1. Shenzhen Key Laboratory for Minimal Invasive Medical Technologies, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, P. R. China
2. Department of Physics, Tsinghua University, Beijing 100084, P. R. China
3. Shenzhen Sixth People's Hospital (Nanshan Hospital), Huazhong University of Science and Technology, Union Shenzhen Hospital, Shenzhen 518052, P. R. China