Computed Tomography (CT) Scan Quiz
Computer tomography scans commonly known as CT scans make use of computer-processed combinations of many X-ray measurements taken at different angles. Take up the quiz below and gauge you knowledge on CT scans. All the best.
Questions and Answers
- 1.
Using _________ reconstruction filter would decrease the appearance of noise in a CT image.1. no2. a sharp3. a smooth
- A.
1 only
- B.
2 only
- C.
2&3
- D.
3 only
Correct Answer
D. 3 onlyExplanation
Using a smooth reconstruction filter would decrease the appearance of noise in a CT image. A smooth filter helps to reduce noise by averaging out the pixel values in the image, resulting in a smoother and less noisy image. A sharp filter, on the other hand, enhances the edges and details in the image, which can amplify the noise. Therefore, using a smooth reconstruction filter is the most effective way to decrease noise in a CT image.Rate this question:
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- 2.
A ___________ scan uses only a single projection.1. conventional, or serial2. helical3. localizer
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1,2,&3
Correct Answer
C. 3 onlyExplanation
A localizer scan uses only a single projection. This type of scan is typically used to obtain a single image that provides an overview or localization of the area of interest. It is often performed before a more detailed scan to help guide the radiologist or technician in positioning the patient and identifying the specific region to be imaged. Unlike conventional or serial scans, which involve multiple projections, a localizer scan is focused on obtaining a single image for localization purposes.Rate this question:
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- 3.
Which of the following statements is FALSE regarding 3D SSD?
- A.
Helical image data is well suited for 3D SSD because there is minimal misregistration or gaps.
- B.
The volume data, from which the 3D SSD is generated, is created by combining transverse, sagittal, and coronal reconstructions
- C.
The tissue surface may be selected by using a threshold value equal to the tissue's CT number.
- D.
Patient motion during the scan is detrimental to the quality of the 3D images
Correct Answer
B. The volume data, from which the 3D SSD is generated, is created by combining transverse, sagittal, and coronal reconstructionsExplanation
The volume data, from which the 3D SSD is generated, is not created by combining transverse, sagittal, and coronal reconstructions. This statement is false because the volume data for 3D SSD is typically acquired directly from the CT scanner, without the need for additional reconstructions. The 3D SSD algorithm then processes this volume data to generate the desired images.Rate this question:
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- 4.
Which type(s) of storage media may hold CT image data?1. internal hard disk2. CD3. re-writable optical disk
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1,2,& 3
Correct Answer
D. 1,2,& 3Explanation
CT image data can be stored on internal hard disks, CDs, and re-writable optical disks. Internal hard disks are commonly used for storing large amounts of data, including CT images. CDs can also be used to store CT image data, providing a portable and easily accessible storage option. Re-writable optical disks offer the advantage of being able to write, erase, and rewrite data, making them suitable for storing and updating CT image data. Therefore, all three options - 1, 2, and 3 - are correct answers.Rate this question:
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- 5.
____________ may have to be edited from the data set to get a diagnostic MIP of a CTA exam.
- A.
Iodinated contrast media
- B.
Vessels of inetrest
- C.
Air
- D.
Bones
Correct Answer
D. BonesExplanation
To obtain a diagnostic MIP (Maximum Intensity Projection) of a CTA (Computed Tomography Angiography) exam, bones may need to be edited from the data set. This is because bones can obstruct the visualization of blood vessels and other structures of interest in the image. By removing the bones from the data set, a clearer and more accurate MIP can be generated, allowing for a better assessment of the vascular system.Rate this question:
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- 6.
Which of the following is NOT an advantage of a helical study compared to a conventional, serial CT study?
- A.
Minimal anatomical mis-registration sometimes caused by inconsistent breath holding
- B.
Shorter total exam time
- C.
Can retrospectively reconstruct a slice at any arbitrary position
- D.
