1. Department of Clinical Neurosciences (M.G., A.G., M.D.H., J.M.O.), University of Calgary, Canada.
2. Department of Radiology (M.G., M.D.H.), University of Calgary, Canada.
3. University Health Network, Toronto, Canada (M.T.).
4. Department of Neuroradiology, University Hospital Basel, Switzerland (J.M.O.).