1. Tissue harmonic imaging: why does it work?;Thomas;J Am Soc Echocardiogr,1998
2. Hwang J, Hope-Simpson D. Ultrasonic diagnostic imaging with harmonic contrast agents. January 13, 1998; U.S. patent 5, 706, 819.
3. Chapman CS, Lazenby JC. Ultrasound imaging system employing phase inversion subtraction to enhance the image. May 27, 1997; U.S. Patent 5, 632, 277.
4. Real-time contrast echo assessment of myocardial perfusion at low emission power: first experimental and clinical results using power pulse inversion imaging;Tiemann;Echocardiography,1999
5. Napolitano DJ, Cole CR, Holley GL. Diagnostic ultrasound imaging method and system with improved frame rate. February 27, 2001; U.S. Patent 6, 193, 663.