CBCT vs Medical CT — MFDS Part 1 MCQ
Instant feedback + full explanation. One question, done properly.
Educational content. Not a substitute for clinical judgement or local policy.
Reveal the answer and explanation
Correct answer: C — It uses a cone-shaped beam and area detector to acquire the volume in one rotational sweep
Explanation lettering: D = shown as A · A = shown as C · C = shown as D
A is correct. Dental CBCT uses a cone-shaped X-ray beam and a flat-panel area detector to collect all projection data during a single rotational sweep, typically over 180–360 degrees, from which a three-dimensional volume is reconstructed. Conventional multidetector CT instead uses a narrowly collimated fan-shaped beam with sequential or helical slice acquisition, so B describes medical CT, not CBCT. Medical CT has superior low-contrast (soft-tissue) discrimination; UK guidance (HPA-CRCE-010) advises conventional CT or MRI when soft-tissue assessment is required, making C incorrect. CBCT dose varies substantially with field of view, rotation arc and exposure factors, so a universal lower-dose claim is unsafe, excluding D. CBCT grey values are affected by scatter and machine-specific factors and are not standardised Hounsfield units comparable between scanners, excluding E.
Reference: Health Protection Agency. Guidance on the Safe Use of Dental Cone Beam CT (Computed Tomography) Equipment (HPA-CRCE-010), 2010. https://assets.publishing.service.gov.uk/media/5a7d4f13ed915d321c2de451/HPA-CRCE-010_for_website.pdf ; Posadzy M et al. Cone beam CT of the musculoskeletal system: clinical applications. Insights Imaging 2018. https://pubmed.ncbi.nlm.nih.gov/29302798/