1. Department of Biomedical Engineering, NIH Resource Center for Ultrasonic Transducer Technology, University of Southern California, Los Angeles, California 90089, USA
2. Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089, USA
3. Geospace Research, Inc., 525 South Douglas Street, Suite 290, El Segundo, California 90245, USA