Deck 26: Magnetic Resonance Imaging

Question 1

Dose in CT is considered to be:

A) independent of size.
B) size dependent.
C) related to the CT numbers.
D) similar to a chest examination.

Answer 1

size dependent.

Question 2

Which two factors affect image quality in CT? (Select all that apply.)

A) Spatial resolution
B) Contrast media
C) Noise
D) Aperture size

Answer 2

Spatial resolution
Noise

Question 3

CT is able to differentiate between tissues with similar densities compared with conventional radiography because of:

A) digital magnification.
B) the use of a computer for data processing.
C) improved contrast resolution.
D) axial slices.

Answer 3

improved contrast resolution.

Question 4

An array of numbers arranged in a grid of rows and columns is called a:

A) pixel.
B) voxel.
C) matrix.
D) scan profile.

Question 5

The most significant geometric factor that contributes to spatial resolution is:

A) detector aperture width.
B) FOV.
C) slice thickness.
D) x-ray beam energy.

Question 6

Contrast is adjusted by windowing,changing window width and window level.Window level determines the:

A) number of gray levels displayed.
B) midpoint of the gray range.
C) size of the field of view.
D) slice thickness.

Question 7

Which generation of CT scanners uses a dual-energy source (two x-ray tubes)?

A) Third generation
B) Fourth generation
C) Fifth generation
D) Sixth generation

Question 8

CT detectors are most commonly _____ detectors.

A) ionization (xenon gas)
B) scintillation (solid state)
C) thermoluminescent
D) phosphorescent

Question 9

Contrast is adjusted by windowing,changing window width and window level.Window width determines the:

A) number of gray levels displayed.
B) midpoint of the gray range.
C) size of the field of view.
D) slice thickness.

Question 10

The measured x-ray transmission values are called:

A) raw data.
B) pixels.
C) voxels.
D) Hounsfield units.

Question 11

The CT system's ability to freeze any motion of a scanned object is termed:

A) detector quantum efficiency.
B) temporal resolution.
C) reconstruction algorithm.
D) spatial resolution.

Question 12

Oral contrast for CT should be mixed so it is:

A) the same as for general diagnostic examinations.
B) more concentrated than for general examinations.
C) less concentrated than for general examinations.
D) contrast media is not necessary.

Question 13

The reference material for CT is _____ and is related to the _____ of the tissue.

A) water; field of view
B) water; linear attenuation coefficient
C) muscle; gray level
D) bone; mass attenuation

Question 14

The most common reporting method of dose reporting on the present scanners is:

A) multiple scan average dose (MSAD).
B) computed tomography dose index (CTDI).
C) dose-length product (DLP).
D) computed tomography dose index volume (CTDIvol).