In DXA, original scanners used ________.

• A. Array-beam (or fan-beam) and multi element detector
• B. Pencil-beam and multiple detectors
• C. Pencil-beam and a single detector
• D. Fan-beam and a single detector

Answer: (C)

DXA’s original scanners used a pencil-beam geometry with a single detector. The pencil beam is a very narrow X‑ray beam that passes through the body and is measured by one detector as the beam is scanned across the area of interest. This simple setup minimizes scatter paths and keeps the image geometry straightforward, making the bone mineral density measurement reliable with uncomplicated data corrections. Later designs introduced fan-beam or array (multi‑element) detectors to speed up scanning and improve coverage, but these are improvements beyond the original configuration.