Equipment Operation and Quality Control Flashcards
7 cards from real ARRT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Equipment Operation and Quality Control flashcards as text
Which CT quality control parameter is most directly affected by X-ray tube focal spot size?
Answer: High-contrast spatial resolution
A smaller focal spot produces sharper images with improved high-contrast spatial resolution because the geometric unsharpness is reduced.
What is the role of the bowtie (beam-shaping) filter in CT equipment operation?
Answer: To equalize X-ray flux across the fan beam, reducing dose at the periphery and minimizing detector saturation
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.
During CT scanner acceptance testing, which test verifies that the displayed scan field of view (SFOV) matches the actual reconstructed area?
Answer: Geometric accuracy/distance accuracy test
The geometric/distance accuracy test uses a phantom with known dimensions to confirm that distances measured on reconstructed images correspond to actual physical distances.
In CT quality control documentation, what is the purpose of establishing 'action limits' for QC measurements?
Answer: To set thresholds that, when exceeded, require investigation and corrective action before clinical use
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.
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?
Answer: Gadolinium oxysulfide (GOS) solid-state scintillators
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.
What does 'afterglow' (or 'ghosting') in CT solid-state detectors cause?
Answer: Residual signal carried over from prior projections, causing streak artifacts
Afterglow occurs when scintillator crystals continue to emit light after X-ray exposure ends, carrying residual signal into subsequent projections and causing streak or shading artifacts.
Which ACR-recommended CT quality control test should be performed if visual image artifacts are noted during clinical scanning?
Answer: Perform artifact analysis using an appropriate phantom and document findings before continuing clinical use
When clinical artifacts are observed, ACR guidelines require phantom-based artifact analysis and documentation before continuing patient scanning to ensure diagnostic image quality.