1. Center for Evidence Based Imaging, Department of Radiology, Brigham and Women's Hospital, Boston, MA 02115, USA
2. Harvard Medical School, Boston, MA 02115, USA
3. Department of Emergency Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
4. Countway Library of Medicine, Boston, MA 02115, USA
5. Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA