Application of the New ICRP Reference Phantoms to Internal Dosimetry: Calculation of Specific Absorbed Fractions of Energy for Photons and Electrons

Abstract

AbstractIntroduction: Connecting the emission of radiation from a contaminated body region with the dose received by a radio-sensitive tissue, the specific absorbed fraction (SAF) of energy is an essential element of internal dose assessment. Here is reported a set of specific absorbed fractions calculated using the male and female reference computational phantoms recently published by the International Commission on Radiological Protection (ICRP). This work was performed simultaneously at the Helmholtz Zentrum München (HMGU, Germany) and IRSN (France) for quality assurance purpose. The results were then compared to the SAF values for mathematic phantoms.At IRSN, the Monte Carlo transport code MCNPX version 2.6f was used to simulate monoenergetic photons and electrons with energies ranging from 15 keV to 10 MeV. The OEDIPE software, developed by IRSN, was used to create the MCNPX input file describing the two voxel phantoms. The particles were emitted from three source organs: lungs, thyroid and liver. SAFs were calculated for several target regions in the body (lungs, colon wall, breast, stomach wall) and compared with the results obtained at HMGU using the EGSnrc Monte Carlo code.The results show general agreement for photons and high-energy electrons with discrepancies less than 6%. Nevertheless, significant differences were found for electrons of lower energy due to statistical uncertainties larger than 10%. The comparison of the SAF values between the new ICRP voxel phantoms and the mathematic ones shows significant differences.The present SAFs calculation for the new ICRP reference phantoms is validated by the intercomparison of results obtained by HGMU and IRSN and gives an insight into the evolution from the former SAFs derived from stylized phantoms.KeywordsSAFICRP reference computational phantomsOEDIPEMonte Carlointernal dosimetry