1 Serviço de Neurorradiologia Hospital Beatriz Ângelo - Loures, Lisbon, Portugal; Serviço de Neurorradiologia Hospital Garcia de Orta- Almada, Portugal. Electronic address: ferrovilela@sapo.pt.
2 Division of Neuroradiology, Joint Department of Medical Imaging, Canada; Division of Neurosurgery, Department of Surgery, Canada; Toronto Western Hospital, University Health Network, Canada; University of Toronto, Canada.