Numerical simulations of heating patterns and tissue temperatureresponse due to high-intensity focused ultrasound

摘要

The results of this paper show-for an existing high intensity,nfocused ultrasound (HIFU) transducer-the importance of nonlinear effectsnon the space/time properties of wave propagation and heat generation innperfused liver models when a blood vessel also might be present. Thesensimulations are based on the nonlinear parabolic equation for soundnpropagation and the bio-heat equation for temperature generation. Thenuse of high initial pressure in HIFU transducers in combination with thenphysical characteristics of biological tissue induces shock formationnduring the propagation of a therapeutic ultrasound wave. The inducednshock directly affects the rate at which heat is absorbed by tissue atnthe focus without significant influence on the magnitude and spatialndistribution of the energy being delivered. When shocks form close tonthe focus, nonlinear enhancement of heating is confined in a smallnregion around the focus and generates a higher localized thermal impactnon the tissue than that predicted by linear theory. The presence of anblood vessel changes the spatial distribution of both the heating ratenand temperature