Which radiographic examination exposes the patient to the LOWEST radiation dose?

Correct answer: D. Panoramic radiograph

• A. A FULL-MOUTH SERIES with ROUND collimation is the highest-dose conventional intraoral examination, since 18–20 separate exposures are taken and round collimation irradiates far more tissue than the beam needs to.
• B. CBCT dose varies enormously with field of view and settings but is substantially higher than a panoramic — a small-field scan may approach several panoramics, and a large field-of-view scan considerably more.
• C. MEDICAL CT delivers by far the highest dose of these — commonly an order of magnitude or more above CBCT for the same region, which is precisely why CBCT was developed for dentistry.
• D. CORRECT. Of these options the PANORAMIC radiograph delivers the lowest effective dose — broadly in the region of 10–25 microsieverts. It uses a narrow moving slit beam and rare-earth intensifying screens, capturing both jaws in a single rotation for a fraction of the dose of a full-mouth series.

Note: Apply ALARA whatever the modality: rectangular collimation (cutting dose by roughly half compared with round), the fastest available receptor (F-speed film or digital sensors), thyroid collar where it will not obscure the region of interest, and — most powerful of all — prescribing radiographs based on individual clinical need rather than a fixed schedule.