallest display field of view (DFOV) possible results in the smallest pixel and voxel dimensions. - Voxels with equal dimensions along the x-, y- and z-axes are described as isotropic.
The slip ring on continuous rotation CT scanners: 1. prevents the high voltage cable from winding up 2. allows the exam to commence more rapidly 3. eliminates the need for the reversal of gantry frame rotation
d. 1, 2 and 3
Which of the following must be included when one is obtaining informed consent for an invasive procedure? 1. explanation of the examination techniques 2. the possible risks and benefits of the exam 3. alternatives to the procedure involved a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2 and 3
d. 1, 2 and 3 - Informed consent must be obtained from the patient prior to any invasive procedure. - The components of informed consent are thorough explanations of the procedure, any possible risks in addition to the proposed benefits, and alternatives to the procedure.
Which of the following is a common site for the intravenous injection of iodinated contrast media? 1. cephalic vein 2. antecubital vein 3. basilic vein a. 1 only b. 3 only c. 2 and 3 only d. 1, 2, and 3
d. 1, 2, and 3 - Common sites for intravenous contrast injection are the antecubital, basilic, cephalic, and accessory cephalic veins.
Components of a comprehensive CT stroke management protocol typically include: 1. pre-contrast sequence of the brain 2. CTA of the brain and carotids 3. CT perfusion (CTP) of the brain a. 2 only b. 1 and 2 only c. 2 and 3 only d. 1, 2, and 3
d. 1, 2, and 3 - Found typically in the emergency setting, a comprehensive acute stroke CT imaging protocol begins with a pre-contrast sequence to evaluate for hemorrhage. - After the IV administration of an iodinated contrast agent, a CTA acquisition is performed through the carotid vessels and brain. - CTP is then performed to evaluate potential cerebral perfusion defects secondary to stroke.
Which of the following factors may affect a patient's calculated glomerular filtration rate (GFR)? 1. age 2. sex 3. race a. 1 and 2 only b. 2 and 3 only c. 1 and 3 only d. 1, 2, and 3
d. 1, 2, and 3 - GFR is calculated using the patient's measured serum creatinine level and takes into account the patient'sage, sex, and race.
Thorough explanation of the CT procedure and proper communication with the patient are vital in ensuring that: 1. breathing instructions are properly followed 2. motion artifact does not occur 3. patient anxiety is kept at a minimum a. 1 and 2 only b. 1 and 3 only c. 2 and 3 only d. 1, 2, and 3
d. 1, 2, and 3 - Good communication between the technologist and patient is an extremely important factor in the production of high-quality CT examinations. - Patients can be made to feel more comfortable, and when they are given detailed instructions, their greater cooperation can improve the CT results.
Which of the following contrast media may be utilized during the CT evaluation of the gastrointestinal tract? 1. diatrizoate meglumine (Gastrografin) 2. effervescent agents 3. iopamidol (Isovue) a. 1 only b. 1 and 3 only c. 2 and 3 only d. 1, 2, and 3
d. 1, 2, and 3 - Opacification of the stomach and bowel loops is imperative during general CT examinations of the abdomen and pelvis. - Effervescent agents may be used to ensure proper gastric distention. Intravenous contrast agents are used to opacify blood vessels and are helpful in anatomic differentiation and evaluation of mass vascularity.
The overall quality of MPR and volume-rendered 3D images for a carotid artery CTA may be improved by: 1. reducing the kVp for an increase in displayed vessel opacification and contrast 2. retrospective reconstructions with a 50% overlap in section increment 3. bolus-tracking software to maximize contrast enhancement a. 2 only b. 1 and 2 only c. 2 and 3 only d. 1, 2, and 3
d. 1, 2, and 3 - Reductions in kVp, overlapping axial sections, and precise bolus timing are all important factors in the production of high-quality CTA examinations.
The data acquisition system (DAS) of a CT scanner is responsible for: 1. measuring transmitted intensity 2. conversion of the transmission data into a digital signal 3. sending the digital information to the computer for processing a. 1 only b. 2 only c. 1 and 3 only d. 1, 2, and 3
d. 1, 2, and 3 - The DAS of a CT scanner consists of the detector array, the analog-to-digital convertor, and a transmission device used to send the converted digital information to the computer for image reconstruction.
Which of the following pelvic bones combine(s) to form the acetabulum? 1. ilium 2. ischium 3. pubis a. 2 only b. 1 and 2 only c. 2 and 3 only d. 1, 2, and 3
d. 1, 2, and 3 - The acetabulum is a cup-shaped cavity that holds the head of the femur, forming the hip joint. It is composed of portions of the ilium, ischium, and pubis.
Which of the following methods may be employed to reduce the radiation dose to the pediatric patient undergoing CT? 1. reduce mA 2. limit phases of acquisition 3. increase pitch a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
d. 1, 2, and 3 - The selected mA should be adapted to each patient according to size and/or weight. - Eliminating unnecessary CT scans at the discretion of the physician is an additional way to reduce pediatric dose.
Prior to the intravenous injection of iodinated contrast material, patients should be questioned regarding their: 1. renal function 2. allergic history 3. cardiac history a. 1 only b. 2 only c. 3 only d. 1, 2, and 3
d. 1, 2, and 3 - The technologist and/or radiologist should always ask the patient about allergic history as well as current renal function status and history of cardiac illness (high bloodpressure, congestive heart failure, and so on) prior to administration of any contrast material.
The mathematical manipulations required during the reconstruction of a CT image are accomplished using a(n): 1. algorithm 2. kernel 3. mathematical filter function a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
d. 1, 2, and 3 - The terms algorithm, kernel, and mathematical filter function may all be used interchangeably in describing the mathematical process used for the complex calculations required during CT image reconstruction.
Advantages of a saline flush immediately following the IV administration of iodinated contrast material include: 1. reduction in required contrast agent dose 2. reduction in the incidence of contrast-induced nephrotoxicity (CIN) 3. reduction of streaking artifact from dense contrast agent in the vasculature a. 1 only b. 3 only c. 2 and 3 only d. 1, 2, and 3
d. 1, 2, and 3 - The use of a saline flush also improves the overall contrast agent utilization efficiency of the CT examination.
A patient in shock may exhibit which of the following symptoms? 1. tachycardia 2. rapid, shallow breathing 3. cyanosis a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
d. 1, 2, and 3 General signs and symptoms that a patient is going into shock include: - rapid breathing - tachycardia - hypotension - weak pulse - pallor - cyanosis and cold - clammy skin.
The use of water as an oral contrast material for CT of the abdomen and/or pelvis has several potential advantages, including: 1. increased palatability and improved patient comfort 2. better demonstration of enhancing bowel wall 3. no interference with 3D applications a. 1 only b. 1 and 2 only c. 1 and 3 only d. 1, 2, and 3
d. 1, 2, and 3d. 1, 2, and 3 - The use of water as a negative contrast agent is becoming increasingly common for many CT applications for the abdomen and pelvis.
Which of the following might be an appropriate protocol for a CT study that is performed for suspected acoustic neuroma? a. 10-mm contiguous slices; standard algorithm; with IV contrast; filmed with a narrow window width b. 8-mm contiguous slices; bone algorithm; without IV contrast; filmed at two separate window settings c. 5-mm slice thickness; 3-mm table increment; without IV contrast; soft (i.e., low contrast) algorithm, filmed with a lung window d. 1.0-mm contiguous slices; reconstructed using both a standard and a bone (i.e., high-contrast) algorithm; with IV contrast; filmed in two separate window settings
d. 1.0-mm contiguous slices; reconstructed using both a standard and a bone (i.e., high-contrast) algorithm; with IV contrast; filmed in two separate window settings - Acoustic neuromas, or more properly vestibular schwannoma, originate in the internal auditory canal (IAC). - Although medium and large acoustic neuromas extend outside the IAC and into the brain cavity, many of these tumors are quite small and are confined to the IAC. - Contrast enhanced CT using a narrow slice thickness is typically needed to detect small acoustic neuromas.
