In this study, the dose distribution has been calculated for the Collaborative Ocular Melanoma Study (COMS) eye plaques at various diameters 10-22 mm, loaded with the 103 -Pd brachytherapy seeds (Model IR06-103 Pd). Several Monte Carlo (MC) simulations have been employed to carry out the gold backing and Silastic insert effect on dose distribution around the eye plaque. Version 5 of the Monte Carlo N-particle (MCNP) code has been used to carry out the simulations. The new palladium seed was

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... lled in three geometric orientations (ideal, vertical and diagonal). Results are compared with the calculated data for COMS eye plaque loaded with Theragenics model 200 and Best model 2335 palladium-103 seeds and model 6711 iodine-125 seeds. The calculated dose rate constant of the IR06-103 Pd seed was found to be 0.692 AE 0.020 cGy h À1 U À1 . The air kerma strength to deliver 85 Gy to tumour apex in a water medium was found to be 4.10 U/seed. The dosimetric parameters calculated in this work for the new palladium seed indicate the IR06-103 Pd seed is suitable for use in brachytherapy. In COMS plaques, the dose distribution to points of interest was compared for three 103 -Pd seed models. With the exception of sclera dose and for a given prescription dose, the IR06 seed delivers lower dose ocular points of interest. Keywords: eye plaque, palladium-103, brachytherapy, dosimetry Modelling, Simulation and Dosimetry of