1. Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
2. Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia, PA 19104, USA
3. Harvard Medical School, Harvard University, Boston, MA 02115, USA
4. Department of Epidemiology, Harvard Chan School of Public Health, Boston, MA 02115, USA
5. The Intervention Centre, Division of Technology and Innovation, Oslo University Hospital, 0424 Oslo, Norway
6. Institute of Clinical Medicine, University of Oslo, 0317 Oslo, Norway