Monte Carlo simulation of uveal melanoma treatment by ocular plaque brachytherapy using gold nanoparticles

Uveal melanoma is a serious ocular disease that can be fatal. One of its treatment methods involves the use of radioactive seeds, which are temporarily attached to a plaque and placed on the eye. The dose distribution around the seeds used in ocular plaques strongly depends on the seeds' structure and the ocular plaque's design. Recently, there has been a high interest in using gold nanoparticles (GNPs) as a biocompatible and non-toxic dose enhancer in cancer treatment via ionizing radiation. This study used the Monte Carlo code GATE 9.1 to calculate the dose distribution in the tumour and the eye components with and without the presence of GNPs using ¹²⁵I, ¹⁰³Pd, and ¹³¹Cs seeds. A 14 mm Collaborative Ocular Melanoma Study (COMS) plaque was simulated, and dosimetry parameters such as depth dose, lateral dose, and Dose-Volume Histogram curves for various eye components and the tumour were obtained. In the next step, GNPs with several concentrations of 5-30 mgAu/g were added to the tumour chemical composition, and the Dose Enhancement Factor for each seed in the presence of GNPs was calculated. The results show that the average doses received by the different eye structures and the tumour vary depending on the seed model. The tumour apex dose increases with increasing concentration of GNPs within the tumour volume, hence reducing the irradiation time. ¹³¹Cs shows the highest dose enhancement, with an increase ranging from 33.87% at 5 mgAu/g to 170.45% at 30 mgAu/g for the tumour apex and from 71.51% at 5 mgAu/g to 377.23% at 30 mgAu/g for the tumour, compared to ¹²⁵I and ¹⁰³Pd. Furthermore, GNPs decreased the dose delivered to surrounding eye components, particularly for ¹⁰³Pd brachytherapy, where the lens has the greatest reduction in dose among all eye components, ranging from 7.57% at 5 mgAu/g to 33.27% at 30 mgAu/g.