1. Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands, Department of Radiology, Maastricht University Hospital, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands, and Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, P.O. Box 616, 6229 ER Maastricht, The Netherlands