Quiz

Question 1

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

Question 2

An increase in _____________ will result in hardening of an x-ray beam.
1. Tissue density
2. Tissue thickness
3. kVp

A. 1 only
B. 2 only
C. 3 only
D. 1, 2, & 3

Question 3

Which of the following are possible results of partial voluming?
1. Decreased sharpness of edges
2. Misleading CT numbers
3. Improvement in resolution

A. 1 only
B. 2 only
C. 1 & 2
D. 1, 2, & 3

Question 4

Which of the following is FALSE about the spatial resolution of an image?
1. Resolution is dependent on matrix size
2. Resolution is dependent on reconstruction FOV
3. Resolution is dependent on scanned FOV

A. 1 only
B. 2 only
C. 3 only
D. 1, 2, & 3

Question 5

Which of the following is NOT directly proportional to mAs?

A. The mean energy of the x-ray photons leaving the tube
B. The number of x-ray photons leaving the x-ray tube
C. X-ray tube heating
D. Dose to the patient

Question 6

Which of the following has the highest patient dose assuming all other parameters are the same?

A. mA=200, rotation time=2 seconds
B. mA=200, rotation time=1 second
C. mA=150, rotation time=3 seconds
D. mA=400, rotation time=1 second

Question 7

Which of the following will result in an increased voxel size?
1. Decreased reconstruction FOV
2. Increased slice thickness
3. Increased matrix

A. 1 only
B. 2 only
C. 2 & 3
D. 1, 2, & 3

Question 8

Which of the following is the conversion equation from CT number to Hounsfield unit?

A. CT number = 0.5 x Hounsfield unit
B. CT number = (Hounsfield unit)2
C. CT number = Hounsfield unit
D. CT number = 2 x Hounsfield unit

Question 9

If the radiologist requires 2 mm thick contiguous slices through the pituitary, and 2.4 cm of coverage, ________ slices are necessary?

A. 8
B. 10
C. 12
D. 13

Question 10

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

Question 11

If a reconstruction FOV of 32 cm and a 512 x 512 matrix are used, the pixel size is _____ mm.

A. 0.35 x 0.35
B. 0.625 x 0.625
C. 1.6 x 1.6
D. 3.25 x 3.25

Question 12

Which of the following is a reason to increase the pitch?
1. A greater volume of anatomy can be covered in a given time
2. A given volume of anatomy can be covered faster
3. Radiation dose to the patient can be increased

A. 1 only
B. 2 only
C. 1 & 2
D. 2 & 3

Question 13

Which of the following would be used to better visualize low contrast resolution?
1. Decreased mAs
2. Sharp reconstruction filter
3. Narrow window width

A. 1 only
B. 2 only
C. 1 & 2
D. 3 only

Question 14

Increasing ______________ results in lowering the patient dose.
1. Pitch
2. mAs
3. Table increment

A. 1 only
B. 1 & 2
C. 1 & 3
D. 1, 2, & 3

Question 15

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

Question 16

A set of images is reconstructed with a 150 mm reconstruction FOV. Keeping all other parameters constant, a second set of images is reconstructed with a 300 mm reconstruction FOV, and then magnified so that the anatomical structures in the first and second set appear the same size. Which of the following statements is FALSE?
1. The resolution of the second set of images is better than the first set
2. The apparent noise in the second set of images is more pronounced than the first set
3. The patient dose of the first set of images is higher than the second set

A. 1 & 2
B. 1 & 3
C. 2 & 3
D. 1, 2, & 3

Question 17

The ____________ determines how penetrating the x-ray beam will be.

A. kVp
B. Rotation time
C. mA
D. Pitch

Question 18

The smallest object that can be resolved if a reconstruction FOV of 24 cm and a 512 x 512 matrix are used is _____ mm.

A. 0.47
B. 1.00
C. 2.13
D. 3.57

Question 19

Which of the following parameters affects the contrast of a CT image?

A. Reconstructed interval
B. mAs
C. kVp
D. CT number

Question 20

Which of the following values for pitch would stretch the x-ray helix the most?

