CT STANDARD PROTOCOLS ARE OF LIMITED VALUE IN ASSESSING ACTUAL PATIENT DOSE

In the last 10 years the use of computed tomography in radiodiagnosis has increased markedly and CT scanners are now present in most distric t general hospitals. Modern CT scanners are versatile in their operati on and offer the operator a wide choice in exposure parameters which a ffect the doses received by the patients. As CT is a major contributor to medical radiation doses, the National Radiological Protection Boar d (NRPB) recommends that an estimate of typical patient dose should be made for commonly used local scanning protocols, A survey has been un dertaken in the Anglia and Oxford region covering 12 CT scanners. Comm on procedures were chosen, concentrating on those mast frequently carr ied out and giving higher effective doses. These included routine head s, routine chests, high resolution chests and abdomen/pelvis examinati ons, Questionnaires were sent out to each CT centre to collect data on standard protocols and to record the procedure used for five actual p atients for each examination type thus enabling a comparison of the tw o methodologies. This study has shown that many examinations are tailo red to the individual patient size and clinical indications, particula rly in the chest/abdomen/pelvis. Thus, assessing doses based on collec ting standard protocols may not give a true indication of the effectiv e doses being received by particular patients.