What is computed tomography?

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

Answer: (D)

The thing this item is testing is understanding what computed tomography is and how it works. A computed tomography scan uses X-ray beams that rotate around the body and, with computer processing, reconstructs many thin cross‑sectional images (slices). These slices can be viewed individually or stacked to form 3D representations, giving detailed information about bone, soft tissue, and blood vessels. This method provides much more detail in a single examination than a plain X‑ray, because it turns multiple 2D projections into 3D-like cross sections. It uses ionizing radiation, unlike ultrasound, and it offers different tissue contrast and speed compared with MRI, which uses magnetic fields and radio waves and generally doesn’t involve radiation. The CT scan is therefore the imaging modality described.