Electron absorbed fractions and S values in a mouse voxel phantom

Mohammadi, A.; Kinase, Sakae   

For preclinical assessments of several radiopharmaceuticals, electron absorbed fractions (AFs) and S values were evaluated in a mouse voxel phantom. The sources were considered to be mono-energetic in the electron energy range 10 keV to 4 MeV. The radiation transport was simulated using the Monte Carlo method. Consequently, it was confirmed that the electron AFs were dependent on the masses of the source/target organs. The electron AFs for organ self-absorption (source = target) decreased with increasing electron energy which proved that it is certainly not always appropriate in small organs to assume a 100% localized electron energy absorption. The electron AFs for organ cross-fire depended on electron energy emitted by the source and the geometries of source and target. In addition, S values in the major organs of the mouse phantom were tabulated for I, Sm, Re, Y and In using the results of the photon and electron AFs. Comparison of S values in abdominal organs for only -spectrum of the nuclides demonstrated that -only S values increased with increasing mean energy of -spectrum of the nuclide. The results of this study will be useful in determining the dose to the organs for mice similar in size to Digimouse.