Multi-detector row CT artifacts that mimic disease

PURPOSE: To determine retrospectively the frequency of two artifact patterns that mimic pathologic lesions on computed tomographic (CT) head images acquired in the axial scanning mode with two different multi-detector row CT systems at the same institution. MATERIALS AND METHODS: The institutional review board approved this Health Insurance Portability and Accountability Act-compliant study and waived informed consent. The study involved two groups of consecutive patients, a group of 22 (nine men, 13 women; mean age, 56 years; age range, 27-85 years) examined with one multi-detector row CT system with four detector rows, and another group of 13 (seven men, six women; mean age, 69 years; age range, 53-81 years) examined with a different four-detector row CT system. Examinations in each group took place in a 4-week period. CT images were retrospectively evaluated by a neuroradiologist and a physicist for presence, appearance, location (within the image set and on individual images), and size of artifacts. Elimination of artifacts was verified by scanning a water phantom after scanner service and repair. RESULTS: A pseudolesion, or artifact, was identified in scans of four of 22 patients examined with the first scanner and eight of 1 3 patients examined with the second scanner. The artifact on images obtained on the first scanner, an approximately 2-cm-diameter faintly hyperattenuating and nonenhancing area with hypoattenuating collar, was found at gantry isocenter on every fourth image. A different pattern was found on images obtained on the second scanner: a 1.1-cm-diameter circular area of hypoattenuation with a faintly attenuating rim, that mimicked a cyst. This artifact was observed also at the CT scanner gantry isocenter on every fourth image. Artifacts disappeared after recalibration (first scanner) or collimator cleaning (second scanner). CONCLUSION: CT scanning in the axial mode can produce a regularly repeating artifact when data from one detector row of a multi-detector row CT scanner are compromised. Because of the risk of misinterpreting such patterns, routine assessment of each detector element is recommended for multi-detector row CT scanners that are routinely used in the axial scanning mode.