Preclinical radiation internal dosimetry in the development of new radiopharmaceuticals using GATE Monte Carlo simulation

The aims of this study were to construct a mouse model based on experimental data and to evaluate two approaches for a radiation dosimetry study on the development of a new radiopharmaceutical based on MIRD Formalism with free software. The first one obtaining S-values from a reference model and with these data calculating the absorbed doses. The second consisting of a specific anatomy mouse considering characteristics such as strain, gender, age, and weight used in preclinical studies comparing the results obtained for the new radiopharmaceutical 99mTc-Ixolaris. A voxelized mouse model (C57BL/6 lineage) based on Computed Tomography images with ten segmented organs was developed by 3D SLICER software and was used as input in GATE Monte Carlo simulations (version 7.1) to determine organ absorbed dose distribution by the proposed approaches. The first method consisted of obtaining the S-values for each source organ by performing separate simulations, and the second method obtained the absorbed dose in each target organ through a single simulation containing all source organs (real radiopharmaceutical biodistributions). Absorbed dose distribution volumetric maps were obtained for each simulation. Using the first method, the numerical data were extracted from volumetric maps to determine the S-values for each source organ and in the second method the absorbed dose was obtained directly from simulation, without S-value tables. The preclinical dosimetry evaluation showed good agreement between both methods but each one has its own advantages and disadvantages: the first has less statistical uncertainties than the second method and the S-values obtained for a standard model can be scaled to other mouse sizes; the second method requires shorter simulation computational time, considering a specific anatomy mouse, using a real biodistribution with all source organs in the simulation without construction of S-value tables. •Development of a voxelized mouse model based on experimental data.•Radiation Dosimetry Swith Monte Carlo simulation with comparison between two methods.•Radiation Dosimetry Evaluation for the new radiopharmaceutical 99mTc-Ixolaris.•Development a free Dosimetry Computational Methodology for preclinical research.