CT Image Production
After performing a thoracic spine scan for trauma, the radiologist requests images of the entire bony thorax. The raw data is still saved on the CT scanner. This will require
Retrospectively reconstructing images with a different display field-of-view (DFOV) When scanning a patient, the raw data usually includes significantly more patient anatomy than the image data. The raw data will include everything in the SFOV. which fills almost the entire gantry. Thoracic spine images use a display field of view that is much smaller than that. As long as the raw data is still on the computer, the entire bony thorax can be reconstructed retrospectively without rescanning the patient. This is accomplished by reconstructing the data into a different DFOV.
Acquiring a z-axis measurement of pathology is possible in which two imaging planes?
Sagittal coronal Z-axis measurements could be evaluated in the sagittal or coronal planes. Sagittal and coronal images both allow for measuring a pathology from superior to inferior in one image.
CTA imaging of the heart is sometimes performed with the CT scanner in the volume acquisition mode. This means that the:
Scan data is acquired in one rotation of the x-ray tube Volume scanning is the preferred way to image the heart
Out-of-field artifact is caused when a part of the patient is outside of the:
Scan field-of-view (SFOV) Out-of-field artifact is exactly what it sounds like; It is an artifact caused by some portion of the patient being outside of the SFOV It is critical to understand that anatomy can be outside of the DFOV without causing artifact. Out-of-field artifact is only created when some portion of the patient is outside of the SFOV.
Which three of the following scan parameters can be changed retrospectively? -Scan start and end locations -Slice thickness -Scan field-of-view (SFOV) -Display field-of-view (DFOV) -Acquisition thickness
Scan start and end locations Slice thickness Display field-of-view (DFOV)
Which of these 3D rendering techniques display only one tissue type? Shaded surface display Volume rendering Maximum intensity projection Minimum intensity projection
Shaded surface display Unlike other 3D rendering techniques, the shaded surface display algorithm will only show one tissue at a time. This is beneficial for rapid construction of the images, but it does limit the diagnostic value.
How does cone beam artifact affect the appearance of the CT image?
Shape distortion of anatomy Cone beam artifact is difficult to identify on the CT image. It is important to understand that when it does appear, the result is slight distortions in the shape of the anatomy.
In the reconstructed image data, the distance from the start of one slice to the start of the next slice is defined as the:
Slice interval
A patient in the emergency department is suspected of having a blowout fracture of the right maxillary sinus. Structural damage to the soft tissue of the eye will be best demonstrated with
Smoothing algorithms All soft tissues, including the soft tissues of the eye, should be evaluated using reconstructed images with a smoothing algorithm. This makes soft tissues look smooth and easier to see. The other algorithms listed create more edge enhancement, which is good for viewing bones but not good for viewing soft tissues.
Which two algorithms are most useful for viewing soft tissue changes around the cranium?
Smoothing algorithms Standard algorithms Unlike the bone algorithm, the standard algorithm and smoothing algorithms decrease edge enhancement. These types of algorithms are commonly used to view soft tissues, including soft tissues around the cranium. Soft tissues should not be viewed with any kind of edge-enhancing or bone algorithm. This would create more image noise that makes the soft tissues difficult to see.
Which of these scenarios will result in images with the best contrast resolution? Soft tissue algorithm with 1.0 mm slices Soft tissue algorithm with 2.0 mm slices Bone algorithm with 1.0 mm slices Bone algorithm with 2.0 mm slices
Soft tissue algorithm with 2.0 mm slices The main issue affecting contrast resolution is image noise. Image noise is reduced by using softening algorithms and thicker reconstruction slices. In this question, the soft tissue algorithm in 2.0 mm slices results in the least amount of image noise and therefore the best contrast resolution. The side effect of this option is a decrease in spatial resolution.
Production of x-rays in a CT machines requires a:
Source of electrons Means of rapid acceleration of electrons Means of rapid deceleration of electrons
What describes the ability of computed tomography (CT) scanners to produce detailed images of small parts?
Spatial Resolution By definition, spatial resolution refers to the ability of a scanner to create detailed images. Various factors contribute to the creation of high spatial resolution images. All other terms listed here refer to other image quality factors, not image detail.
What is measured in line-pairs per centimeter?
Spatial resolution Spatial resolution is measured in line pairs per centimeter. Sometimes it might be measured in line pairs per millimeter, but the idea is stil the same. Since spatial resolution is the ability of a scanner to create detailed images of small parts, it makes sense that spatial resolution is measured by imaging a tool with very small line pairs.
The slice thickness of a reformation will affect what
Spatial resolution Image noise Reformation slice thickness affects the image in the same way as reconstruction slice thickness. The slice thickness affects the spatial resolution and the image noise. For example, increasing the reformation slice thickness results in decreased spatial resolution and decreased image noise.
Which of the following multiplanar reformations are impossible to create? -1.0 mm coronal reformation from 5.0 mm axial reconstructions -5.0 mm sagittal reformation from 1.0 mm axial reconstructions -Bone reformation from bone algorithm reconstruction -Standard reformation from bone algorithm reconstruction
Standard reformation from bone algorithm reconstruction Multiplanar reformations can make several changes to the original image data, but it cannot change the algorithm. Image data created in the bone algorithm will always be in the bone algorithm. Creating images in a new algorithm requires retrospective reconstruction, not multiplanar reformation.
While imaging an infant, the rotation time may be decreased to prevent motion artifacts. A decrease in rotation time represents a change in:
Temporal resolution A change in rotation time affects the temporal resolution. Changing the rotation time has some negative effects, but it can help to improve the temporal resolution and decrease the appearance of motion artifacts on the images.
The motion artifact is a quality control issue related to:
Temporal resolution The appearance of motion is a result of low temporal resolution. This motion artifact could be reduced by increasing the temporal resolution, such as increasing the speed of the scan.
Consider four different CT scanners, each with a different minimum rotation time. What is the main image quality factor affected by the difference in minimum rotation time? Scanner 1 = 0.1 seconds Scanner 2 = 0.2 seconds Scanner 3 = 0.3 seconds Scanner 4 = 0.4 seconds
Temporal resolution The rotation time primarily affects the temporal resolution, which is the ability of the scanner to produce clear images of moving parts. The faster images can be acquired, the better the temporal resolution.
Which of the following statements regarding the SFOV are true - The SFOF is larger than the DFOV - Data in the SFOV is sent to the radiologist - Data in the SFOV is saved on the CT computer system - The size of the SFOV is set by the technologist using the scout images
The SFOF is larger than the DFOV Data in the SFOV is saved on the CT computer system
If the reconstruction slice thickness is set to 3.0 mm, which of these statements is also true? -The image data is 3.0 mm thick -The image data is greater than 3.0 mm thick -The image data is less than 3.0 mm thick -The acquisition thickness is also 3.0 mm
The image data is 3.0 mm thick Reconstruction is a process through which image data is created. The image data is organized into slices, just like a loaf of bread is organized as slices. If the reconstruction slice thickness is set to 3.0 mm, the image data will be created at 3.0 mm. The reconstruction slice thickness is the same as the image slice thickness.
The sequential acquisition mode is described by which of these statements?
The patient table moves only between x-ray exposures
Changing the thickness of a voxel may also change:
The tissue types included in the voxel Changing the thickness of a voxel may also change the tissue types included in the voxel. The size of a voxel is important because it changes how much tissue gets included in the voxel display. As slice thickness increases, the voxel thickness increases, and more tissue is averaged into that voxel. This potentially changes the appearance of the voxel when it is displayed as a pixel on the CT image.
What two combinations of reconstruction parameters could be used to create detailed images of the bony trabeculae?
