1. Department of Radiation Oncology, University Hospital Tübingen, Tübingen, Germany;
2. Clinic for Radiation Oncology, Oberschwaben Hospital Group, Ravensburg, Germany;
3. Clinic for Radiology and Radiation Oncology, ALB FILS Clinics Hospital on the Eichert, Goppingen, Germany;
4. Department of Radiation Oncology, Section Medical Physics, University Hospital Tübingen, Tübingen, Germany;
5. Clinic for Radiation Oncology, University Hospital Heidelberg, Heidelberg, Germany