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20 Cards in this Set
- Front
- Back
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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 |
c. 1 & 2
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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 seconds |
c. mA=150, rotation time=3 seconds
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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. -200 d. above +100 |
b. below -300
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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 = 500 2. window level = +300, window width = 500 3. window level = +100, window width = 1000 a. 1 only b. 2 only c. 3 only d. 2 & 3 |
a. 1 only
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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 |
c. noise
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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 |
d. 1, 2 & 3
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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 |
c. increased mAs
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A CT Number Calibration Test should be performed:
a. weekly b. annually c. monthly d. daily |
d. daily
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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 |
c. 1 & 2
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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 |
c. 3 only
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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 |
d. 1, 2 & 3
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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 |
b. 40
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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 |
b. 2 only
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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 |
b. 0.625 X 0.625
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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 |
b. 2 only
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Which of the following is t he 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 |
c. CT number = Hounsfield unit
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There are ______________ total pixels in a 1024 X 1024 matrix.
a. 2048 b. 524,288 c. more than 1 million d. more than 2 million |
c. more than 1 million
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Which of the following occurs when slice thickness is reduced?
1. appearance of noise in the image increases 2. the number of photons used in making the slice decreases 3. partial volume averaging decreases a. 1 only b. 2 only c. 3 only d. 1, 2 & 3 |
d. 1, 2 & 3
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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 |
c. 1 & 3
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___________________ affects the CT number of water.
a. No imaging parameter b. The slice thickness c. The kVp d. The mAs |
a. No imaging parameter
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