1. NIH Resource Center for Medical Ultrasonic Transducer Technology, Department of Biomedical Engineering, University of Southern California, Los Angeles, California 90089, USA
2. Department of Medical Biotechnology, Dongguk University, Seoul, South Korea
3. Department of Information and Communication Engineering, Daegu Gyeongbuk Institute of Science & Technology, Daegu, South Korea
4. Department of Electronic Engineering, Kwangwoon University, Seoul, South Korea