In a preliminary scout view of a patient, the abdomen is determined to be 360mm in length. In this 4 slice CT system, the gantry makes a 360° rotation each second. The protocol at this institution calls for a 5-mm slice thickness. To cover the entire abdominal area in a single helical scan, which set of parameters could be selected? a. 10-second total acquisition time, 1 pitch b. 10-second total acquisition time, 1.2 pitch c. 15-second total acquisition time, 1 pitch d. 15-second total scan acquisition, 1.2 pitch
d. 15-second total scan acquisition, 1.2 pitch - The distance covered in an MDCT helical scan sequence can be calculated using the following formula: Pitch × total acquisition time × 1 rotation time × (ST × slices per rotation). Therefore, (a) 1 × 10 × 1 × (5mm × 4) = 200mm (b) 1.2 × 10 × 1 × (5mm × 4) = 240mm (c) 1 × 15 × 1 × (5mm × 4) = 300mm (d) 1.2 × 15 × 1 × (5mm × 4) = 360mm
Positioning the patient with the knees flexed over a foam cushion during a CT examination of the lumbar spine assists in: 1. decreasing the kyphotic curvature of the lumbar spine 2. making the patient more comfortable throughout the exam 3. decreasing the lordotic curvature of the lumbar spine a. 1 only b. 2 only c. 3 only d. 2 and 3 only
d. 2 and 3 only - During a CT examination of the lumbar spine, a foamcushion should be placed under the patient's flexed knees. - This maneuver reduces strain on the lower back, making the patient more comfortable and cooperative. - It alsoreduces the lordotic curve of the lumbar spine, allowingfor more accurate imaging of the intervertebral disc spaces.
During the use of CT fluoroscopy for guided interventional procedures, which of the following technical considerations may be used to reduce occupational radiation exposure? 1. increased kVp 2. lead shielding 3. use of a needle holder a. 2 only b. 1 and 2 only c. 1 and 3 only d. 2 and 3 only
d. 2 and 3 only - Low values for kVp and mA and short CT fluoroscopy time all reduce occupational radiation exposure. - Greater distance from the source, as with the use of a needle holder to keep the operator's hands out of the CT fluoroscopy field, also greatly diminish exposure. - Additional methods of exposure reduction are lead shielding, leaded patient drapes, and the utilization of a last-image-hold function to cut down on continuous CT fluoroscopy.
The specialized CT examination of the bladder in which an iodinated contrast agent is directly administered under gravity into the bladder via Foley catheter is termed: a. CT IVP b. CT urogram c. CT enteroclysis d. CT cystography
d. CT cystography - A CT cystogram involves the administration of an iodinated contrast agent directly into the bladder via a Foley catheter.
Number 8 on the figure corresponds to which of the following? a. duodenum b. descending colon c. jejunum d. ascending colon
d. ascending colon
Which of the following components of CT image quality are being evaluated in the figure? 1. low-contrast detectability 2. noise 3. uniformity a. 2 only b. 1 and 2 only c. 1 and 3 only d. 2 and 3 only
d. 2 and 3 only - Noise is most commonly measured by scanning a water-filled phantom with a consistent set of technical factors. - The image noise is equal to the standard deviation of pixel values within a region of interest (ROI) measurement of the image. - Uniformity may also be evaluated by positioning several ROI measurements at different locations along the center and periphery of the image. - The CT values should not differ by more than 2 HU from one location to another. ! Water Phantom = Noise & Uniformity
Which of the following technical adjustments may be employed to improve the temporal resolution of an MDCT system? 1. decrease in section width 2. image segmentation 3. physiologic gating a. 1 only b. 3 only c. 1 and 2 only d. 2 and 3 only
d. 2 and 3 only - Technical adjustments to improve the temporal resolution of the CT system may help reduce involuntary motion artifacts. - Reductions in scan time (gantry rota-tion), image segmentation, and physiologic gating can be used to reduce the effects of involuntary motion.
Which of the following technical factors is/are involved in the determination of section width for MDCT images? 1. scan field of view (SFOV) 2. beam collimation 3. detector configuration a. 2 only b. 1 and 2 only c. 1 and 3 only d. 2 and 3 only
d. 2 and 3 only - The thickness of the reconstructed section is controlled primarily by the detector configuration in an MDCT system. - Beam collimation also exerts an indirect effect on section width by controlling the portion of the detector array exposed to transmitted radiation.
A complete CT study of the orbits should include: a. 5 mm x 5 mm axial sections only b. 10 mm x 10 mm axial and coronal sections c. 3 mm x 3 mm coronal sections only d. 2.5 mm x 2.5 mm axial and coronal sections
d. 2.5 mm x 2.5 mm axial and coronal sections - Narrow sections (1-3 mm) are required in both the axial and coronal planes to properly demonstrate the orbits. - Isotropic MDCT acquisition may provide multiplanar reformation images of sufficient quality to preclude the need for an additional scan in a second plane.
The maximum beam collimation for an MDCT system with a detector array of 64 detectors, each 0.625 mm wide, is: a. 1.25 mm b. 5.00 mm c. 10.00 mm d. 40.00 mm
d. 40.00 mm - At a maximum, the MSCT cone beam may be collimated to a dimension equal to the entire multirow detector array. - In the example, the total dimension of the detector array along the z-axis is 40.00 mm, or 64 x 0.625 mm. ! Detector Array x Slice Thickness
The recommended scan field of view (SFOV) for a CT examination of the cervical spine is: a. 9.6 cm b. 15.0 cm c. 25.0 cm d. 50.0 cm
d. 50.0 cm - Acquisition of the cervical spine is performed with a large SFOV, 48 to 50 cm. - Targeted reconstructions are made using a display field of view (DFOV) between 10 and 15 cm. - Larger DFOV reconstructions may be used to retrospectively display a greater anatomic area as clinical indication dictates.
What matrix size was used to reconstruct an image with the display characteristics DFOV 25 cm and pixel area 0.25 mm^2? a. 80 x 80 pixels b. 256 x 256 pixels c. 320 x 320 pixels d. 512 x 512 pixels
d. 512 x 512 pixels - The matrix size used to reconstruct an image can be calculated by dividing the display field of view (DFOV) by the pixel dimension. - A pixel whose area is 0.25 mm^2 has a linear dimension of 0.5 mm. - Dividing the DFOV of 250 mm by the pixel dimension 0.5 mm gives a matrix size of approximately 512x512 pixels.
Power output for a modern MDCT x-ray tube has an approximate range of: a. 3-5 kilowatts (kW) b. 15-20 kilowatts (kW) c. 40-48 kilowatts (kW) d. 60-100 kilowatts (kW)
d. 60-100 kilowatts (kW) - The power output of modern MDCT systems is vendor-specific,within a typical range of 60 to 100 kilowatts (kW).
Normal range for oxygen (O2) saturation is: a. 20%-25% b. 50%-60% c. 80%-85% d. 95%-100%
d. 95%-100% - Normal range of O2 saturation as measured by a pulseoximeter is between 95% and 100%. - Saturation levels below 95% may indicate respiratory insufficiency.
What part of the CT system is responsible for converting the digitized data into shades of gray? (CT) a. Photodiode b. Arrayprocessor c. Displayprocessor d. Analog-to-digital converter
d. Analog-to-digital converter - The digitized data are sent from the reconstruction processor to the display processor, which then converts it to shades of gray. ! Shades of gray/ADC
Refer to Figure 24-12. Name the structure indicated by arrow #1. a. Descending colon b. Jejunum/ileum c. Inflamed appendix d. Ascending colon
d. Ascending colon
Comparing the Spatial Resolution of CT to other Modalities? (CT) a. CT i superior to general radiography, MRI, and Ultrasound b. CT is superior to general radiography, but is inferior to MRI c. CT is comparable to all other modalities d. CT is inferior to general radiography
d. CT is inferior to general radiography - The spatial resolution of a CT image does not compare favorably with other modalities. - Where CT Excels is in its Low Contrast Resolution, for which it is superior to all other clinical modalities. ! CT = Better Low Contrast; Other Modalities = better Spatial resolution
Comparing the spatial resolution of CT to other modalities: a. CT is superior to general radiography, MRI, and ultra- sound. b. CT is superior to general radiography, but is inferior to MRI. c. CT is comparable to all other modalities. d. CT is inferior to general radiography.
d. CT is inferior to general radiography. - The spatial resolution of a CT image does not compare favorably with other modalities. - Where CT excels is in its low-contrast resolution, for which it is superior to all other clinical modalities. ! CT Good for Low Contrast, Bad for Spatial Resolution
Refer to Figure 24-14. Name the structure indicated by arrow #4. a. Basilar artery b. Vertebral artery c. Internal jugular vein d. Common carotid artery
d. Common carotid artery
Digital CT images are networked and archived in accordance with a standardized computer protocol identified by which of the following abbreviations? a. HIPAA b. HTTP c. TCP/IP d. DICOM
d. DICOM - The Digital Imaging and Communications in Medicine(DICOM) standard confirms the process of recording,storing, printing, and transmitting medical image data.
