Analysis of effects of posture on organ doses by internal photon emitters using voxel phantoms

Sato, Kaoru   ; Endo, Akira   

In order to clarify the effects of posture on organ doses due to internal exposures, SAFs for photons from 0.01 to 4 MeV were calculated using JM2 (upright) and JM (supine) phantoms whose designs were based on CT images of two postures obtained from the same person. Differences in the SAFs of JM2 and JM are within a factor of 2 in most cases, although significant differences in SAFs exist in several cases for low energy photons. Organ doses due to photons from intake of unit activity of 8 radionuclides with different biokinetics and decay characteristics were calculated from the SAFs of JM2 and JM. It was found the organ doses in the testes, bone marrow, lower large intestine wall, lungs and stomach wall, which are important for calculating effective dose, in the two postures roughly agree, the maximum difference being 14%. These results indicate that the impact of posture on the organ doses and effective doses from internal photon emitters is limited.