1Radiology, University of Bonn, Bonn, Germany, 2MR and CT Contrast Media Research, Bayer Healthcare, Berlin, Germany, 3Innovative Technologies, Research Laboratories, Philips Technologie GmbH, Aachen, Germany, 4Department of Radiology, Neuroradiology, Sonography and Nuclear Medicine, Brüderkrankenhaus Trier, Trier, Germany