The kidneys are located in the retro peritoneum and are bound by a band of fibrous connective tissue called: a. Cooper's ligament b. Camper's fascia c. linea alba d. Gerota's fascia
d. Gerota's fascia - The kidneys are located in a portion of the retro peritoneum known as Gerota's space. They are held in place by fibrous connective tissue commonly referred to as Gerota's fascia.
What causes ring artifacts? (CT) a. Electrical surges (i.e., a "short-circuit") within the x-ray tube b. Involuntary patient motion (e.g., heart motion) c. Irregularly shaped objects that have a pronounced difference in density from surrounding structures d. Imperfect detector elements—either faulty or simply out of calibration
d. Imperfect detector elements—either faulty or simply out of calibration - Sometimes ring artifacts can be eliminated simply by recalibrating the scanner. - If that fails, a service engineer must be called to repair the defective detector.
Which of the following factors should be adjusted when slice thickness is decreased from 10 to 3 mm? a. Increase display field b. Decrease matrix size c. Lower window level d. Increase mAs
d. Increase mAs - Because of the increased collimation, a narrower slice results in fewer x-ray photons. - To compensate, mAs must be increased.
An image of the abdomen is greatly degraded by quantum mottle. The scan parameters used are as follows: DFOV = 38cm; slice thickness = 5mm; mA = 240; tube rotation = 0.5 seconds; kVp = 120. What action will have the best chance of reducing or eliminating the quantum mottle for subsequent scans? (CT) a. Increase DFOV to 44 cm. b. Decrease slice thickness to 2 mm. c. Decrease mA to 125 and increase the tube rotation time to 1.0 second. d. Increase the mA to 300 and increase the tube rotation time to 0.8 seconds.
d. Increase the mA to 300 and increase the tube rotation time to 0.8 seconds. - Quantum mottle occurs when there are an insufficient number of photons detected and results in image noise. - Doubling the mAs of the study increases the number of photons detected per pixel by approximately 40%. ! Quantum Mottle aka Noise = Insufficient mAs
Refer to Figure 24-9. Name the structure indicated by arrow #2. a. Brachiocephalicartery b. Ascendingaorta c. Right pulmonary vein d. Superior vena cava
d. Superior vena cava
The window width of a specific CT image is set at 120 and the level (or center) is set at 50. How is a structure with a measurement of −40 HU displayed? (CT) a. It is white. b. It is a light shade of gray. c. It is a dark shade of gray. d. It is black.
d. It is black. - The window width selects the range of HU that is to be represented as shades of gray on the image. - The window level determines which, of all the possible HU, are to be included. - In this example, the total HU to be represented is 120. Because the center is set at 50, the HU depicted are −10 to 110. - This is calculated by dividing 120 in half, then subtracting the quotient from the center (50) to find the lower limit. - Add the quotient to 50 to find the upper limit. Every- thing that falls below this range appears black, whereas everything above this range appears white. 120/2 = 60 -60 + 50 = -10 60 + 50 = 110 (-10,110)
The abdominal aorta bifurcates at the level of: a. T10 b. T12 c. L2 d. L4
d. L4 - The abdominal aorta descends to the level of the fourth lumbar vertebra (L4), where it bifurcates into the left and right common iliac arteries.
Refer to Figure 24-10. Name the structure indicated by arrow #5. a. Superior mesenteric artery b. Superior mesenteric vein c. Splenicartery d. Left adrenal
d. Left adrenal
Which of the following can be described as possessing high inherent contrast? (CT) a. Soft tissue b. Kidneys c. Liver d. Lungs
d. Lungs - The lungs are considered to have high inherent contrast because they are primarily composed of air and provide a background that makes nearly any object contained within the lung easy to see. - - On the contrary, the physical properties of the body's soft tissues and many other organs possess low inherent contrast, often making it difficult to differentiate adjacent structures - To increase the inherent contrast in these organs, iodinated contrast medium is often administered.
Refer to Figure 24-15. Name the structure indicated by arrow #4. a. Phalange (proximal) b. Distal tibia (medial malleolus) c. Navicular bone d. Metatarsal bone
d. Metatarsal bone
What is an example of a computer output device? (CT) a. CT detector mechanisms b. Microprocessor c. Touch-sensitive plasma screen d. Monitor
d. Monitor - Output devices accept processed data from the computer. - Other examples of output devices are laser cameras, printers, and archiving equipment such as optical disks or magnetic tape. - CT detector mechanisms and touch-sensitive plasma screens are examples of input devices that feed data into the computer. - The microprocessor is part of the CPU.
Which image artifact can result from an improperly centered patient? a. Edge gradient artifact b. Undersampling artifact c. Tube arc artifact d. Out-of-field artifact
d. Out-of-field artifacts - occur when portions of the patient lie outside the selected scan field of view.
Refer to Figure 24-7. Name the structure indicated by arrow RAD #4. a. Basilar artery b. Sigmoid sinus c. Anterior cerebral artery d. Pineal body (calcified)
d. Pineal body (calcified)
Which of the following statements regarding predetector collimation of the CT x-ray beam is true? a. Pre-detector collimation reduces patient radiation dose. b. Pre-detector collimation reduces the production of scatter radiation. c. Pre-detector collimation determines the scan field of view (SFOV). d. Pre-detector collimation removes scatter radiation before it reaches the detectors.
d. Pre-detector collimation removes scatter radiation before it reaches the detectors. - The purposes of pre-detector or post-patient collimation are to remove scatter radiation and to shape the portion of the beam that is incident on each detector. ! Pre Detector Collimation = Radiation Removal pre Detectors
Which of the following could be retrospectively reconstructed for MDCT data that acquires four 2.5-mm slices with each gantry rotation? a. Slices can be divided to produce sixty-four 0.15-mm slices b. Slices can be divided to produce thirty-two 0.31-mm slices c. Slices can be combined to produce eight 5-mm slices d. Slices can be combined to produce two 5-mm slices
d. Slices can be combined to produce two 5-mm slices - The thinnest that images can be reconstructed for a data set is predetermined by the slice thickness used for data acquisition. - Images can be added together to create thicker slices for viewing, but in many cases data cannot be divided to produce thinner slices. - On systems that will allow data to be divided, the slice can never be thinner than the smallest detector element.
The streaking artifact that occurs in the area of the posterior fossa during a CT examination of the brain may be referred to as? (CT) a. cupping b. the "boiled egg" artifact c. stairstep d. the Hounsfield bar
d. The Hounsfield bar - The dense bony areas of the posterior fossa of the skull are especially prone to beam-hardening artifacts. - Hounsfield bar is commonly used to describe this particular artifact.
Which of the following is an imaging challenge that depends on spatial resolution? (CT) a. A liver lesion that is surrounded by healthy liver tissue b. Distinguishing between the white matter and gray mat- ter of the brain c. A large abdominal abscess d. Tiny, contrast-filled arteries that are just 1 mm apart
d. Tiny, contrast-filled arteries that are just 1 mm apart - Spatial resolution is also called detail resolution. - - Spatial resolution is the system's ability to resolve, as separate forms, small objects that are very close together. Synonym: Spatial Resolution = Detail Resolution
When do scan protocols incorporate the use of gapped slices? a. When the object of interest is very small (>2 mm) b. When metallic objects are present in the area scanned c. When the patient is unable to hold still for the duration of the scan d. When a survey of an area is needed
d. When a survey of an area is needed - Gapped images are taken when representative slices are sufficient and imaging every part of the region is not required. - Because some areas are not exposed, studies comprising gapped slices will reduce the radiation dose to the patient.
Which of the following refers to the surgical resection of the pancreas and duodenum for treatment of pancreatic carcinoma? a. endoscopic retrograde cholangiopancreatography (ERCP) b. cholecystectomy c. Roux-en-Y anastomosis d. Whipple procedure
d. Whipple procedure - Whipple procedure is the surgical resection of the pancreas and duodenum (pancreaticoduodenectomy) for the treatment of pancreatic carcinoma.
