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Effects of nonlinearity on propagation through the skull

As an ultrasound wave propagates nonlinearly energy is transferred to higher frequencies where it is more strongly attenuated. Compared to soft tissue the skull has a strongly heterogeneous material parameters. We characterize with experiments and establish a numerical method that can describe the effects of the skull on the nonlinear components of ultrasonic wave propagation for application to high intensity focused ultrasound (HIFU) therapy in the brain.