Simulation analysis for organ doses of mouse and human upon neutron exposure by use of voxel phantoms

Satoh, Daiki   ; Sato, Kaoru   ; Takahashi, Fumiaki  ; Endo, Akira   ; Miyahara, Nobuyuki*; Tsuji, Atsushi*; Omachi, Yasushi*

The present study intends to calculate the organ doses and analyze the characteristics of the radiation field inside the bodies of a mouse and human. The voxel phantom of mouse had already been developed for an 8-week-old CH/HeNs mouse in the previous work. We upgraded this phantom to improve the resolution (voxel size: 0.10.10.1 mm), and add the nine solid organs. The JM phantom is the voxel phantom of a Japanese adult male developed for the analysis of internal exposure from photons and electrons. We have converted the JM phantom to use in the dose calculation on external neutron exposure, and verified it through the calculation of the absorbed dose per unit neutron fluence at each organ for monoenergetic neutrons. The calculation results showed a good agreement with the reference values reported by ICRP. From the comparison between the organ doses of the mouse and human, it was found that the relativistic dose contribution of electron in the human body is greater than that in the mouse body. This is because the neutrons are moderated inside a large receptor such as the human body, and causes the thermal neutron capture reaction that generates ray and consequently electron.