As a general rule, this is set at a point that has roughly the same value as the average attenuation number of the tissue of interest. What is it? a. The x axis in a histogram b. Standard deviation c. Sampling rate d. Window level
d. Window level
During which of the following CT examinations is a misregistration artifact most likely to occur? a. brain b. pelvis c. neck d. abdomen
d. abdomen - Misregistration is the loss of anatomic information that occurs when a patient suspends respiration at different depths during consecutive scans. - It occurs only during CT examinations in which suspended respiration of the patient is necessary. - The ability of MDCT systems to volumetrically acquire entire anatomic areas in a single,short breath-hold has greatly reduced the occurrence of misregistration artifact.
During which of the following CT examinations is a misregistration artifact most likely to occur? (CT) a. brain b. pelvis c. neck d. abdomen
d. abdomen - Misregistration is the loss of anatomic information that occurs when a patient suspends respiration at different depths during consecutive scans. - It occurs only during CT examinations in which suspended respiration of the patient is necessary. - - The ability of MDCT systems to volumetrically acquire entire anatomic areas in a single, short breath-hold has greatly reduced the occurrence of misregistration artifact. ! Respiration
During which of the following CT procedures is the patient required to give informed consent? a. non-contrast CT of the chest b. renal stone survey c. 3D reconstruction of the hip d. abdomen scan after IV contrast agent administration
d. abdomen scan after IV contrast agent administration - The patient is required to provide informed consent prior to the start of any invasive procedure. - The administration of intravascular contrast material is invasive in nature and requires the informed consent of the patient.
Which of the following is considered an equipment- induced CT image artifact? a. step artifact b. metallic artifact c. cupping artifact d. aliasing artifact
d. aliasing artifact - Aliasing is a type of streak artifact caused when an insufficient number of views (data samples) is obtained during data acquisition. - It is typically due to a technical failure of the CT system. ! Aliasing = Streak = Insufficient Views
Which of the following would be best suited for intravenous injection of contrast material with a power injector? a. butterfly needle b. central venous line c. 23-gauge spinal needle d. angiocatheter
d. angiocatheter - Angiocatheters and higher-gauge needles are preferred for administration of a contrast agent with the use of a power injector. - The stability of an angiocatheter maintains proper placement within the vein while withstanding the high pressure applied by the power injector.
The component of the CT scanner responsible for the mathematical calculations of the image reconstruction process is the: a. DAS b. analog-to-digital converter (ADC) c. digital-to-analog converter (DAC) d. array processor
d. array processor - The array processor is a specialized component of the CT computer system. - It is capable of performing the massive calculations required for CT image reconstruction.
A region of interest (ROI) measurement placed over a portion of a CT image provides which of the following? a. distance (mm) b. diameter (mm) c. linear attenuation coefficient (m) d. average CT number (HU)
d. average CT number (HU) - The region of interest (ROI) measurement provides a quantitative analysis of the Hounsfield values of a specific anatomic area. - System software calculates the average CT number in HUs within the defined ROI. - The average ROI measurement provides information regarding tissue characteristics that may be helpful for clinical diagnosis.
For a CT of the foot the patient is positioned supine, legs flat on the table, toes pointing straight up. There is no gantry tilt. Images acquired are in the direct _____ plane. a. sagittal b. oblique c. coronal d. axial
d. axial - The axial plane is parallel to the plantar surface of the foot.
Number 5 on the figure corresponds to which of the following? a. posterior communicating artery b. anterior communicating artery c. internal carotid artery d. basilar artery
d. basilar artery
During CT examinations of the chest and abdomen, the highly radiosensitive breast tissue can be protected with minimal image artifact with the use of specialized shielding composed of: a. barium b. aluminum c. lead d. bismuth
d. bismuth - In-plane bismuth shielding of particularly radio sensitive areas such as the orbits, thyroid, and breast tissue can substantially reduce effective radiation dose.
Number 4 corresponds to which of the following? a. external auditory meatus b. internal auditory canal c. vestibule d. carotid canal
d. carotid canal
Which of the following is NOT a portion of the small bowel? a. duodenum b. jejunum c. ileum d. cecum
d. cecum - The small bowel consists of the duodenum, the jejunum, and the ileum. - The cecum is the proximal portion of the large bowel; it is connected to the small bowel at the ileocecal valve.
The image in the figure was produced using the following parameters: large (full) SFOV; maximum DFOV (48 cm); 200 mA, 120 kVp; soft tissue algorithm. Which of the following technical adjustments would serve to reduce the artifact present? a. switching to a detail or bone algorithm b. using a smaller SFOV c. increasing the mA to 240 and the kVp to 140 d. centering the patient within the SFOV
d. centering the patient within the SFOV - The out-of-field artifact present in this image could be easily reduced by properly centering the patient within the scan field of view.
Which of the following image artifacts is unique to multislice CT (MSCT) systems? a. step artifact b. aliasing artifact c. out-of-field artifact d. cone beam artifact
d. cone beam artifact - Cone beam artifacts are unique to the cone beam geometry of MDCT systems and typically manifest much like partial volume artifacts.
During CT x-ray exposure, the product of the selected mA setting and the scan time is called the: a. effective mAs b. peak mAs c. absorbed mAs d. constant mAs
d. constant mAs - The mA setting in coordination with the scan time (seconds) gives the constant mAs for a CT acquisition. ! mA x s = Constant mAs
_____ made helical imaging possible. a. multi-row detector scanners b. the introduction of second-generation technology c. the introduction of fourth-generation technology d. continuous rotation scanners
d. continuous rotation scanners
The bolus duration of any IV contrast agent administration can be calculated as the product of injection flow rate and: a. scan time b. osmolality c. cardiac output d. contrast agent volume
d. contrast agent volume - Bolus duration,or the time required to inject a specific volume of contrast agent, may be calculated as the product of injection flow rate and total contrast volume.
The drug SOLU-CORTEF may be classified as which of the following? a. anticholinergic b. bronchodilator c. antihistamine d. corticosteroid
d. corticosteroid - SOLU-CORTEF is a brand name for hydrocortisone,which is a type of corticosteroid. - This drug, or other types of corticosteroids, may be used during the treatment of anaphylactoid reactions to iodinated contrast materials.
If measurements taken around the perimeter of a water phantom are different from those taken at the center of the phantom, than there is a problem with the system's a. linearity. b. slice-thickness accuracy. c. photon absorption. d. cross-field uniformity.
d. cross-field uniformity. - Cross-field uniformity refers to the ability of the scanner to yield the same CT number in a homogeneous object (i.e., water phantom) regardless of the location of the region of interest.
Number 4 on the figure corresponds to which of the following? a. gastric artery b. inferior vena cava (IVC) c. superior mesenteric artery (SMA) d. descending aorta
d. descending aorta
The angiographic assessment known as a "CT runoff" evaluates the peripheral arterial tree from the renal arteries through the: a. aortic arch b. superior mesenteric artery c. aortic bifurcation d. distal lower extremity
d. distal lower extremity - The angiographic assessment of the peripheral arterial tree from the renal arteries through the feet is commonly referred to as a "CT runoff."
To maintain security and patient privacy when medical images are transmitted across a network, the images may be coded in a form decipherable only by software at the destination location. This process is referred to as: a. write-once, read-many (WORM) b. hypertext transfer protocol (HTTP) c. teleradiology d. encryption
d. encryption - Digital encryption is used to encode data that is transferred across a network into a form decipherable only by software at the destination location.
Number 1 on the figure corresponds to which of the following? a. vocal cords b. uvula c. aryepiglottic fold d. epiglottis
d. epiglottis
Which of the following phases of renal contrast enhancement best demonstrates transitional cell carcinoma (TCC) of the bladder? a. early arterial b. corticomedullary c. nephrographic d. excretory
d. excretory - Excretory phase acquisitions after a delay of 3 to 15 minutes demonstrate the urinary tract while it is opacified with a contrast agent. - Transitional cell lesions of the urothelium appear as filling defects within the bladder, ureters, and/or renal pelvis.
The escape of contrast material from a needle or blood vessel into the subcutaneous tissues is called: a. infusion b. extraversion c. influxation d. extravasation
d. extravasation - The escape of contrast material from a needle or blood vessel into the subcutaneous tissues is called extravasation. - It is also sometimes referred to as infiltration.
