Electron absorbed fractions and s values in a mouse voxel phantom

Abstract

Electron absorbed fractions (AFs) and S values were evaluated in a voxel mouse phantom for preclinical evaluations of radiopharmaceuticals. 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 volume, density and geometry of the source/target organs. The electron AFs for organ self-absorption, i.e., target is source, 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 source and the geometries of source and target. In addition, S values in the major organs of the mouse phantom were tabulated for 131I, 153Sm, 188Re, 90Y and 111In using the results of the photon and electron AFs. Comparison of S values in abdominal organs for only β-spectrum of the nuclides demonstrated that β-only S values increased with increasing mean energy of β-spectrum of the nuclides. The results of this study will be useful in determining the dose to the organs for mice similar in size to the mouse in this study.