1. Institute of Neuroscience and Medicine, INM-5: Nuclear Chemistry; Forschungszentrum Jülich GmbH; 52425 Jülich Germany
2. Institute of Radiochemistry and Experimental Molecular Imaging; University Clinic Cologne; Kerpener Str. 62 50937 Cologne Germany
3. Max Planck Institute for Metabolism Research; Gleueler Str. 50 50931 Cologne Germany