Which of the following mathematical reconstruction methods is used by most modern CT scanners? a. back-projection b. iterative methods c. Fourier transform d. filtered back-projection
d. filtered back-projection - The filtered back-projection, or convolution, method of image reconstruction is used by most modern CT scanners. ! Convolution = Filtered Back Projection
The primary method of reducing beam-hardening artifacts is? (CT) a. increasing mAs. b. decreasing slice thickness. c. using a helical technique. d. filtering the x-ray beam.
d. filtering the x-ray beam. - As x-ray beams pass through an object, lower-energy photons are preferentially absorbed, creating a "harder" beam. - Individual rays are hardened to differing degrees, and this variation cannot be adjusted for by the reconstruction algorithm. CT systems use three features to minimize beam hardening: filtration, calibration correction, and beam-hardening correction software. - Filtering the beam with a material such as aluminum filters out the lower-energy components of the beam before they pass through the patient.
During CT x-ray production, the electromagnetic steering of the electron beam from the cathode to two alternating targets is referred to as: a. prospective gating b. ultrafast CT c. twin CAT d. flying focal spot
d. flying focal spot - The oversampling technology known as flying focal spot involves the electromagnetic steering of the electron beam emitted from the cathode. - The beam of electrons is directed toward two separate locations on the rotating anode, resulting in two sources of x-radiation. - As the tube rotates around the patient, the number of data samples is essentially doubled because of the electronic switching between the two focal spots, improving the system's temporal and spatial resolution.
During CT x-ray production, the electromagnetic steering of the electron beam from the cathode to two alternating targets is referred to as? a. prospective gating b. ultrafast CT c. twin CAT d. flying focal spot
d. flying focal spot - The oversampling technology known as flying focal spot involves the electromagnetic steering of the electron beam emitted from the cathode. - The beam of electrons is directed toward two separate locations on the rotating anode, resulting in two sources of x-radiation. - As the tube rotates around the patient, the number of data samples is essentially doubled because of the electronic switching between the two focal spots, improving the system's temporal and spatial resolution.
Statistical noise appears as __________ on a CT image. a. decreased contrast b. increased brightness c. concentric circles d. graininess
d. graininess - Statistical noise is a term that may be used for quantum noise, or mottle. - Caused by an insufficient number of photons being detected, this type of noise appears as graininess on the CT image.
The pathologic process indicated by number 3 on the figure most likely corresponds to: a. atelectasis b. lymphadenopathy c. pleural effusion d. ground-glass opacity
d. ground-glass opacity - Ground-glass opacities are hazy areas of increased attenuation in the lungs and are often associated with the interstitial lung disease evaluated by HRCT.
A __________ is a benign, highly vascular mass commonly found in the liver. a. hematoid b. vasculoma c. hemogenic carcinoma d. hemangioma
d. hemangioma - A hemangioma is a congenital, benign mass containing blood-filled spaces. - It is commonly found in the liver and spleen.
Arterial phase CT imaging of the liver is used to optimally demonstrate which of the following? a. fatty infiltration b. hepatic cysts c. portal vein thrombosis d. hepatocellular carcinoma (HCC)
d. hepatocellular carcinoma (HCC) - Hepatocellular carcinomas(HCCs) are hypervascularlesions that appear hyperdense in comparison with surrounding normal hepatic parenchyma during the arterial phase of contrast enhancement.
Which of the following describes the situation in which an assumption is made that an unconscious or otherwise physically unable patient consents to medical treatment? a. informed consent b. witnessed consent c. patient proxy d. implied consent
d. implied consent - Implied consent occurs when a patient is in need of immediate medical services but is unconscious or physically unable to consent to treatment. - The assumption is made that the patient would consent if able.
Number 4 on the figure corresponds to which of the following? a. superior facet b. pedicle c. transverse process d. lamina
d. lamina
The proper scan field of view (SFOV) for a CT of the abdomen of a patient who measures 42 cm is: a. head (25 cm) b. small (25 cm) c. medium (35 cm) d. large (48 cm)
d. large (48 cm) - The SFOV chosen must be larger than the width of the patient in order to eliminate out-of-field artifacts. - Some CT scanners may have limited choices for SFOV values. - Other common terminology includes full- or half-field,and body-cal and head-cal.
Number 4 in the figure corresponds to which of the following? a. spleen b. duodenum c. left adrenal gland d. large colon
d. large colon
Which of the following anatomic organs is located within the peritoneal cavity? a. pancreas b. kidneys c. uterus d. liver
d. liver - The peritoneal cavity is formed by the membranous sac called the peritoneum. - It contains the stomach, liver, gallbladder, spleen, ovaries, transverse colon, and most of the small bowel.
Areas of a CT image that contain minimal changes in tissue density are electronically represented by: a. positive CT numbers b. high spatial frequencies c. negative CT numbers d. low spatial frequencies
d. low spatial frequencies - The contrast of a CT image is controlled by the spatial frequencies of the tissue(s) within the section. - Tissues of differing densities are represented electronically by different spatial frequencies. - Adjacent tissues with similar densities or areas of tissue with minimal differences in density are represented by low spatial frequencies.
Areas of a CT image that contain minimal changes in tissue density are electronically represented by? (CT) a. positive CT numbers b. high spatial frequencies c. negative CT numbers d. low spatial frequencies
d. low spatial frequencies - The contrast of a CT image is controlled by the spatial frequencies of the tissue(s) within the section. - Tissues of differing densities are represented electronically by different spatial frequencies. - - Adjacent tissues with similar densities or areas of tissue with minimal differences in density are represented by low spatial frequencies. ! Low Spatial Resolution = Minimal Differences of Densities
Scanning to the adrenal glands in a CT study of the thorax is sometimes performed because a. it ensures that the technologist has scanned the entire lung field. b. kidney function can be assessed. c. the adrenal glands are part of the respiratory system. d. lung cancer may metastasize to the adrenal glands.
d. lung cancer may metastasize to the adrenal glands. - In many institutions the protocol for a thoracic CT extends to the adrenal glands when patients have a history of lung cancer.
Which of the following units is used to express the total patient dose froma helically acquired CTexamination? a. roentgens (R) b. curies (Ci) c. R-cm (roentgens per centimeter) d. mGy-cm (milligrays per centimeter)
d. mGy-cm (milligrays per centimeter) - The dose length product (DLP) is the total patient dose over a given scan acquisition length (z) and can be illustrated as the product of CTDIvol and scan length. - The DLP is expressed in units of milligrays per centimeter(mGy-cm).
Which of the following reformation techniques best describes the image in the figure? a. volume-rendered 3D b. multiplanar reformation (MPR) c. minimum intensity projection (min-IP) d. maximum intensity projection (MIP)
d. maximum intensity projection (MIP)
During a PET-CT examination, the amount of FDG uptake in an anatomic region is directly proportional to the area's: a. size b. central vs. peripheral location c. radiosensitivity d. metabolic activity
d. metabolic activity - Malignant cells demonstrate an increase in metabolic activity and glucose utilization. - Once administered, fludeoxy glucose F 18 (FDG) mimics glucose and is taken up by normal and abnormal tissue. - The amount of FDG uptake is directly proportional to the area's metabolic activity. - Malignant cells will take up a disproportionately larger amount of FDG than metabolically normal tissue.
Air trapping within the trachea and bronchial tree may be optimally demonstrated with multiplanar volume reconstructions (MPVRs) of the thorax known as: a. maximum intensity projections (MIPs) b. 3D volume renderings c. shaded-surface displays (SSDs) d. minimum intensity projections (min-IPs)
d. minimum intensity projections (min-IPs) - In the minimum intensity projection technique, displayed pixels represent the minimum attenuation value encountered along each sampled ray. Also referred to as min-IP, this type of multiplanar volume reconstruction (MPVR) can be applied to a volume of the thorax to demonstrate air trapping within the trachea and bronchial tree.
Which of the following best describes the type of image featured in the figure? a. direct coronal acquisition b. sagittal MIP c. coronal MPR d. oblique sagittal MPR
d. oblique sagittal MPR - The image is a multiplanar reformation (MPR) image through the orbit in the oblique sagittal plane.
Which of the following archival media is capable of storing the largest number of CT images? a. floppy disk b. magnetic tape c. VHS tape d. optical disk
d. optical disk - Magnetic optical disks vary in storage capacity, with some capable of storing several thousand 5122 matrix CT images. - This is considerably more than magnetic tape, which had previously been the standard choice for CT image archival.
A common area for inflammation, the primary drainage opening within the sinus cavities is referred to as the: a. mucosal fossa b. adenovestibular complex c. external olfactory canal d. ostiomeatal complex
d. ostiomeatal complex - The ostiomeatal complex is an important sinus opening that allows for drainage of the frontal, ethmoid, and maxillary sinuses. - It is a common area for sinusitis, or inflammation of the sinuses.