Thin slices Edge-enhancing algorithms Several variables affect the detail, or spatial resolution, of an image. The best detail and best spatial resolution can be achieved by using thin slices and edge enhancing algorithms. This creates more image noise, but it allows for the visualization of smaller parts.
A hospital stores old radiographic patient films in an unlocked room. Is this a Health Insurance Portability and Accountability Act (HIPAA) violation?
This is a HIPAA violation
Results from a magnetic resonance imaging (MRI) scan are accidentally mailed to the wrong person. Is this a Health Insurance Portability and Accountability Act (HIPAA) violation?
This is a HIPAA violation
A hospital employee left a telephone message with the daughter of a patient that detailed the results of a recent medical examination. Is this a Health Insurance Portability and Accountability Act (HIPAA) violation?
This is a HIPAA violation only if the daughter has not been identified to receive protected health information on behalf of her mother This situation is very common. Sometimes it is a HIPAA violation and sometimes it is not. It is only a HIPAA violation if the daughter has not been identified to receive protected health information on behalf of her mother. If she does not have this permission, it is absolutely a HIPAA violation.
Due to a miscommunication, The Health Insurance Portability and Accountability Act (HIPAA) law is not assigned as a part of an employee's annual training. Is this considered a HIPAA violation?
This is a HIPAA violation only if the employee has access to protected health information Not all employees require HIPAA education. But if an employee has access to protected health information, HIPAA Law requires that they be educated on HIPAA requirements. If the employee does not receive HIPAA education, this in itself a HIPAA violation.
After performing the procedure, a technologist views the radiology report on their older sibling using the organization's Picture Archiving and Communication System (PACS) system. Is this a Health Insurance Portability and Accountability Act (HIPAA) violation?
This is a HIPAA violation only if the technologist did not have consent from the sibling to view the report Technologists are only allowed to view patient health information when they have permission to do so or when it is a required part of performing their job. If the sibling does not have consent to view the report, this would be a HIPAA violation.
A technologist leaves a radiology requisition in a public bathroom near the sink. Is this defined as a breach of Health Insurance Portability and Accountability Act (HIPAA) law?
This is a breach of HIPAA law
Consider this scenario: The director of the radiology department is brought to the emergency department unconscious following a severe motor vehicle accident. After a CT head is performed, the radiology staff not involved in the case gather around the Picture Archiving and Communication System (PACS) monitor to view the images. Is this a breach of the Health Insurance Portability and Accountability Act (HIPAA) law?
This is a breach of HIPAA law
Someone in the radiology clerical staff places a billing statement in a waiting room trash can. Is this a breach of the Health Insurance Portability and Accountability Act (HIPAA) law?
This is a breach of HIPAA law
A patient requests a paper copy of their radiology report. If the paper report is provided directly to the patient, is this a Health Insurance Portability and Accountability Act (HIPAA) violation?
This is not a HIPAA violation
A radiologist requested that a repeat scan be performed on a CT patient, stating, "The patient's head was not positioned correctly' If the technologist views the original images to identify the mistake, is this a Health Insurance Portability and Accountability Act (HIPAA) violation?
This is not a HIPAA violation
What quality control test evaluates the ability of the CT scanner to produce the same CT number for the same material regardless of where the region of interest (ROl) is placed?
Uniformity Uniformity is the test used to ensure that the CT scanner produces the same CT number reading for the same material regardless of where the -material is measured on the image. In other words, CT numbers should be uniform throughout the image in a homogeneous structure.
When scanning a water phantom for quality control, you notice that a region of interest (ROl) in the center of the phantom reads 0 hounsfield unit (HU) but an ROl on the edge of the phantom reads 4 HU. This is a problem with:
Uniformity When evaluating an image of a homogeneous structure, like a water phantom, the scanner should produce the same CT number regardless of where the ROl is placed in the image. In this question, the CT numbers are different. The numbers are not uniform within the image, so this is referred to as a problem with uniformity.
A physician is requesting a 3D imaging showing several tissues with various levels of transparency. The appropriate rendering technique is:
Volume rendering Volume rendering allows the technologist to create 3D images with different tissues and different levels of transparency. For example, volume rendering is sometimes used to create images of the thorax that show the lungs as well as the surrounding bony structures. Shaded surface display shows only one tissue at a time. Maximum intensity and minimum intensity projections cannot provide transparency.
What CT scanning method requires a large detector array with numerous data collection channels?
Volume scanning
A three-dimensional block of image data in CT is called a:
Voxel A two-dimensional picture element is called a pixel. When a pixel is given a third dimension, this is called a voxel. Voxel stands for volume pixel.
Consider the following scenario: Several quality control (QC) tests were performed on four different scanners. Based on the results of these tests, which scanner has the best computed tomography (CT) number accuracy? -Water phantom average = - 0.5 hounsfield units (HU) Water phantom standard deviation = 1.2 Line pairs = 12 Ip/cm -Water phantom average = 1.0 hounsfield units (HU)Water phantom standard deviation = 3.1 Line pairs = 14 lp/cm -Water phantom average = -11 hounsfield units (HU)Water phantom standard deviation = 0.2 Line pairs = 13 lp/cm -Water phantom average = 2.0 hounsfield units (HU)Water phantom standard deviation = 2.0 Line pairs = 10 lp/cm
Water phantom average = - 0.5 hounsfield units (HU) Water phantom standard deviation = 1.2 Line pairs = 12 Ip/cm CT number accuracy refers to the ability of the scanner to produce a HU reading that is very similar to the expected reading. A water phantom should produce an average HU very close to zero. In this question, -0.5 hounsfield units is the closest number to zero.
Consider the following scenario: Several quality control (QC) tests were performed on four different scanners. Based on the results of these tests, which scanner has the least amount of image noise? -Water phantom average = - 0.5 hounsfield units (HU) Water phantom standard deviation = 1.2 Line pairs = 12 lp/cm -Water phantom average = 1.0 hounsfield units (HU) Water phantom standard deviation = 3.1 Line pairs = 14 Ip/cm -Water phantom average = -11 hounsfield units (HU) Water phantom standard deviation = 0.2 Line pairs = 13 Ip/cm -Water phantom average = 2.0 hounsfield units (HU) Water phantom standard deviation = 2.0 Line pairs = 10 lp/cm
Water phantom average = -11 hounsfield units (HU) Water phantom standard deviation = 0.2 Line pairs = 13 Ip/cm Image noise is based on the standard deviation. The lowest standard deviation represents the least amount of image noise. In this question, the lowest standard deviation is 0.2.
Which of these scenarios will result in gaps in the reconstructed image information? -When the slice interval is equal to the slice thickness -When the slice interval is greater than the slice thickness -When the slice interval is less than the slice thickness
When the slice interval is greater than the slice thickness Normally, the slice interval should be set equal to the slice thickness. In this scenario, one slice ends and the next life starts with no gaps. Gaps are created in the data set when the slice interval is greater than the slice thickness. It would be like adding gaps in between the slices of a loaf of bread.
A technologist completed a non-contrast scan of the heart for calcium scoring. If the technologist uses a window width (WW) of 300 and a window level (WL) of 30, how will dense calcifications in the heart be displayed?
White Based on the window width and window level, all pixel values between -120 and +180 will be displayed as a shade of gray. Since calcifications are expected to have a value of above 180 hounsfield units (HU), they will be displayed as white.
Which of these windowing techniques will result in the brightest overall image? Window width = 450, window level = 45 Window width = 1500, window level = 40 Window width = 300, window level = 100 Window width = 40, window level = -30
Window width = 40, window level = -30 40 window width and -30 window level will result in the brightest overall image. In this question, only the window level affects image brightness, so the window width values can be disregarded. The brightest image is the one with the lowest window level. Lowering the window level results in more CT numbers getting assigned as white, which in effect brightens the image.
