1 Molecular Imaging and Radiochemistry, Department of Nuclear Medicine, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany.
2 Department of Nuclear Medicine, Medical University Innsbruck, Innsbruck, Austria.
3 Department of Chemistry, University Oslo, Oslo, Norway.
4 Institute of Radiochemistry and Experimental Molecular Imaging, University Clinic Cologne and Max Planck Institute of Metabolic Research, Cologne, Germany.