1. Department of Neuroradiology, Hirslanden Clinic, Zurich, Switzerland
2. Department of Neuroradiology, University Hospital of Basel, Basel, Switzerland
3. Laboratory of Hemodynamics and Cardiovascular Technology, Federal Institute of Technology, Lausanne, Switzerland
4. Department of Neurosurgery, University of Vienna, Vienna, Austria
5. Department of Neuroradiology, University of Essen, Essen, Germany