1. University of Copenhagen, Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Blegdamsvej 9, Copenhagen 2100, Denmark
2. Center for Medical Physics and Biomedical Engineering, General Hospital Vienna, 4L, Waehringer Guertel 18-20, Vienna 1090, Austria
3. University of Copenhagen, Department of Computer Science, Universitetsparken 5, Copenhagen 2100, Denmark