1. CAS Key Laboratory for Biomedical Effects of Nanomaterials and NanosafetyInstitute of High Energy Physics and National Center for Nanosciences and TechnologyChinese Academy of Sciences Beijing 100049 China
2. Department of Medical ImagingShanxi Medical University Taiyuan Shanxi 030001 China
3. College of Materials Science and Optoelectronic TechnologyUniversity of Chinese Academy of Sciences Beijing 100049 China
4. Engineering Research Center of Molecular and Neuro Imaging of Ministry of EducationSchool of Life Science and TechnologyXidian University Xi'an Shaanxi 710126 China