Number 3 in the figure corresponds to which of the following? a. duodenum b. splenic vein c. jejunum d. pancreas
d. pancreas
Number 6 on the figure corresponds to which of the following? a. duodenum b. terminal ileum c. appendix d. pancreas
d. pancreas
The abnormal density located in the posterior portion of the left lung field on the figure has an average attenuation value of +5.0 Hounsfield units. This density most likely represents: a. pneumothorax b. hemothorax c. atelectasis d. pleural effusion
d. pleural effusion - Pleural effusions are commonly seen in the posterior portion of the lung field on images obtained with the patient in a supine position on the CT table. - Differentiation between pleural effusion and pleural thickening is made when region of interest (ROI) measurements reveal fluid with density readings at or slightly above zero. - Pleural effusion may be caused by multiple pathologic processes, including infection, neoplasm, and congestive heart failure.
Which of the following is a common complication of CT-guided biopsy of the lung? a. pulmonary embolism b. aspiration c. pneumoconiosis d. pneumothorax
d. pneumothorax - Pneumothorax is one of the most common complications of CT-guided needle biopsy of the lung. - The term pneumothorax describes a collection of air in the pleural space. - A pneumothorax causes a portion of the lung to collapse, often resulting in the placement of a chest tube to re-inflate the lung.
Which of the following is the preferred contrast enhancement phase for CT acquisition of the spleen? a. pre-contrast phase b. equilibrium phase c. arterial phase d. portal venous phase
d. portal venous phase - The preferred timing for CT acquisition of the spleen is the portal venous phase (60-70 sec), when a morehomogeneous pattern of enhancement is demonstrated.
During HRCT of the lungs, edematous changes in the posterior lungs may be differentiated by positioning of the patient in the __________ position. a. supine b. right lateral decubitus c. left lateral decubitus d. prone
d. prone - HRCT images with the patient in the prone position can be acquired to differentiate the dependent edematous changes often seen in the lung bases.
The measurement of transmitted radiation made by an individual detector is called a(n): a. attenuation coefficient b. Hounsfield value c. CT number d. ray sum
d. ray sum - The measurement of transmitted radiation made by an individual detector is called a ray sum. - It equals the total attenuation occurring along a straight-line path from tube to detector.
Number 1 on the figure corresponds to which of the following? a. psoas muscle b. gluteus medius muscle c. iliacus muscle d. rectus abdominis muscle
d. rectus abdominis muscle
Which of the following corresponds to the low attenuation area indicated by Number 3 on the figure? a. renal cortex b. renal pelvis c. renal calyx d. renal pyramid
d. renal pyramid - The renal pyramids are cone-shaped regions of the renal medulla. - The wider bases of the renal pyramids border the renal cortex.
Which of the following most likely describes the patient position during the formation of the image in the figure? a. supine b. prone c. left lateral decubitus d. right lateral decubitus
d. right lateral decubitus - The location of the liver on the inferior portion of the image indicates that this patient is in the right lateral decubitus position.
Which of the following artifacts is not affected by the CT technologist? a. motion b. partial volume c. edge gradient d. ring
d. ring - Although the CT technologist must be able to readily identify them, ring artifacts are caused by detector malfunction and are beyond his/her control. - Patient motion, partial volume averaging, and edge gradient artifacts can all be limited by the CT technologist through adequate preparation and careful scan procedures.
Number 2 on the figure corresponds to which of the following? a. capitate b. lunate c. hamate d. scaphoid
d. scaphoid
A hardware component of a CT system that resembles small shutters with an opening that adjusts, dependent on the operator's selection of slice thickness, is a? (CT) a. bowtie filter. b. slipring. c. referencedetector. d. source collimator.
d. source collimator. - The source collimator is located near the x-ray source and limits the amount of x-ray emerg ing to thin ribbons. - Because it acts on the x-ray beam before it passes through the patient it is sometimes referred to as prepatient collimation.
Number 4 on the figure corresponds to which of the following? a. superior rectus muscle b. superior ophthalmic vein c. levator palpebrae superioris muscle d. superior oblique muscle
d. superior oblique muscle
Number 1 on the figure corresponds to which of the following? a. navicular b. cuboid c. calcaneus d. talus
d. talus
The streaking artifact that occurs in the area of the posterior fossa during a CT examination of the brain may be referred to as: a. cupping b. the "boiled egg" artifact c. stairstep d. the Hounsfield bar
d. the Hounsfield bar - The dense bony areas of the posterior fossa of the skull are specially prone to beam-hardening artifacts. - Hounsfield bar is commonly used to describe this particular artifact.
Number 1 on the figure corresponds to which of the following? a. spinal root b. superior articular recess c. anterior arch d. transverse foramen
d. transverse foramen
MDCT systems that contain parallel rows of equal size detectors are called? (CT) a. adaptive arrays. b. hybrid arrays. c. fourth-generation arrays. d. uniform arrays.
d. uniform arrays. - MDCT systems with detectors that contain thinner rows centrally are called adaptive arrays, nonuniform arrays, or hybrid arrays. - Fourth generation scanners (in which detectors are situated in a complete ring) are not used in MDCT systems because too many detector elements would be required.
42. Number 4 on the figure corresponds to which of the following? a. left ovary b. bladder c. sigmoid colon d. uterus
d. uterus
Number 3 on the figure corresponds to which of the following? a. cricoid cartilage b. piriform sinus c. aryepiglottic fold d. vocal cord
d. vocal cord
During CT examination of the larynx, the patient is often instructed to phonate the letter "E" in order to properly evaluate the: a. epiglottis b. uvula c. trachea d. vocal cords
d. vocal cords - The patient should be instructed to phonate the letter "E"during CT scanning of the larynx. - As data are acquired during scanning, the patient's phonation requires vibration of the vocal cords, thus allowing for thorough evaluation of their mobility.
The 3D CT technique that includes all of the acquired voxel information in the reconstructed model with adjustments to its opacity is termed: a. surface rendering b. maximum intensity projection (MIP) c. curved multiplanar reformation d. volume rendering
d. volume rendering - Volume rendering adjusts the opacity of voxels included in the 3D model according to their tissue characteristics. - Unlike the thresholding concept used for shaded-surfacedisplay (SSD), or surface rendering, volume rendering does not exclude voxels, but instead alters their appearance so that the 3D model contains the entire volume data set.
Which of the following is an example of a mild reaction to iodinated intravenous contrast media? a. dyspnea b. shock c. pulmonary edema d. vomiting
d. vomiting - Examples of mild adverse reactions to iodinated contrast material are nausea, vomiting, mild urticaria, and a warm, flushed sensation. - Dyspnea is a moderate reaction, whereas pulmonary edema and shock are severer reactions to contrast media.
The region of interest (ROI) measurement in the figure provides an average density of +1.9 HU. This material is most likely? a. fat b. blood c. tumor d. water
d. water - Water has a CT number at or near zero. - This area in the ROI in the figure most likely represents a hepatic cyst.
The region of interest (ROI) measurement in the figure provides an average density of þ1.9 HU. This material is most likely: a. fat b. blood c. tumor d. water
d. water - Water has a CT number at or near zero. - This area in the ROI in the figure most likely represents a hepatic cyst.
The mathematical process that allows MDCT images to be reconstructed at any point along the acquired volume is commonly referred to as: a. iteration b. filtered back-projection c. Fourier reconstruction d. z-filtering
d. z-filtering - Multiple-detector row CT systems utilize the process called z-filtering during image reconstruction. Z-filtering allows for thin sections to be reconstructed at any point along the acquired z-axis volume. - This interpolation technique utilizes multiple complimentary rays beyond those immediately above and below the particular slice plane.
Window Width and HU Range Calculation. (CT) WW 300 & WL 100 HU = 280 What will the image look like?
ex. WW is 300, WL is 100 Step1. 300/2= 150 Step2. - 150 + 100 = -50 as the Low end Step3. + 150 + 100 = 250 as the High end -50 ------ 0 ------ 250 280 will be out of range to the right so it will be all white
Spondylolisthesis (CT)
forward "slipping" of an upper vertebral body over the lower as a result of degenerative changes of the facet joints.
