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