Variations in x-ray exposures to patients.

X-ray exposures to patients were measured in 30 rooms in Toronto hospitals. For a given procedure, the total exposure for a satisfactory examination differed from one room to another by as much as a factor of 30, skin exposures reaching 90 R and more for barium enemas and barium meals. The factors primarily responsible for these large differences in exposure were fluoroscopic exposure rate (0.65-12 R/min) and time 1.5-12 min), kVp and filtration (8:1), choice of screen-film combination (6:1) and attenuation of table tops and phototimers (4:1). The increase by a factor of 5 in exposure of pelvic organs, when using beams directed AP instead of PA, requires that remote-controlled GI machines be used cautiously, particularly on women of childbearing age. It is also important that these machines have tables with low attenuation. The use in some rooms of minimal fluoroscopic exposure rates and 70 mm fluorography at total exposures of less than 5 R shows that radiographic examinations can be made virtually "safe" with modern, properly adjusted equipment.