Which statement best describes scan factors in CBCT?

• A. Hundreds of basis images (frames) taken around the patient
• B. X-ray source and reciprocating detector rotate around the patient
• C. Basis images look like cephalometric images at different angles
• D. Scan factors do not affect acquisition geometry

Answer: (B)

Scan factors describe how the imaging system collects data around the patient, specifically the rotation of the X-ray source and the detector around the patient. This rotating geometry, often spanning a full 360 degrees or a partial arc, creates the cone-beam projections used to reconstruct a 3D volume. The way the source and detector move around the patient directly shapes acquisition geometry, including how many projections are taken, the angular range, voxel size, field of view, and dose.

Why this is the best description: the key idea is the rotating setup that generates the 2D projection images from multiple angles to build the 3D dataset. The other statements aren’t accurate descriptions of scan factors: while many frames are acquired, the essential concept is the rotation geometry itself; basis images resembling cephalometric views is not a defining feature of CBCT projections; and scan factors do influence, not ignore, the acquisition geometry.