Abstract

Full Wave Ultrasonic Field and Temperature Simulations in Inhomogeneous Biological Tissue

F.P.Curra, S.G.Kargl, L.A.Crum (Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, USA)

e-mail: fcurra@apl.washington.edu

In order to simulate ultrasound propagation and subsequent thermal effects in biological media in which blood vessels and other structures may be present, a 3-dimensional model has been developed that eliminates the need for symmetry constraints. The model is based on the coupled solution of the full-wave nonlinear equation of sound in a lossy medium with the bioheat equation for temperature computation. It includes nonlinear acoustic propagation, an arbitrary frequency power law for attenuation, and is capable of treating material inhomogeneities. Unlike other models based on parabolic approximations, it is not restricted to near-axis solutions and can account for multiple reflections and backscattered fields. Numerical solutions are obtained by a pseudospectral method in the time domain applied to the first order system of the constitutive acoustic equations. Propagation losses are included and modeled by two independent relaxation processes. A finite difference time domain approach, couples the transfer of energy from the ultrasound beam to the medium to predict the temperature dynamics. Time varying, temperature dependent, material parameters are also easily included in the model [Work supported in part by DARPA].

Section : 1