1. Department of Diagnostic and Interventional Radiology, Medical Faculty, University Hospital of Dusseldorf, D-40225 Dusseldorf, Germany
2. Department of Orthopedics and Trauma Surgery, Medical Faculty, University Hospital of Dusseldorf, D-40225 Dusseldorf, Germany
3. Department of Diagnostic and Interventional Radiology, University Hospital Aachen, D-52074 Aachen, Germany
4. Department of Diagnostic and Interventional Radiology, Medical Faculty, University Hospital of Tübingen, D-72076 Tübingen, Germany