Which tube-detector geometry is used by third-generation CT scanners, where the X-ray tube and detectors rotate around the patient to collect views from many angular positions?

• A. Stationary-rotate geometry
• B. Rotate-rotate technology
• C. Electron gun-detector array
• D. All of the above

Answer: (B)

In third-generation CT, the X-ray tube and the curved detector array are mounted on a gantry and rotate around the patient together. This rotate-rotate setup means many angular views are collected during a single gantry rotation, enabling fast and consistent image acquisition for cross-sectional slices. The idea is that both source and detector move in concert around the patient, which is why this design is distinctive of third-generation scanners.

Other descriptions don’t fit that geometry. A stationary detector with a rotating tube describes a different, older arrangement, not the third-generation approach. An electron gun-detector array isn’t a description of the rotation pattern. And saying all of the above would be incorrect because only the rotate-rotate configuration matches how third-generation CT actually collects data.