1. Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis St, Boston, MA 02115.
2. Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland.
3. Department of Biostatistics, Harvard University, Boston, MA.
4. Department of Radiology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada.
5. Ottawa Hospital Research Institute, Ottawa, ON, Canada.