1. The Royal London Hospital, London, UK
2. Department of Clinical Neurosciences, Western General Hospital, Edinburgh, UK
3. Department of Interventional Neuroradiology, John Radcliffe Hospital, Oxford, UK
4. Department of Interventional Neuroradiology, University Hospitals Coventry and Warwickshire, Warwickshire, UK
5. Department of Interventional Neuroradiology, The Royal Victoria Hospital, Belfast, UK