Ring artifact

Ring artifacts are a CT phenomenon that occurs due to the miscalibration or failure of one or more detector elements in a CT scanner. Less often, it can be caused by insufficient radiation dose or contrast material contamination of the detector cover ². They occur close to the isocenter of the scan and are usually visible on multiple slices at the same location. They are a common problem in cranial CT.

Recalibration of the scanner will usually rectify the artifact. Occasionally detector elements need replacing, which can be costly. The referring clinician should be notified that the concerning ring shadows are artifactual.