Offers the best image quality for a brain exam
Correct Answer
D. Offers the best image quality for a brain examExplanation
A helical study is a type of CT scan that uses a continuous spiral motion to capture images of the body. One advantage of a helical study is that it minimizes anatomical mis-registration caused by inconsistent breath holding. This means that the images obtained are more accurate and aligned properly. Another advantage is that it allows for shorter total exam time, as the continuous motion eliminates the need to stop and reposition the patient between each scan. Additionally, a helical study can retrospectively reconstruct a slice at any arbitrary position, providing flexibility in image analysis. However, the given answer states that a helical study does not offer the best image quality for a brain exam, suggesting that other types of CT studies may provide better image quality specifically for brain examinations.Rate this question:
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- 7.
Which of the following utilizes convolution?1. 3D SSD2. fourier transform3. filtered back projection
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2, & 3
Correct Answer
C. 3 onlyExplanation
Filtered back projection is the only option that utilizes convolution. Convolution is a mathematical operation that combines two functions to produce a third function. In the case of filtered back projection, convolution is used to filter the raw data obtained from a CT scan before reconstructing the image. This filtering process helps to remove noise and enhance the quality of the final image. Both 3D SSD and Fourier transform do not involve convolution in their operations.Rate this question:
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- 8.
In which technique are tissues other than the surface of structure excluded by setting a threshold value and eliminating pixels above or below that threshold?
- A.
Volume rendering
- B.
Multi-planar reconstruction
- C.
Maximum intensity projection
- D.
3D shaded surface display
Correct Answer
B. Multi-planar reconstructionExplanation
Multi-planar reconstruction is a technique in which tissues other than the surface of a structure are excluded by setting a threshold value and eliminating pixels above or below that threshold. This technique allows for the creation of multiple planes or slices through a 3D volume, which can be viewed individually or in combination to provide a comprehensive understanding of the structure's internal features. By eliminating pixels that do not meet the threshold criteria, only the desired tissues are visualized, enhancing the clarity and accuracy of the reconstructed images.Rate this question:
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- 9.
From which of the following can the most diagnostic multi-planar reconstructions be generated?1. stacked transverse images from a helical scan2. stacked transverse images from a conventional, serial scan3. stacked localizer images
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2, & 3
Correct Answer
A. 1 onlyExplanation
Stacked transverse images from a helical scan can generate the most diagnostic multi-planar reconstructions. Helical scanning is a technique that allows continuous acquisition of data during the scan, resulting in a volumetric dataset. This volumetric dataset can be reconstructed into various planes, including sagittal, coronal, and oblique, providing a comprehensive view of the anatomy. In contrast, conventional serial scans acquire data slice by slice, resulting in a limited dataset for multi-planar reconstructions. Stacked localizer images are typically used for initial scan planning and do not provide as much diagnostic information as the stacked transverse images from a helical scan.Rate this question:
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- 10.
The actual attenuation data measured by the detectors from all projections during a scan is contained in CT ____________ data.1. image2. convolved3. raw
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2, & 3
Correct Answer
D. 1, 2, & 3Explanation
CT image data contains the actual attenuation data measured by the detectors from all projections during a scan. This data is obtained by convolving the raw data, which is also included in the CT image data. Therefore, the correct answer is 1, 2, & 3.Rate this question:
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- 11.
Which of the following is TRUE regarding the slice thickness of an image reconstructed from a helical scan?1. on a multi-row detector scanner, the thickness is equal to the beam collimation.2. on a single-row detector scanner, the thickness is equal to the beam collimation.3. on a single-row detector scanner, the thickness can be varied retrospectively.
- A.
1 only
- B.
2 only
- C.
2 & 3
- D.
1, 2, & 3
Correct Answer
C. 2 & 3Explanation
The correct answer is 2 & 3. On a single-row detector scanner, the thickness of the image slice is equal to the beam collimation. Additionally, on a single-row detector scanner, the thickness can be varied retrospectively, meaning that it can be adjusted or changed after the scan has been completed. This allows for greater flexibility and customization in the resulting image.Rate this question:
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- 12.
A retrospective reconstruction, in which the reconstruction field-of-view is varied, uses:
- A.
A reconstructed image in the sagittal plane
- B.
CT raw data
- C.
More photons
- D.
