Numerical Simulation of High Intensity Focused Ultrasound (HIFU) Using a Fully Compressible Multiscale Model
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A fully compressible multiscale model for simulation of bubble enhanced High Intensity Focused Ultrasound (HIFU) is presented. The non-linear ultrasound field is modeled using compressible Navier-Stokes equations on a fixed grid, while the microbubbles are tracked as discrete singularities in a Lagrangian fashion. These two models are two-way coupled to each other such that both the acoustic field and the bubbles influence each other. The energy absorbed by the medium locally due to the focused ultrasound and bubble dynamics is then used to compute the temperature rise in the focal and surrounding regions by solving a heat transfer equation over the insonation time period. We first simulate the HIFU field without microbubbles and characterize the pressure and temperature fields and compare against available experiments. Experimental validation in the presence of microbubbles is then carried out to demonstrate the accuracy of the model. We then study the effect of the microbubbles on altering the temperature rise obtained in the focal region.