1. The National Hospital for Neurology & Neurosurgery, University College London Hospitals NHS Foundation Trust, London WC1N 3BG, UK
2. University College London Centre for Medical Imaging, London W1W 7TS, UK
3. Surgery and Cancer, Imperial College London, London W12 0BZ, UK
4. Charing Cross Hospital, Imperial College NHS Healthcare Trust, London W6 8RF, UK
5. Barnet Hospital, Royal Free London NHS Foundation Trust, London EN5 3DJ, UK
6. University College London Division of Surgery and Interventional Science, London WC1E 6BT, UK
7. Royal Preston Hospital, Lancashire Teaching Hospitals NHS Trust, Preston PR2 9HT, UK