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arXiv · 2303.09796

Nonlinearity parameter imaging in the frequency domain

Barbara Kaltenbacher·William Rundell
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Abstract

Nonlinearity parameter tomography leads to the problem of identifying a coefficient in a nonlinear wave equation (such as the Westervelt equation) modeling ultrasound propagation. In this paper we transfer this into frequency domain, where the Westervelt equation gets replaced by a coupled system of Helmholtz equations with quadratic nonlinearities. For the case of the to-be-determined nonlinearity coefficient being a characteristic function of an unknown, not necessarily connected domain $D$, we devise and test a reconstruction algorithm based on weighted point source approximations combined with Newton's method. In a more abstract setting, convergence of a regularised Newton type method for this inverse problem is proven by verifying a range invariance condition of the forward operator and establishing injectivity of its linearisation.

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Barbara Kaltenbacher, William Rundell. 2023-03-17. Nonlinearity parameter imaging in the frequency domain. https://arxiv.org/abs/2303.09796

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