1Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany, 2Department of Neurosurgery, University Hospital Essen, Essen, Germany, 3High Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany, 4Medical Physics in Radiology, German Cancer Research Center (dkfz), Heidelberg, Germany