1. Department of Physics, University of Oslo, Oslo, Norway;
2. Department of Medical Physics, Oslo University Hospital, Oslo, Norway;
3. Department of Oncology, Oslo University Hospital, Oslo, Norway;
4. Institute for Cancer Research, Oslo University Hospital, Oslo, Norway;
5. Department of Radiology and Nuclear Medicine, Oslo University Hospital, Oslo, Norway;
6. Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, The Netherlands;
7. Department of Cell Biology, University Medical Center Groningen, University of Groningen, The Netherlands