Acute Idiosyncratic Reaction (CT)
usually classified as: - Mild: Short duration and self-limiting - Moderate: Not immediately life threatening, although they may progress to be so - Severe: Potentially or immediately life threatening
Window Widths & Window Levels General (CT)
ww 80 wl 40 - Brain ww 400 wl 40 - Chest or Soft Tissue ww 1500 wl -400 - Lung ww 400 wl 50 - Abdomen ww 500 wl 60 - C-Spine/Soft Tissue ww 1600 wl 300 - C-Spine/Bone
Patient In Shock (CT)
- tachycradia - rapid-shallow breathing - cyanosis
View (CT)
- A complete set of Ray Sums. - Many views are needed t create an image.
Interpolation (CT)
- A mathematical method of estimating the value of an unknown value using the known values on either side of the value. - mathematical technique used in the reconstruction process of the spiral CT image. - It involves the estimation of an unknown value from information above and below it.
Monitors and HU's (CT)
- A monitor can only display 256 shades of gray Hounsfield Units out of the more than 2000.
Which system component coverts the projection attenuation data into the proper digital form for the array processor? (CT)
- ADC Analog to Digital Converter
Raw Data or Scan Data (CT)
- Actual data that is collected during the scan process - Is what is used to to reconstruct the image - Include all measurements obtained from the detector array - Require much more computer storage than that of image data - Data at the computer waiting to made into an image
To Reformat a (CT) Examination
- All of the source source images msut have an identical DFOV, image center, and gantry tilt, and they must be contiguous. - Even a small amount of motion will seriously degrade the reformatted image, so lining up the images is vital.
Helical Scan Mode (CT)
- Allows for uninterrupted imaging
Solid State Detectors (CT)
- Also called Scintillation Detectors because they use crystal Fluoresces. - If the detector is made from a solid-state scintillator material, the energy of the x-ray photons detected is converted to light. - energy of the x-ray photons detected is converted to light when struck by an X-ray photon. - Efficient and absorb nearly %100 of the photons that reach it. - More sensitive to fluctuation in temperature and moisture.
Retrospective Reconstruction (CT)
- Although many parameters can be changed retrospectively, the images that result are always in the same plane and the same orientation as were the original images.
Aliasing and Undersampling Artifact (CT)
- An adequate number of projections, as well as an adequate amount of data within each projection, must be available to reconstruct a CT image of optimal quality. - Insufficient projection data (for instance, when the helical pitch is greatly extended) is known as undersampling. - Undersampling causes inaccuracies related to reproducing sharp edges and small objects and results in an artifact known as aliasing, in which fine stripes appear to be radiating from a dense structure. - Because aliasing artifacts consist of evenly spaced lines they are easy to distinguish from anatomic structures and, therefore, seldom do they render an image undiagnostic.
Fast Fourier Transform FFT (CT)
- An efficient algorithm that is used in image analysis - Fourier transform is an important image-processing tool that decomposes an image into components - Think of a chord in music being separated into notes
Artifact (CT)
- An object seen on the image but not present in the object scanned.
Analog to Digital Converter ADC (CT)
- Analog signals form the detector are converted into digital format.
Window Level Table (CT)
- Assume 0 is selected as the level; 300 as the width - The HUs that are represented as a shade of gray on this image will range from -150 to 150
Linear Interpolation (CT)
- Assumes that an unknown point falls along a straight line between two known points.
Detector (CT)
- Can be Solid State or Xenon Gas filled chambers
Helical Data Incrementation (CT)
- Can be changed retrospectively . - This is often done to produce overlapping images, which are then used in multiplanar or 3D reformations.
Out of Field Artifacts (CT)
- Can occur if any part of the patient lies outside the SFOV. - Changing DFOV will affect image quality by changing the amount of raw data that is averaged together for each pixel.
Etiology (CT)
- Cause, set of causes, or manner of causation of a disease or condition.
The medication commonly given to sedate small children undergoing CT exams? (CT)
- Chloral hydrate
Isotropic Voxel Size (CT)
- Compare the pixel size to the slice thickness. - A voxel is Isotropic when the "xy" direction is equal to the slice thickness. - When voxels are isotropic in the source data, MPR's created in any plane will have the same image quality as the original axial reconstruction. - When voxels are not isotropic in the source data, image quality can be improved by using overlapping source images. - Smaller Slices, Slower Pitch
Geometric Efficiency (CT)
- Defined as the amount of space occupied by the detector collimator plates relative to the surface area of the detector.
Display Field of View DFOV (CT)
- Determines how much of the raw data is used to create an image. - Image Center, and Reconstruction algorithm can be changed retrospectively on both axial and helical data. - Changing DFOV will also alter the size of the image on the screen. - Changing the DFOV affects image quality by changing the pixel size - DFOV cannot be larger than the SFOV - Also called the "Reconstruct" View
Scan Field of View SFOV (CT)
- Determines the area within the gantry from which the raw data are acquired. - Always collected around the isocenter. - SFOV selection determines the number of detector cells collecting data
Z Axis (CT)
- Determines the thickness of the cross sectional slice.
Filter Functions (CT)
- Filtering is used to minimize streaks on the image that result from back projection - Filtering is done by a series of complicated mathematic steps, often referred to as a reconstruction algorithm - Applying a filter function to an attenuation profile is called convolution - You will also hear the term filtered back project used to describe convolution These filter functions have a big impact on image quality - Reduces artifacts but also reduces spatial resolution - Others enhance contrast by accentuating the difference between neighboring pixels - Improves spatial resolution, but at the cost of low-contrast resolution - Filter functions may be referred to as algorithms, convolution filters, or kernels - Filter functions can only be applied to raw data
Region of Interest ROI (CT)
- If an ROI is placed over an area the reading is an average of the HU within the area.
Window Width / Window Level (CT)
- If the window width is set at 300, which 300 Hounsfield values, from the more than 2,000 possible, will be displayed? - Window width selects the quantity of HU - Window level selects the range of HU
Focal Spot Small (CT)
- Improves spatial resolution but, because they concentrate heat onto a smaller portion of the anode, they cannot tolerate as much heat.
Thinner Slices (CT)
- Increased Dose - Easier to see smaller structures - Better Resolution
Advantages of automatic power injectors over the manual bolus method of intravenous contrast administration? (CT)
- Increased tissue enhancement due to faster injection times, and uniform contrast administration over the entire length of the study.
Parenteral Route of Medication Administration (CT)
- Intramuscular
Angiography (CT)
- Is a test that combines the technology of a conventional CT scan with that of traditional angiography to create detailed images of the blood vessels in the body.
Image Magnification (CT)
- Is not the same as decreasing the display field of view. - Magnifying the image does not improve its image quality, it simply makes the image larger. - Uses only Image Data not raw data
Thicker Slices (CT)
- Less dose - More likely to miss smaller structures - Less Resolution
Source Collimators/ Prepatient Collimation (CT)
- Located near the x-ray source and limits the amount of x-ray emerging to thin ribbons. - Because it acts on the x-ray beam before it passes through the patient it is sometimes referred to as prepatient collimation. - The source collimator affects patient dose and determines how the dose is distributed across the slice thickness (i.e., dose profile). - The source collimator resembles small shutters with an opening that adjusts, dependent on the operator's selection of slice thickness.
High Frequency Generators (CT)
- Located within the Gantry. - Power capacity is listed in Kilowatts (kW) and determines the range of exposures. - Increasing kV = Increases penetrability, and reduces patient dose.
Window Width General (CT)
- Lung WW 1500 WL-700 - Bone WW 2000 WL 500 - Soft Tissue WW 400 WL 50 - Brain WW 140 WL 40 - Remember that these will vary from place to place
Data Acquisition System DAS (CT)
- Measures the number of photons that strike the detector, converts the information to a digital signal, and sends the signal to the computer - Converts the analog signal from the detector into a digital signal - To create an image, information from the DAS must be translated into a matrix. - To do so, the system assigns each pixel in the matrix one value, or density number. - This density number, in Hounsfield units, is the average of all attenuation measurements for that pixel. - detector/digital signal/computer
Parenteral Injection (CT)
- Medicine Taken into the body or administered in a manner other than through the digestive tract, as by intravenous or intramuscular injection.
Monitors and Digital to Analog Converters DAC (CT)
- Monitors used in CT require analog signals, therefore, it is necessary to convert the digital signal form the computers memory back to an analog format using DAC.
