Deck 11: Quality Control for Magnetic Resonance Imaging Equipment

Question 1

The ability of the MR system to differentiate between adjacent tissues having minimal differences in signal intensities is known as

A) signal-to-noise ratio.
B) high-contrast resolution.
C) low-contrast resolution.
D) spatial linearity.

Answer 1

C
Low-contrast resolution is a measure of the MR system's ability to differentiate between adjacent tissues having minimal differences in signal intensities.

Question 2

The amount of geometric distortion in the image is the

A) signal-to-noise ratio.
B) image uniformity.
C) spatial resolution.
D) spatial linearity.

Answer 2

D
Geometric accuracy, also referred to as spatial linearity, refers to the amount of geometric distortion in the image due to displacement or improper scaling of the distance between points being displayed on the image.

Question 3

An acquisition with a 200-mm field of view and 256 x and y encodes yields a pixel size of ____ mm².

A) 0.78
B) 1.56
C) 2.08
D) none of the above

Answer 3

A
200 mm FOV ÷ 256 frequency encodings = 0.78 mm.

Question 4

Nonuniformity in the magnetic field can be caused by

A) a homogenous main magnetic field.
B) uniformity in the RF coil.
C) the presence of ferromagnetic material within the bore of the magnet.
D) All of the answer options are correct.

Question 5

Luminance uniformity of soft-copy displays used in MRI systems should be within ____ of the maximum brightness measured in the center of the screen.

A) 10%
B) 20%
C) 30%
D) 50%

Question 6

The ACR slice position deviation in MR scanners should not exceed ____ mm.

A) 1
B) 2
C) 3
D) 5

Question 7

What is the maximum luminance for soft-copy display devices as suggested by the ACR?

A) Less than 1.2 nit
B) Greater than 50 nit
C) Greater than 90 nit
D) Less than 150 nit

Question 8

What is the resonant frequency in a unit with a 1.0-T magnet and a gyromagnetic ratio of 42.57 MHz/T?

A) 12.77 MHz
B) 21.29 MHz
C) 42.57 MHz
D) 63.86 MHz

Question 9

The ability of an MR scanner to resolve small objects is known as

A) signal-to-noise ratio.
B) high-contrast resolution.
C) spatial resolution.
D) spatial linearity.

Question 10

A change in the strength of the main magnetic field can be caused by

A) cryogen boiloff.
B) external ferromagnetic materials.
C) shim coil failure.
D) All of answer options are correct.