Development of zebrafish (Danio rerio) mesh-type model at multi-life stages and Monte Carlo simulations of dosimetric parameters

As socioeconomic development progresses, nuclear energy and technology advance rapidly. Concurrently, nuclear accidents may result in the release of additional radioactive isotopes into the environment. Groundwater and oceans are key pathways for radioactive nuclides in the environmental cycle, with aquatic organisms being particularly vulnerable to radiation exposure. Aquatic model organisms are essential for studying radiation effects on non-human species in aquatic environments and for extrapolating dose-response relationships to humans. However, current models for calculating radiation doses in the aquatic model organism zebrafish remain underdeveloped. To better elucidate the mechanisms of radiation damage effects, integrating Micro-CT and 3D modeling techniques, a series of zebrafish mesh-type models (including adults and larvae, named zebrafish-mesh family: ZF-mesh family) with multiple internal organs are established in this study. The Monte Carlo software PHITS is used to simulate and calculate the Absorbed Fractions (AFs) and S-values for single-energy electrons ranging from 0.001 to 10 MeV, single-energy photons from 0.001 to 5 MeV, and eight radioactive nuclides commonly found in nuclear power plant liquid effluents: ³H, ¹⁴C, ⁹⁰Sr, ¹⁰⁶Ru, ¹³⁴Cs, ¹³⁷Cs, ⁶⁰Co, ¹³¹I, across various source-target organ configurations. The results indicate that the mesh-type models of zebrafish at multiple developmental stages can be used for radiation dosimetry calculations. Analysis of the dosimetry parameter database, established through Monte Carlo calculations with this series of mesh-type models, shows that the maximum difference in self-AFs between the geometric and curved models reaches 52.8%. Comparisons between models at different developmental stages show that the impact of radioactive nuclides on internal organs depends on both the decay properties of the nuclides and the organ volumes. For adult fish, the dose contribution from ⁹⁰Sr is most significant, reaching up to 1.81 $\times {10}^{-5}m\text{Gy}{·\text{MBq}}^{-1}·s^{-1}$ in the heart of male fish. In larvae fish, ¹⁴C has the most notable impact, with a dose rate of 4.38 $\times {10}^{-3}m\text{Gy}{·\text{MBq}}^{-1}·s^{-1}$ in the heart at 48 h post-fertilization (hpf). Comparisons of yolk mass changes at various developmental stages in larvae fish reveal that organ location is a key factor influencing self-AFs. This influence is often more significant than the variations caused by changes in organ volume. Due to the small size of zebrafish organs, the increase in energy deposition caused by secondary electrons is not evident in adult fish. In the smallest larvae hearts, no increase in energy deposition is observed. In summary, detailed surface modeling of model organisms across multiple developmental stages and the establishment of a comprehensive dosimetric parameter database are crucial. This approach significantly improves the reliability of radiation impact assessments for non-human species.