1. Medical Physics San Raffaele Scientific Institute Milano Italy
2. Department of Radiation Oncology University Hospital Zurich University of Zurich Switzerland
3. Protontherapy Department Trento Hospital and TIFPA‐INFN Trento Italy
4. Department of Radiation Oncology The Netherlands Cancer Institute Amsterdam The Netherlands
5. Department of Radiation Oncology Leiden University Medical Center Leiden The Netherlands
6. Department of Radiation Oncology Erasmus MC Cancer Institute Rotterdam The Netherlands