P C Shrimpton, M C Hillier, M A Lewis and M Dunn
Publication date: March 2005
A new UK computed tomography (CT) survey has provided a useful snapshot of patient doses for 2003. Scan details for nearly 850 standard protocols and 2,000 individual patients relating to 12 common CT examinations on adults and children were collected by questionnaires voluntarily submitted by a widely-distributed sample of 126 scanners. This represented more than a quarter of all UK scanners and included 37% with multislice capability. Scanner-specific normalised CT dose data published by ImPACT were used to estimate standard dose indices CTDI w and CTDI vol for each sequence and, with knowledge of scan lengths, DLP for each examination. Effective doses were subsequently estimated from the calculated values of DLP. Wide variations in practice were still apparent between CT centres, although the overall levels of exposure were in general lower by 10-40% than previous UK survey data for 1991. There was, however, an apparent trend for slightly increased doses from multislice (4 ) (MSCT) relative to single slice (SSCT) scanners for adult patients. Values of CTDI vol were broadly similar to recent survey data for MSCT from Europe for 2001. Effective doses to very young patients (aged 0-1 years) were typically higher than corresponding values for adults. Doses to individual patients were on average similar to those for the standard protocols established for each scanner, although significant variations were also apparent.
The report includes summaries of the dose distributions observed and, on the basis of third quartile values, presents national reference doses for examinations on adults (separately for SSCT and MSCT) and children. The PREDICT (Patient Radiation Exposure and Dose in CT) database established by the survey represents a sustainable national resource for monitoring continuing developments in CT through the ongoing collation of further survey data.
Last reviewed: 17 September 2009