Physics Colloquium, November 14, 2006
Nonlinear ultrasonic imaging: a tool for probing the beating heart James G. Miller

Washington University, St. Louis, Missouri

The standard of care for imaging the hearts of patients is the use of echocardiography based on nonlinear ultrasound. The human heart is an inhomogeneous, anisotropic medium that exhibits uniaxial symmetry if viewed at the mid ventricular wall. The scattering of ultrasound resulting from the inhomogeneous nature of the heart enables echocardiographic imaging, which is a backscatter-based modality. Ultrasonic signals propagate in the heart with phase velocity and attenuation that conform to the local symmetry properties. Unfortunately, subtle variations in the material properties along the path to and from the heart result in phase and amplitude aberrations that significantly degrade images formed with linearly propagating ultrasound. Nonlinear ultrasound reduces the impact of these degrading effects. The basis for this significant improvement in echocardiographic image quality can be understood by an examination of the way in which initially sinusoidal finite amplitude waves distort as they propagate, promoting energy from the fundamental frequency to harmonics of that frequency.

Dr. Miller's Web Site

4:00 p.m., Physics Research Building (PRB), Room 1080

Reception at 3:45 p.m., Atrium, PRB