ASA 126th Meeting Denver 1993 October 4-8

2pPA2. Absorption of finite-amplitude ultrasound in biomedical tissue.

Ping-Wah Li David T. Blackstock

Appl. Res. Labs., Univ. of Texas, Austin, TX 78713-8029

A theoretical investigation of the absorption of finite-amplitude ultrasound in biomedical tissue is reported. The tissue is modeled as a medium having multiple relaxation processes. A generalized Burgers equation, which includes the effects of nonlinearity and relaxation, is derived. Analytical and numerical solutions of this equation for a step shock, a periodic wave, and a temporal Gaussian pulse are presented. The results are used to calculate the finite-amplitude absorption coefficient and temperature rise in the tissue. It is found that nonlinear distortion causes the absorption and the temperature rise to be significantly higher than that for small-signal ultrasound. [Work supported by NIH, ONR, and ARL:UT IR&D.]