Ion Beam Radiotherapy

Highly resolved three-dimensional (3D) dose measurements are of great importance in radiotherapy to verify that the dose distribution is delivered to the patient as planned. In spite of available commercial dose verification systems, the measurement of truly 3D dose distributions is still an unsolved problem in ion beam radiotherapy. For photon beams, radiation-sensitive gel dosimeters may be used for 3D dosimetry. For ion beams, however, most of these gel dosimeters show a severe under-response (‘quenching’) in regions of high linear energy transfer (LET), limiting their application in proton and carbon radiotherapy. An exception is the so-called nanoclay (NC)-Fricke gel in combination with magnetic resonance (MR) readout of the T1-relaxation time (Bayer et al 2024). This promising gel dosimeter system is investigated and optimized in close cooperation with the research groups Translational Research for Ion Beam Therapy and Medical Engineering as well as with the Division of Medical Physics in Radiology and the Junior Group Translational Radiotheranostics. This interdisciplinary project involves radiation physics of ion beams, MR imaging, 3D printing and radiochemistry. Current research focuses on the development and optimization of accurate and efficient irradiation and MR readout protocols as well as on increasing the radiosensitivity of the NC-Fricke gel system. The final goal is to develop a dosimetry system that can be used in anthropomorphic phantoms to simulate patient treatments within end-to-end tests (Bakhtiari Moghaddam et al. 2025).