Which generation of scanners typically exhibits ring artifacts?

The presence of ring artifacts is most commonly associated with third-generation CT scanners. These scanners utilize a rotating fan beam and a set of detectors that continuously move around the patient, and any inconsistencies or errors in the detector response can result in these artifacts. Ring artifacts arise due to differences in the sensitivity of the detectors or calibration errors caused by malfunctioning detectors.

In contrast, first-generation scanners are primarily focused on a linear array of detectors and perform only a limited rotation, which does not contribute to ring artifacts. Second-generation scanners improved upon this by introducing a wider fan beam and multiple detector rows, but they still don't create the same type of ring artifacts prevalent in third-generation systems. Fourth-generation scanners utilize a stationary ring of detectors surrounding the patient with a rotating x-ray tube, which minimizes the occurrence of ring artifacts by avoiding issues related to detector inconsistencies.

Thus, the explanation for the third generation’s propensity for ring artifacts lies in their design, making them more susceptible to issues with the detector systems compared to other generations.