Step and Shoot Scan Mode (CT)
- Older Method
Xenon Gas Detectors (CT)
- Older Technology - the striking photon ionizes the xenon gas. These ions are accelerated by the high voltage on the detector plates
%50 Overlap (CT)
- On helical data from either SDCT or MDCT systems, image incrementation can be changed. - This is often done to produce overlapping images that are then used in multiplanar or 3D reformations. - When the slice thickness is wider or the FOV is larger, it is common practice to reconstruct images with an overlap of approximately 50% whenever multiplanar or 3D post-processing is expected to occur. Ex. a case scanned with a slice thickness of 5mm would be reconstructed every 2.5mm.
Slip Rings (CT)
- Permits the Gantry Frame to rotate continuously, making Helical Scan methods possible.
Which interaction between x-ray beam and matter results in the largest amount of patient dose? (CT) (RAD)
- Photoelectric Effect
Algorithm (CT)
- Precise set of steps to be performed in a specific order to solve a problem. - Are used in CT to convert information obtained from the detector array into information suitable for image display.
Incrementation, Feed, Step, Index (CT)
- Process of moving the table by a specific measure. - "Z" Axis
Hounsfield Units (CT)
- Quantify the degree that a structure attenuates an X-ray beam. There are 2000 Hu's for natural occurring atomic structures. -1000 = Air 0 = Water 1000+ = Bone
Dynamic Range (CT)
- Ratio of the maximum signal measured to the minimal signal the detectors can measure.
Operators Console (CT)
- Reconstructing raw data to create new images can only be from the operators console.
Prospective Data (CT)
- Reconstruction that is automatically produced during scanning.
Low Contrast Resolution (CT)
- Refers to the ability of a system to differentiate, on the image, objects with similar densities. ! Similar Density Differences
Temporal Resolution (CT)
- Refers to the ability of the scanner to image moving objects effectively. - Also refers to the speed that the scanner acquires data. - Particularly important to reduce or eliminate artifacts that result from object motion, such as those commonly seen when imaging the heart. - Often associated with cardiac imaging.
Capture efficiency (CT)
- Refers to the ability with which the detector obtains photons that have passed through the patient.
Absorption efficiency (CT)
- Refers to the number of photons absorbed by the detector and is dependent on the physical properties of the detector face (e.g., thickness, material).
Spacial Resolution (CT)
- Represents the ability to discriminate objects of varying density, a small distance apart, against a uniform background. - Synonym: Detail Resolution...?
Image Data (CT)
- Result once the computer has processed the raw data and displayed an image - Once the computer has processed the data into pixels One HU is assigned to each pixel - Image data requires about one fifth of the computer space as does raw data - If only image data are available, data manipulation is limited, Meaning you can change the way the image data is displayed but you cannot change the scanning parameters such as slice thickness
Retrospective Scanning (CT)
- Reuses Raw Data to generate new images.
Window Level - (CT)
- Selects "which" HU values are displayed as shades of gray. - Mechanism that selects the center CT value of the window width. - Also called window center - The window level should be set at a point that is roughly the same value as the average attenuation number of the tissue of interest.
Window Width - Contrast (CT)
- Selects the "quantity" of HU values to be displayed as shades of gray. - By selecting the center value, the window width selects the range of HU that will be displayed. - All Values higher than the range = White. - All Values lower than the range = Black.
Interval (CT)
- Spacing between adjacent slices. - Is independent of slice thickness in helical CT. - The z-position of any given slice is determined by which projection is used to start the slice. - Remember that to reconstruct an entire slice, you need 180 (plus fan angle) degrees of projection data. - In helical CT, each projection is done at a different z-position, therefore depending on which projection you use to start the slice, your slice is centered at a different z-position.
Stenosis (CT)
- The abnormal narrowing of a passage in the body.
To form an Image (CT)
- The computer assigns one HU value to each pixel. This value is the average of all attenuation measurements for that pixel.
Scannable Range (CT)
- The degree to which the table can move Horizontally.
Ray Sum (CT)
- The detector reads each arriving ray and measures how much of the beam is attenuated.
Effusion (CT)
- The escape of fluid from the blood vessels or lymphatics into the tissues or a cavity. - A collection of the fluid effused.
Matrix (CT)
- The grid formed from the rows and columns of pixels. - Where all the information from all the profiles is projected onto.
Gray Scale (CT)
- The human eye can differentiate only a fraction of the 256 shades of gray displayed by a monitor - To solve the problem of more Hounsfield units than discernible shades of gray, the gray scale is used - The display processor assigns a certain number of HU to each level of gray - The number of HU assigned to each level of gray is determined by the Window Width - By convention, the gray scale assigns higher HU values for lighter shades of gray and lower HU values for darker shades of gray
Scan Field Size (CT)
- The number of detector cells that collect data is controlled by?
Image Reconstruction Detailed (CT)
- The path that the x-ray beam takes from the tube to the detector is called a ray - The DAS "reads" each arriving ray and measures how much of the beam is attenuated, This is a ray sum - Many ray sums make up a view - Many views are needed to create an image - An attenuation profile is created for each view The system accounts for the attenuation properties of each ray sum and correlates it to the position of the ray - Information from all the profiles is projected onto a matrix - The process of converting the data from the attenuation profile to a matrix is known as back projection - Back projection compiles the information from all of the attenuation profiles to create an image
Ray (CT)
- The path the X-ray beam takes form the tube to the detector.
Volume Averaging or Partial Volume Effect (CT)
- The process by which different tissue attenuation's are averaged to produce one less accurate pixel reading. - Slice Thickness is responsible for
Convolution (CT)
- The process of applying a Filter Function to an attenuation profile. - Associates w/ Filter
Back Projection (CT)
- The process of converting the data from the attenuation profile to a matrix - Associates w/ Matrix
Image Reconstruction Simple (CT)
- The process of manipulating data collected from the detectors to produce a useful image that can be sent to a display device. - Created with raw data
Standard Deviation (CT)
- The standard deviation indicates the amount of CT number variances within the ROI. - A standard deviation of 0 indicates that every pixel within the ROI has the same HU, or Homogeneous.
Viscosity (CT)
- The state of being thick, sticky, and semifluid in consistency, due to internal friction
Attenuation Profile (CT)
- The system accounts for the attenuation properties of each ray sum and correlates them with the position of the ray. - Is created for each view in the scan.
Window Width Gray Scale (CT)
- To illustrate, assume we have just 10 shades of gray available - 300 is selected as the window width - 300 density values will be represented on the image as a shade of gray (in this example 10 HU will be included in each shade of gray) - All others will be either black or white
Beta Blockers (CT)
- Used in cardiac CT studies. - Control heart rate - b-Adrenergic receptor blocking agents (b-blockers) may be used to reduce a patient's heart rate. - Sixtyfive beats per minute (65 bpm) is the preferred rate for optimal imaging on most multislice CT (MSCT) systems - ex. Nitroglycerin ! 65 BPM preferred in cardiac studies
IV Contrast for Musculoskeletal (CT)
- Usually not needed - If needed 2 mL/s with a 60 sec delay
Referencing the Table or Zeroing (CT)
- When an Anatomical landmark is chosen and the position is manually set to zero.
Polychromatic Beam (CT)
- X-ray beam in CT is of varying photon energies.
64-slice+ & Pharmaceutical Intervention (CT)
- capable of acquiring adequate cardiac CT images at higher heart rates. - This capability may preclude the need for pharmaceutical intervention as clinically indicated
Metastatic (CT)
- the spread of a disease-producing agency (as cancer cells) from the initial or primary site of disease to another part of the body
X-ray photons are produced by a fast-moving electron? (CT)(RAD) 1. colliding with an atomic nucleus 2. passing close to an atomic nucleus 3. colliding with an electron within an atom and ejecting
1, 2 and 3
Narrow Window Widths CT
50-500 HU - Are best for tissue types that with similar densities, and will provide greater density discrimination and contrast.
Wide Window Widths (CT)
500-2000 HU - Are best for imaging tissue types that vary greatly.
Detector Efficiency (CT)
Is the product of a number of factors. These are: 1) stopping power of the detector material 2) scintillator efficiency (in solid-state types) 3) charge collection efficiency (in xenon types) 4) geometric efficiency, defined as the amount of space occupied by the detector collimator plates relative to the surface area of the detector 5) scatter rejection.
Factors that produce a high standard deviation are: (CT)
Mixed attenuation tissue ROI that includes streak or artifact Incorrectly placed ROI
(CT) Phases
Phase 1 = Data Acquisition (Get Data) Phase 2 = Image Reconstruction (Use Data) Phase 3 = Image Display (Show Data)