Quantitative Promise of Vibro-acoustography and Vibrometry

Friday, November 12, 2004 - 1:25pm - 2:25pm
Vincent 570
James Greenleaf (Mayo Clinic)
Vibro-acoustography is a method of imaging and measurement that uses ultrasound 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 cyclic radiation stress of limited spatial extent on or within the object of interest. The resulting harmonic displacement of the object is detected by its acoustic emission, with ultrasound Doppler measurement, with a laser interferometer or the resulting acoustic emission is detected with a hydrophone. The displacement is a complicated function of the object material parameters. However, significant low speckle and high contrast images and measurements can be made with this arrangement. Vibro-acoustography can produce images of biologically relevant objects such as breast microcalcification, vessel calcifications, heart valves, and normal arteries. In addition vibrations placed in specific geometrically shaped tissues such as arteries can be used to induce modal responses that can be used to solve for material properties. Specific examples of these results will be described.