Photon fluence-to-effective dose conversion coefficients calculated from a Saudi population-based phantom

Abstract

In this work we will present a new set of photon fluence-to-effective dose conversion coefficients using the Saudi population-based voxel phantom developed recently by our group. The phantom corresponds to an average Saudi male of 173cm tall weighing 77kg. There are over 125 million voxels in the phantom each of which is 1.37×1.37×1.00mm3. Of the 27 organs and tissues of radiological interest specified in the recommendations of ICRP Publication 103, all but the oral mucosa, extrathoracic tissue and the lymph nodes were identified in the current version of the phantom. The bone surface (endosteum) is too thin to be identifiable; it is about 10μm thick. The dose to the endosteum was therefore approximated by the dose to the bones. Irradiation geometries included anterior–posterior (AP), left (LLAT) and rotational (ROT). The simulations were carried out with the MCNPX code version 2.5.0. The fluence in free air and the energy depositions in each organ were calculated for monoenergetic photon beams from 10keV to 10MeV to obtain the conversion coefficients. The radiation and tissue weighting factors were taken from ICRP Publication 60 and 103. The results from this study will also be compared with the conversion coefficients in ICRP Publication 116.