Model-based dose calculations for eye plaque brachytherapy

Eye plaque brachytherapy is a common treatment for uveal melanoma. Despite treatment outcomes comparable to those for enucleation, doses are currently calculated using the TG-43 formalism, which assumes a homogeneous water environment. This work aims to develop a comprehensive understanding of dosimetry using model-based dose calculations for ocular brachytherapy. A representative model of the human eye and surrounding tissues is developed, and dose is calculated for a range of plaque models encountered in clinical practice for three photon-emitting radionuclides, I-125, Pd-103 and Cs-131. Doses to ocular structures for the full eye model are compared to those for a homogeneous water phantom, both including and excluding (TG-43) inter-seed and eye plaque effects. Doses for the full eye model simulations are shown to deviate significantly from simulations that assume the eye to be water equivalent, with and without the plaque, highlighting the need for accurate model-based dose calculations in ocular brachytherapy.