1. Department of Neurosurgery, Rheinische Friedrich-Wilhelms-University, Bonn, Germany and Institute for Surgical Research, Klinikum Großhadern, Ludwig-Maximilians-University, Munich, Germany.
2. Fraunhofer Institut für Biomedizinische Technik, St. Ingbert, Germany.
3. Institute for Surgical Research, Klinikum Großhadern, Ludwig-Maximilians-University, Munich, Germany.