Research of the nonlinear interaction of an acoustic wave with biological tissues for the purposes of acoustic elastography

The purpose of the research is investigation of the parameters of nonlinear interaction of low-frequency acoustic radiation with biological tissues to improve the accuracy of determining structural changes in organs and tissues by elastography. Methods. Improving the accuracy of determining the degree and nature of structural changes in human organs and tissues is an urgent task today. The use of nonlinear effects of the interaction of powerful low-frequency acoustic radiation with biological tissues will allow obtaining new information characteristics, as well as improving the accuracy of differentiation of various degrees of structural changes in tissues and organs at the initial stages of diseases. In the framework of this work, the relationship between the viscoelastic and nonlinear characteristics of biological media and the processes of propagation of elastic transverse waves in them is considered. The physical foundations of the processes of formation and propagation of harmonic components of a transverse acoustic wave, as well as the change in its ratio N to the fundamental frequency wave, are also considered. Results. The results of mathematical modeling of the processes of changing the correlation between the amplitude of the fundamental frequency wave and the third harmonic formed in the medium due to the nonlinearity of the interaction of acoustic radiation with biological tissues are obtained. The results were the graphs of the dependence of the change in N with distance for liver tissues at various stages of fibrosis and fatty hepatosis. Conclusion. The obtained dependences allow us to conclude that the use of nonlinear effects of the interaction of low-frequency acoustic radiation with biological tissues will improve the quality of diagnostics of structural changes in organs and tissues in the early stages of diseases, when standard linear methods are less informative.