Deck 25: Computed Tomography

Question 1

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.

Answer 1

temporal resolution.

Question 2

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.

Answer 2

number of gray levels displayed.

Question 3

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.

Answer 3

less concentrated than for general examinations.

Question 4

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

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

Question 5

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 6

CT detectors are most commonly _____ detectors.

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

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 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.

Question 9

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 10

The measured x-ray transmission values are called:

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

Question 11

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 12

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).

Question 13

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 14

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.