Method of Calculating the Backscatter Factor for Diagnostic X-rays Using the Differential Backscatter Factor

Abstract

The backscatter factor is necessary for evaluating the skin dose of patients irradiated by diagnostic x-rays. In this study, backscatter factors for x-rays of various irradiation conditions were calculated by means of the Monte Carlo method. The backscatter factors calculated for X-rays, which had the same HVL but different tube potentials, did not always coincide with each other. From this result, it was evidenced that the backscatter factor obtained from the BSF data table with a parameter of HVL were uncertain. To avoid such uncertainties, a new convolution method to obtain backscatter factors using an x-ray spectrum and differential backscatter factors was developed. This new calculation method could be installed in a computer program with an approximating equation of x-ray spectra, and accurate backscatter factors for any x-ray and/or any irradiation field could be obtained easily.