1 The Third Affiliated Hospital of Southern Medical University, Guangzhou 510500, China.
2 Paul C. Lauterbur Research Center for Biomedical Imaging, Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.
3 Shenzhen Key Laboratory for Molecular Imaging, Shenzhen 518055, China.
4 Department of Physics, University of Vermont, Burlington, VT 05405, USA.