The generalized geometry of eye plaque therapy

Area of Science:

• Ophthalmology
• Medical Physics
• Radiation Oncology

Background:

• Choroidal melanoma is a serious eye cancer requiring precise radiation therapy.
• Plaque brachytherapy using Iodine-125 (125I) seeds is a common treatment modality.
• Accurate dose assessment is crucial for treatment efficacy and minimizing damage to surrounding ocular tissues.

Purpose of the Study:

• To develop a rapid calculation method for assessing radiation dose rates within the eye during 125I plaque brachytherapy for choroidal melanoma.
• To provide a tool for ophthalmologists and radiation oncologists to evaluate treatment adequacy.
• To integrate with existing brachytherapy treatment planning systems.

Main Methods:

• A computational method was developed based on spherical geometry to calculate dose rates.
• The method uses a Cartesian coordinate system derived from ophthalmologist-provided tumor dimensions on fundus diagrams.
• Calculated data files serve as input for conventional brachytherapy treatment planning programs.

Main Results:

• The calculation enables rapid assessment of dose rates at critical ocular structures (lens, optic nerve).
• The method facilitates visualization of dose distribution within a plane containing the tumor's major axis.
• This visualization aids in assessing the adequacy of the treated volume.

Conclusions:

• The described calculation method offers a rapid and effective way to assess radiation dose distribution for choroidal melanoma treatment.
• This approach supports precise treatment planning and evaluation in ophthalmic plaque brachytherapy.
• The integration with treatment planning software enhances the clinical utility of the method.