1. Department of Biomolecular Nanotechnology, MESA+ Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
2. Department of Medical Imaging, Radboud University Medical Center, Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
3. Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen,
P.O. Box 30.001, 9700 RB Groningen, The Netherlands