Fluorescence 125I eye applicator

A new approach to optimize curative eye plaque brachytherapy is presented. The application of ophthalmic plaques is a common therapy modality for small and medium sized intraocular turners. At Essen University Hospital eye applicators with photon emitting I-125 seeds are used for the treatment of tumors with a thickness from 5 to 10 mm. Our clinical experiences indicate that the dose distributions of these applicators - used so far worldwide -are not optimal. A steeper dose falloff would meet the radiobiological requirements better, to provide the eradication of all tumor cells as well as sufficient occlusion of tumor supplying blood vessels. Our investigations for eye plaque optimization are based both on measurements and Monte Carlo simulation. For fast dosimetric measurements we have built a computer controlled device which allows reading out, directly and simultaneously, 16 1 mm(3) scintillators. For the numerical simulations of the dose distribution of I-125 eye plaques we have adapted a Monte Carlo program originally developed to calculate the synchrotron radiation in particle physics. We have investigated the influence of geometric as well as physical eye plaque parameters on the dose distribution: Shielding of the primary radiation, penumbra modification, and energy conversion by exploiting fluorescence x-radiation have been considered. New types of fluorescence eye applicators have been designed which are more suitable for the prevention of radiopathic effects on structures at risk. (C) 1999 American Association of Physicists in Medicine. [S0094-2405(99)04011-0].