CABT Imaging Systems 5

Question 1

In MRI, which parameter is adjusted to change T1 contrast between tissues?

Accepted Answer

Repetition time (TR)

Answer

Repetition time (TR) controls how much T1 relaxation occurs between pulses; a short TR emphasizes T1 differences between tissues, producing T1-weighted contrast.

Question 2

Which ionizing radiation interaction with matter is the dominant process for diagnostic X-ray energies (20–150 keV) in soft tissue?

Accepted Answer

Compton scattering

Answer

Compton scattering dominates in soft tissue over the diagnostic energy range because photon energy greatly exceeds electron binding energies, making interaction probability nearly independent of atomic number.

Question 3

A technologist notices vertical line artifacts on a flat-panel X-ray detector image. The most likely cause is:

Accepted Answer

Defective column(s) of detector elements

Answer

Vertical line artifacts on a flat-panel detector typically indicate one or more dead or malfunctioning columns of detector pixels that produce no signal or a constant incorrect value.

Question 4

The primary advantage of iterative reconstruction over filtered back projection (FBP) in CT is:

Accepted Answer

Reduction of image noise at the same or lower dose

Answer

Iterative reconstruction algorithms model the acquisition physics and reduce noise more effectively than FBP, allowing diagnostic images at lower tube current and reduced patient dose.

Question 5

In nuclear medicine, the physical half-life of Technetium-99m (Tc-99m) is approximately:

Accepted Answer

6 hours

Answer

Tc-99m has a physical half-life of approximately 6 hours, which is short enough to limit patient dose while long enough to complete most nuclear medicine procedures.

(CABT) Certified Associate in Biomedical Technology Practice Test

(CABT) Certified Associate in Biomedical Technology Practice Test

CABT Imaging Systems 5