Calculation of Specific Absorbed Fraction and S Factor for internal dosimetry of 177Lu in Zubal phantom using GATE Monte Carlo code

Specific absorbed fraction is one of the important parameters for estimating the internal dose. In this paper, the specific absorbed fraction for a number of body organs has been calculated using the Zubal Voxel phantom. The GATE Monte Carlo code version 7.2 was used to simulate the single-energy photons and electrons related to the radioactive isotope 177Lu. kidney, liver, and spleen were considered as source organs in this simulation and the specific absorbed fractions of these source organs were compared with the values ​​obtained from previous studies. The most relative difference between the values of this study and previous studies was observed to be 41% and related to the photons with the energy of 71 keV when the spleen and liver were considered as the source and target organs, respectively. In most data, discrepancies are acceptable and the obtained data are consistent with the previous data and have been verified. Using the data obtained from this study, the S-factors used for dosimetric calculations in the MIRD method were calculated and presented.