[1] St Michaels Hosp, Div Diagnost & Therapeut Neuroradiol, Dept Med Imaging, Toronto, ON, Canada
[2] Univ Toronto, Dept Med Imaging, Toronto, ON, Canada
[3] Univ Med Ctr Hamburg Eppendorf, Dept Diagnost & Intervent Neuroradiol, Hamburg, Germany
[4] Harvard Med Sch, Brigham & Womens Hosp, Dept Radiol, Boston, MA 02115 USA
[5] Harvard Med Sch, Massachusetts Gen Hosp, Dept Radiol, Boston, MA 02115 USA
[6] NeuroSpine Surg Res Grp NSURG, Sydney, NSW, Australia
[7] Prince Wales Private Hosp, Sydney, NSW, Australia
[8] Univ Toronto, Dept Surg, Div Neurosurg, St Michaels Hosp, Toronto, ON, Canada