Nonlinearity parameter imaging in the frequency domain
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 , 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.
Cite
@article{arxiv.2303.09796,
title = {Nonlinearity parameter imaging in the frequency domain},
author = {Barbara Kaltenbacher and William Rundell},
journal= {arXiv preprint arXiv:2303.09796},
year = {2023}
}