1. Department of Radiotherapy; Medical Physics Section, University Hospital Essen; Essen North Rhine-Westphalia Germany
2. Centre for Cardiovascular Science, Clinical Research Imaging Centre, University of Edinburgh; Edinburgh UK
3. Department of Radiation Oncology; Charité Universitätsmedizin Berlin; Berlin Germany
4. Department of General and Visceral Surgery at Evangelical Hospital Wesel; Wesel North Rhine-Westphalia Germany