In order to irradiate tumors with high accuracy and precision, the tumor must be precisely determined both regarding its extent and its position. With the means of computed tomography (CT) and magnetic resonance imaging (MRI), anatomical, structural and functional information of the volume of interest can be obtained. In addition, positron emission tomography (PET) depicts metabolism. The fusion of the different imaging modalities provides a detailed three-dimensional representation of the tissue of interest and enables the classification of different tissues, which is the basis for radiation treatment planning.

Figure 1: Computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) are different imaging techniques that can be used to visualize anatomical, structural and metabolic changes.

3D and 4D imaging / novel markers for positioning

Tumors in the head and neck Region are relatively immobile. Conversely, many other tumors in the body move, such as those originated from the lung, liver or pancreas. The pancreas, for example, moves continuously through the heartbeat, breathing and the varying filling of the stomach or small intestines. Therefore, it is necessary to consider the movement of the tumor and of the surrounding risk organs whenever planning highly precise irradiation in these tumor sites, so-called four-dimensional (4D) Radiation planning.

One research focus of the group is on 3D and 4D imaging techniques for high-precision radiation therapy of (mobile) tumors. Innovative techniques will first be examined in detail and then transferred to clinical application.

Another research focus is on the use of innovative fiducial markers for tumor demarcation in photon or proton beam Iiradiation. By means of Ttese markers, positioning of the tumor can be performed highly accurately and precoisely prior to each treatment fraction, and can be monitored during irradtiation. Examples of these markers are thin gold threads and gel markers that are implanted at the tumor boundaries and can be easiliy seen on X-rays (including CT) and on MRI.

Figure 2: Treatment plan for the proton irradiation of a pancreatic cancer patient. The gold markers (blue circles) enable the treatment volume (red) to be accurately and precisely positioned prior to irradiation.

Individualized treatment

The images that are obtained from each patient for diagnosis, treatment planning and position verification is also available for treatment monitoring. By doing so, the treatment course and effectiveness can be checked and, if necessary, a treatment adaption performed. Patients thus receive a personalized treatment aimed at delivering the maximum dose to the tumor while causing minimal harm to the surrounding healthy tissues.

Despite the sensitivity of the current imaging techniques, microscopoic tumor cell infiltration cannot be detected. In order to ensure that these volumes receive a sufficiently high radiation dose, a rather generous safety margin is applied around the detectable tumor. Previously published work on microscopic tumor extensions has been conducted in relatively small patient cohorts using outdated methods. In order to meet the current challenges of adaptive photon and proton therapy, we have initiated dedicated research projects on this topic. The group is therefore developing methods to predict the presence and extent of microscopic tumor extension as precisely as possible and on an individual patients basis.

In addition to clinically relevant research - in close cooperation between OncoRay and the Department of Radiotherapy and Radiation Oncology - the novel therapeutic strategies are also being developed and translated within networks with national and international research partners (DKFZ, DKTK, NCT, NCRO; Horizon 2020 Projects IMMUNOSABR and INSPIRE).