3 CT Image Quality

D. 1&2&3 1. The resolution of the second set of image 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 does of the first set of images is higher than the second set

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 image 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 does 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

d. 1,2 & 3

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.1 & 2 d. 1,2 & 3

C. 3 only Reconstruction is dependent on scanned FOV

C. 3 only Reconstruction is dependent on scanned FOVWhich 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. Reconstruction is dependent on scanned FOV A. 1 only B. 2 only C. 3 only D. 1,2&3

B. Below -300

CT ____ numbers would appear black if a window width of 400 and it went to level of -100 are used. A. Above +200 B. Below -300 C. Below -200 D. Above +100

A. mAs

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

D. Daily

ECT number calibration test should be performed: A. weekly B. annually C. monthly D. daily

D. 2&3 2.as pitch increases, patient dose decreases 3.as slice thickness increases, patient dose decreases

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

B. 0.625 x 0.625

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

C. Increased mAs

If a thin slice is used, which of the following would help reduce the apparent image noise? A. Reduced re-construction field of view B. Increased matrix C. Increased mAs D. Increased kVp

A. 1 only window level= 0, window width= 500

If 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

C. 12

If the radiologist requires 2MM thick contiguous slices through the pituitary, and 2.4 CM of coverage, ___ slices are necessary? A. 8 B. 10 C. 12 D. 13

B. 40

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

C. 1&3 1. Pitch 3. Table increment

Increasing ___ results lowering the patient dose. 1. Pitch 2. mAs 3. Table increment A. 1 only B. 1&2 C. 1&3 D. 1,2&3

A. number of rows of detectors and the size of the detectors whose attenuation data gets combined

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

C.4

On a conventional, or seial, CT scan, if we want 5mm slices with 1 mm of overlap, the table increment should be ___ mm. A. 1 B. 3 C. 4 D. 5

A. kVp

The ___ determines how penetrating the x-ray beam will be. A. kVp B. Rotation time C. mA D. Pitch

A. Temporal resolution

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

A. table increment

The distance that the table travels between slices is called: A. table increment B. collimation C. rotation D. reconstruction interval

A. 0.47

The smallest object 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

C. More than 1 million

There are ____ total pixels in 1024 x 1024 matrix. A. 2048 B. 524,288 C. More than 1 million D. more than 2 million

C. 1 & 2 only 1. Decreased sharpness of edges 2. Misleading CT numbers

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

B. 1&2 1. the slice thickness from an MDCT helical scan 2.the slice overlap from a single-row detector scanner helical

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 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

c.noise

Which of the following determinants of CT image quality is responsible for how grainy or speckled a CT image appears? a. resolution b.lineartiy c.noise d.contrast

2. pixel size in increased

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

C. mA= 150, rotation time= 3 seconds

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 seconds C.mA=150, rotation time= 3 seconds D.mA=400, rotation time= 1 seconds

C. 1&2 only 1. A greater volume of anatomy can be covered in a given time 2. A given volume of anatomy can be covered faster

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

A. The mean energy of the x-ray photons leaving the tube

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

C. CT number= Hounsfield unit

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

A. 0 +- 3

Which of the following is the expected result of a CT Number Calibration est performed on a water phantom? A. 0 +- 3 B. 0 +- 5 C. 100 +- 3 D. 1000 +-5

C. kVp

Which of the following parameters affects the contrast of a CT image? A. Reconstruction interval B. mAs C. kVp D. CT number

A. reconstruction interval

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

B. reconstruction interval

Which of the following parameters causes helical slices top be reconstructed so the y overlap? A. table increment B. reconstruction interval C. Pitch D. collimation

C. slice thickness

Which of the following parameters is responsible for partial volume averaging? A. matrix size B. kVp C. slice thickness D. patient dose

D. 2&3 2. Increasing magnification increases resolution 3. Magnification decreases the size of displayed anatomy

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

A. 1.5

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

B. 2 only

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

D. 1, 2&3 1.reduced slice thickness 2.reduced reconstruction FOV 3. sharp reconstruction filter

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

D. 3 only Narrow window with

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

D. Increasing, level

___ 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

A. No imaging parameter

____ affects the CT number of water. A. No image parameter B. The slice thickness C. The kVp D. The mAs