1. Department of Radiology, Division of Nuclear Medicine and Molecular ImagingMassachusetts General Hospital and Harvard Medical School 55 Fruit Street Boston MA 02114 USA
2. Shanghai Engineering Research Center of Molecular Therapeutics and New Drug DevelopmentSchool of Chemistry and Molecular EngineeringEast China Normal University 500 Dongchuan Road Shanghai 200241 China
3. Department of Physiology and PharmacologyWake Forest School of Medicine Winston Salem NC 27157 USA
4. Athinoula A. Martinos Center for Biomedical ImagingDepartment of RadiologyMassachusetts General Hospital and Harvard Medical School 55 Fruit Street Boston MA 02114 USA
5. Department of Chemistry and BiochemistryUniversity of Oklahoma Norman OK 73019 USA