Image Processing, Quality Assurance, and Radiation Safety
Image formation and processing
Understand the chain: exposure → receptor signal → digitization → display. Know window/level (contrast/brightness), lookup tables, and the difference between spatial and contrast resolution. Recognize artifacts: motion, double exposure, sensor bending, and processing errors. In CBCT, know beam-hardening, metal, and ring artifacts and how they arise.
Quality assurance
Know the purpose of QA: consistent image quality at lowest dose. Typical tests include kVp/mA calibration, collimation and field-size checks, receptor uniformity and resolution (line-pair phantom), and processor/film checks. Establish baselines and tolerances; repeat testing after service. In CBCT, verify geometric accuracy, uniformity, noise, and artifact behavior.
Radiation safety
Apply ALARA and justification/optimization. Know dose quantities: absorbed dose (Gy), equivalent dose (Sv, with radiation weighting), effective dose (Sv, tissue-weighted). Recall typical effective doses: intraoral ~micro-Sv, panoramic ~tens of µSv, CBCT ~tens to hundreds of µSv depending on FOV, medical CT higher. Use lead aprons and thyroid collars appropriately, and understand that collimation and reducing FOV lower dose. Know occupational dose limits and the principle of dose monitoring (personnel dosimeters).
Traps
Questions confuse absorbed vs equivalent vs effective dose, or ask whether a thyroid collar should be used with panoramic imaging (it can shadow anatomy). Watch for claims that digital imaging eliminates need for QA or that higher kVp always lowers dose.
Rule of thumb
When comparing modalities, compare effective dose (Sv), not absorbed dose; and remember that smaller FOV and tighter collimation reduce dose without necessarily reducing diagnostic yield.