1. Division of Anaesthesia, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom.
2. Section of Neurosurgery, Department of Surgery, University of Manitoba, Winnipeg, Manitoba, Canada.
3. Clinician Investigator Program, University of Manitoba, Winnipeg, Manitoba, Canada.
4. Section of Brain Physics, Division of Neurosurgery, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom.