1. Institute of Transfusion Medicine, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany, Max-Planck Institute of Colloids and Interfaces, MagneticFluids, Köpenicker Landstrasse 203, D-12437 Berlin, Germany D-14476 Golm/Potsdam, Germany, Neurologische Klinik und Poliklinik, Charité-Universitätsmedizin Berlin, Germany, and Department of Radiology, CVK, Charité-Universitätsmedizin Berlin, Germany