CT image data
Correct Answer
B. CT raw dataExplanation
A retrospective reconstruction refers to the process of reconstructing an image using CT raw data. This raw data consists of a series of measurements taken by the CT scanner, which are then processed to create a detailed image. By varying the reconstruction field-of-view, different aspects of the image can be emphasized or highlighted. Therefore, the correct answer for this question is CT raw data.Rate this question:
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- 13.
Which of the following is common to both localizer scan and a conventional, serial CT scan?
- A.
They both produce saggital images
- B.
The patient table moves at a constant velocity
- C.
They both produce cross-sectional images
- D.
The x-ray tube makes complete 360 degree rotations
Correct Answer
A. They both produce saggital images -
- 14.
Which of the following statements are TRUE?1. the amplified electrical signal obtained from the detectors must be digitized.2. digital CT images are numerical representations of cross-sectional anatomy.3. digital signals may be formed by sampling analog signals at discrete time intervals.
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2, & 3
Correct Answer
D. 1, 2, & 3Explanation
The given answer is correct because all three statements are true. Statement 1 is true because the amplified electrical signal from detectors in CT scans needs to be converted into digital form for further processing and analysis. Statement 2 is true because digital CT images are indeed numerical representations of cross-sectional anatomy, allowing for detailed analysis and manipulation. Statement 3 is true because digital signals can be formed by sampling analog signals at discrete time intervals, which is a common method of converting analog signals into digital form.Rate this question:
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- 15.
___________________ is the mathematical process used by single row detector scanners to reconstruct CT image from raw data.
- A.
Weighted averaging
- B.
Filtered back projection
- C.
The fourier transform
- D.
Integration of the area under the curve
Correct Answer
B. Filtered back projectionExplanation
Filtered back projection is the mathematical process used by single row detector scanners to reconstruct CT images from raw data. This process involves filtering the raw data and then back projecting it onto a two-dimensional image space. The filtering helps to remove noise and artifacts from the raw data, while the back projection reconstructs the image by tracing the path of the X-ray beams through the patient's body. This technique is widely used in CT imaging as it allows for fast and accurate reconstruction of images.Rate this question:
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- 16.
3D shaded surface displays are performed on CT:1. image data2. raw data3. attenuation profiles
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2, & 3
Correct Answer
A. 1 onlyExplanation
3D shaded surface displays are performed on CT image data. This technique involves creating a three-dimensional representation of the scanned object using the image data obtained from the CT scan. The shading is applied to the surface of the object to enhance its visual appearance and provide depth perception. Raw data refers to the unprocessed data obtained from the CT scan, and attenuation profiles are measurements of the radiation absorption by the tissues. However, neither raw data nor attenuation profiles are directly used for creating shaded surface displays. Therefore, the correct answer is 1 only, indicating that shaded surface displays are performed on CT image data.Rate this question:
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- 17.
A pixel is a :
- A.
Bright artifact on a film
- B.
Single 3D volume element within a volume of anatomical data
- C.
Single 2D picture element within the image plane
- D.
Range of gray levels on a CT image
Correct Answer
C. Single 2D picture element within the image planeExplanation
A pixel is a single 2D picture element within the image plane. In digital imaging, an image is composed of a grid of pixels, each representing a specific color or intensity value. Pixels are the smallest units of an image, and they come together to form the overall picture. Each pixel contains information about its position and color, allowing it to be displayed on a screen or printed on paper. Therefore, a pixel is a fundamental building block of a digital image, representing a specific point in the 2D space of the image plane.Rate this question:
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- 18.
The pencil thin section of the x-ray fan beam that strikes a single detector is called a:
- A.
Line
- B.
Projection
- C.
View
- D.
Ray
Correct Answer
D. RayExplanation
The correct answer is "ray" because in x-ray imaging, a fan beam is used to project a narrow section onto a single detector. This narrow section is referred to as a "ray" because it represents a straight line of x-ray radiation that is emitted from the source and passes through the patient's body before reaching the detector. The term "ray" accurately describes the pencil thin section of the fan beam that strikes a single detector.Rate this question:
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- 19.
A kernel is a:
- A.
Component in the x-ray tube
- B.
Post-processing filter applied to image data
- C.
