Dual-source strength seed loading for eye plaque brachytherapy using eye physics eye plaques: A feasibility study.

Area of Science:

• Ophthalmology
• Radiation Oncology
• Medical Physics

Background:

• Uveal melanoma is the most common primary intraocular malignancy.
• Brachytherapy with eye plaques is a standard treatment for uveal melanoma.
• Optimizing radiation dose distribution is crucial for treatment efficacy and minimizing toxicity.

Purpose of the Study:

• To quantify the dosimetric impact of using dual iodine-125 (¹²⁵I) seed source strengths in eye plaques for uveal melanoma.
• To evaluate the effect of this technique on prescription depth and doses to critical ocular structures.

Main Methods:

• Retrospective planning of 15 clinical uveal melanoma cases using Plaque Simulator.
• Three tumor types were analyzed: shallow/large base, near optic nerve, and very shallow/moderate base.
• Dual-source strength loading involved placing higher strength seeds near the plaque periphery or notch.

Main Results:

• Dual-source strength loading decreased prescription depth in most cases.
• Scleral dose was consistently reduced (-25% to -45%).
• Dose to the optic disc and fovea varied, showing increases in some cases (up to 20% and 12%, respectively).

Conclusions:

• Dual-source strength loading can effectively reduce scleral dose, potentially sparing the adjacent retina.
• The impact on optic disc and fovea radiation dose is tumor-location and size-dependent.
• Individualized clinical assessment and quality assurance are necessary before adopting this technique.