Assessment of neutron fluence to organ dose conversion coefficients in the ORNL analyticaladult phantom

Abstract

Neutron fluence to absorbed dose conversion coefficients have been evaluated for the analyticalORNL modified adult phantom in 21 body organs using MCNP4C Monte Carlo code. Thecalculation used 20 monodirectional monoenergetic neutron beams in the energy range10−9–20 MeV, under four irradiation conditions: anterior–posterior (AP), posterior–anterior(PA), left-lateral (LLAT) and right-lateral (RLAT). Then the conversion coefficients arecompared with the data reported in ICRP publication 74 for mathematical MIRD typephantoms and by Bozkurt et al for the VIPMAN voxel model. Although the ORNL resultsshow fewer differences with the ICRP results than the Bozkurt et al data, one candeduce neither complete agreement nor disparity between this study and other datasets. This comparison shows that in some cases any differences in applied MonteCarlo codes or simulated body models could significantly change the organ doseconversion factors. This sensitivity should be considered for radiological protectionprogrammes. For certain organs, the results of two models with major differences canbe in a satisfactory agreement because of the similarity in those organ models.