Mesh adaptation for pseudospectral ultrasound simulations

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Mesh adaptation for pseudospectral ultrasound simulations

Wise, Elliott Steven; (2018) Mesh adaptation for pseudospectral ultrasound simulations. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

High-intensity focussed ultrasound (HIFU) is an emerging cancer therapy that holds great promise, as it is minimially invasive, requires no ionising radiation, and can treat small volumes precisely. However, currently therapies are hindered by an inadequate capacity for treatment planning, as the interactions between the sound waves and tissue are complex and difficult to simulate. The Fourier pseudospectral method is one way of efficiently performing these simulations, as it can provide high accuracies with low computational costs. However, it is typically used with uniform computational meshes, wasting resolution in regions of the simulation where only low frequencies are present, and typically under-resolving the acoustic field in the focal region. This thesis addresses this problem in two ways: First, a bandwidth-based measure of the spatial resolution requirements for a model solution is developed and integrated into a moving mesh method. This allows spatially and temporally-varying resolution requirements to be met. Bandwidth-based meshes are shown to perform very well when compared with current mesh adaptation approaches. Second, a technique is presented for discretising arbitrary acoustic source distributions that does not rely on the source's region of support coinciding with the mesh. This not only allows sources to be represented with adaptive meshes, but greatly improves the accuracy of source discretisations for uniform meshes as well. These two contributions are of vital importance in the context of HIFU simulation, and can easily be applied to the many other problems for which the Fourier pseudospectral method is used.

Type:	Thesis (Doctoral)
Qualification:	Ph.D
Title:	Mesh adaptation for pseudospectral ultrasound simulations
Event:	UCL (University College London)
Open access status:	An open access version is available from UCL Discovery
Language:	English
Additional information:	Copyright © The Author 2018. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms.
UCL classification:	UCL UCL > Provost and Vice Provost Offices UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
URI:	https://discovery.ucl.ac.uk/id/eprint/10061936