Evaluation of absorbed doses in voxel-based and simplified models for small animals

小動物におけるボクセルモデルと単純モデルでの吸収線量評価

Mohammadi, A.; 木名瀬 栄   ; 斎藤 公明  

Mohammadi, A.; Kinase, Sakae; Saito, Kimiaki

Internal dosimetry in non-human biota is desirable from the viewpoint of radiation protection of the environment. The ICRP proposed the Reference Animals and Plants using simplified models, such as ellipsoids and spheres, and calculated absorbed fractions (AFs) for whole bodies. In this study, photon and electron AFs in whole bodies of voxel-based rat and frog models have been calculated and compared with reported AFs in the ICRP Reference models. It was found that the voxel-based and the reference frog (or rat) models can be consistent for the whole-body AFs within discrepancy of 25%, as source uniformly distributed in the whole body. The electron SAFs (specific absorbed fractions) in the whole body could predict organs SAFs with discrepancies up to 40% for all organs as source distributed uniformly per mass however the differences were up to 260% for the lungs as source distributed uniformly per volume. It can be stated that whole-body SAFs or values in simplified models without internal organs are not sufficient for accurate internal dosimetry because they do not reflect SAFs or values of all individual organs as source was not distributed uniformly in whole body. Thus, voxel-based models would be good candidates for dosimetry in non-human biota in case that further accuracy in environmental dosimetry would be desired.