* Professor, ∥ Master Student, Institute of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan. † Associate Professor, # Professor, National Institutes of Health Resource Center on Medical Ultrasonic Transducer Technology, Department of Biomedical Engineering, University of Southern California, Los Angeles, California. ‡ Professor, Department of Anesthesiology, University of Colorado Health Sciences Center, Aurora, Colorado. § Associate Professor, ** Assistant Professor, Department of Anesthesiology, Taipei Veterans General Hospital and School of Medicine, National Yang-Ming University.