Consider the following scenario: A radiologist is requesting changes to the brightness and contrast of images used for a CT-guided biopsy in the pelvis. Which of these windowing techniques will result in the darkest image with the highest contrast? Window width = 450, window level = 45 Window width = 1500, window level = 40 Window width = 300, window level = 30 Window width = 40, window level = 100
Window width = 40, window level = 100 The highest contrast is achieved by the smallest window width, which in this scenario is 40. The darkest image, the image with the least amount of brightness, is achieved by the largest window level, which in this scenario is 100.
Consider an imaging protocol that calls for very high contrast images of the brain. Which of these settings will display an image with the highest contrast? Window width = 550, window level = 45 Window width = 1500, window level = 50 Window width = 300, window level = 80 Window width = 40, window level = 30
Window width = 40, window level = 30 40 window width and 30 window level will display an image with the highest contrast. Only window width controls the contrast of the image. In this question, the window level can be disregarded. The highest contrast is achieved by the smallest window width. This is because there is less gray and more black and white forming the image.
Physical components located inside the CT gantry typical includes:
X-ray tube High-voltage generator
Shifting the center of a sagittal image requires changes to which two data coordinates?
Y-axis Z-axis When the center of a sagittal image is changed, this requires changing the y-axis coordinate, or the z-axis coordinate, or both. A change in the y-axis will shift the image center in terms of anterior and posterior. A change in the z-axis coordinate will shift the image inferior or superior.
To avoid violation of The Health Insurance Portability and Accountability Act (HIPAA) law, paper medical records must be stored:
locked rooms or file cabinets According to HIPAA law, all medical records must be protected and secured. Paper records must be locked in rooms or file cabinets. Electronic records must be password protected.
helical scanning AKA
spiral scanning
Acquisition thickness refers to the
thickness of active detective rows
Spatial resolution is defined as the ability to:
visualize small parts By definition, spatial resolution is the ability to visualize small parts. It is also the ability to clearly visualize spaces between those small parts, which is why it is called spatial resolution. The other definitions here refer to other image quality characteristics.
When using an 80 window width (WW) and 30 window level (WL), what range of pixel intensities will be assigned a shade of gray?
-10 to 70 Pixel values in the range of -10 to 70 will be assigned a shade of gray when using 80 WW and 30 WL. To find the specific values, add half of the window width above the window level, and half of the window width below the window level. 30 + 40 = 70. 30 - 40 = -10.
The signal produced by a detector is a(n):
-Analog electrical signal
Consider a voxel that includes equal parts bone (+1000 hounsfield units [HU]) and air (-1000 HU). In the reconstructed image, the displayed pixel value will be approximately:
0 HU The displayed pixel value will be approximately 0 HU. The appearance of a voxel on the displayed CT image is the average of all tissues within that voxel. In this case, the average of equal parts bone and air equals O hounsfield units.
Calculate the pixel size of a CT image created with the following variables: Matrix size = 512 × 512 Display field-of-View = 12 cm Scan field-of-view = 25 cm Reconstruction thickness = 1.25 mm
0.023 cm The pixel size is equal to the display field of view divided by the matrix size. In this question, 12 cm/512 = 0.023 cm. This means each pixel will be 0.023 cm wide, by 0.023 cm tall. This is very small!
Of the following options, what reconstruction slice thickness will display images with the highest level of spatial resolution? 0.625 mm 1.25 mm 5.0 mm 3.75 mm
0.625 mm Using a very thin reconstruction slice thickness will produce images with the highest spatial resolution. Of the options listed in this question, 0.625 mm represents the thinnest slice and therefore has the best spatial resolution. The major side effect of using thin reconstructed slices is an increase in image noise.
What is the pitch of a scan using the following variables? Acquisition thickness = 0.5 mm Detector rows = 20 Rotation time = 0.8 seconds Tube current = 250 milliamperes (mA) Table movement = 10 mm
1 Pitch is calculated as the table movement divided by the beam width. The beam width is calculated as the detector rows multiplied by the acquisition thickness. In this question the table movement equals 10 mm, and the beam width equals 10 millimeters. 10 divided by 10 equals 1.
Which of these reconstruction slice thicknesses is least likely to have partial volume averaging errors? 1 mm 3 mm 5 mm 10 mm
1 mm Partial volume averaging can be prevented by using very thin reconstruction slices. In this question, the thinnest slice is 1 mm.
If the pitch is equal to 1.1, how far is the patient table moving during each rotation of the tube?
1.1 times the beam width
Which of these axial data sets would be best suited for creating 5 mm coronal reformatted images through the abdomen? 1.25 mm axial images 2.5 mm axial images 5 mm axial images 10 mm axial images
1.25 mm axial images Multiplanar reformations should always be created from the thinnest available slices, even when they are being reformatted into thicker slices. Using thick axial slices results in blurriness in the reformatted images.
Which of these scenarios will produce cervical spine images with the best spatial resolution? 12 cm display field-of-view (DFOV) 15 cm display field-of-view (DFOV) 17 cm display field-of-view (DFOV) 22 cm display-field-of-view (DFOV)
12 cm display field-of-view (DFOV) The smallest DFOV will produce images with the best spatial resolution. This is because the pixels become smaller and have the ability to produce sharp images of smaller objects. That's the idea of high spatial resolution.
calculate the total beam width of a CT scan using 32 detector rows, 0.5mm detectors, 100 mA and 140 kVp
16mm 32 rows x (0.5 mm) row = 16mm
Which of these matrices will have the best spatial resolution? 1024 × 1024 512 × 512 256 × 256 2048 × 2048
2048 × 2048 The largest matrix will always have the best spatial resolution. Compressing more pixels into the same area makes the pixels smaller. Smaller pixels are able to create detailed images of smaller objects. This is the idea of high spatial resolution.
Which of these scans will have the best contrast resolution? -600 milliamperage (mA), 0.3 second rotation time, 1.0 mm slices, bone algorithm -500 milliamperage (mA), 0.4 second rotation time, 2.0 mm slices, standard algorithm -400 milliamperage (mA), 0.5 second rotation time, 3.0 mm slices, bone algorithm -300 milliamperage (mA), 1.0 second rotation time, 4.0 mm slices, standard algorithm
300 milliamperage (mA), 1.0 second rotation time, 4.0 mm slices, standard algorithm Contrast resolution is affected by all variables listed here. The mA and rotation time should be considered together, since mAx rotation time results in the total mAs. The highest total mAs will increase contrast resolution. Contrast resolution is also increased by thicker slices and smoothing algorithms, such as the standard algorithm. This is because all these characteristics will reduce the amount of image noise.
Based on feedback from an American College of Radiology (ACR) site-visit, your imaging department needs to design a new low-dose CT protocol for patients who weigh less than 30 pounds. Which of these detector configurations would be most suited for this protocol? 1 mm x 16 rows 2 mm x 8 rows 4 mm × 4 rows 8 0.5 x 8 rows
4 mm × 4 rows 8 For patients who weigh less than 30 pounds, 4mm x 4 rows should be used. Thicker detector rows allow for a decrease in radiation and patient dose. This is because the detector rows have a larger surface area to absorb radiation. Less radiation is required, which results in a decrease in patient dose. In this question, 4 mm detector rows is the largest option and therefore allows for the lowest dose.
Which of these window settings would be appropriate for viewing the major organs of the abdomen? -2500 window width (WW) and 600 window level (WL) -400 window width (WW) and 40 window level (WL) -1800 window width (WW) and -600 window level (WL) -80 window width (WW) and 30 window level (WL)
400 window width (WW) and 40 window level (WL) Technologists should understand the normal WW and WL assignments for certain body sections. An appropriate window display for the abdomen is 400 WW and 40 WL, however, different facilities will sometimes use slightly different numbers.
