ARRT Equipment Operation and Quality Control 3

Question 1

Which CT quality control parameter is most directly affected by X-ray tube focal spot size?

Accepted Answer

High-contrast spatial resolution

Answer

A smaller focal spot produces sharper images with improved high-contrast spatial resolution because the geometric unsharpness is reduced.

Question 2

What is the role of the bowtie (beam-shaping) filter in CT equipment operation?

Accepted Answer

To equalize X-ray flux across the fan beam, reducing dose at the periphery and minimizing detector saturation

Answer

The bowtie filter is thicker at the edges and thinner at the center, compensating for the cylindrical shape of patients to equalize detector flux and reduce peripheral skin dose.

Question 3

During CT scanner acceptance testing, which test verifies that the displayed scan field of view (SFOV) matches the actual reconstructed area?

Accepted Answer

Geometric accuracy/distance accuracy test

Answer

The geometric/distance accuracy test uses a phantom with known dimensions to confirm that distances measured on reconstructed images correspond to actual physical distances.

Question 4

In CT quality control documentation, what is the purpose of establishing 'action limits' for QC measurements?

Accepted Answer

To set thresholds that, when exceeded, require investigation and corrective action before clinical use

Answer

Action limits define tolerance thresholds for QC parameters; if a measurement falls outside these limits, the scanner must be taken out of service for investigation and repair.

Question 5

Which type of CT detector material is most commonly used in modern multi-detector CT (MDCT) systems due to its high conversion efficiency and fast decay time?

Accepted Answer

Gadolinium oxysulfide (GOS) solid-state scintillators

Answer

Modern MDCT scanners predominantly use solid-state scintillator detectors such as gadolinium oxysulfide because of their high X-ray absorption efficiency and rapid afterglow decay.

(ARRT) American Registry of Radiologic Technologists Computed Tomography Certification Practice Test

(ARRT) American Registry of Radiologic Technologists Computed Tomography Certification Practice Test

ARRT Equipment Operation and Quality Control 3