Comparison between dose distribution from ¹⁰³Pd, ¹³¹Cs, and ¹²⁵I plaques in a real human eye model with different...

Knowledge of the energy deposition in different eye components is a critical decision-making to the overall effectivity of ocular melanoma treatment with plaques loaded with low-energy sources. The aim of this study is using the GATE 8.2 Monte Carlo code to calculate the 3D dose distribution in a realistic eye model. At first, we validated the GATE simulation for ¹²⁵I, ¹⁰³Pd, and ¹³¹Cs seeds by calculating the dose rate constant, radial dose function, and anisotropy function of the three radioactive sources. Then, a 12-mm Collaborative Ocular Melanoma Study (COMS) eye plaque was simulated in the eye phantoms to evaluate dose distribution due to low-energy gamma emitters on the three simulated medium-sized tumors. The findings of this study indicate that the estimated doses received by different eye substructures strongly depend on the source type. The results show that the type of seeds used in the plaque, as well as the size of the eye tumor, have significant effects on the dose deposition in the different structures of the eye and dose deposition uniformity. Moreover, comparing different radionuclides showed that the COMS plaque fully loaded with ¹⁰³Pd presents a higher dose delivery to the tumor and a lower one to the critical structures for medium-sized tumors, while the plaque fully loaded with ¹³¹Cs produces the most uniform dose distribution in the tumor.