[1] Kings Coll London, Sch Biomed Engn & Imaging Sci, London, England
[2] Guys & St Thomas NHS Fdn Trust, NIHR Biomed Res Ctr, London, England
[3] Kings Coll London, London, England
[4] Kings Coll Hosp NHS Fdn Trust, Dept Neuroradiol, London, England
[5] Univ Hlth Network, Toronto Western Hosp, Dept Med Imaging, Div Neuroradiol, Toronto, ON, Canada
[6] Univ Hlth Network, Toronto Western Hosp, Dept Surg, Div Neurosurg, Toronto, ON, Canada