Palladium 103 ophthalmic plaque radiotherapy
P. T. Finger, D. M. Moshfeghi and T. K. Ho
Department of Ophthalmology, North Shore University Hospital-Cornell University Medical College, Manhasset, NY 11030.
We compared the ocular radiation distribution of palladium 103 (103Pd) vs
iodine 125 (125I) ophthalmic plaques sewn to 12 human donor eyes. We then
performed preoperative comparative simulations on the first seven patients
to be treated with palladium 103 plaque therapy for choroidal melanoma. The
in vitro experiment involved palladium 103 seeds placed into a Silastic
seed holder, which was affixed into standard 14-mm gold eye plaques. Then
the plaques were sewn onto 12 human donor eyes so as to approximate either
the nasal (six eyes) or temporal (six eyes) equator. Three sets of two
thermoluminescent dosimeters were used to quantify the amount of radiation
delivered by the episcleral plaques. Thermoluminescent dosimeters were sewn
to the sclera in three locations: on the center of the cornea, on the
sclera beneath the macula, and at the equator in a position opposite the
plaque. This experiment was then repeated with iodine 125 seeds and
thermoluminescent dosimeters. After the plaques were adjusted to equalize
their activity (plaque strength), the palladium 103 plaques were found to
deliver less radiation to the three target points. Comparative clinical
dosimetry also reflected this difference. Preoperative simulations
comparing equal doses to the tumors' apex revealed that the palladium 103
ophthalmic plaques delivered more radiation to the tumor and less radiation
to most normal ocular structures.