Type of detector
- D.
Filter applied to the CT raw data
Correct Answer
D. Filter applied to the CT raw dataExplanation
A kernel is a filter applied to the CT raw data. In CT imaging, raw data is collected from the X-ray detectors and then processed to create the final image. The kernel is a mathematical filter that is applied to this raw data to enhance or modify certain aspects of the image, such as sharpness or noise reduction. By applying different kernels, the radiologist can adjust the image appearance according to the specific diagnostic needs. Therefore, a kernel is a filter applied to the CT raw data to improve the quality and diagnostic value of the resulting image.Rate this question:
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- 20.
An increase in ___________ does NOT occur in the resulting images when applying a sharp, or high-pass reconstruction filter during the image reconstruction of CT raw data.1. contrast resolution2. edge enhancement3. the appearance of noise
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2, & 3
Correct Answer
C. 3 onlyExplanation
When applying a sharp or high-pass reconstruction filter during the image reconstruction of CT raw data, an increase in contrast resolution and edge enhancement may occur. However, the appearance of noise does not increase. Therefore, the correct answer is 3 only.Rate this question:
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- 21.
CTA images come from a __________ scan.1. conventional, or serial2. helical3. localizer
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2, & 3
Correct Answer
B. 2 onlyExplanation
CTA images come from a helical scan. Helical scanning is a technique used in computed tomography (CT) imaging where the x-ray tube rotates continuously while the patient is moved through the scanner. This allows for a continuous spiral or helical path of data acquisition, resulting in high-resolution images. Conventional or serial scans involve stopping the patient at various intervals to acquire images, while a localizer scan is used to determine the exact position and orientation of the patient before acquiring the actual images. Therefore, the correct answer is 2 only, as CTA images specifically come from a helical scan.Rate this question:
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- 22.
If an image matrix has 360 rows and 360 columns, how many pixels are there in the image?
- A.
21,600
- B.
129,600
- C.
259,200
- D.
379,800
Correct Answer
B. 129,600Explanation
An image matrix with 360 rows and 360 columns would have a total of 360 x 360 = 129,600 pixels.Rate this question:
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- 23.
The ______________ determines the intensity of the laser beam in a laser camera.1. intensifying grid2. pixel values in the image data3. mgnifying power of the lens
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2 & 3
Correct Answer
B. 2 onlyExplanation
The pixel values in the image data determine the intensity of the laser beam in a laser camera. This is because the image data captured by the camera represents the intensity of the laser beam at each pixel. By analyzing these pixel values, the intensity of the laser beam can be determined. The intensifying grid and magnifying power of the lens may affect other aspects of the image, but they do not directly determine the intensity of the laser beam.Rate this question:
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- 24.
Which of the following is a reconstruction technique applied to the raw data after the primary reconstruction has already been accomplished?
- A.
Maximum intensity projection
- B.
Volume rendering
- C.
Retrospective reconstruction
- D.
Multi-planar reconstruction
Correct Answer
C. Retrospective reconstructionExplanation
Retrospective reconstruction is a technique applied to the raw data after the primary reconstruction has already been accomplished. It involves reprocessing the data using different parameters or algorithms to obtain additional information or improve the image quality. This technique allows for a more detailed analysis and interpretation of the data, and can be particularly useful in cases where the initial reconstruction did not provide sufficient information or clarity.Rate this question:
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- 25.
What does convolution do to the image quality when it is added to the back projection reconstruction process?
- A.
Normalizes the attenuation coefficients to ensure tissues are displayed with correct CT numbers.
- B.
Increases the number of projections thereby reducing streaking artifacts
- C.
Improves contrast resolution by reducing scatter radiation
- D.
Enhances important characteristics of attenuation profiles thus reducing streak and star artifacts
Correct Answer
D. Enhances important characteristics of attenuation profiles thus reducing streak and star artifactsExplanation
Convolution enhances important characteristics of attenuation profiles, which in turn reduces streak and star artifacts in the image. This means that the process of convolution improves the quality of the image by reducing the unwanted artifacts, resulting in a clearer and more accurate representation of the tissues.Rate this question:
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- 26.
