4D treatment plan optimization and motion detection via radiography

• Applicant: Professor Dr. Christoph Bert
• Subject Area: Nuclear Medicine, Radiotherapy, Radiobiology
• Term: from 2008 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 59368893

Ion beam radiotherapy, narrow scanning beams are used to deliver highly localized dose distributions to the patient. In treatments of organs moving during the beam delivery interplay effects between the two motions occur, resulting in undesired dose distributions. To minimize those effects, several motion mitigation techniques were proposed. This project concentrates on gating (beam delivered only in a particular motion phase) and tracking (target motion followed by the beam).To enable their clinical implementation, dedicated 4D treatment planning as well as a high precision detection of the actual target position is necessary.Within the first PhD-project we plan to implement 4D optimization of treatment plans for scanned ion beam therapy. These offer the advantage that the additional degrees of freedom given by the moving target are exploited in the optimization process. We will focus on 4D optimization for beam tracking with the aim to achieve tracking without energy variation and beam gating.For determination of the internal target position, we will investigate ion radiography in second PhD-work. Radiography provides the potential of high contrast images gained at low dose. The pixelized semiconductor detector “Timepix” will be used to register single ions behind the patient. Based on the measurement of their energy deposition in the detector, direction and fluence, imaging techniques will be developed. The technique with the best performance to visualize moving targets at a minimal dose to the patient will be identified.If successful, the techniques of dedicated 4D treatment plan optimization and target position detection will allow improved radio-therapeutic treatments of tumors in moving organs like lung, liver and pancreas by scanning ion beams. The techniques will be clinically implemented at the HIT facility in Heidelberg in the near future, what enables to exploit this high-end radiotherapy for radioresistant tumors in those new locations.

• DFG Programme: Clinical Research Units
• Subproject of: KFO 214: Heavy Ion Therapy in Radiation Oncology