Development of a system for treatment planning of ocular tumours taking into account the nhomogeneities of the surface dose rate distribution of the radiation sources

• Applicants: Professor Dr. Johannes Albrecht; Dr. Dirk Flühs
• Subject Area: Medical Physics, Biomedical Technology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 528648187

Brachytherapy with Ruthenium-106 eye plaques is an effective method for successfully treating ocular tumours. However, the surface dose rate distribution of the plaques is not homogeneous. So-called hot and cold spots complicate planning, and there is no system for detailed measurement of these inhomogeneities in the clinic. Furthermore, there is a lack of software to support therapy planning and to visualise the three-dimensional dose distribution in order to be able to precisely assess compliance with the tumour control rate and the influence on risk structures. In this project, a system to support therapy planning for brachytherapy of intraocular tumours is to be developed. In this system, the inhomogeneities of the surface dose profile of the eye plaques are to be included in the planning to achieve the goal of maintaining the tumour control rate while at the same time providing the best possible protection of the risk structures. The challenges of developing this system will be overcome by combining the methods and expertise of particle physics with experience in clinical medical physics. To measure the surface dose rate distribution of the plaques, an apparatus is being developed that can be integrated into daily clinical practice. The measurements are performed in air, and the type of set-up prevents the generation of Cherenkov radiation by an integrated air shaft in front of the scintillator. The positioning uncertainties of previous systems for measuring the surface dose profile are minimised, and the complexity of the set-up is kept low. The apparatus will be used to investigate the extent to which the measuring points specified by the applicator manufacturer are sufficient to represent the surface dose profile. Parallel to the development of the apparatus, software for 3D therapy planning for brachytherapy of ocular tumours is to be created. In this project, a model is to be developed in which the surface of the applicator is divided concentrically into individual segments, and the standard dose distribution of a segment is calculated. The weighting of the segments should then allow the Monte Carlo simulation of the inhomogeneities of the surface dose rate distribution. The implementation of the dose values measured with the developed apparatus will be enabled. Furthermore, the development of neural networks should allow the generation of dose profiles without Monte Carlo simulations in order to be able to estimate the first effects on the risk structures. Subsequently, further neural networks will be used to develop the possibility of optimising the treatment by varying the positioning and orientation of the eye plaque. The programme will allow visualisation of the resulting dose distributions of brachytherapy in a three-dimensional eye model so that a precise assessment of the success of the therapy as well as the challenges can be made.

• DFG Programme: Research Grants