THE RELATIONSHIP OF EFFECTIVE DOSE TO PERSONNEL AND MONITOR READING FOR SIMULATED FLUOROSCOPIC IRRADIATION CONDITIONS

The exposure of staff during fluoroscopic procedures was simulated for overcouch x-ray tube/undercouch image intensifier and undercouch x-ray tube/overcouch image intensifier geometries. A Rando phantom with film badge dosimeters attached to the skin surface at seven commonly used monitoring sites and loaded with lithium fluoride thermoluminescent dosimeters was irradiated for an extended period in the vicinity of a patient couch. Scattered radiation generated from the irradiation of an anthropomorphic phantom using primary radiation in the range of 70 kVp-110 kVp was used. The radiation dose to organs which were shielded by a lead apron was estimated from the unattenuated organ dose readings by applying an experimentally determined scattered radiation transmission factor. The ratio of effective dose to film badge reading was obtained for a range of irradiation conditions and lead apron thicknesses. For most irradiation conditions studied, a dosimeter worn above the lead apron will significantly overestimate effective dose by a factor of between 2 and 60, depending on the irradiation conditions. A dosimeter worn under the apron at either waist or chest level, will generally yield a closer (although usually an underestimate of) effective dose, typically within a factor of 7 for the most common lead apron thicknesses and irradiation conditions. No single dosimeter can accurately monitor effective dose for all irradiation conditions in fluoroscopy.