1. Department of Radiology and Bio-X Program, Stanford University, 1201 Welch Road, P087, Stanford, California 94305, United States
2. Beijing National Laboratory for Molecular Sciences (BNLMS), (The State Key Laboratory of Rare Earth Materials Chemistry and Applications), College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P.R. China
3. Department of Radiology, The Fourth Hospital of Harbin Medical University, Heilongjiang, 150001, P.R. China
4. Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health (NIH), Bethesda, Maryland 20892, United States