ICRP_87_CT_s幻灯片.pptVIP

Managing Patient Dose in Computed Tomography (CT) International Commission on Radiological Protection Information abstracted from ICRP Publication 87 Available at Task Group: M.M. Rehani, G. Bongartz, S.J. Golding, L.Gordon, W. Kalender, T. Murakami, P. Shrimpton, R. Albrecht, K. Wei Use and disclaimer This is a PowerPoint file It may be downloaded free of charge It is intended for teaching and not for commercial purposes This slide set is intended to be used with the complete text provided in ICRP Publication 87 Contents Situation analysis Why increased frequency? Why increased dose? Is the dose really high? How high? What can be done to manage patient dose? What can operator do? Action for manufacturer Action for physician radiologist Situation analysis CT continues to evolve rapidly despite many advances in other imaging modalities It is one of the most important radiological examinations worldwide The frequency of CT examinations is increasing rapidly from 2% of all radiological examinations in some countries a decade ago to 10-15 % now Patient doses in CT have not decreased in contrast to radiography where nearly 30% reduction has been documented in last decade Why increased frequency? 20 years ago, a standard CT of the thorax took several minutes while today similar information can be accumulated in a single breath hold making it attractive, patient user friendly Advances in CT technology have made possible CT fluoroscopy and interventional procedures, in some cases replacing ultrasound guided interventions Recently CT screening is picking up Why increased dose… Unlike radiography where over-exposure results in blackening of film, better image quality is obtained with higher exposures in CT There is a tendency to increase the volume covered in a particular examination Modern helical CT involves volume scanning with no inter-slice gap and with possibility of overlapping scans Repeat CT examinations Why increased dose (cont’d) Same exposure factors u