Week 5

Question 1

Ability to differentiate small, nearby objects of similar density

Answer 1

Spatial resolution

Question 2

The lack of sharpness that occurs when a true point in the object being scanned is not represented as a true point on the image is called:

Answer 2

Point spread function

Question 3

Describes the unsharpness when a linear source is not represented as a clear line on the image

Answer 3

Line spread function

Question 4

The CT system’s ability to differentiate between similar tissues is called:

Answer 4

Contrast resolution

Question 5

Image noise can be reduced by:

Answer 5

Increasing slice thickness

Question 6

The ability of the CT scanner to image moving objects effectively is called:

Answer 6

temporal resolution

Question 7

Correct assignment of HU values

Answer 7

Linearity

Question 8

The ability of the CT scanner to consistently assign the correct HU numbers

Answer 8

Uniformity

Question 9

The path pf the x-ray beam from the tube to the detectors

Answer 9

Beam geometry

Question 10

All of the following result from an increase in kVp, EXCEPT
-reduced absorption
-higher average beam energy
-increased scatter
-increased image contrast

Answer 10

increased image contrast

Question 11

Broad, dark streaks between or along dense objects; type of beam hardening artifact

Answer 11

Streaking artifact

Question 12

Occurs when similar tissues within a voxel are averaged as one Hounsfield unit

Answer 12

Partial volume averaging artifact

Question 13

Occurs when impurities in the x-ray tube cause a short circuit

Answer 13

Tube arcing

Question 14

Artifact caused by faulty detectors and faulty digital acquisition systems

Answer 14

Ring artifacts

Question 15

Appear as shadowing on the image; corrected by using interpolation

Answer 15

low-frequency artifacts

Question 16

Caused by abrupt longitudinal changes of the body; corrected using algorithms

Answer 16

high-frequency artifacts

Question 17

Artifacts appearing as streaks that originate from body structures with tissues that vary significantly in density, such as bone and soft tissue interfaces, are called:

Answer 17

Edge gradient artifacts

Question 18

Occurs when peripheral anatomy interferes with the signal

Answer 18

out-of-field artifacts

Question 19

Which tests the performance of a computed tomography (CT) scanner on a number of parameters and compares the performance with a standard?

Answer 19

Quality control

Question 20

Which of the following is not an essential step in a QC program?
a. Phantom construction
b. Routine performance evaluation
c. Error correction
d. Acceptance testing

Answer 20

A

Question 21

The average CT number of water QC test should be done:

Answer 21

Daily

Question 22

T/F: Often a QC program can result in reduced downtime.

Answer 22

True

Question 23

What is the most upfront way to reduce or eliminate the motion of an object?

Answer 23

Increase scan speed

Question 24

What is defined as the smallest object that can be visualized at a given contrast level and dose?

Answer 24

Low-contrast performance

Question 25

How do beam-hardening artifacts appear on a CT image?

Answer 25

Shading