Simulations of photon specific absorbed fractions in a mouse voxel phantom

Mohammadi, A.; Kinase, Sakae   

For preclinical assessments of several radiopharmaceuticals, photon specific absorbed fractions (SAFs) were evaluated in a mouse sophisticated model and a new set of photon SAFs were tabulated for photon energies from 10 keV to 4 MeV. In the present study, Digimouse voxel phantom was used as a sophisticated model and converted to an input file for EGS4 code, in conjunction with an EGS4 user code, UCSAF. Consequently, it was confirmed that the photon SAFs for self-irradiation depended on the photon energy and the mass of the target/source organ. The photon SAFs for cross-irradiation also was an energy dependent function but did not change by the mass of target and it might be affected by source size, target size, their shape and distance between the source and target. Organ dose evaluation should be performed in the phantom with the Monte Carlo method since the minor changes in the geometry had a large effect on photon-only S values and organ dose.