Dose coefficients for the ICRP pediatric mesh-type reference computational phantoms under idealized external photon exposure geometries

Abstract

The International Commission on Radiological Protection (ICRP) recently released the pediatric mesh-type reference computational phantoms (MRCPs) through ICRP Publication 156 to overcome the limitations of the pediatric voxel-type reference computational phantoms (VRCPs) of ICRP Publication 143. In the present study, these pediatric MRCPs were implemented into the Geant4 Monte Carlo code to produce a comprehensive dataset of dose coefficients for idealized external photon exposure geometries. This dataset includes 29 individual organ/tissue dose coefficients and effective dose coefficients, covering six irradiation geometries (i.e., AP, PA, LLAT, RLAT, ROT, and ISO) and 55 monoenergetic photon energies ranging from 10 keV to 10 GeV. The dataset comparison with the adult MRCPs of ICRP Publication 145 revealed substantial differences in effective dose coefficients throughout most energy ranges, primarily due to the age-related variations in organ/tissue depths, the differences reaching up to a factor ∼9. In addition, the comparisons with the pediatric VRCPs identified notable differences in effective dose coefficients, reaching up to a factor ∼4, for photon energies below 50 keV, due to the differences in phantom geometries and updates in simulation setups. For photon energies above 50 keV, deviations in effective dose coefficients between the pediatric MRCPs and VRCPs remained within 10 %.