1. Department of Radiology, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts 02115, Institute of Bioinorganic and Radiopharmaceutical Chemistry, Research-Center Rossendorf, Dresden, Germany, Department of Nuclear Medicine, University of Heidelberg, Heidelberg, Germany, Department of Inorganic Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Clinical and Experimental Medicine, University of Ferrara, Ferrara 44100, Italy