1. Department of Neurosurgery, Hannover Medical School, Hannover, Germany;
2. Department of Neurosurgery, Hospital Merheim of the Clinics Cologne, University of Witten/Herdecke, Witten, Germany;
3. Department of Radiation Oncology, Hannover Medical School, Hannover, Germany;
4. Institute for Diagnostic and Interventional Neuroradiology, Hannover Medical School, Hannover, Germany