Which artifact appears as concentric circles on a CT image?

Ring artifacts appear as concentric circles on a CT image due to imperfections in the detector's response or alignment. This can occur when there is a malfunction in one or more of the detectors in the CT system, leading to a systematic error in the data collection. As the machine rotates around the patient and captures images, these errors manifest as distinct patterns—specifically, the characteristic concentric circles associated with the affected area.

Understanding ring artifacts is critical for interpreting CT images accurately, as their presence can obscure or mimic pathology, potentially leading to misdiagnosis. They are typically resolved through calibration of the imaging system or software corrections in the reconstruction algorithms. Recognizing the distinct look of ring artifacts helps radiologists and technologists identify and address issues within the imaging process.