Dosimetric Investigation of Ru-106/Rh-106 Ophthalmic Plaque Brachytherapy in Small-sized Uveal Melanoma Tumors Using Monte Carlo Stimulation

Background and Concave eye applicators of Ru-106, a beta emitter source, have a lot of use in brachytherapy of intraocular tumors. This has led to the need of knowing the exact dose distribution caused by beta radiation to the tumor and its normal surrounding tissue. The purpose of this study was the 3D calculation of dose distribution for three Ru-106 plaques: CCA, CCB, and CGD in a human eye model using the MCNP-4C code in treatment of uveal melanoma with 5mm thickness from the sclera surface. In this regard, eye’s different parts including the sclera, choroid, retina, cornea, etc., and also Ru-106 plaques with their real properties were simulated by MCNP-4C code. Dose rate of three plaques in tumor and sensitive surrounding tissues were studied. According to this study and the ALARA principle (which aims to deliver the maximum dose to the tumor and minimizing the dose to healthy tissues), full knowledge of the shape and size of tumor is essential before treatment by aforementioned plaques. To minimize damage to adjacent healthy tissue using CCA plaques are recommended in treatment of small-sized tumors < 5mm depth. CCA plaque with a lowest absorbed dose in the healthy tissue around the tumor such as sclera and lens showed better results than other studied plaques, thus it is recommended for the treatment of small-sized melanoma tumors.