Development of new radiopharmaceuticals is carried out on a small animal such as a mouse. With the aim to well-assess internal absorbed dose reaching various organs of a mouse, physical quantities defined by MIRD methodology known as specific absorbed fractions (SAFs) were evaluated using a voxelized mouse phantom. In our study, in order to provide more accurate photon SAFs, we used recent chemical compositions and densities of human organs taken from ICRP publication number 110. A new computational Geant4-based code called InterDosi has been developed to calculate SAFs for source-target organ pairs in Digimouse phantom irradiated by discrete monoenergetic photons of energies ranging from 0.015 to 4 MeV. Results show that, photon self-irradiation SAFs decrease with increasing energy or mass. For a cross-irradiation case, the photon SAFs were found to depend on distance source-to-target and organs close to the source have the most important photon SAFs. A comparison between our results and those reported in an earlier study with similar values of voxel sizes, masses, densities and chemical compositions, generally shows a significant agreement between them. Therefore, for a given configuration (energy, source), a smooth variation was found in the case of a self-irradiation. Contrariwise, medium discrepancy (less than 24%) was found in the case of a cross-irradiation, which can be attributed to the strong impact of the implementation of physics of the simulation in the two different codes and also the large statistical uncertainties associated to the calculation of SAFs in distant organs.

新的放射性药物的开发是在小动物如小鼠上进行的。为了很好地评估到达小鼠各个器官的内部吸收剂量，使用体素化的小鼠体模对由MIRD方法定义的称为特定吸收级分（SAF）的物理量进行了评估。在我们的研究中，为了提供更准确的光子SAF，我们使用了来自ICRP出版物编号110的最新化学成分和人体器官的密度。已经开发了一种名为InterDosi的新的基于Geant4的计算代码，用于计算源靶器官的SAF。对数位幻影模型中的双对，其能量范围为0.015至4 MeV的离散单能光子。结果表明，光子自辐照SAF随着能量或质量的增加而降低。对于交叉照射的情况，发现光子SAF依赖于源到目标的距离，靠近源的器官具有最重要的光子SAF。将我们的结果与早期研究中报道的体素大小，质量，密度和化学成分相似的值进行比较，通常可以得出显着的一致性。因此，对于给定的配置（能量，源），在自辐照的情况下会发现平滑变化。相反，在交叉辐照的情况下发现中等差异（小于24％），这可以归因于两种不同代码中模拟物理实施的强大影响以及与之相关的巨大统计不确定性远处器官SAF的计算。