Of the following options, what reconstruction slice thickness will display images with the highest level of contrast resolution? 0.625 mm 1.25 mm 5.0 mm 3.75 mm
5.0 mm
Which of these scans will have the best spatial resolution? -600 milliamperage (mA), 1.0 second rotation time, 1.0 mm slices, bone algorithm -500 milliamperage (mA), 1.0 second rotation time, 2.0 mm slices, standard algorithm -400 milliamperage (mA), 0.5 second rotation time, 3.0 mm slices, bone algorithm -300 milliamperage (mA), 0.5 second rotation time, 4.0 mm slices, standard algorithm
600 milliamperage (mA), 1.0 second rotation time, 1.0 mm slices, bone algorithm Just about every factor of a CT scan potentially affects the spatial resolution. In this question, the largest mA is desirable because this is expected to reduce the amount of image noise and increase the clarity of spatial resolution in the image. The longest rotation time is preferred because longer rotation times result in more projections through the patient and better spatial resolution. Thinner slices improve spatial resolution since small slices can visualize smaller parts. The bone algorithm, like other edge enhancing algorithms, increases spatial resolution by adding more sharpness to the image.
The phrase "8-slice scanner" referse to a CT imaging system that has:
8 detector rows
What are the common voltage settings used in CT?
80, 100, 120, 140 kVp
Thicker slices are suitable for
Abdominal imaging thoracic imaging Thicker slices are good for viewing images with minimal noise, but there are some times that thick slices should never be used. Thick slices should never be used for multiplanar reformations as this results in blurriness in the images. Thick slices should also never be used for protocols requiring high spatial resolution, such as angiographic imaging.
After performing a CT of the chest, a region of interest (ROI) placed in the air outside of the patient yields an average CT number of -1,223. This error represents a problem with:
Accuracy All CT scanners should be calibrated so that they accurately display the same CT number for the same materials. For example, all CT machines should be calibrated so that they provide a CT number of -1000. In this question, the CT number for air is significantly different from the expected number. This number is not accurate, so it is referred to as an error in CT number accuracy.
When imaging a patient's paranasal sinuses, which of the following procedures may help prevent beam-hardening artifact?
Angle the gantry to avoid dental implants Beam hardening artifact is caused by very dense objects in the scan field. If a patient has dental implants, the technologist should angle the gantry to prevent the dental implants from appearing in the scan. In this question, no other answer options will have any effect on beam hardening artifact.
What portion of the patient is processed for viewing on the technologist computer monitor:
Any part of the patient within the display-field-of -view
What portion of the CT data collected during a scan is saved by the scanner but not reconstructed for viewing?
Any portion of the patient within the scan field-of-view (SFOV),but outside of the display field-of-view (DFOV)
What portions of a patient receive radiation exposure during CT scanning?
Any portion of the patient within the scanner gantry
The specific process that accelerates electron in an x-ray tube is
Application of a voltage
Which part of the Picture Archiving and Communication System (PACS) system houses all of the historic digital image data along with the current digital data being generated by the modalities?
Archive Server The Archive Server is the central part of PACS and houses all of the historic data along with the current data being generated. The archive serves as the central hub that receives all images before they are sent to the Radiologist reading room.
What component of a Picture Archiving and Communication System (PACS) network provides for permanent storage of image information?
Archive server The image archive server is the component of PACS that allows for the storage and recall of performed imaging studies.
A Picture Archiving and Communication System (PACS) network consists of
Archive server Imaging modality Display workstations
What is the relationship between acquisition thickness and spatial resolution?
As acquisition thickness increases, spatial resolution decreases
Which three of these measurements is usually acquired using a simple region-of-interest (ROI) tool? Average hounsfield unit (HU) value Milligray (mGy) Standard deviation Area (cm2) Dose Area Product (DAP)
Average hounsfield unit (HU) value Standard deviation Area (cm2)
Consider a voxel in a multiplanar reformation that includes equal portions of water, fat, and bone. What hounsfield unit (HU) will be displayed on the pixel?
Average of all HU in the voxel Typically, multiplanar reformations average all tissues in the voxel and display the average. This only changes when the technologist purposefully modifies the reformation to minimum intensity projections or maximum intensity projections.
What CT scanning mode may induce patient motion artifact from several stops and starts of the gantry table during data acquisition?
Axial mode
During what CT acquisition mode does the patient table move between x-ray exposures?
Axial scanning
What CT data acquisition mode collects a series of adjacent axial sections
Axial scanning
What two CT scanning modes activate the x-ray tube only while the patient table is stationary?
Axial scanning Volume scanning
What mathematical process prevents star-like artifacts from appearing on the CT images?
Back-projection filter Filtered back projection is the specific aspect of reconstruction used to prevent star artifacts on the CT image. Unfiltered back projection creates the same image, but the image will be filled with star-like artifacts.
During a CT of the abdomen and pelvis, using fluoroscopy-grade barium rather than CT-grade barium for rectal contrast will likely result in an image degradation called:
Beam hardening artifact Barium contrast for fluoroscopy is significantly more dense than barium used in CT. If fluoroscopy barium is mistakenly used, it absolutely will cause a significant amount of beam hardening artifact. CT scanners have much higher contrast resolution and are more sensitive to large changes in density.
What computed tomography (CT) artifact may result from excessive absorption of the x-ray beam?
Beam hardening artifact Beam hardening artifacts are the result of excessive absorption of the X-ray beam. The detectors do not receive enough information and this results in the streaks that extend from the dense objects.
An overly concentrated bolus of intravenous (IV) contrast may result in an error called:
Beam hardening artifact Beam hardening is caused by anything in the scan field that absorbs an excessive amount of radiation. This can even include a very concentrated bolus of iodinated contrast.
While imaging a CT chest, leaving an electrocardiogram (EKG) line in the exposure field may result in:
Beam hardening artifact Beam hardening is caused by very dense objects in the imaging field, especially metal. EKG lines include metal wires, so there is a chance this will cause beam hardening artifact.
While acquiring the scout images for a bony pelvis CT, you notice the patient has a hip prosthesis. The axial images may have:
Beam hardening artifact Beam hardening is caused by very dense objects, including metal, in the scan field. A hip prosthesis is made of metal, so it is expected to cause beam hardening artifact. This will appear as dark or light streaks extending from the interface between the tissue and the metal.
Pitch is defined as the ratio of the table movement to the:
Beam width Pitch is a ratio that describes the relationship between the movement of the table and the width of the beam.
According to the Health Insurance Portability and Accountability Act (HIPAA) law, protected health information includes which three of the following? -Employment status and employer -Billing and payment for care received -Patient health conditions -Treatment received for health conditions -Highest level of education received
Billing and payment for care received Patient health conditions Treatment received for health conditions Essentially all aspects of a patient's health information is protected by HIPAA. This includes the patient's conditions, the treatment they received for those conditions, and billing and payment for care received. Other patient information, such as employment and education, is generally not documented within their health record and not protected by HIPAA law.
A region of interest (ROI) indicating an average hounsfield unit (HU) of +39 mostly likely corresponds to
Blood Different tissues in the body have different average hounsfield units. Fat is significantly less than zero, water is approximately equal to zero, bone is as high as +1,000, and blood is very close to +39.
Which of these reconstruction algorithms are likely to produce the best spatial resolution?
Bone algorithm Different algorithms create different levels of sharpness, or spatial resolution, in the reconstructed images. Edge enhancing algorithms, such as the bone algorithm in this question, create more sharpness and better spatial resolution. The major side effect of using edge-enhancing algorithms is an increase in image noise.
What anatomical section is typically displayed with a window width (WW) of 80 and a window level (WL) of 30?
Brain The typical windowing technique for the brain is 80 WW and 30 WL. The WL of 30 is set to approximately match the HU of the brain matter, while the WW of 80 controls the overall grayscale of the image.
