Quality Control and Image Evaluation
This domain tests quality assurance, equipment constancy testing, image critique and artifact recognition. It asks whether an image is diagnostically acceptable and whether the imaging system is performing within tolerance.
Core rules
- Quality assurance is the overall program; quality control is the set of measurements and corrective actions.
- Daily, weekly and periodic tests depend on the modality: collimation, uniformity, resolution, monitor performance, reject analysis and dose indicators.
- Image evaluation covers positioning, contrast, noise, sharpness, artifact, inclusion and markers.
- Reject analysis identifies correctable causes: positioning, exposure, processing, equipment and patient factors.
- Acceptance testing follows installation or major repair; constancy testing detects drift.
Worked example
A department finds a reject rate of 9%, above its 5% action level. The reasoning is to classify rejects by cause rather than blame individuals. If most are rotated chests, retrain positioning and check whether the room's centering aids are misaligned. If most are overexposed, review AEC calibration and technique charts. The corrective action should be measurable and re-audited.
Traps
Do not confuse a single rejected image with a system fault. Do not evaluate monitor contrast as if it were acquisition contrast. Do not ignore artifact direction and shape, which may identify the cause. Do not stop at measuring a problem; document corrective action and recheck.