1. Laboratory of Stem Cell Biology, and Huaxi MR Research Center (HMRRC) Department of Radiology National Clinical Research Center for Geriatrics Functional and Molecular Imaging Key Laboratory of Sichuan Province West China Hospital Sichuan University Chengdu Chengdu 610041 P. R. China
2. School of Pharmacy Fujian Medical University Fuzhou 350122 China
3. Department of Radiology Southwest Hospital Third Military Medical University (Army Medical University) Chongqing 400038 China
4. Amgen Bioprocessing Centre Keck Graduate Institute Claremont CA 91711 USA