1. Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072, China
2. NIH Resource Center for Medical Ultrasonic Transducer Technology and Department of Biomedical Engineering, University of Southern California, Los Angeles, California 90089, USA
3. Department of Bioengineering, School of Engineering and Applied Sciences, University of California, Los Angeles, California 90095, USA
4. Division of Cardiology, Department of Medicine, School of Medicine, University of California, Los Angeles, California 90095, USA