If a multiplanar reformation is rendered as a maximum intensity projection, what CT number will be displayed for a voxel containing mostly air, lung, fluid, and a small amount of iodinated contrast?
CT number for contrast The CT number for contrast wil be displayed for a voxel containing mostly air, lung, fluid, and a small amount of iodinated contrast. Maximum intensity reformations will display the highest intensity material within the voxel. in this case contrast has the highest intensity, or highest density, so it will be displayed on the pixel. Unlike normal multiplanar reformations, the pixel does not display the average of all tissues; Only the maximum density material is displayed.
A CT myelogram calls for a 2100 window width (WW) and a 700 window level (WL). What pixel values will be displayed as black?
CT numbers below -350 CT numbers below -350 will be displayed as black. The window level is the centerpoint of all displayed pixel values. The window width is the total number of displayed pixel values, with half being above the window level and half being below the window level. Pixel values below the lowest portion of the window width will be displayed as black. To find this number, subtract half of the window width from the window level. In this scenario, 700 - 1050 = -350.
Which of these methods is used to estimating a patient's risk of coronary artery disease (CAD)?
Calcium scoring CAD can be correlated to the amount of calcium in a patient's coronary arteries. More calcium is associated with an increased risk. Calcium scoring is a special quantitative method in CT used to create a calcium score (Agatston grade). The score is used in conjunction with a physician assessment to evaluate a patient's risk of coronary artery disease
Patients with an Agatston grade greater than 400 have a severe risk of major adverse cardiac events. The Agatston grade for coronary calcification is acquired using which of these methods?
Calcium scoring The Agatston score is created using calcium scoring in CT. The score is created by a quantitative post processing technique that measures the amount of calcium in the patient's coronary arteries.
Which of the following statements correctly describes the flow of electrons through an x-ay tube?
Cathode to anode
The helical acquisition mode is the most common technique used for imaging which three body sections?
Chest abdomen extremities
Which of these CT protocols generally use thin slices? -Circle of Willis for arterial-venous malformation -Abdomen for ulcerative colitis -Chest for cancer evaluation -Head for hemorrhage
Circle of Willis for arterial-venous malformation Compared to the other scan protocols, The Circle of Willis can certainly use the thinnest slices. The Circle of Willis includes several tiny blood vessels, which must be evaluated using thinner slices. Remember, thinner slices are better for evaluating smaller parts.
If ring artifact is identified in a scan, this might be prevented in future scans by:
Cleaning the detector array There are numerous reasons for ring artifact. One potential reason Is contrast on the detector array. If a ring artifact is identified, the first step is to clean the detector array to remove any residual contrast.
The width of the x-ray beam is controlled by:
Collimation
Increasing the acquisition thickness of a CT scan means:
Combining detector rows together to function as one detector row
To avoid violation of federal law on patient data protections, access to electronic medical records (EMR) should be protected with
Complex passcode requirements Anti-hacking software Encryption
Out-of-field artifact might be prevented by: -Administering a beta blocker -Using electrocardiogram (EKG) gating -Using a larger display field-of-view (DFOV) -Compressing the patient with straps
Compressing the patient with straps To prevent out-of-field artifact, the technologist must ensure that no portion of the patient is outside of the scan field-of-view (SFO). You cannot see the SFOV, but compressing the patient can help.
Which component of the CT imaging system is responsible for creating reconstructed image data?
Computer system
Consider a CT scan used to evaluate the brain for metastatic disease. If the average CT number of the tumors differs only slightly from the surrounding brain matter, what characteristic of the scanner might cause limited visibility of the tumors?
Contrast Resolution Since the tumors have CT numbers very similar to the surrounding brain matter, it's important for this scan to have very high contrast resolution. If the contrast resolution is not high enough, these tumors would be impossible to visualize. Contrast resolution is the ability to see the difference between obiects that have very similar physical densities.
In CT imaging, window width (WW) controls the:
Contrast of the displayed image Range of the Hounsfield values in the displayed image In CT imaging, window width is a term referring to the range of Hounsfield values displayed within the image and directly affects the contrast of the displayed image. Window width defines the number of CT pixel values that get their own shade of gray. Anything outside of this window becomes black or white. As window width increases, the image becomes more gray and therefore has less contrast.
The ability of the scanner to visually discriminate between objects with similar physical density is called:
Contrast resolution Contrast resolution is the ability to create contrast. The scanner should be able to discriminate, or create contrast, between objects with similar physical density. Compared to a conventional radiograph, CT scanning has a very high contrast resolution. Objects that blend together in a radiograph can be clearly distinguished from each other in CT.
The mathematical filtration of CT data to enhance the appearance of specific tissue types is called:
Convolution
When scanning a patient's chest, the axial images demonstrate ring artifact. This might be prevented in the future by:
Correctly calibrating the detector array There are several causes of ring artifact. One cause is miscalibration of the detector array, which can be corrected by simply recalibrating the scanner.
How is anatomical data from the scan field -of-view (SFOV) used during CT image production?
Data from the SFOV is used for image reconstruction
A CT detector configuration is changed from 0.625 mm x 16 rows to 1.25 mm x 8 rows. The change may result in:
Decrease patient dose decrease spatial resolution
Which of these variable changes is most likely to improve the contrast resolution of the resulting images? Decrease patient size Decreased reconstruction slice thickness Decreased acquisition thickness Decreased milliamperage (mA)
Decrease patient size A decrease in patient size results in increased contrast resolution. All of the other options actually decrease contrast resolution by creating more noise in the image. This question assumes that no other variables are changing. In practice, there are multiple variables changing at the same time that all need to be considered.
Which of these variable changes can a technologist make to increase the spatial resolution of a CT image? Increase the matrix size Decrease the matrix size Increase the display field-of-view (DFOV) Decrease the display field-of-view (DFOV)
Decrease the display field-of-view (DFOV) Of these options, two changes will increase the spatial resolution: increase matrix size and decreased DFOV. However, the technologist cannot change the matrix size because this is a fixed characteristic of the scanner. This leaves decreasing the DFOV as the only option.
Increasing the window level (WL) of a CT image will result in:
Decreased brightness Increasing the window level results in decreased brightness. In other words, the CT image gets darker. This occurs because increasing the window level causes more and more pixels to fall below the window width. Any CT numbers below the window width are displayed as black.
How will increasing the window width (WW) of a digital image affect the overall appearance of the image?
Decreased contrast In CT imaging, window width is a term referring to the contrast of the displayed image. Window width defines the number of CT pixel values that get their own shade of gray. Anything outside of this window becomes black or white. As window width increases, the image becomes more gray and therefore has less contrast.
Using a larger reconstruction slice thickness results in
Decreased image noise Decreased spatial resolution
Compared to a 1.25 mm image data, 3.75 mm image data will demonstrate:
Decreased image noise Fewer total slices Thicker slices will always result in decreased image noise, decreased spatial resolution, and fewer total slices. Thicker slices are not as good at imaging small parts, which is why the spatial resolution decreases.
A computed tomography (CT) of the cranium calls for 2.0 mm slices in the posterior fossa and 5.0 mm slices through the vertex. What change in image quality will be observed in the 5.0 mm slices?
Decreased noise Compared to 2.0 mm slices, 5.0 mm slices will demonstrate decreased image noise. The major side effect of using these thicker slices is a decrease in spatial resolution.
Consider two identical scanning protocols, where one protocol uses a pitch of 0.73 and the other uses a pitch of 0.87. The protocol using a pitch of 0.87 will result in which two of the following differences?
Decreased scan time Decreased patient dose
Helical (spiral) scanning mode is usually preferred over axial scanning mode for what three reasons?
