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Title
  • alireza kharazmy
alireza kharazmy

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Abstract

                                      a variety of concave eye applicators  with beta-ray sources, such as 90Sr/90Y and 106Ru/106Rh,  are usually used in brachytherapy treatment of superficial intraocular tumors  as uveal melanoma. However, in this study, a new plaque with 66Ni/66Cu  beta-ray source has been designed and proposed. 66Ni/66Cu is an ideal  radio isotope for this kind of brachytherapy due to its suitable half-life and  beta energy. In this work, the designed 66Ni/66Cu plaque  is compared with 90Sr/90Y and 106Ru/106Rh  plaques which are more commonly used in this kind of treatment. The aim of this  work is based on calculating the 3D dose distribution induced by beta-ray eye applicators  on a mathematical model of the human eye using the Monte Carlo code MCNPX in  order to treat a posterior uveal melanoma with 3.5 mm thickness from the choroid  surface and compare the results. Three mathematical models were developed for 90Sr/90Y,  106Ru/106Rh  and 66Ni/66Cu ophthalmic applicators. The  mathematical model of applicators were attached to the eye model in order to  calculate the dose distribution using the MCNPX *F8 tally. The average dose rate in all regions of the eye model was assessed. The *F8  tally results showed that the deposited energy due to the applicator with the  radionuclide 106Ru/106Rh is higher in all eye regions,  including tumor. However the relative energy deposition in the tumor compared  to the lens is significantly higher for the 66Ni/66Cu applicator,  with a factor of 88 to 1, whereas this ratio is 22 to 1 and 40 to 1 for 90Sr/90Y  and106Ru/106Rh  plaques respectively. Therefore, the 66Ni/66Cu  applicator delivers a high amount of dose to the tumor without inflicting a  drastic effect to the lens. This feature of 66Ni/66Cu  plaque makes it a better option for critical organ safety in this kind of  treatment compared to 90Sr/90Y and106Ru/106Rh  plaques.            zz