Medical Physics in Radiation Oncology

Our research focuses on physical methods used in radiation therapy in order to improve the therapy.

Present research priorities

The central research questions deal with image-guided therapy, i.e. the integration of daily anatomical images taken immediately before, or during therapy. For this purpose, both X-ray-based images (so-called Cone Beam CT) and MR images are used. The aim is to use these images to adapt the therapy on the respective treatment day (so-called adaptive therapy). These procedures enable us to optimally adapt the therapy to the actual anatomical situation and to spare healthy tissue. The tasks to be addressed, start with image processing (in particular tracking the anatomical structures, for which a so-called deformable image registration is necessary), in order to correctly take the actual anatomical conditions into account. This is followed by the recalculation and optimization of the dose based on clinical requirements, as well as the review of the radiation parameters (quality assurance) before they are used for the treatment. Since all steps are time-critical, the use of modern AI-based algorithms is essential.

All of the topics mentioned above are also being researched in our division for radiation therapy with proton and ion beams, which is becoming even more important due to the potentially higher accuracy of this treatment modality.

Our research topics are complemented by the development of novel measurement techniques that can be used for dosimetry and for the monitoring of therapy during irradiation. Radiobiological investigations of the effectiveness of proton and ion beams are also highly relevant, as they directly influence clinical strategies for the use of this therapy techniques.

Current developments

In close collaboration with the Clinical Cooperation Unit Radiotherapy at the DKFZ, we have developed and implemented a modular system for MR-guided radiotherapy (MARS) that is particularly suitable for the integration of functional MR imaging into adaptive therapy (Kim et al. 2024).

This system is being evaluated in several clinical trials, e.g. in a study on cervical cancer (Weykamp et al. 2024) or in the multicenter study we initiated to investigate the role of MR-guided radiotherapy for non-small cell lung tumors (PUMA Trial). One of the goals of this study is to use MR scans to determine during therapy whether patients are responding to the therapy or whether there are also early signals for the development of side effects.

In the field of ion beam therapy, a patient study as part of a clinical trial for the introduction of therapy with helium ions at the Heidelberg Ion Beam Therapy Center (HIT) was completed at the end of 2024. Here, we contributed to radiobiological studies on the effectiveness of helium ions and thus also to the precise measurement of the radiation dose (Hintz et. al 2022).

In a project on MR-guided therapy with ion beams (the ARTEMIS Project), we were able to make significant contributions in the field of dosimetry of ion beams in magnetic fields (Marot et al. 2023, Surla et al. 2024), dose calculation in magnetic fields (Burigo et al. 2022), the development of new methods for quality assurance and novel methods for patient positioning in an MRI scanner (Beyer et al. 2024). The ARTEMIS Project was funded by the Federal Ministry of Education and Research (FMER).

At the beginning of 2025, we also received a grant from the Carl Zeiss Foundation to develop the possibility of a completely new form of radiation therapy with miniaturized accelerators together with the Karlsruhe Institute of Technology (KIT). These accelerators are based on a physical mechanism recently discovered at KIT for accelerating electrons using laser light, which is based on structures that are only a few centimeters in size. This means that the ultra-compact electron accelerators might in the future be inserted into the body using minimally invasive endoscopy, where electron beams are then generated directly in the body close to the tumor. This would enable high-precision treatment while sparing healthy tissue (Ultracompact electron accelerators for internal radiotherapy (UCART)).

Methods and technologies

The methods we develop and use are based in particular on computer algorithms, especially in the area of therapy planning. New algorithms are developed and then tested in prototypes. Simulation codes (so-called Monte Carlo simulations) are an important tool, allowing us to examine in detail the physical interactions of radiation with matter in order to optimize the respective application. 

Another major research area are algorithms based on artificial intelligence. These are mostly algorithms that help to automate and accelerate time-consuming tasks that usually have to be performed by hand. This requires large amounts of clinical data, which we obtain from clinical studies conducted by our partner institutes.

Many members of our division are physicists who come from the field of particle physics. We are therefore trying to use measurement systems from particle physics for applications in radiation therapy. One example of this is the MediPix detector, which is used in the so-called Large Hadron Collider (LHC) at Cern in Geneva, Switzerland. We use this detector for therapy monitoring and also to develop novel imaging with ion beams.

In recent years, we have also acquired extensive expertise in the field of rapid prototyping based on 3D printing processes. These are used in particular to develop realistic, dynamically variable body phantoms for various areas of the body. These so-called anthropomorphic phantoms are needed to test complex methods and algorithms for radiation therapy before they can be used clinically.

Finally, we have many years of expertise in conducting radiobiological investigations, which, in particular, enables us to compare the effects of ion beams with those of X-rays using various models. This is crucial for optimizing ion beam therapy.

Goals and societal relevance

Our work aims to further optimize radiation therapy and to adapt the treatment based on individual circumstances of each patient (so-called personalized oncology). In particular, daily anatomical changes are also taken into account. Furthermore, the radiation dose can be optimally adapted to the tumor volume in each case. This makes radiation therapy more precise and thus more tolerable and effective. In the long term, further clinical parameters and, for example, genomic data of each patient will also be included in this optimization. In this way, we are contributing to the further development of radiation therapy, which is one of the most important tools in oncological therapy. The development of ultra-compact internal radiation devices together with the KIT could help to ensure sustainable radiation therapy for tumor patients in less developed countries of the world as well.

Last but not least, we engage strongly in education and teaching as well as in outreach activities. This includes workshops and summer schools for students at all levels, postgraduate education and advanced trainings in radiation therapy and medical physics, as well as informing the general public in lectures and activities we organize for school classes, e.g. as part of the International Day of Medical Physics on 7 November every year.