Modeling nonlinear acoustic wave fields in media with inhomogeneity in theattenuation and in the nonlinearity

Biomedical tissues usually show inhomogeneity in their acoustic mediumparameters. These inhomogeneities cause refraction and scattering of diagnosticand therapeutic ultrasound waves. A method that is able to model the effects ofinhomogeneity in the attenuation and in the nonlinearity is essential for thedesign of transducers for new ultrasound modalities and the development of novelultrasound applications. The Iterative Nonlinear Contrast Source (INCS) methodhas originally been designed for the accurate modeling of nonlinear acousticwave fields in homogeneous media. It considers the nonlinear term from theWestervelt equation as a distributed contrast source, and the correspondingintegral equation is solved using an iterative Neumann scheme. This paperpresents an extension of the INCS method that can handle inhomogeneity in theattenuation and in the coefficient of nonlinearity. Results are presented forthe one-dimensional case. These show that in this case the presented methodcorrectly predicts the effects related to nonlinear propagation and scatteringby inhomogeneities in the attenuation and the coefficient of non-linearity.