[1] Guys & St Thomas Natl Hlth Serv Fdn Trust, Dept Radiol, London SE1 7EH, England
[2] Guys & St Thomas Natl Hlth Serv Fdn Trust, Dept Gen Surg, London SE1 7EH, England
[3] Guys & St Thomas Natl Hlth Serv Fdn Trust, Dept Gastroenterol, London SE1 7EH, England
[4] Guys & St Thomas Natl Hlth Serv Fdn Trust, Dept Dermatol, London SE1 7EH, England
[5] Kings Coll London, Div Imaging Sci & Biomed Engn, London, England