Research Group Applied Medical Radiation Physics

Group leader: Prof. Dr. Christian Karger


The efficiency of radiotherapy can be improved by increasing the dose to the tumor while keeping the dose to the organs at risk below specific thresholds. This paradigm lead to the development of several modern treatment techniques such as stereotactic radiosurgery fractionated 3D-conformal radiotherapy, intensity-modulated radiotherapy (IMRT) and heavy charged particle radiotherapy. These techniques have already been introduced into clinical routine, while others (e.g. image guided and adaptive radiotherapy) are still under development.
Aim of the research group applied medical radiation physics is to accompany the clinical introduction of these new treatment techniques by developing tools for quality assurance, dosimetry, patient setup and monitoring of intra-fractional target movements. The geometrical and dosimetric accuracy achieved in clinical applications of the new techniques is investigated. Basic radio-biological parameters are determined from animal models and predictive outcome-parameters are derived from clinical data. Models for the prediction of the radiation response in normal tissues and tumors are developed and applied.
The work of the research group includes experimental as well as clinical investigations. It is focussed on high precision radiotherapy, however is not restricted to a specific treatment technique or to a specific step in the radiotherapy process. The research group applied medical radiation physics is also part of the Clinical Research Group Medical Physics at the University Clinic Heidelberg.

Research topics

Heavy ion therapy (in close cooperation with the research group heavy ion therapy)

  • Routine quality assurance and clinical treatment planning for the heavy ion project at GSI
  • Development of new quality assurance methods, e.g. dosimetry tools for treatment plan verification
  • Experimental investigations on the radiation response of normal tissues and tumors in animal models, e.g. measurements of the tolerance dose TD50, the fractionation parameter of the linear-quadratic model  and the relative biological efficiency (RBE) of Carbon ions

Analysis of Clinical data

  • Quantification of function loss of the salivary glands after irradiation of head-and-neck tumors for different treatment modalities, e.g. conventional radiotherapy with and without radio-protectors, intensity modulated radiotherapy (IMRT), determination of dose response curves
  • Analysis of side effects after stereotactic radiosurgery of lung tumors, Determination of dose response curves, dose-volume effects and predictive dosimetric parameters

Biological Models

  • Cell-based simulation of tumor growth and radiation response using Monte-Carlo methods. Modeling of angiogenesis and oxygen-transport in tissues.
  • Extension of the tumor response model to clinical tumors, temporal prediction of the oxygen-distribution tumors
  • Evaluation of the tumor response model in an animal model, experimental determination of tumor-parameters

Geometrical accuracy of images and image registration

  • Image distortions in Magnetic resonance imaging
  • Geometrical accuracy of multimodal image registration (CT, MRT, PET, SPECT)

Patient positioning and tracking

  • Stereo-camera-systems for patient positioning
  • Tracking of patient surface and external Markers
  • Correlation between external markers and internal structures
  • Quantification of inter- and intra-fractional setup errors

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