Palladium 103 ophthalmic plaque radiotherapy

Area of Science:

• Ophthalmology
• Radiation Oncology
• Medical Physics

Background:

• Ophthalmic plaques are used for localized radiation therapy of choroidal melanoma.
• Palladium 103 (103Pd) and iodine 125 (125I) are commonly used isotopes for these plaques.
• Understanding the radiation distribution is crucial for optimizing treatment efficacy and minimizing side effects.

Purpose of the Study:

• To compare the ocular radiation distribution of palladium 103 (103Pd) versus iodine 125 (125I) ophthalmic plaques.
• To evaluate the dosimetric differences between 103Pd and 125I plaques in a preclinical setting and through patient simulations.

Main Methods:

• In vitro experiment using 12 human donor eyes with 103Pd and 125I plaques sewn to the episclera.
• Quantification of radiation dose using thermoluminescent dosimeters at the cornea, macula, and opposite equator.
• Preoperative comparative simulations for seven patients undergoing 103Pd plaque therapy for choroidal melanoma.

Main Results:

• Equalized activity 103Pd plaques delivered less radiation to target points (cornea, macula, opposite equator) compared to 125I plaques in vitro.
• Comparative clinical dosimetry confirmed these dosimetric differences.
• Preoperative simulations showed 103Pd plaques delivered higher radiation doses to the tumor apex but less to most normal ocular structures.

Conclusions:

• Palladium 103 ophthalmic plaques demonstrate a different radiation distribution profile compared to iodine 125 plaques.
• 103Pd plaques may offer a more conformal dose distribution, potentially increasing tumor dose while sparing normal ocular tissues.
• Further clinical studies are warranted to confirm the therapeutic benefits of 103Pd plaque therapy for choroidal melanoma.