CT - Computed Tomography
An image was produced with a 1.0 mm aperture size and was displayed using a 512² matrix and a 15 cm DFOV. The voxel dimensions for this image would be: (1) 0.29 mm x 0.29 mm x 1.0 mm (2) 2.9 mm x 2.9 mm x 1.0 mm (3) 3.4 mm x 3.4 mm x 1.0 mm (4) 0.29 mm x 0.29 mm x 1.0 cm
(1) 0.29 mm x 0.29 mm x 1.0 mm Pixel dimension may be calculated by dividing the DFOV by the matrix size. This 2 dimensional pixel size is then multiplied by the length of the voxel.
Which of the following manipulations involves the use of image data: (1) Adjusting the width and level of a window setting. (2) Decreasing the DFOV (3) Changing the algorithm selection. (4) Increasing the matrix size.
(1) Adjusting the width and level of a window setting. Adjusting the window width or level is a computer manipulation of the image data. The image has already be reconstructed from scan or "raw" data. The window only changes the range of pixel values that will be assigned a shade of gray. Adjustment in the algorithm, DFOV, or matrix require the raw data so that the image may be retrospectively reconstructed.
Which of the following technical considerations in necessary to differentiate hydronephrosis from parapelvic cysts on a CT exam: (1) Administration of of an iodinated IV contrast agent (2) Prone acquisition (3) Administration of an oral contrast agent (4) Valsalva maneuver
(1) Administration of of an iodinated IV contrast agent Parapelvic cysts are simple cysts arising within the renal pelvis. They are similar in appearance to the distention of the pelvis and calyces known as hydronephrosis. Delayed imaging after IV contrast agent administration opacifies the renal pelvis, clearly differentiating hydronephrosis from parapelvic cysts.
Which of the following is NOT an improvement is CT chest imaging due to the development of multidetector technology. (1) An overall reduction in patent radiation dose (2) Reduction in partial volume artifact (3) Elimination of misregistration artifacts (4) Improved contrast enhancement
(1) An overall reduction in patent radiation dose The drawback of MDCT is the potential for an increase in overall patient radiation dose.
Which of the following window settings would optimally display CT colonography images: (1) Level = -400, Width = 1600 (2) Level = +50, Width = 400 (3) Level = +150, Width = 1000 (4) Level = +250, Width = 4000
(1) Level = -400, Width = 1600 CT colonography images are best displayed in a wide "lung type" window setting.
The normal range for the International Normalized Ratio (INR) for prothrombin time (PT) results is: (1) 0.2 - 0.5 (2) 0.8 - 1.2 (3) 2.2 - 3.5 (4) 6.1 - 8.6
(2) 0.8 - 1.2
A CT scanner capable of reproducing an image that is a perfect reproduction of the actual anatomic section is said to have an MTF of: (1) 0 (2) 1 (3) 10 (4) 100
(2) 1 The modulation transfer function (MTF) of a CT scanner measures the ability of the system to faithfully reproduce the area of anatomy. It can be thought of as a comparison of the actual anatomy with the image produced. If the two are exactly alike, the MTF of the scanner is 1. If the image produced contains no useful information, the MTF is 0. The MTF of most CT scanners falls somewhere in between.
Assuming a bolus injection of iodinated contrast agent at a rate of at least 4 mL/sec, an appropriate scan delay for a CTA examination of the mesenteric vasculature would be in the range of: (1) 5-8 sec (2) 20-30 sec (3) 45-60 sec (4) 70-90 sec
(2) 20-30 sec Dual phase imaging including the arterial phase (20-30 sec) and portal venous phase (60-70 sec) is typically preformed for a complete evaluation of the mesenteric vasculature.
The normal range of cerebral blood volume (CBV) contained within 100g of brain tissue is: (1) 0.6-1.0 mL/100g (2) 4.0-5.0 mL/100g (3) 15-19 mL/100g (4) 30-40 mL/100g
(2) 4.0-5.0 mL/100g
_______ is a term that refers to an excessive amount of nitrogenous materials in the blood and is a symptom of renal failure. (1) Hydronephrosis (2) Azotemia (3) Oliguria (4) Diuresis
(2) Azotemia This condition is also commonly called Uremia azotemia, it is a symptom of renal insufficiency and may occur during chronic renal failure.
The approximate CT density of the unenhanced spleen is: (1) Less than 0 HU (2) Between +40 and +60 HU (3) Between +75 and +90 HU (4) Greater than +100 HU
(2) Between +40 and +60 HU The unenhanced spleen CT density is approximately 10 HU less than that of the unenhanced liver.
Which of the following vessels would NOT be used as a site for the injection of iodinated contrast material? (1) Cephalic vein (2) Brachial artery (3) Antecubital vein (4) Basilic Vein
(2) Brachial artery: Intraarterial injections of contrast material are not routinely preformed for CT examinations.
The term ______ describes the ability of a CT scanner to differentiate objects with minimal differences in attenuation coefficients. (1) Spatial resolution (2) Contrast resolution (3) Linearity (4) Modulation
(2) Contrast resolution The systems ability to differentiate objects with similar densities. This ability is also referred to as the low-contrast resolution or the sensitivity of the CT scanner.
