Question 1

Patient dose values for CT scans should remain within ____ of the manufacturer's specifications.
A)$\pm$2%
B) $\pm$5%
C) $\pm$10%
D) $\pm$20%

Accepted Answer

No acceptable maximum levels of radiation are specified for the permissible dose to a patient during a CT procedure. In addition, the results can vary according to patient location and distance from the x-ray source. However, most experts agree that the values should remain within ±10% of the manufacturer's specifications when a fixed technique is used.

Question 2

The uniformity of the CT number of water should not vary by more than ____ HU from the center of the phantom to the periphery.
A) 2
B) 3
C) 5
D) 10

Accepted Answer

Edge-to-center mean CT number difference must be less than 5 HU for all four edge positions.

Question 3

Section thickness should not vary by more than ____ mm for sections greater than 5 mm.
A) $\pm$0.5
B)$\pm$1.0
C) $\pm$2.0
D) $\pm$5.0

Accepted Answer

If the slice thickness is 5 mm or more, the slice thickness should not vary more than ±1 mm from the intended slice thickness. If it is 5 mm or less, the slice thickness should not vary more than ±0.5 mm.

Question 4

The laser light field and radiation field should coincide to within ____ mm.
A) 0.5
B) 1.0
C) 2.0
D) 5.0

Accepted Answer

For optimal performance, the light field should coincide with the radiation field to within 2 mm.

Question 5

A visual inspection of a CT unit should be evaluated at least _____ for ACR accreditation programs.
A) daily.
B) weekly.
C) monthly.
D) semi-annually.

Accepted Answer

The visual inspection is part of the CT technologist's monthly duties for ACR accreditation.

Question 6

The minimum distance between two objects that allows them to be seen as separate and distinct would define what CT imaging parameter?
A) Low-contrast resolution
B) Uniformity
C) High-contrast resolution
D) Image noise

Accepted Answer

High-contrast spatial resolution is described as the minimum distance between two objects that allows them to be seen as separate and distinct.

Question 7

The CT number of water should not deviate by more than ____ CT numbers from 0.
A) 2
B) 3
C) 5
D) 10

Accepted Answer

The water values should be 0 ±5 Hounsfield units (HU), but must be 0 ±7 HU.

Question 8

For a slice thickness of 5 mm or less, the slice thickness should not vary by more than ____ mm.
A) 0.5
B) 1.0
C) 2.0
D) 3.0

Accepted Answer

If the slice thickness is 5 mm or more, the slice thickness should not vary more than ±1 mm from the intended slice thickness. If it is 5 mm or less, the slice thickness should not vary more than ±0.5 mm.

Question 9

For ACR CT accreditation, the Water CT Number and Standard Deviation (Noise) should be evaluated by the CT technologist
A) quarterly.
B) monthly.
C) weekly.
D) daily.

Accepted Answer

The Water CT Number and Standard Deviation (Noise) evaluation is part of the CT technologist's daily duties for ACR accreditation.

Question 10

The CTDI_vol pass/fail criterion for an adult abdomen is ____ mGy. A) 20 B) 40 C) 30 D) 80

Accepted Answer

See Table 12-1 ACR CT Accreditation Dose Pass/Fail Criteria and Reference Levels.

Quiz 10: Quality Control in Computed Tomography

Patient dose values for CT scans should remain within ____ of the manufacturer's specifications.

The uniformity of the CT number of water should not vary by more than ____ HU from the center of the phantom to the periphery.

Section thickness should not vary by more than ____ mm for sections greater than 5 mm.

The laser light field and radiation field should coincide to within ____ mm.

A visual inspection of a CT unit should be evaluated at least _____ for ACR accreditation programs.

The minimum distance between two objects that allows them to be seen as separate and distinct would define what CT imaging parameter?

The CT number of water should not deviate by more than ____ CT numbers from 0.

For a slice thickness of 5 mm or less, the slice thickness should not vary by more than ____ mm.

For ACR CT accreditation, the Water CT Number and Standard Deviation (Noise) should be evaluated by the CT technologist

The CTDIvol pass/fail criterion for an adult abdomen is ____ mGy.

The CTDI_vol pass/fail criterion for an adult abdomen is ____ mGy.