The ratio between effective doses due to external exposure to electrons for tomographic and mathematical models

The development of new, sophisticated Monte Carlo codes, and of tomographic or voxel based human phantoms motivated the International Commission on Radiological Protection (ICRP) to call for a revision of traditional exposure models, which have been used in the past to calculate organ and tissue as well as effective dose coefficients for stylized MIRD5- type phantoms. This paper reports about calculations made with the recently developed tomographic MAX (Male Adult voXel) and FAX (Female Adult voXel) phantoms, as well as with the gender-specific MIRD5-type phantoms ADAM and EVA, coupled to the EGS4 and to the MCNP4C Monte Carlo code, for external whole-body irradiation with electrons. Effective doses for the tomographic and for the stylized exposure models will be compared separately as function of the replacement of the Monte Carlo code, of human tissue compositions, and of the stylized by the tomographic anatomy. The results indicate that for external exposures to electrons the introduction of voxel-based exposure models causes changes of the effective dose between +40% and - 60% depending on the energies and geometries considered compared to corresponding data of the MIRD5-type phantoms. (author)