1. Department of Neurosurgery, University Hospital of Münster, Germany;
2. Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan;
3. Department of Neuroradiology, Clinic of Radiology and Nuclear Medicine, University Hospital Basel, Switzerland;
4. Department of Diagnostic and Interventional Neuroradiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;
5. Carl Zeiss Meditec AG, Oberkochen, Germany; and
6. University of British Columbia, Vancouver, British Columbia, Canada