High intensity focussed ultrasound (HIFU) treatment planning with geometrical optics acoustics

Lead Research Organisation: University College London


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Description Two ray-based approaches to modelling nonlinear waves in acoustics:
- Uses a simple asymptotic expansion to simplify the general governing equations for acoustic waves. This produces rays, which move perpendicular to the wavefronts, that are the same as ones found for linear wave equation. The amplitude of the wave along each ray was found by solving nonlinear equation in one dimension. This model does not include diffraction thus an artificial sound speed is created to mimic diffraction using refraction of the rays. This model does not model the asymmetric behaviour of nonlinear focused waves such as in HIFU.
- Second method used a more complicated asymptotic expansion with more flexibility on the small parameter. This produced new nonlinear rays which depend upon the amplitude of the wave meaning waves will bend away from high pressure areas as desired. This model does not require any artificial sound speed however the strength of bending is not enough since again there is a lack of diffraction included in the model.
Both these methods have issues and inaccuracies but they both run quicker than other full wave solvers for linear and nonlinear waves.
Exploitation Route The funding is still active, so the work is being directly progressed to produce a model which incorporates the diffraction effects of waves and thus accurately model the acoustic wave from HIFU.
HIFU simulations take a long time to run, the current findings are quick to run but will be progressed to better model HIFU while keeping the speed increase.
Sectors Healthcare