Ultrasound stimulated vibro-acoustography

Vibro-acoustography is a method of imaging and measurement that uses ultrasound to produce radiation force to vibrate objects. The radiation force is concentrated laterally by focusing the ultrasound beam. The radiation force is limited in depth by intersecting two beams at different frequencies so that there is interference between the beams at the difference frequency only at their intersection. This results in a radiation stress of limited spatial extent on or within the object of interest. The resulting harmonic displacement of the object is detected by acoustic emission, ultrasound Doppler, or laser interferometery. The displacement is a complicated function of the object material parameters. However, significant images and measurements can be made with this arrangement. Vibro-acoustography can produce high resolution speckle free images of biologically relevant objects such as breast micro-calcification and vessel calcifications, heart valves, and normal arteries. Vibro-acoustography can also make spot measurements such as microbubble contrast agent concentration in vessels. Several examples of these results will be described.