Abstract (Invited)

Nonlinear Imaging Techniques in Diagnostic Ultrasound

M.A.Averkiou (Philips Ultrasound/ATL, Bothell, WA, USA)

e-mail: mike.averkiou@philips.com

In the recent years the interest on nonlinear acoustics has dramatically increased in diagnostic ultrasound. There are two main areas of nonlinear imaging: ultrasound contrast microbubble (contrast agents) imaging and tissue harmonic imaging. Although similar approaches are used in both of these areas, they are very different in that contrast imaging is based on the nonlinear scattering from resonant microbubbles whereas tissue harmonic imaging is based on the nonlinear propagation of sound in tissue. In contrast imaging there are two approaches: high amplitude (mechanical index.MI) that causes quick bubble destruction and very broadband signals, and low amplitude (MI) for stable harmonic oscillations without destruction. The use of low MI.s for non-destructive imaging is challenging because it tries to generate nonlinear signals with extremely low excitations. In tissue harmonic imaging where high MI.s are always used, the efforts in the recent years were concentrated in broadband techniques like pulse inversion and in ways of improving beamforming to enhance harmonic generation. Simple physical explanations and clinical examples will be used in this presentation to demonstrate the nonlinear imaging techniques for both contrast microbubbles and tissues.

Section : 5