[1] Univ Munster, Dept Med B, D-48129 Munster, Germany
[2] Royal Free Hosp, Dept Diagnost Radiol, London NW3 2QG, England
[3] Univ Turin, Dept Radiol, Turin, Italy
[4] CHU Toulouse, Hop Rangueil, Dept Radiol, Toulouse, France
[5] Univ Catholique Louvain, St Luc Univ Hosp, Dept Radiol, B-1200 Brussels, Belgium
[6] Univ Munster, Dept Med Stat, D-48129 Munster, Germany