Decreased scan time Improved intravenous (IV) contrast timing Improved post-processing
Excessive noise in a CT image may result in
Decreased spatial resolution Decreased contrast resolution Image noise has the potential to affect both spatial resolution and contrast resolution in a negative way. Noise or mottle in the image decreases the ability to see detail in the images, which is the same as decreased spatial resolution. Noise also makes it difficult to see the difference between structures that have similar physical densities. This is the same as a decrease in contrast resolution. Temporal resolution is incorrect because it is affected only by the speed of the scanned, not by the appearance of noise in the image.
Histogram analysis is useful for which of these applications? -Real-time tracking of contrast enhancement -Measuring the size of a suspicious lesion -Evaluating the efficiency of heart contractions -Defining the range of computed tomography (CT) numbers in a region of interest (ROI)
Defining the range of computed tomography (CT) numbers in a region of interest (ROI)
By definition, the acquisition thickness is the same as the:
Detector row thickness
X-ray tubes in CT are most similar to the radiation source used within which modality
Diagnostic radiography
Imaging and archiving systems in radiology communicate using a digital format called:
Digital Imaging and Communication in Medicine (DICOM) DICOM is a special computer language that is designed to function on all PACS systems, regardless of vendor or facility. Simply put, DICOM is the language of PACS.
What defines standards for radiology image formatting?
Digital Imaging and Communication in Medicine (DICOM) Regardless of the manufacturer of the PACS network in place or the facility that is using it, DICOM is the language that allows for the fluid communication of all PACS networks.
The localizer images are used by the technologist to assign which variable of a CT scan
Display-field-of-view (DFOV)
If mA is decreased by a factor of 2, how is the radiation does of other patient changed if all other factors remain unchanged
Dose is decreased by a factor of 2
Which two algorithms are preferred for viewing bone?
Edge-enhancing algorithms Bone algorithms Edge-enhancing algorithms and bone algorithms are preferred for viewing bone. However, it should also be understood that bone algorithms enhance the edges of objects in the display, which is helpful for viewing bones. Bone algorithms are a type of edge-enhancing algorithm.
Adjacent areas with significant density differences can cause an artifact called:
Edge-gradient artifact Edge-gradient artifact is a form of beam hardening artifact. It occurs in areas where the adjacent structures have very different densities. A common area for edge-gradient artifact to appear is at the interface between contrast and air. Normally, contrast does not cause edge-gradient artifact. But if contrast is directly adjacent to the area, the large gradient and density may cause streak artifact.
Dark streaks extending from the interface between the contrast and air in the gastrointestinal (Gl) tract is called:
Edge-gradient artifact Edge-gradient artifact is a form of beam hardening. It appears as streaks extending from the interface between objects that have very different physical densities. In this scenario, the large difference in density between the air and contrast in the Gl tract is known to cause a small amount of edge-gradient artifact.
Motion artifact in the heart can be minimized by using:
Electrocardiogram (EKG) gating There are multiple ways to minimize the appearance of motion artifact. In this question, the preferred way of reducing motion artifact is to use EKG gating. This process synchronizes the CT scan with the beating of the heart. Images are only acquired when the heart motion is limited.
Patient records are shared between medical providers using:
Electronic Health Record (EHR) The EH is an inter-facility health record, as opposed to the EMR, which is an intra-facility health record. The HR can be used by multiple providers at different locations to better track a patient's care.
What software program is used for digital documentation of all patient health information?
Electronic Medical Record (EMR) The EMR allows an institution or physician's office to track all of a patient's medical information in a digital format, rather than a paper copy.
Ejection fraction analysis in computed tomography (CT) is used for:
Evaluating the efficiency of heart contractions The contraction of the heart chambers causes the ejection of blood from one chamber to another chamber, or from one chamber into the great vessels. The efficiency of these contractions can be measured by evaluating the ejection fraction. As the ejection fraction increases, this represents highly efficient contractions of the heart. A low ejection fraction represents low efficiency and poor heart health.
Which of the following statements accurately describes the orientation of the x-axis in CT imaging? -Extends horizontally across the scanner -Extends vertically across the scanner -Represents data coordinates in terms of right and left -Represents data coordinates in terms of anterior and posterior
Extends horizontally across the scanner Represents data coordinates in terms of right and left If the patient center is shifted to the right or left, this is a change in the x-axis position.
Statements that accurately describes the orientation of the z-axis in CT imaging
Extends longitudinally through the scanner Represents data coordinates in terms of superior and inferior
A region of interest (ROI) placed over an abnormal lesion yields an average CT number of -52. This lesion may be composed of:
Fat Only a few types of tissue will have a hounsfield value less than zero. This includes air and lungs, as well as fat. In this question, the only possible answer is fat. Water, blood, and cerebrospinal fluid will all have hounsfield values equal to 0 or more.
If using a 400 window width (WW) and 40 window level (WL), the cerebral spinal fluid in the brain will appear as:
Gray Cerebrospinal fluid is slightly more dense than water, giving it a hounsfield value of + 15. This falls within the window width, which means this fluid will be displayed with some shade of gray. Had this number been above the window width, it would be displayed as white. If it was below the window width, it would be displayed as black.
During helical scanning, if the table moves a greater distance than the width of the beam the pitch will be:
Greater than 1
During which acquisition mode is the patient table in constant motion?
Helical scanning
The principle advantage of thin detector rows is
Higher spatial resolution
If a radiologist needs to know the ratio of fluid to blood in a cerebral lesion, what quantitative tool can help to estimate this ratio?
Histogram analysis Histogram analysis is sometimes used to evaluate the frequency of specific tissue types within an area of concern. A simple ROI tool only shows the average of all hounsfield values, but the histogram analysis shows the frequency of all values. Histogram analysis can be used to compare the amount of blood in a lesion compared to fluid in the lesion.
Which of these quantitative analysis methods in computed tomography (CT) can be used to identify the maximum Hounsfield value in an area of concern? Region-of-interest ellipse Histogram analysis Ejection fraction Calcium scoring
Histogram analysis Histogram analysis is useful when specific hounsfield values need to be evaluated. A region of interest only shows the average hounsfield values and standard deviation. If the technologist or radiologist needs to see maximum values, the histogram must be used.
When a region of interest (ROI) is placed over a homogenous structure, which of these values represent the image noise?
Hounsfield unit (HU) standard deviation The standard deviation represents the image noise in a homogeneous structure. Standard deviation is basically the average difference from the average. A large standard deviation means that the HU varies significantly from the average which results in a large amount of image noise. A small standard deviation means that the HU varies only a little from the average, which results in a small amount of image noise.
When diagnostic studies are viewed and interpreted directly through the Picture Archiving and Communication System (PACS) server, this presents what potential disadvantages?
If the PACS server goes down, all images are inaccessible In a server-based system, all images must be accessed by the Radiologist through the PACS server directly. If the PACS server goes down, all studies become inaccessible.
When a Picture Archiving and Communication System (PACS) network runs through a standard web-based network, this can result in which of these disadvantages?
If the internet is slow, images take longer to access Without a dedicated Picture Archiving and Communication System (PACS) network, a web-based network must rely on the efficiency of the available internet connection at any given moment. If this connection is to become bogged down by large amounts of data, the entire system slows down.
The process of reconstruction in the CT computer system creates:
Image Data Reconstruction is the process through which raw data is converted into image data. This image data is sometimes called processed data, because it has been processed into viewable images.
Scanning a large patient without changing the exposure factors could result in increased:
Image noise Scanning a large patient without changing the exposure factors is expected to increase image noise. If auto milliamperage (mA) is used, the scanner might prevent this problem by automatically increasing the mA. If some type of automatic tube modulation is not being used, the technologist must increase the mA or the kilovoltage peak (kV) in order to maintain an acceptable level of image noise.
