EFFECT OF ELECTRON-ENERGY DISTRIBUTION ON BREMSSTRAHLUNG SPECTRUM

We calculated bremsstrahlung spectra using the Monte Carlo method taki ng into consideration electron energy distribution and multiple scatte ring in a target, which were neglected in the semiempirical models of Birch and Marshall (BM) [Phys. Med. Biol. 24 (1979) 505) and Tucker et al. (TBC) [Med. Phys. 18 (1991) 211]. We compared our results with th e spectra measured by Fewell et al. and those calculated by BM- and TB C-models, and discussed the effects of the electron energy distributio n on the bremsstrahlung spectra. Our results agreed with the spectra m easured by Fewell et al., for a variety of radiographic conditions use d in medical diagnosis. Spectra calculated using the BM model agreed r oughly with measured data, but tended to deviate as target angle decre ased. Spectra calculated using the TBC model agreed with measured data for an X-ray tube with the target angle of 10-degrees, but disagreed for other X-ray tubes. As a result, we showed that electron energy dis tribution had significant effects on the calculation of bremsstrahlung spectra for medical use.