Interspecies Scaling of Self-Organ Doses from a Voxel Mouse to Voxel Humans

Knowledge of interspecies scaling of organ doses from experimental animals such as mice to humans is important in the preclinical evaluation of new radiopharmaceuticals. Interspecies scaling factors should be reliably determined since the dose-response relationships in mice would be translated to those in humans. To obtain reliable interspecies scaling factors of organ doses from mice to humans, absorbed fractions (AFs) are needed for sophisticated models on both mice and humans. In the present study, self-AFs for photons and electrons in the spleen, kidneys, and liver of both a mouse and humans were evaluated using Monte Carlo simulations. For the mouse and human models, voxel phantoms based on computed tomography were used. The sources were assumed to be monoenergetic in the energy range 10 keV to 4 MeV and to be uniformly distributed in the spleen, kidneys, and liver. Interspecies scaling factors were determined using the results of the self-AFs for the voxel mouse and voxel human. Consequently, interspecies scaling factors were found to be dependent upon energy emitted in the source organ. It was found that the scaling factor for the photon self-AF, which is corrected by the cube root of the organ mass, shows a similar trend as a function of energy with the scaling factor for the electron self-AF.