Which imaging modality uses a rotating X-ray source to acquire multiple slices?

• A. Ultrasound
• B. MRI
• C. CT
• D. X-ray fluoroscopy

Answer: (C)

Computed tomography uses a rotating X-ray source to acquire multiple slices. In a CT scan, the X-ray tube and detectors rotate around the patient, capturing X-ray projections from many angles during a single rotation (and often as the patient moves through the gantry). These numerous projections are then processed by computer algorithms to reconstruct thin, cross-sectional images—slices—of the body. This rotation and reconstruction is what allows CT to turn 2D projections into detailed 3D views and multiplanar reconstructions.

Ultrasound uses sound waves and produces images from echoes, not X-ray projections. MRI relies on magnetic fields and radiofrequency signals. X-ray fluoroscopy provides real-time 2D images rather than reconstructed slices from multiple angles.