1. West German Proton Therapy Centre Essen WPE Essen Germany
2. Faculty of Medicine University of Duisburg‐Essen Essen Germany
3. University Hospital EssenWest German Cancer Center WTZ Essen Germany
4. Radiation Oncology and Imaging German Cancer Consortium DKTK Heidelberg Germany
5. Technische Universität Dortmund Otto‐Hahn‐Str. 4a Dortmund44227Germany
6. Faculty of Physics Heinrich Heine University Düsseldorf HHU Düsseldorf Germany
7. Department of Particle Therapy University Hospital Essen Essen Germany