Global approach for transient shear wave inversion based on the adjoint method: a comprehensive 2D simulation study. Arnal, B, Pinton, G, Garapon, P, Pernot, M, Fink, M, & Tanter, M Physics in Medicine and Biology, 58(19):6765–6778, October, 2013.
Global approach for transient shear wave inversion based on the adjoint method: a comprehensive 2D simulation study [link]Paper  doi  abstract   bibtex   
Shear wave imaging (SWI) maps soft tissue elasticity by measuring shear wave propagation with ultrafast ultrasound acquisitions (10 000 frames s−1). This spatiotemporal data can be used as an input for an inverse problem that determines a shear modulus map. Common inversion methods are local: the shear modulus at each point is calculated based on the values of its neighbour (e.g. time-of-flight, wave equation inversion). However, these approaches are sensitive to the information loss such as noise or the lack of the backscattered signal. In this paper, we evaluate the benefits of a global approach for elasticity inversion using a least-squares formulation, which is derived from full waveform inversion in geophysics known as the adjoint method. We simulate an acoustic waveform in a medium with a soft and a hard lesion. For this initial application, full elastic propagation and viscosity are ignored. We demonstrate that the reconstruction of the shear modulus map is robust with a non-uniform background or in the presence of noise with regularization. Compared to regular local inversions, the global approach leads to an increase of contrast (∼+3 dB) and a decrease of the quantification error (∼+2%). We demonstrate that the inversion is reliable in the case when there is no signal measured within the inclusions like hypoechoic lesions which could have an impact on medical diagnosis.
@article{arnal_global_2013,
	title = {Global approach for transient shear wave inversion based on the adjoint method: a comprehensive {2D} simulation study},
	volume = {58},
	issn = {0031-9155, 1361-6560},
	shorttitle = {Global approach for transient shear wave inversion based on the adjoint method},
	url = {https://iopscience.iop.org/article/10.1088/0031-9155/58/19/6765},
	doi = {10.1088/0031-9155/58/19/6765},
	abstract = {Shear wave imaging (SWI) maps soft tissue elasticity by measuring shear wave propagation with ultrafast ultrasound acquisitions (10 000 frames s−1). This spatiotemporal data can be used as an input for an inverse problem that determines a shear modulus map. Common inversion methods are local: the shear modulus at each point is calculated based on the values of its neighbour (e.g. time-of-flight, wave equation inversion). However, these approaches are sensitive to the information loss such as noise or the lack of the backscattered signal. In this paper, we evaluate the benefits of a global approach for elasticity inversion using a least-squares formulation, which is derived from full waveform inversion in geophysics known as the adjoint method. We simulate an acoustic waveform in a medium with a soft and a hard lesion. For this initial application, full elastic propagation and viscosity are ignored. We demonstrate that the reconstruction of the shear modulus map is robust with a non-uniform background or in the presence of noise with regularization. Compared to regular local inversions, the global approach leads to an increase of contrast (∼+3 dB) and a decrease of the quantification error (∼+2\%). We demonstrate that the inversion is reliable in the case when there is no signal measured within the inclusions like hypoechoic lesions which could have an impact on medical diagnosis.},
	language = {en},
	number = {19},
	urldate = {2023-04-12},
	journal = {Physics in Medicine and Biology},
	author = {Arnal, B and Pinton, G and Garapon, P and Pernot, M and Fink, M and Tanter, M},
	month = oct,
	year = {2013},
	pages = {6765--6778},
}

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