Intercomparison of patient CTDI surveys in three countries.

The results of large-scale computed tomography (CT) patient dose surveys from the USA, UK and Germany undertaken during the period 1999-2001 were reviewed. The mean values for volume-weighted CT dose index (CTDI(vol)) and dose length product (DLP) were extracted. For head CT examinations, the reported values for the three surveys were similar with a mean CTDI(vol) of 59±6 mGy and a mean DLP of 760±90 mGy cm. For the body, the values for CTDI(vol) in the USA (21±5 mGy) were nearly double those in the European countries (12±2 mGy). Average head CTDI(vol) values are comparable with the diagnostic reference levels (DRLs) recommended by the European Commission  and the UK Health Protection Agency, but lower than the value of 75 mGy, which is currently used in the USA. DRLs for abdominal imaging are nearly a factor of 2 lower in the UK (14 mGy) than in other parts of the European Community and the USA (25 mGy).