1. Department for Experimental Molecular Imaging, University Clinic and Helmholtz Institute for Biomedical Engineering; RWTH - Aachen University; Pauwelsstrasse 20 52074 Aachen Germany
2. Matricel GmbH; Kaiserstraße 100 52134 Herzogenrath Germany
3. Department of Controlled Drug Delivery, MIRA Institute for Biomedical Engineering and Technical Medicine; University of Twente; PO Box 217 7500 AE Enschede The Netherlands