MRI

Question 1

A change in the strength of the main magnetic field can be caused by:
a. All are correct.
b. cryogen boiloff.
c. external ferromagnetic materials.
d. shim coil failure.

Answer 1

A

Question 2

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

Answer 2

0.78

Question 3

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

Answer 3

30%

Question 4

Nonuniformity in the magnetic field can be caused by:

Answer 4

the presence of ferromagnetic material within the bore of the magnet.

Question 5

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

Answer 5

5

Question 6

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

Answer 6

high-contrast resolution.

Question 7

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

Answer 7

low-contrast resolution

Question 8

The amount of geometric distortion in the image is the:

Answer 8

spatial linearity.

Question 9

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

Answer 9

Greater than 90 nit

Question 10

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

Answer 10

42.57 MHz