Figure 4.

Illustration of four generations of CT scanner geometries. First and second generations were often referred to as translate/rotate geometries because the tube first translated across the patient and then the gantry rotated about the patient. Third generation was often referred to as rotate/rotate geometry because both the tube and the detector array rotated about the patient. Fourth generation was often referred to as rotate/stationary geometry, because the tube rotated about the patient while the ring of detectors remained stationary.