A. 1.5
B. 1.0
C. 0.8
D. 0.5

Question 21

There are ___________ total pixel in a 1024 x 1024 matrix.

A. 2048
B. 524,288
C. more than 1 million
D. more than 2 million

Question 22

For a given distance of coverage, which of the following is TRUE?
1. As reconstruction FOV increases, patient dose increases
2. As pitch increases, patient dose decreases
3. As slice thickness increases, patient dose decreases

A. 1 only
B. 2 only
C. 3 only
D. 2 & 3

Question 23

Which of the following statements is FALSE?
1. Magnification requires the raw data
2. Increasing magnification increases resolution
3. Magnification decreases the size of displayed anatomy

A. 1 only
B. 2 only
C. 3 only
D. 1, 2, & 3

Question 24

Compared to a CT scan protocol without iterative reconstruction applied, when using iterative reconstruction the scan parameter most likely to be reduced is:

A. mAs
B. Matrix
C. Pitch
D. Scan field-of-view

Question 25

A CT Number Calibration Test should be performed:

A. Weekly
B. Annually
C. Monthly
D. Daily

Question 26

If the slice thickness is changed from 5 mm to 7 mm and all other parameters are held constant, ______% more photons will be used in making the slice.

A. 30
B. 40
C. 60
D. 80

Question 27

____________ the window _____________ will make the image appear darker so that bony structures can be evaluated.

A. Increasing, width
B. Decreasing, level
C. Decreasing, width
D. Increasing, level

Question 28

Which of the following is the expected result of a CT Number Calibration Test performed on a water phantom?

A. 0 +/- 3
B. 0 +/- 5
C. 100 +/- 3
D. 1000 +/- 5

Question 29

______________ affects the CT number of water.

A. No imaging parameter
B. The slice thickness
C. The kVp
D. The mAs

Question 30

Which of the following parameters allows adjacent slices to be overlapped without increasing the dose to the patient?

A. Reconstruction interval
B. Slice thickness
C. Table increment
D. Pitch

Question 31

Which of the following can be changed retrospectively?
1. The slice thickness from an MDCT helical scan
2. The slice overlap from a single-row detector scanner helical scan
3. The slice thickness from a single-row detector scanner helical scan

A. 1 only
B. 1 & 2
C. 2 & 3
D. 1, 2, & 3

Question 32

Which of the following would be used in a high resolution study of the temporal bones?
1. Reduced slice thickness
2. Reduced reconstruction FOV
3. Sharp reconstruction filter

A. 1 only
B. 2 only
C. 3 only
D. 1, 2, & 3

Question 33

The ability to scan a moving organ without seeing motion artifacts on the images is an example of an exam performed with high:

A. Temporal resolution
B. Spatial resolution
C. Contrast resolution
D. Noise

Question 34

On a conventional, or serial, CT scan, if we want 5 mm slices with 1 mm of overlap, the table increment should be ____ mm.

A. 1
B. 3
C. 4
D. 5

Question 35

On MDCT, the final reconstructed slice thickness is determined by the:

A. Number of rows of detectors and the size of the detectors whose attenuation data gets combined
B. Pitch
C. Reconstruction interval
D. Collimation of the x-ray beam

Question 36

Which of the following parameters is responsible for partial volume averaging?

A. Matrix size
B. kVp
C. Slice thickness
D. Patient dose

Question 37

The distance that the table travels between slices is called:

A. Table increment
B. Collimation
C. Rotation
D. Reconstruction interval

Question 38

Which of the following parameters causes helical slices to be reconstructed so they overlap?

A. Table increment
B. Reconstruction interval
C. Pitch
D. Collimation

Question 39

Which of the following does NOT occur when reconstruction FOV is decreased?
1. Spatial resolution is increased
2. Pixel size is increased
3. Noise in the image increases

A. 1 only
B. 2 only
C. 3 only
D. 1, 2, & 3

Question 40

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. WL = 0, WW = 500
2. WL = +300, WW = 500
3. WL = +100, WW = 1000

A. 1 only
B. 2 only
C. 3 only
D. 2 & 3