Dosimetry of indigenously developed 106Ru-106Rh ophthalmic plaque

Abstract

PURPOSETo evaluate the dosimetric performance of indigenously developed 106Ru-106Rh ophthalmic plaques for treatment of eye cancer, utilizing Monte Carlo simulation, a custom-built phantom, radiochromic films, and diode detectors. METHODS AND MATERIALS106Ru/106Rh round type eye plaques has been developed from recovered fission product 106Ru, by Bhabha Atomic Research Centre (BARC), India, to treat retinoblastoma and choroidal melanoma. The plaque is made up of three silver layers of purity 99.9%, namely, a 15.8 mm diameter and 0.9 mm thick backing plate, a 13.3 mm diameter and 0.2 mm thick silver substrate that contains 106Ru, and a 0.1 mm thick silver window. The assembly is spherically shaped with a radius of 12 mm and sealed in a controlled environment during the production process. For dosimetry of the plaques, sources with less than 20% non-uniformity in activity distribution were considered. The dosimetry was carried out using Monte Carlo simulation, a custom-built phantom, radiochromic films, and diode detector. In order to validate the accuracy of the dosimetry methodology, dosimetry parameters for a BEBIG CCA type eye plaque (Eckert & Ziegler BEBIG, Berlin, Germany), were generated and compared. RESULTSThe non-uniformity of the activity distribution within the plaque was determined to be within 14%. The absorbed dose rates to water on the central axis at depths of 1 mm and 2 mm were measured as 138.32 mGy/min and 106.26 mGy/min, respectively, with an extrapolated dose at zero depth of 170.70 mGy/min. For BEBIG CCA, these values were found to be 6.8%, 135.32 mGy/min, 103.74 mGy/min, and 172.50 mGy/min, respectively. Monte Carlo simulated and measured percentage depth dose values exhibit good agreement with each other. Additionally, the measured dose rate for the BARC eye plaque closely aligns with the recommended values outlined in the GEC-ESTRO guidelines. CONCLUSIONSThe dosimetry of the indigenously developed 106Ru-106Rh eye plaque was carried out using indigenously designed and developed eye phantom. A robust dosimetry methodology was formulated and rigorously tested against data obtained from a commercially available eye plaque. This cost-effective ophthalmic plaque can be a promising asset in the field of ocular oncology, offering the potential for highly efficient and targeted treatments while minimizing potential harm to healthy ocular structures.