Which of the following may occur during the interscan delay of a conventional, or serial, CT scan performed on a continuous rotation scanner?1. the table position is incremented 2. the tube continues to rotate in the same direction as during the scan3. the tube assembly makes a 360 degree rotation.
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2, & 3
Correct Answer
D. 1, 2, & 3Explanation
During the interscan delay of a conventional CT scan performed on a continuous rotation scanner, all three of the mentioned actions may occur. The table position may be incremented, allowing for the movement of the patient or object being scanned. The tube may continue to rotate in the same direction as during the scan, ensuring a continuous and smooth scanning process. Additionally, the tube assembly may make a 360-degree rotation, completing a full rotation before the next scan begins.Rate this question:
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- 27.
____________ allows helical data to be converted into planar raw data.
- A.
Retrospective reconstruction
- B.
Interpolation
- C.
Cone beam reconstruction
- D.
Convolution
Correct Answer
B. InterpolationExplanation
Interpolation is the correct answer because it is a mathematical technique used to estimate values between known data points. In the context of converting helical data into planar raw data, interpolation can be used to fill in the missing information and create a smooth, continuous image. It helps to reconstruct the data by estimating the values at positions that were not directly sampled, allowing for a more complete representation of the original helical data in a planar format.Rate this question:
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- 28.
What is the most common type of film used for recording CT images?
- A.
Thermal
- B.
Double emulsion
- C.
Single emulsion
- D.
Paper
Correct Answer
B. Double emulsionExplanation
Double emulsion is the most common type of film used for recording CT images. This type of film has two layers of emulsion, which allows for better image quality and sensitivity to X-rays. The double emulsion film is designed to capture the varying densities of tissues in the body, making it ideal for CT imaging. Thermal film is not suitable for CT imaging as it is used for thermal printing. Single emulsion film is less commonly used in CT imaging. Paper is not used for recording CT images as it does not have the necessary sensitivity to X-rays.Rate this question:
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- 29.
A helical scan performed on a 64 slice MDCT scanner is reconstructed with:
- A.
Back projection
- B.
Simple reconstruction because it is a single projection scan
- C.
No reconstrction filter
- D.
Cone beam reconstruction
Correct Answer
D. Cone beam reconstructionExplanation
The helical scan performed on a 64 slice MDCT scanner is reconstructed using cone beam reconstruction. This technique is commonly used for helical or spiral scans, where the X-ray source and detector continuously rotate around the patient as they move through the scanner. Cone beam reconstruction takes into account the cone-shaped X-ray beam and the curved path of the detector, allowing for accurate reconstruction of the 3D image from the acquired data. This method is necessary for helical scans to ensure proper image quality and spatial resolution.Rate this question:
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- 30.
_____________ yields an image that appears 3D but also shows anatomical details above and below the 3D surface.
- A.
SSD
- B.
VR
- C.
MIP
- D.
Multi-planar reconstruction
Correct Answer
B. VRExplanation
VR stands for virtual reality. Virtual reality technology can create a realistic and immersive 3D environment. In the context of medical imaging, VR can be used to visualize anatomical structures in a way that gives the illusion of depth and allows the user to explore the image from different angles. This technology can provide a more comprehensive understanding of the anatomical details by showing structures both above and below the 3D surface, making it the correct answer for the given question.Rate this question:
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- 31.
MDCT scanners capable of collection 64 slices in a ingle rotation do NOT:
- A.
Perform conventional CT scans
- B.
Perform helical CT scans
- C.
Use filtered back projection as their method of image reconstruction
- D.
Perform localizer scans
Correct Answer
C. Use filtered back projection as their method of image reconstructionExplanation
MDCT scanners capable of collecting 64 slices in a single rotation do not use filtered back projection as their method of image reconstruction. Filtered back projection is an older method of image reconstruction that is used in conventional CT scans. MDCT scanners use a different method called iterative reconstruction, which allows for higher image quality and reduced radiation dose. Therefore, MDCT scanners with 64-slice capabilities do not rely on filtered back projection for image reconstruction.Rate this question:
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- 32.
MIP images:
- A.
