Room: Davidson Ballroom A
Purpose: To investigate the dosimetric impact of new mesh-type reference computational phantoms (MRCPs), recently developed in the International Commission on Radiological Protection (ICRP) to address the limitations of the current voxel-type reference computational phantoms (VRCPs) of ICRP Publication 110 due to their limited voxel resolutions.
Methods: The MRCPs were implemented in Geant4 for Monte Carlo dose calculations. Organ and effective dose coefficients (DCs) were calculated for photons, neutrons, electrons, and helium ions in the external irradiation geometries considered in ICRP Publication 116. Specific absorbed fractions (SAFs) for selected source regions (cortical bone, thyroid, lungs, and liver) were calculated for photons and electrons. The calculated values were then compared with the current reference values of ICRP Publications 116 and 133 produced with the VRCPs and supplemental stylized phantoms.
Results: The DCs of the MRCPs were similar to those of the ICRP 116 for photons and neutrons, but for electrons and helium ions, significant differences were found for some organs (e.g., active marrow and skin) and even effective doses, the ultimate protection quantity. For electrons, for example, the effective doses of the MRCPs were greater by up to ~10 times, which is mostly influenced by the skin dose differences due to the 50-Âµm-thick skin target layer in the MRCPs. Likewise, the SAFs of the MRCPs were similar to the values of ICRP 133 for photons, whereas for electrons, significant differences were found, mostly due to anatomical improvements of the MRCPs.
Conclusion: The MRCPs provide similar DCs and SAFs to the current reference values for uncharged particles, which demonstrates that the original anatomy of the VRCPs is faithfully preserved in the MRCPs. On the other hand, for charged particles, the MRCPs provide more reliable values, which is due to the improvements of the MRCPs over the VRCPs.
Funding Support, Disclosures, and Conflict of Interest: This work was funded by the intramural program of the National Institutes of Health, National Cancer Institute, Division of Cancer Epidemiology and Genetics. The contents are solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.