1. Department of Medical Imaging, The Ottawa Hospital, 1053 Carling Ave, Ottawa, ON K1Y 4E9, Canada
2. Department of Radiology, University of Ottawa, Ottawa, ON, Canada
3. Center for Stroke Research Berlin, Charité Universitätsmedizin Berlin, Berlin, Germany
4. Department of Radiology, University of Cincinnati Medical Center, Cincinnati, OH
5. Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA