Gastrointestinal fluoroscopy: patient dose and methods for its reduction

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Abstract
A method which could be used to identify factors which contribute to the radiation exposure to patients from fluoroscopy during contrast examinations of the gastrointestinal tract. Measurements of exposure made at the level of the X-ray tube collimator were extrapolated to obtain entrance exposure at the center of the field and used as an index of the integral dose to the patient. Such data have heretofore been unavailable. The population studied included 65 patients ranging in age from 1 mo.-21 yr. In an initial study, median entrance exposure at the field center for Ba swallow examinations ranged from 0.98-1.7 mC/kg (3.8-6.6 R); Ba meal: 1.9-5.7 mC/kg (7.4-22 R); Ba meal with small bowel: 1.4-7.7 mC/kg (5.3-30 R); Ba enema: 0.93-7.7 mC/kg (3.6-41). Gonadal dose, measured in males, ranged from undetectable to 0.71 mGy [milliGrays] (71 mrad). The presence of contrast medium in the fluoroscopic field increased the exposure from a single 100 mm spot film, taken with automatic exposure control, by a factor of up to 16 and fluoroscopic exposure rate, using automatic brightness control, by a factor of 2 or more. Modifications are recommended in the operation and design of fluoroscopic equipment, especially when fitted with brightness and exposure controls, for the reduction of patient exposure. Implementation of 2 modificaitons, a high/low dose switch and a variable aperture iris diaphragm, reduced patient exposure from 1.4 to 3.4 times.