The type of hemorrhage that occurs between the skull and the outer layer of the dura in a traumatic brain injury is referred to as: (1) Subdural hematoma (2) Epidural hematoma (3) Subarachnoid hematoma (4) Subcutaneous hematoma
(2) Epidural hematoma an epidural hematoma occurs between the skull and the outer most meningeal covering of the brain called the dura matter. Subdural hematomas occur between the dura matter and the next inner layer of the meninges, known as the arachnoid. The inner most layer of the meninges is known as the pia matter.
The ability of a CT scanner to image a small high density object is controlled by the _____ of the scanner: (1) Contrast resolution (2) Spatial resolution (3) Sensitivity
(2) Spatial resolution The spatial resolution of a CT scanner controls its ability to image small objects.
Patients whose posterior depending artery branches from the right coronary artery, and whose left posterior ventricular branches arise from the left circumflex artery, are said to be: (1) Right dominant (2) Left dominant (3) Codominant (4) Posteriorly dominant
(3) Codominant 7% of the population is said to be codominant, meaning that the posterior descending artery (PDA) is supplied by the right coronary artery (RCA), and the left posterior ventricular branches arise from the left circumflex artery.
Cardiac CT images are typically acquired during which phase of the hearts cycle: (1) Systolic phase (2) Equilibrium phase (3) Diastolic phase (4) Ejection phase
(3) Diastolic phase The heart is optimally imaged with the least artifact from motion during its period of relaxation, also known as the diastolic phase of the heard cycle.
Which of the following types of CT scanners is best suited for the evaluation of coronary artery disease: (1) PET-CT (2) 4th generation (3) Electron beam CT (EBCT) (4) 2nd generation
(3) Electron beam CT (EBCT) EBCT scanners are designed to acquire information at an extremely rapid rate. These ultra fast CT systems can greatly reduce cardiac and pulmonary motion, allowing detailed evaluation of anatomic areas.
Which of the following stages of IV contrast agent administration, provides the best gastric and intestinal wall enhancement: (1) Early arterial (2) Corticomedullary (3) Portal Venous (4) Excretory
(3) Portal Venous
Which of the following types of image noise can be most easily reduced by the CT technologist: (1) Electronic noise (2) Artifactual noise (3) Quantum noise (4) Detector noise
(3) Quantum noise The quantum or statistical noise of a CT image can be reduced by increasing the number of x-ray photons absorbed by the detectors for each voxel of tissue. This can be accomplished with increases in technique (mAs) and with increases in the pixel and voxel dimensions.
Which of the following units is used to quantify effective dose? (1) Roentgens (R) (2) Grays (Gy) (3) Sieverts (Sv) (4) Curies (Ci)
(3) Sieverts (Sv) Effective does approximates the relative risk from exposure to ionizing radiation and is based on the radiosensitivity of a given tissue type.
The tortuous S-shaped portion of the internal carotid artery as it enters the bony skull may be referred to as the carotid: (1) Lordosis (2) Kyphosis (3) Siphon (4) Sinus
(3) Siphon Carotid siphon refers to the portion of the internal carotid artery as it enters the bony skull and bifurcates into the anterior cerebral and middle cerebral arteries.
The ______ gland is located in the anterosuperior portion of the mediastinum and is often identified with CT during scanning of younger patients. (1) Thyroid (2) Luschka (3) Thymus (4) parathyroid
(3) Thymus It is most easily visible prior to puberty. After puberty if becomes increasingly infiltrated with fat, so it is more difficult to image with CT.
Which of the following corresponds to the longitudinal dimension of the CT image voxel: (1) X - axis (2) Y - axis (3) Z- axis (4) Orthogonal axis
(3) Z- axis
A solitary pulmonary nodule can be assumed benign when its average density is within which of the following ranges: (1) 10-30 HU (2) 45-80 HU (3) 100-140 HU (4) 165-200 HU
(4) 165-200 HU
Which of the following pathologic conditions cannot be easily diagnosed from a CT scan of the brain: (1) Astrocytoma (2) Traumatic hemorrhage (3) Cerebra infarct (4) Alzheimer's disease
(4) Alzheimer's disease Alzheimer's disease may present with an enlargement of the temporal horns, but this is typically not specified on CT examinations.
Iodine is commonly use in radiopaque contrast media because of its: (1) Radiolucency (2) Viscosity (3) Osmolality (4) High atomic number
(4) High atomic number Iodine's high atomic number causes it to attenuate a large portion of the primary beam.
Which of the following technical factors exhibits an effect upon longitudinal spatial resolution. (1) Detector pitch (2) Interpolation algorithm (3) Display field of view (DFOV)
1 & 2
Which of the following symptoms indicate(s) a vagal reaction to an intravenous iodinated contrast agent: (1) Bradycardia (2) Systolic pressure below 80 mm Hg (3) Diastolic pressure above 90 mm Hg
1 & 2 A combination of bradycardia (heart rate below 50 beats per minute) and hypotension (systolic pressure below 80 mm Hg) indicates a vagal reaction.
