1. Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, China
2. Department of Ultrasound, Peking University Third Hospital, Beijing 100191, China
3. Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
4. Department of Bioengineering, College of Engineering, Rice University, Houston, Texas 77005, United States