1. Department of Radiation Oncology University Medical Center Groningen University of Groningen Groningen The Netherlands
2. Department of Experimental and Clinical Medicine Magna Graecia University Catanzaro Italy
3. Center for Proton Therapy Paul Scherrer Institute Villigen Switzerland
4. Department of Biomedical Physics in Radiation Oncology Deutsches Krebsforschungszentrum (DKFZ) Heidelberg Germany
5. Department of Physics and Astronomy Heidelberg University Heidelberg Germany
6. Department I of Internal Medicine Center for Integrated Oncology Cologne, University Hospital of Cologne Cologne Germany