Are most frequently used for visualizing air-filled spaces
- B.
Can NOT be run in a cine loop
- C.
Are most accurate when a large volume of interest is selected
- D.
Do NOT demonstrate detail beneath the brightest pixel
Correct Answer
D. Do NOT demonstrate detail beneath the brightest pixelExplanation
MIP (Maximum Intensity Projection) images are a type of visualization technique commonly used to display air-filled spaces in medical imaging. They are not able to be run in a cine loop, which means they cannot be displayed as a continuous moving image. MIP images are most accurate when a large volume of interest is selected, allowing for a comprehensive view of the air-filled spaces. However, they do not demonstrate detail beneath the brightest pixel, meaning that any structures or information below the brightest point may not be visible in the image.Rate this question:
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- 33.
Multi-planar reconstructions are performed on which of the following?1. image data2. raw data3. attenuation profiles
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2 & 3
Correct Answer
A. 1 onlyExplanation
Multi-planar reconstructions are performed on image data. This technique allows for the creation of two-dimensional images from three-dimensional data, enabling visualization of structures from different angles and planes. Raw data refers to the unprocessed data acquired by the imaging system, while attenuation profiles are measurements of the attenuation of radiation as it passes through an object. However, multi-planar reconstructions are not directly performed on raw data or attenuation profiles. Therefore, the correct answer is 1 only.Rate this question:
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- 34.
The________ move(s) during a helical scan on a third-generation scanner.1. x-ray tube2. patient table3. detector elements
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2, & 3
Correct Answer
D. 1, 2, & 3Explanation
During a helical scan on a third-generation scanner, all three components mentioned in the options - the x-ray tube, patient table, and detector elements - move. The x-ray tube moves in a circular motion around the patient, emitting x-rays from different angles. The patient table moves longitudinally, allowing the patient to be scanned continuously. The detector elements also move synchronously with the x-ray tube and capture the x-rays that pass through the patient, producing the necessary data for image reconstruction. Therefore, all three components are involved in the helical scan process.Rate this question:
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- 35.
A CT system manufacturer has a scanner in which the focal spot of the x-ray beam can move to two, slightly separated distinct locations. What benefis does the dual focal spot provide compared to an identical scanner possessing a single focal spot?1. the number of projections is doubled2. the numble of rays in a single projection is doubled3. the patient dose halved
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2, & 3
Correct Answer
A. 1 onlyExplanation
The dual focal spot in the CT scanner allows for the number of projections to be doubled. This means that more images can be obtained from different angles, providing a more comprehensive view of the patient's anatomy. This can lead to improved image quality and accuracy in diagnosis. However, the dual focal spot does not directly affect the number of rays in a single projection or the patient dose, so options 2 and 3 are not correct.Rate this question:
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- 36.
Which of the following tissues appears the brightest (most radiodense) on a typical computed tomography (CT) scan without contrast?
- A.
Air in the lungs
- B.
Muscle tissue
- C.
Bone
- D.
Fat
Correct Answer
C. BoneExplanation
On a CT scan, bone appears the brightest because it is highly radiodense, meaning it absorbs more X-rays compared to other tissues like muscle, fat, or air. This high density results in a bright white appearance on the scan. Air in the lungs appears black, while fat and muscle appear in shades of gray. CT scans are widely used to assess bone injuries, internal organs, and other abnormalities by differentiating tissue densities.Rate this question:
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- 37.
A smooth, or low-pass, reconstruction filter is typically NOT selected for a(n)_________ exam.
- A.
Pituitary
- B.
Kidneys
- C.
Liver
- D.
Internal auditory canals
Correct Answer
D. Internal auditory canalsExplanation
A smooth, or low-pass, reconstruction filter is typically not selected for an internal auditory canals exam because this type of filter is used to remove high-frequency noise and artifacts from images. However, the internal auditory canals exam focuses on imaging the structures within the ear, specifically the pathway for sound transmission, and does not require the removal of high-frequency noise. Therefore, a smooth reconstruction filter is not necessary for this type of exam.Rate this question:
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- 38.
In a _________, the highest pixel values from a stack of CTA images are projected along many "rays".
