Radionuclide Internal Dosimetry Using GATE and PENELOPE for Experimental Validation in Geometrical Phantoms

The aim of this study is to investigate the use of two freely available Monte Carlo (MC) codes to model simple geometrical radionuclide configurations, which could be compared to experimental measurements or analytical calculus for internal dosimetry. Three spherical geometries were simulated using GATE 7.1 and PENELOPE 2008: (1) a point source centered in a 10 cm radius sphere; (2) a 5 cm radius sphere with homogeneous radioactive distribution inside a 10 cm radius sphere; (3) two separated spheres (5 and 10 cm radius) 5 cm apart, the first acting as source and the second as target. All spheres were filled with water and sources produced 108 primary gamma emissions from 99mTc. Total absorbed doses were analyzed using 3D Dose Point Kernel (DPK). Results obtained with GATE and PENELOPE simulations were, respectively: (1) 15 and 14.25 mGy, with 5.2% difference; (2) 7.4 and 8.51 mGy, showing higher difference (13.04%); (3) 0.93 and 0.97 mGy, in target sphere. Concluding, GATE and PENELOPE MC codes can be easily used to simulate simple geometries, allowing for comparison against experimental measurements or analytical calculations. Further studies are required to compare these simulation results with experimental data designed to the clinical practice.