ARRT Equipment Operation and Quality Control

Question 1

Which daily CT quality control test verifies that CT numbers (Hounsfield Units) remain accurate and consistent?

Accepted Answer

CT number accuracy/linearity test

Answer

The CT number accuracy/linearity test confirms that scanned materials produce the expected HU values, ensuring diagnostic consistency.

Question 2

What is the primary purpose of performing a daily air calibration (warm-up scan) on a CT scanner?

Accepted Answer

To calibrate detector channels and normalize dark current

Answer

The daily air calibration normalizes detector channel responses and corrects for dark current drift, maintaining uniform image quality.

Question 3

Which CT quality control phantom is most commonly used to evaluate CT number accuracy, noise, uniformity, and spatial resolution?

Accepted Answer

AAPM CT performance phantom

Answer

The AAPM CT performance phantom contains inserts for testing multiple image quality parameters including HU accuracy, noise, and spatial resolution.

Question 4

On a CT scanner, what does image uniformity testing evaluate?

Accepted Answer

The consistency of CT numbers across the field of view in a homogeneous phantom

Answer

Image uniformity testing measures whether a homogeneous phantom (e.g., water) produces consistent HU values across the entire reconstructed image.

Question 5

Which factor is evaluated by the modulation transfer function (MTF) in CT quality control?

Accepted Answer

High-contrast spatial resolution

Answer

The MTF describes how faithfully the CT system reproduces spatial detail, directly measuring high-contrast spatial resolution performance.

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