Fluorescence I-125 eye applicator

A new approach to optimize curative eye plaque brachytherapy is presented. The application of ophthalmic plaques is a common therapy modality for smal l and medium sized intraocular turners. At Essen University Hospital eye ap plicators with photon emitting I-125 seeds are used for the treatment of tu mors with a thickness from 5 to 10 mm. Our clinical experiences indicate th at the dose distributions of these applicators - used so far worldwide -are not optimal. A steeper dose falloff would meet the radiobiological require ments better, to provide the eradication of all tumor cells as well as suff icient occlusion of tumor supplying blood vessels. Our investigations for e ye plaque optimization are based both on measurements and Monte Carlo simul ation. For fast dosimetric measurements we have built a computer controlled device which allows reading out, directly and simultaneously, 16 1 mm(3) s cintillators. For the numerical simulations of the dose distribution of I-1 25 eye plaques we have adapted a Monte Carlo program originally developed t o calculate the synchrotron radiation in particle physics. We have investig ated the influence of geometric as well as physical eye plaque parameters o n the dose distribution: Shielding of the primary radiation, penumbra modif ication, and energy conversion by exploiting fluorescence x-radiation have been considered. New types of fluorescence eye applicators have been design ed which are more suitable for the prevention of radiopathic effects on str uctures at risk. (C) 1999 American Association of Physicists in Medicine. [ S0094-2405(99)04011-0].