Monte Carlo-based dosimetric comparison of CCA and CCB radioactive eye plaques for uveal melanoma

This study conducted a comprehensive dosimetric analysis of three beta-emitting radionuclides ⁹⁰Sr, ¹⁰⁶Ru, and ¹⁴²Pr embedded in two ophthalmic plaque models, the Concave Circular Applicator (CCA) and Concave Circular Brachytherapy (CCB), with different backing materials (gold, silver, and gadolinium). Using Geant4-based Monte Carlo simulations, dose distributions within ocular structures were analyzed to optimize tumor coverage while minimizing radiation exposure to critical tissues. Validation with EBT3 radiochromic films demonstrated dose discrepancies below 5%, confirming the accuracy of the model. The results showed that ¹⁴²Pr combined with a gadolinium-backed CCB plaque achieved the most favorable therapeutic ratio, delivering a high tumor dose while reducing radiation to the lens and optic nerve. Gadolinium exhibited an advantageous balance between backscatter enhancement and moderate bremsstrahlung emission compared to gold and silver. These findings highlight the potential of ¹⁴²Pr-Gd-CCB configurations for personalized ocular brachytherapy, particularly for small to medium uveal melanomas. Future research should integrate patient-specific anatomical models to further optimize treatment planning and clinical translation.