Using edge-enhanced images for volume rendering is expected to result in which of the following? Loss of contrast Image noise Poor spatial resolution Partial volume averaging
Image noise Volume rendered images should always be created with smoothing algorithms, like the standard algorithm. Failure to do so will result in significant image noise in the 3D images. This is true even when creating volume rendered images of bones.
Consider a Picture Archiving and Communication System (PACS) network in which imaging studies are distributed directly to specific reading stations and to the PACS archive server. What are two main advantages of this distribution system?
Images are duplicated in the PACS archive server and at the reading workstation If the archiver server goes down, images can still be sent to specific reading stations There are two different paths by which images are distributed to both, the PACS servers and the Radiologist's reading station in this type of network. The advantage to this type of system is that if the PACS server fails, images can still be sent to the Radiologist reading station. Another advantage is having multiple copies of the same study. One copy is sent to the PACS archive server and one copy is sent directly to the Radiologist reading station. This makes it less likely that entire studies could be lost in the PACS servers.
Which of the following accurately describes where raw CT data is stored?
In the CT computer system
If the rotation time of a scan is decreased, what other exposure parameter should be changed to maintain the image quality?
Increase mA
An increase of which of the following exposure factors would increase the total number of x-ray photons exposing the detectors
Increase milliamperage (mA) Increased kilovoltage peak (kVp) Increase rotation time
Increasing the mA and voltage of a CT scan will usually result in which two of the following:
Increase patient dose Decrease image noise
The inner rows of a non-uniform detector array have the advantage of?
Increased Spatial Resolution The inner rows of a non-uniform detector arrav are thinner than the outer rows. As a result, the inner rows have the ability to create images with higher spatial resolution. A scan requiring high spatial resolution will use only the inner rows.
A technologist modifies the image windowing from -100 window level (WL) to -700 window level (WL). Following this change the image will demonstrate:
Increased brightness As window level decreases, the image becomes brighter. A very low window level, such as -700, is expected to result in a very bright image.
Which of the following effects occur when milliamperage (mA) is increased in CT?
Increased dose of the patient Increased beam intensity Increased exposure to the detector elements
During a routine CT scan of a pediatric chest, the radiologist requests that the technologist reconstruct the image data with 1.25 mm slices rather than 2.5 mm slices. One negative effect of this change will be:
Increased image noise In this scenario, the slice thickness is being decreased from 2.5 mm down to 1.25 mm, which will increase image noise because there is less information averaged into each slice. The spatial resolution increases, but this is a positive effect!
What technical change is expected to increase the penetrating ability of an x-ray beam
Increased kilovoltage peak (kVP)
Which of the following changes will increase the spatial resolution of a computed tomography (CT) image? -Increased pixel size -Increased matrix size -Increased field-of-view -Increased reconstruction thickness
Increased matrix size There are several ways to increase the spatial resolution of a CT image. In this question, the only variable that creates high spatial resolution is increased matrix size. This results in more pixels being put into the CT images. Increasing the pixel size increasing the field-of-view, and increasing the reconstruction thickness will all decrease the spatial resolution.
Which of these variable changes will increase temporal resolution? Increased pitch Increased rotation time Increased reconstruction thickness Increased kilovoltage potential
Increased pitch Increasing the pitch increases the temporal resolution because increased pitch results in a faster overall scan, which helps to reduce motion artifact. "Any variable change that makes the scan faster results in less motion artifact and better temporal resolution.
Which of these variable changes may decrease the spatial resolution of the resulting computed tomography (CT) images? •Increased rotation time •Increased reconstruction thickness •Increased edge-enhancement •Increased matrix size
Increased reconstruction thickness Increasing the reconstruction slice thickness results in a decrease in spatial resolution. Sometimes an increase in size thickness is preferred to decrease the image noise, but this does result in a decrease in spatial resolution.
What is the effect of using overlapping slices for volume rendered images?
Increased smoothing in the images When possible, overlapping axial slices should be used for 3D imaging. This helps to smooth out the image and prevent the appearance of slices in the images.
What is the primary reason for decreasing the detector thickness for CT angiography examination
Increased spatial resolution
Which of these image-processing techniques in CT are only used in helical scanning? Interpolation Filtration Convolution Back-projection
Interpolation Interpolation is the process of estimating an unknown value when the surrounding values are known. Interpolation is an important part of helical scanning, which is what allows the spiral-shaped raw data to be converted into axial image data.
Estimating an unknown value in a series of known values is a mathematical process called:
Interpolation Interpolation is the process of estimating an unknown value when the surrounding values are known. Interpolation is an important part of helical scanning. This is what allows the spiral-shaped raw data to be converted into axial image data.
The individual pixels in a computed tomography image are not visible to the unaided eye because modern CT equipment uses:
Large matrices Individual pixels cannot be seen in a CT image because modern equipment uses large matrices. A large matrix is composed of very small pixels that cannot be seen without significantly magnifying the image.
Compared to general radiography, CT x-ray tubes require which of the following?
Larger heat capacity Longer exposure time, more radiation, and higher mA settings
Which of the statements correctly describes the creation of multiplanar reformations (MPRs)? -MPRs must be created from the raw data -MPRs must be created in the same slice orientation as the image data -MPRs must be created with the same algorithm as the image data -MPRs must be created with the same slice thickness as the image data
MPRs must be created with the same algorithm as the image data Multiplanar reformations are only created in the same algorithm as the original. This is a post-processing technique that does not reconstruct the data or change the original algorithm. It is true that the algorithm remains the same. Multiplanar reformations are created from image data, not raw data. Multiplanar reformations can be created in any slice orientation, not the same as the original. Multiplanar formations can be created with any slice thickness, they are not fixed to the original slice thickness,
What multiplanar rendering technique is used to display images maximizing visibility of airways within the lungs?
Minimum intensity projection Minimum intensity projections will display the least dense materials or tissues within each voxel, such as the airways within the lungs. Average intensity projections display the average of all tissue types. Maximum intensity projections display the high density material or tissue.
If a routine helical scan of the chest is pre-programmed to use 16 detector rows and a pitch of 1.13, how will the resulting views comprise the scan data?
Missing views in the scan data A pitch greater than 1 means the table movement per rotation of the tube is greater than the thickness of the x-ray beam. This results in faster scanning, but there are missing views in the scanned data. This is simply noticed as a small decrease in image quality. A pitch greater than one is like stretching out the spiral.
During a CT angiography (CTA) of the neck, the patient is instructed not to swallow in order to avoid what image quality issue?
Motion artifact Any form of movement, including swallowing, can result in motion on the CT image. When evaluating the arteries of the neck it is especially important that the patient not swallow. Swallowing may cause motion around these arteries and prevent a proper diagnosis.
Consider this scenario: When reviewing the standard algorithm of a patient's head, you see what looks like a subdural hematoma. However, when reviewing the bone images you see the hematoma is just a double image of the patient's cranium bone. This error is most likely the result of:
Motion artifact Motion artifact can sometimes create the appearance of tissues or _pathologies that are not actually there. A double image is alwavs the result of patient motion.
Which three of the following is considered a "post-processing" application of the CT image data? L -Multiplanar Reformation -Retrospective Reconstruction -3D Rendering -Region-of-Interest (ROI) measurements -Prospective Reconstruction
Multiplanar Reformation 3D Rendering Region-of-Interest (ROI) measurements Post processing refers to any manipulation of CT image data, not the raw data. Retrospective reconstruction and prospective use the raw data to create a new image data, so this is not considered post-processing.
Thick reconstruction slices (greater than 3 m) are not suitable for
Multiplanar reformations Angiographic imaging Thicker slices are good for viewing images with minimal noise, but there are some times that thick slices should never be used. Thick slices should never be used for multiplanar reformations as this results in blurriness in the images. Thick slices should also never be used for protocols requiring high spatial resolution, such as angiographic imaging.
