1. From the Division of Neuroradiology, Department of Medical Imaging, University of Toronto, Toronto Western Hospital, Toronto, Ontario, Canada
2. The Service de Neuroradiologie Diagnostique et Thérapeutique, Hôpital de Bicetre, Le Kremlin-Bicetre; Paris, France
3. The Departments of Neuroradiology and Neurosurgery, University Hospital Aachen; Germany
4. The Department of Diagnostic Imaging, the Hospital for Sick Children, University of Toronto; Toronto, Ontario, Canada