ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

4aPAb4. The propagation of ultrasonic waves through a bubbly liquid into tissue: A linear analysis.

Quan Qi

John G. Harris

Theor. Appl. Mech. UIUC, 216 Talbot Lab., 104 S. Wright St., Urbana, IL 61801

William D. O'Brien

Elec. Comput. Eng., UIUC, Urbana, IL 61801

The steady-state response induced by an ultrasonic wave in a structure comprised of two layers, a bubbly liquid, and a viscoelastic solid with a rigid boundary, is studied in the linear approximation. This structure models a steadily cavitating liquid in contact with tissue. The upper surface of the liquid is driven harmonically and models the source. The lower surface of the solid is rigid and models bone. Though the cavitation processes are nonlinear, the propagation is approximated as linear. The model of the bubbly liquid is a simple continuum one, supplemented by allowing for a distribution of different bubble radii and for damping of the oscillations of each bubble. The model contains three functions, the probability distribution describing the distribution of bubble radii, and two functions modeling the mechanical response of, respectively, the individual bubble and the tissue. Numerical examples are worked out by adapting data taken from various published sources to deduce the parameters of these functions. These examples permit an assessment of the overall attenuation of the structure, and of the magnitude of the pressure and particle velocity in the bubbly liquid, and of the traction and the particle displacement in the tissue. [Partial support from Arjo, Inc., Morton Grove, IL.]