Enhanced accuracy in radiation dose estimation for astronauts using mesh-type reference computational phantoms

With the increasing ambition of deep space missions, the accurate estimation of radiation doses to astronauts has become a critical concern. Traditional radiation dose estimation methods may often overestimate the biological impact due to their limitations in accurately modelling thin-layered organs. This study employs advanced Mesh-type Reference Computational Phantoms (MRCPs) along with the Geant4 simulation toolkit to calculate dose conversion coefficients and quality factors for various radiations, including protons, alpha particles, carbon, magnesium, and iron ions using both ICRP and NASA radiation quality factor models. The results demonstrate improvements in dose estimations, particularly for organs with thin structures, such as the skin. For example, at energies below 10 MeV/u, the absorbed dose to the skin calculated using the MRCP phantom was up to 30 % lower than that obtained from the Voxel-type Reference Computational Phantoms (VRCPs), due to the MRCP's ability to distinguish between sensitive and insensitive skin layers. Similarly, the quality factors for heavy ions (e.g., iron and magnesium) calculated using the MRCP were 10-20 % lower at intermediate energies (10-100 MeV/u) compared to VRCP-based values, reflecting more accurate LET-dependent biological effectiveness calculations. Additionally, the body-mean quality factor for protons at low energies (<100 MeV/u) showed a 15 % reduction when using MRCPs, correcting previous estimations from VRCP-based methods. The improved accuracy in dose and quality factor calculations enables better-informed decisions regarding mission planning, shielding requirements, and radiation protection strategies.