Instrumentation Quality Assurance and Regulatory Compliance
Core concepts
QA programs ensure instrumentation performs within specifications. Daily checks typically include energy peaking, flood uniformity, and background. Weekly/monthly checks include bar phantom resolution, COR, and high-count floods. Annual or acceptance testing covers sensitivity, resolution, and calibration. Regulatory frameworks include NRC rules (10 CFR Part 35) for byproduct material, agreement states, and ** accrediting bodies** (e.g., ACR, Intersocietal Accreditation Commission) with their own QA requirements. Medical physicist oversight, written directives, and records retention are commonly tested. Dose calibrator QA (constancy, linearity, geometry, accuracy) is a frequent exam topic. Instrument logs and corrective actions must be documented.
Traps
- Confusing daily vs annual test frequency; many questions hinge on timing.
- Dose calibrator linearity uses decaying sources or shields and must be checked across the clinical range.
- Records retention periods differ by regulation; don't assume a single number.
- Corrective action must be documented when QC fails - not just repeated.
Rule of thumb
If a daily flood or energy check fails, perform corrective action and document before clinical use; do not image patients with a failing camera.
Worked example: A dose calibrator constancy check reads 10% high against a reference source; investigate geometry and source decay before use, and document the corrective action.