Parenteral routes of medication administration include which of the following: (1) Subcutaneous (2) Intradermal (3) Transdermal
1 & 2 Parenteral routes of medication administration include intramuscular, intravenous, intradermal, and subcutaneous.
Which of the following factor(s) play(s) a roll in the production of an isotropic dataset (1) Section width (2) Scan field of view (SFOV) (3) Display field of view (DFOV)
1 & 3 Isotropic resolution is approached by choosing the thinnest detector collimation available to produce the thinnest slices available, and by reconstructing the acquired data with the smallest DFOV allowed according the the part of interest. Minimizing these 2 factors results in voxels approaching equal length in all directions.
Which of the following laboratory values is used to measure the coagulation ability of a patient prior to an invasive CT study? (1) PTT (2) Hematocrit (3) PT
1 & 3: Prothrombin Time (PT) & Partial Thromboplastin Time each attempt to detect deficiencies in the various clotting factors.
The excretion half-time of intravenous iodinated contrast media in a patient with normal renal function is between:
1 and 2 hours: Excretion half-time is a value describing the amount of time necessary for 50% of the contrast media to be filtered by the renal system.
Each 1.0% change in contrast between adjacent objects amount to a difference in pixel value of approximately how many HU?
10 HU
Prior to resuming normal breastfeeding, it is recommended that a patient who has undergone an IV administration of iodinated contrast agent should pump and discard breast milk for period of:
12-24 hours Because the plasma half-life of iodinated contrast material is approximately 2 hours, the level in breast milk after 24 hours is essentially negligible.
For trauma indications, CT exams of the hips and pelvis, may include which of the following advanced applications: (1) CT enteroclysis (2) CT angiography (3) CT cystography
2 & 3 Contrast-enhanced MDCT acquisitions of the post-traumatic pelvis may include CTA evaluation for vascular injury as well as assessment of the bladder via CT cystography.
What is the maximum number of line pairs per centimeter (lp/cm) the smooth algorithm can demonstrate?
8.1
A voxel may be defined as what:
A volume element It is represented within a matrix by a pixel
The best method of reducing contrast-induced nephrotoxicity (CIN) is:
Adequate patient hydration.
On a female patient gonadal shielding may be applied during which of the following examinations: (1) Chest (2) Abdomen (3) Brain
All 3 Gonadal shielding may be used whenever the gonads do not lie withing the area of clinical interest. Gonadal shielding in the female patient is most difficult during CT scanning of the pelvis.
Azimuth setting refers to what:
Azimuth setting refers to the relationship between the x-ray tube and detectors during scout or localizer production.
An IV contrast enhanced specialized CT evaluation of the small bowel after the oral administration of a low density (0.1%) barium sulfate solution is termed:
CT Enterography
Evaluation of the venous vascular structures of the brain is known as:
CT Venography (CTV) CTV of the brain is a variation of the CTA technique whereby the timing of data acquisition is optimized for the period of peak venous opacification.
The approximate radiation dose measured during a scan of a 100-mm pencil ionization chamber is termed the:
CTDI CTDI is a fixed measurement taken with a 100-mm long pencil ionization chamber inserted into an acrylic phantom. The CTDI standardizes the dose measurement from a single axial scan, and can be used to compare doses from different scan techniques.
The primary indication for a non-contrast cardiac MDCT examination is:
Coronary artery calcium quantification: Coronary artery calcium (CAC) quantification is for the assessment of atherosclerotic disease.
A patient is scheduled for an intravenous iodinated contrast-enhanced CT scan of the kidneys. Prior to injection the involved medical professional personnel should examine recently measured laboratory values for which of the following? (1) CBC (2) Creatinine (3) PT
Creatinine: The serum creatinine level is a laboratory value used to measure renal function, and abnormally elevated values are often signs of renal failure.
Following a CTA of the chest for pulmonary embolism, an additional acquisition may be preformed through the lower extremities to evaluate for:
Deep vein thrombosis (DVT) DVT, the formation of blood clots in the distal blood vessels, is common in the popliteal and femoral veins of the lower extremities
Each iliac artery bifurcates into the internal and external iliac arteries at about the level of:
L5-S1
Severe reactions to intravenous iodinated contrast material occur in approximately _______ of all patients:
Less than 1%
The period of peak hepatic parenchymal enhancement following rapid bolus injection of iodinated contrast is termed the:
Portal venous phase
Which of the following oral contrast agents offers the best visualization of the enhancing GI wall on post IV-contrast CT examinations (1) Low-osmolar water-soluble iodinated solution (2) High-osmolar water-soluble iodinated solution (3) Water (4) Barium sulfate suspension
Water Water as a negative oral contrast agent improves visualization of the enhancing enteral wall when an IV contrast agent is administered.
Increasing the detector pitch during a spiral CT exam adversely affects the spatial resolution along which axis?
Z-axis: Spatial resolution along the Z-axis is decreased as detector pitch is increased.
