A computer-assisted procedure for estimating patient exposure and fetal dose in radiographic examinations

A computer program for calculating patient entrance exposure and fetal dose for 11 common radiographic examinations was developed. The output intensity measured at 70 kVp and a 30-inch (76-cm) source-to-skin distance was entered into the program. The change in output intensity with changing kVp was examined for 17 single-phase and 12 three-phase x-ray units. The relationships obtained from a least squares regression analysis of the data, along with the technique factors for each examination, were used to calculate patient exposure. Fetal dose was estimated using published fetal dose in mrad (10(-5) Gy) per 1,000 mR (258 microC/kg) entrance exposure values. The computations are fully automated and individualized to each radiographic unit. The information provides a ready reference in large institutions and is particularly useful at smaller facilities that do not have available physicians who can make the calculations immediately.