1. School of Mechatronics Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan 611731, China,
2. School of Mechatronics Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan 611731, China
3. Medical Systems Development Center, Toshiba Dalian Co. Ltd., Dalian 116600, P.R. China