- A.
SSD
- B.
MIP
- C.
PR
- D.
VR
Correct Answer
B. MIPExplanation
MIP stands for Maximum Intensity Projection. In this technique, the highest pixel values from a stack of CTA (Computed Tomography Angiography) images are projected along multiple "rays". This allows for the visualization of the maximum intensity or brightness along each ray, resulting in a clear representation of the blood vessels or structures with the highest contrast in the images.Rate this question:
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- 39.
The x-ray beam used in CT scanning is __________ the patient's tissues.1. reflected off of2. attenuated by3. generated by
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2, & 3
Correct Answer
B. 2 onlyExplanation
The x-ray beam used in CT scanning is attenuated by the patient's tissues. This means that the beam is weakened or reduced in intensity as it passes through the different structures and organs in the body. Attenuation occurs due to the absorption and scattering of the x-rays by the tissues, which helps create the detailed images produced by the CT scan.Rate this question:
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- 40.
Which of the following are possible results of partial voluming?1. decreased sharpness of edges2. misleading CT numbers3. improvement in resolution
- A.
1 only
- B.
2 only
- C.
1 & 2
- D.
1, 2, & 3
Correct Answer
C. 1 & 2Explanation
Partial voluming refers to the mixing of different tissues within a voxel, resulting in a loss of sharpness at the edges of structures. This can lead to a decreased sharpness of edges (option 1) and also to misleading CT numbers (option 2). Option 3, improvement in resolution, is not a possible result of partial voluming.Rate this question:
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- 41.
Which of the following has the highest patient dose assuming all other parameters are the same?
- A.
MA=200, rotation time=2 sec.
- B.
MA=200, rotation time=1 sec.
- C.
MA=150, rotation time=3 sec.
- D.
MA=400, rotation time=1 sec.
Correct Answer
C. MA=150, rotation time=3 sec.Explanation
The patient dose is determined by the product of mA (milliamperage) and rotation time. In this case, all other parameters are the same except for mA and rotation time. The higher the mA and the longer the rotation time, the higher the patient dose. Therefore, the combination of mA=150 and rotation time=3 sec has the highest patient dose compared to the other options.Rate this question:
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- 42.
CT numbers _____________ would appear black if a window width of 400 and a window level of -100 are used.
- A.
Above +200
- B.
Below -300
- C.
Below -200
- D.
Above +100
Correct Answer
B. Below -300Explanation
If CT numbers below -300 are used with a window width of 400 and a window level of -100, they would appear black. This is because the window level of -100 is lower than the CT numbers below -300, causing them to fall outside the range of the window and appear as the darkest shade, which is black.Rate this question:
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- 43.
If a calcification with a CT number of +300 appears pure white on an image, which of the following could be the window width and window level selected?1. window level = 0, window width = 5002. window level = +300, window width =5003. window level = +100, window width = 1000
- A.
1 only
- B.
2 only
- C.
3 only
- D.
2 & 3
Correct Answer
A. 1 onlyExplanation
If a calcification with a CT number of +300 appears pure white on an image, it means that the window level is set to a value higher than +300. Option 1 suggests a window level of 0, which is lower than +300, and therefore the calcification would not appear pure white. Option 2 suggests a window level of +300, which matches the CT number of the calcification, and the window width of 500 would determine the contrast of the image. Option 3 suggests a window level of +100, which is lower than +300, and therefore the calcification would not appear pure white. Therefore, the correct answer is 1 only.Rate this question:
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- 44.
Which of the following determinants of CT image quality is responsible for how grainy or speckled a CT image appears?
- A.
Resolution
- B.
Linearity
- C.
Noise
- D.
Contrast
Correct Answer
C. NoiseExplanation
Noise is responsible for how grainy or speckled a CT image appears. Noise in CT images refers to random variations in pixel values, which can result in a loss of image clarity and detail. Higher levels of noise can make the image appear more grainy or speckled, while lower levels of noise result in a smoother image appearance. Therefore, the level of noise in a CT image directly affects its overall quality and can impact the ability to accurately diagnose and interpret the image.Rate this question:
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- 45.