Consider this scenario: A new CT scanner in the radiology department has a matrix size of 1024 × 1024. What variable change can increase the matrix size? Increase the display field-of-view (DFOV) Increase the scan field-of-view (SFOV) Increase the acquisition thickness None of these changes will affect of the matrix
None of these changes will affect of the matrix Nothing changes the matrix size of a CT scanner without completely replacing the computer system. The matrix size is a fixed quality of the imaging system.
During an axial scan, the total amount of anatomical coverage per tube rotation is dependent on which of the following two variables
Number of activated detector rows Thickness of activated detector rows
In the context of a digital matrix, 1024 × 1024 refers to the:
Number of pixels in the matrix 1024 × 1024 refers to the number of pixels in the matrix. This matrix would have 1024 pixels in each row and 1024 pixels in each column.
What portion of the patient can be visualized through the process of retrospective reconstruction
Only parts of the patient within the scan-field-of-view
Centering the patient too high or too low in the gantry can result in which image artifact?
Out-of-field artifact It is important to position the patient in the exact center of the scanner. If the patient is too high or too low, this may cause some part of the patient to be outside of the scan field-of-view (SFOV). If this happens, out-of-field artifact may occur.
While imaging a large bariatric patient, you notice the patient's abdomen is touching the gantry in several areas. This might result in what kind of artifact?
Out-of-field artifact The scan field-of-view (SFO) is slightly smaller than the size of the gantry opening. If the patient is touching the gantry opening, they are certainly outside of the SFOV in those areas. Any time any portion of the patient is outside of the SFOV, out-of-field artifact is expected.
A CT scanning protocol is set to use a pitch of 0.79. This will result in:
Overlap in the scan data A pitch less than one means the table is moving a distance less than the width of the X-ray beam. This causes the scanned data to overlap on itself. This is often done intentionally to create high-resolution scans with extra detail. If the pitch was greater than 1, this is like stretching out the spiral. There will be small gaps in the scanned data.
when the pitch is less than one, how do the resulting views comprise the scan data
Overlapping views in the scan data
Consider this scenario: When reviewing 2.5 mm slices of a CT angiography (CTA) abdomen, you see what looks like an embolism. However, when reviewing the 1.25 mm slices the embolism is not visible. This is most likely an error called:
Partial volume averaging Partial volume averaging is an artifact caused by using thick slices. In this case, the thicker slices average certain tissues together and create the appearance of an embolism. The thinner slices do not show the embolism, so this error is called partial volume averaging.
The use of thick reconstruction slices can result in an error called:
Partial volume averaging Thick reconstruction slices can result in partial volume averaging. This artifact results in tissues or pathologies being lost in the image because the slice is too thick. Thick slices average a significant amount of tissue together, which can cause small pathologies in small portions of tissue to disappear. The result of tissue averaging can also create the appearance of objects or pathologies in the image that are not actually there.
Positioning the patient comfortably on the CT table is important in order to prevent which type of image degradation?
Patient motion Patient comfort is imperative when preventing patient motion. If the patient is comfortable, they are less likely to move. Patient comfort has no effect on the other artifacts listed in this question.
The Health Insurance Portability and Accountability Act (HIPAA) created health care laws regarding which of the following? -Patient right to access their health information -Health information privacy -Patient right to medical treatment -Health information security -Medical treatment liability
Patient right to access their health information Health information privacy Health information security
What does acronym PACS stand for?
Picture Archiving and Communication System PACS, or the Picture Archiving and Communication System, is the central. hub for all image networking and storage in a modern radiology department.
What is used for long-term storage of digital image data?
Picture Archiving and Communication System (PACS)
What combination of variables will result in the least amount of image noise? -Pitch = 0.9, Reconstruction Thickness = 5.0, Tube voltage = 140,Matrix Size = 512 × 12 -Pitch = 1.0, Reconstruction Thickness = 3.5, Tube voltage = 130,Matrix Size = 512 x 12 -Pitch = 1.1, Reconstruction Thickness = 2.0, Tube voltage = 120, Matrix Size = 1024 × 1024 -Pitch = 1.2, Reconstruction Thickness = 1.0, Tube voltage = 110, Matrix Size = 1024 × 1024
Pitch = 0.9, Reconstruction Thickness = 5.0, Tube voltage = 140,Matrix Size = 512 × 12 Of the options listed here, the tube voltage (kVp) is the primary factor influencing the image noise. Using a large voltage, such as 140 KVp, will increase the amount of photons getting to the receptors and therefore decrease the image noise.
When scanning a patient's chest, beam-hardening artifact can be prevented by:
Placing the patient's arms above his/her head Leaving the patient's arms in the scan field is a common cause of beam hardening artifact. The bones of the arms are very dense and absorb an excessive amount of radiation, even more so because they are in line with the spine. This can be prevented by placing the patient's arms above their head and out of the scan field.
Consider this scenario: A server-based Picture Archiving and Communication System (PACS) system is designed with a backup distribution network used to send imaging studies to specific reading stations. In the event that the PACS server becomes inaccessible, what are the two main disadvantages of sending images to specific reading stations?
Prior imaging studies are not accessible Imaging studies are not accessible at all PACS reading stations
In a server-based Picture Archiving and Communication System (PACS) network, what are two main advantages of accessing the archive server through a dedicated PACS network?
Prior studies are immediately accessible Only one radiologist can access the study for interpretation In a server-based PACS network, all images stored on the PACS server are accessible at any radiologist reading station. This makes comparing prior studies to current images easier and more fluid. Another advantage is the "warning" that a radiologist receives if they attempt to read a study that is already being dictated by another radiologist.
Temporal resolution is defined as the ability to:
Produce still images of objects in motion Temporal resolution refers to the ability of the scanner to produce still images of objects in motion. Temporal resolution is similar to the shutter speed of a camera. The other definitions provided here refer to other image quality characteristics.
A single "view" acquired during a CT scan is also called a
Projection
What is the main difference between production in CT and image production in radiology
Projections are compiled into a 3D volume of data
A Picture Archiving and Communication System (PACS) network is used to connect
Radiologist reading station Imaging equipment PACS servers
The process of assigning a specific level of edge-enhancement to the CT image data is controlled by mathematical filters called:
Reconstruction algorithms Reconstruction filters Reconstruction kernels Reconstruction is the mathematical process that converts raw data into image data. This process includes assigning some level of edge enhancement. Reconstruction is accomplished by mathematical filters that are sometimes called reconstruction algorithms, reconstruction filters, or even reconstruction kernels (all of these terms refer to the same thing). The bone algorithm and standard algorithm are common examples of these reconstruction algorithms.
The thickness of a voxel in CT is defined by which of these variables?
Reconstruction thickness The thickness of a voxel is determined by the reconstruction thickness. If the slice thickness is 3.0 mm, the voxel will be 3.0 mm deep.
Iterative reconstruction is an alternative to traditional reconstruction and helps to do
Reduce patient dose Increase image quality
Concerning personal health records, federal laws does NOT allow a patient to: -Remove their health records from a system database -Request a copy of their health records -Request corrections to their health records -Review who has seen their health records
Remove their health records from a system database
After performing an abdominal scan for trauma, the radiologist requests reconstructed images of the lumbar spine. The raw data is not saved on the CT scanner, so this will require:
Rescanning the patient Retrospective reconstruction can never be done without raw data on the CT scanner. If the raw data is gone, there is absolutely no way to reconstruct new images. In this scenario, the patient must be scanned again.
After completing a CT of the abdomen, you notice that your images do not include the entire abdomen. Which of the following methods can be used to retrieve this information?
Retrospective reconstruction
