Radiation Dose Alert: CT Overexposure As a Result of Patient Off-Centering.

A high cumulative radiation dose (3394 mGy.cm, 51 mSv) delivered by two acquisitions on the abdomen and pelvis and corresponding to more than 10 times the local median dose for this examination was retrospectively detected thanks to the Dose Archiving and Communicating System (DACS). Retrospective analysis of the examination showed that the cause of this high dose was an off-centering of the patient-the table being in a too high position-disabling a correct diagnosis of an umbilical herniation that was visible on a repeated acquisition. Interestingly, the CTDIvol of the second acquisition was 40% lower than that of the first acquisition, a well-known effect of off-centering on automatic exposure control systems.