Which of the following statements is FALSE?1. magnification requires the raw data2. increasing magnification increases resolution3. magnification decreases the size of displayed anatomy
- A.
1 only
- B.
3 only
- C.
3 only
- D.
1, 2 & 3
Correct Answer
D. 1, 2 & 3Explanation
The given answer states that statements 1, 2, and 3 are all false. However, upon analyzing the statements, we can see that statement 1 is true because magnification does require raw data. Statement 2 is also true because increasing magnification does increase resolution. Therefore, the given answer is incorrect.Rate this question:
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- 46.
If a thin slice is used, which of the following would help reduce the apparent image noise?
- A.
Reduced reconstruction field of view
- B.
Increased matrix
- C.
Increased mAs
- D.
Increased kVp
Correct Answer
C. Increased mAsExplanation
Increasing the mAs (milliamperes per second) would help reduce the apparent image noise when using a thin slice. Image noise refers to random variations in brightness or color that can degrade image quality. By increasing the mAs, more X-ray photons are used to create the image, resulting in a higher signal-to-noise ratio. This means that the signal (desired image information) is stronger compared to the noise (unwanted variations), leading to a clearer and less noisy image. Therefore, increasing the mAs would help reduce the apparent image noise in this scenario.Rate this question:
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- 47.
A CT number calibration test should be performed:
- A.
Weekly
- B.
Annually
- C.
Monthly
- D.
Daily
Correct Answer
D. DailyExplanation
A CT number calibration test should be performed daily to ensure accurate and consistent results. Daily testing helps identify any variations or drift in the CT scanner's performance, allowing for timely adjustments and calibration. This is crucial in maintaining the quality and reliability of the CT images produced. Regular calibration also helps in detecting any potential issues or malfunctions early on, minimizing the risk of diagnostic errors and ensuring patient safety. Therefore, performing a CT number calibration test on a daily basis is necessary for optimal performance and accuracy of the CT scanner.Rate this question:
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- 48.
Which of the following is a reason to increase the pitch?1. a greater volume of anatomy can be covered in a given time2. a given volume of anatomy can be covered faster3. radiation dose to the patient can be increased
- A.
1 only
- B.
2 only
- C.
1 & 2
- D.
2 & 3
Correct Answer
C. 1 & 2Explanation
Increasing the pitch in this context refers to increasing the speed at which a given volume of anatomy can be covered during a medical procedure. This allows for a greater volume of anatomy to be covered in a given time, as well as enabling the coverage of a given volume of anatomy at a faster rate. Increasing the pitch does not have any direct impact on the radiation dose to the patient, so option 3 is not correct. Therefore, the correct answer is option 1 & 2.Rate this question:
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- 49.
An increase in _____________ will result in hardening of an x-ray beam.1. tissue density2. tissue thickness3. kVp
- A.
1 only
- B.
2 only
- C.
3 only
- D.
1, 2, & 3
Correct Answer
D. 1, 2, & 3Explanation
An increase in tissue density, tissue thickness, and kVp (kilovolt peak) will result in hardening of an x-ray beam. When tissue density increases, more photons are absorbed by the tissue, causing the remaining photons to have higher energy and a harder beam. Similarly, an increase in tissue thickness results in more absorption and a harder beam. Finally, increasing the kVp increases the energy of the x-ray photons, leading to a harder beam. Therefore, all three factors contribute to the hardening of an x-ray beam.Rate this question:
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- 50.
If the slice thickness is changed from 5mm to 7mm and all other parameters are held constant, _______________ % more photons will be used in making the slice.
- A.
30
- B.
40
- C.
60
- D.
80
Correct Answer
B. 40Explanation
If the slice thickness is changed from 5mm to 7mm and all other parameters are held constant, 40% more photons will be used in making the slice. This is because as the slice thickness increases, more photons are required to penetrate the increased depth of tissue. Therefore, a 40% increase in slice thickness will result in a 40% increase in the number of photons needed.Rate this question:
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Current Version
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Sep 04, 2024Quiz Edited by
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Aug 03, 2010Quiz Created by
Radgirl86
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