DEXA Quality Assurance & Equipment Calibration Flashcards
6 cards from real DEXA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 DEXA Quality Assurance & Equipment Calibration flashcards as text
Which measurement is used to evaluate in-vitro precision of a DEXA scanner?
Answer: Root mean square coefficient of variation (RMS-CV%)
RMS-CV% quantifies the percentage variability of repeated phantom or patient measurements and reflects scanner precision.
What is the recommended minimum number of repeat scans used to calculate an in-vivo precision assessment for a DEXA technologist?
Answer: 30 patients scanned twice or 15 patients scanned three times
ISCD guidelines recommend 30×2 or 15×3 repeat scans on real patients to calculate a clinically valid precision error.
A DEXA technologist calculates an in-vivo spine precision of 1.8% RMS-CV. What is the least significant change (LSC) at 95% confidence?
Answer: ~5.0%
LSC at 95% confidence = 2.77 × RMS-CV; 2.77 × 1.8% ≈ 5.0%, meaning a change must exceed ~5% to be considered real.
Which factor most directly degrades technologist repositioning precision in spine DEXA?
Answer: Inconsistent patient positioning and ROI placement between visits
Repositioning errors from inconsistent patient setup and ROI placement are the leading cause of poor in-vivo precision.
A DEXA facility is switching from one manufacturer's system to another. What must be done before comparing serial BMD results?
Answer: Perform cross-calibration using ISCD-recommended methods and ideally rescan patients on both systems
Different DEXA systems are not interchangeable; cross-calibration studies are required to establish BMD conversion equations.
What is the typical acceptable long-term coefficient of variation (CV) for a well-maintained DEXA phantom?
Answer: Less than 0.5–1.0%
A well-maintained DEXA system should achieve long-term phantom CV of less than 0.5–1.0%, indicating stable and reproducible performance.
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