1. Academic Department of Surgery, St Thomas' Hospital, London SE1 7EH, UK
2. Department of Interventional Radiology, St Thomas' Hospital, London SE1 7EH, UK
3. Department of Ultrasonic Angiology, Guys and St Thomas' Hospital Trust, London SE1 7EH, UK
4. Department of Anaesthetics, St Thomas' Hospital, London SE1 7EH, UK