Purpose: To investigate the suitability of a combination of two irradiation approaches for intraocular tumors. In tumors with a height of 6 mm and more, brachytherapy with Ruthenium-106 applicators does not deliver the required dose at the tumor apex. Simultaneous therapy with an X-ray tube could provide a dose boost. If the irradiation position and angle is chosen accordingly, the lens and other organs at risk are spared. In addition, the brachytherapy plaque may serve as an absorber of the X-rays after crossing the tumor tissue.
Methods: A simulation workflow was developed to process patient data and fundus images of completed treatments to create a three-dimensional model of the tumor entity. The software workflow uses algorithms in Visual Basics for Applications and Fusion360. The output is a complete three-dimensional model of the affected eye and a Ruthenium-106 applicator positioned as in the previously performed therapy. The created files are then read into a Geant4 simulation. Both irradiation modalities, the brachytherapy and different incident fields of photons, are simulated and the dose distributions in the tumor and in the individual components of the eye are produced. Based on these data dose volume histograms are generated. By weighting the modalities, the improvement of combined therapy compared to only using brachytherapy can be assessed.
Results: First data sets of real patient geometries have been fully simulated and are currently being evaluated. A first comparison between the combined therapy and brachytherapy alone shows that the tumor can be irradiated more homogeneously without significantly increasing the dose in organs at risk.
Conclusion: This work demonstrates the potential improvement in treating intraocular tumors by combining brachytherapy and teletherapy. The simulation workflow will be applied to more patient data in the future to investigate the suitability of the proposed therapy for different tumor entities.
Funding Support, Disclosures, and Conflict of Interest: The project is funded by the German Research Foundation and has the project number 455163177.