1. Department of Radiology and Nuclear Medicine; Radboud University Medical Center; Nijmegen the Netherlands
2. Dutch Expert Centre for Screening (LRCB); Wijchenseweg 101 Nijmegen SW 6538 The Netherlands
3. Physics Department; Carleton University; Ottawa Canada
4. Department of Physics and Astronomy; University of Victoria; Victoria Canada
5. Department of Biomedical Engineering; University of Florida; Gainesville FL USA
6. Department of Radiological Sciences; David Geffen School of Medicine; University of California, Los Angeles; Los Angeles USA
7. Physics Department and Institute of Energy Technologies; Universitat Politecnica de Catalunya; Barcelona Spain
8. Department of Radiation Oncology; Virginia Commonwealth University; Richmond VA USA