1. Department of Radiology, Cambridge University Hospitals NHS Foundation Trust, Cambridge CB2 0QQ, UK
2. University of Alberta, Edmonton, AB, Canada T6G 2B7
3. University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, P.O. Box 218, Cambridge CB2 0QQ, UK
4. Division of Gastroenterology & Hepatology, Cambridge University Hospitals NHS Foundation Trust, Cambridge CB2 0QQ, UK