1. Department of Neurosurgery and Spine Surgery, University Hospital Essen, Essen, Germany
2. Institute for Medical Informatics, Biometry and Epidemiology, University Hospital Essen, Essen, Germany
3. Institute for Diagnostic and Interventional Radiology, Department of Neuroradiology, University Hospital Essen, Essen, Germany
4. Department of Radiotherapy, University Hospital Essen, Essen, Germany