1 Centre Hospitalier de l'Université de Montréal (CHUM), Notre-Dame Hospital, Department of Radiology, Montreal, Quebec, Canada. Electronic address: jean.raymond@umontreal.ca.
2 Centre Hospitalier de l'Université de Montréal (CHUM), Notre-Dame Hospital, Department of Radiology, Montreal, Quebec, Canada.
3 University of Alberta Hospital, Mackenzie Health Sciences Centre, Department of Surgery, Division of Neurosurgery, Edmonton, Alberta, Canada.