1 Department of Diagnostic and Interventional Radiology, University Hospital Ulm, Albert-Einstein-Allee 23, 89081 Ulm, Germany.
2 Department of Diagnostic and Interventional Neuroradiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675 Munich, Germany.
3 TUM-Neuroimaging Center, Klinikum rechts der Isar, Technical University of Munich, 81675 Munich, Germany.
4 Department of Clinical Neurophysiology, Kuopio University Hospital, P.O. Box 100, 70029 KYS Kuopio, Finland.
5 Department of Applied Physics, University of Eastern Finland, 70210 Kuopio, Finland.