Please use this identifier to cite or link to this item: https://doi.org/10.1016/j.ultras.2013.08.009
Title: Reconstructing 3-D maps of the local viscoelastic properties using a finite-amplitude modulated radiation force
Authors: Giannoula, A.
Cobbold, R.
Bezerianos, A. 
Keywords: FEM model
Inverse reconstruction
Radiation force
Shear waves
Issue Date: Feb-2014
Citation: Giannoula, A., Cobbold, R., Bezerianos, A. (2014-02). Reconstructing 3-D maps of the local viscoelastic properties using a finite-amplitude modulated radiation force. Ultrasonics 54 (2) : 563-575. ScholarBank@NUS Repository. https://doi.org/10.1016/j.ultras.2013.08.009
Abstract: A modulated acoustic radiation force, produced by two confocal tone-burst ultrasound beams of slightly different frequencies (i.e. 2.0 MHz ± Δf/2, where Δf is the difference frequency), can be used to remotely generate modulated low-frequency (Δf ≤ 500 Hz) shear waves in attenuating media. By appropriately selecting the duration of the two beams, the energy of the generated shear waves can be concentrated around the difference frequency (i.e., Δf ± Δf/2). In this manner, neither their amplitude nor their phase information is distorted by frequency-dependent effects, thereby, enabling a more accurate reconstruction of the viscoelastic properties. Assuming a Voigt viscoelastic model, this paper describes the use of a finiteelement- method model to simulate three-dimensional (3-D) shear-wave propagation in viscoelastic media containing a spherical inclusion. Nonlinear propagation is assumed for the two ultrasound beams, so that higher harmonics are developed in the force and shear spectrum. Finally, an inverse reconstruction algorithm is used to extract 3-D maps of the local shear modulus and viscosity from the simulated sheardisplacement fields based on the fundamental and second-harmonic component. The quality of the reconstructed maps is evaluated using the contrast between the inclusion and the background and the contrastto- noise ratio (CNR). It is shown that the shear modulus can be accurately reconstructed based on the fundamental component, such that the observed contrast deviates from the true contrast by a root-meansquare- error (RMSE) of only 0.38 and the CNR is greater than 30 dB. If the second-harmonic component is used, the RMSE becomes 1.54 and the corresponding CNR decreases by approximately 10-15 dB. The reconstructed shear viscosity maps based on the second harmonic are shown to be of higher quality than those based on the fundamental. The effects of noise are also investigated and a fusion operation between the two spectral components is applied to enhance the reconstruction quality. Finally, a modified shearwave spectroscopy technique, shown to be more robust to noise, is described for the estimation of the viscoelastic properties inside and outside the spherical inclusion under conditions of increased noise. © 2013 Elsevier B.V. All rights reserved.
Source Title: Ultrasonics
URI: http://scholarbank.nus.edu.sg/handle/10635/128728
ISSN: 0041624X
DOI: 10.1016/j.ultras.2013.08.009
Appears in Collections:Staff Publications

Show full item record
Files in This Item:
There are no files associated with this item.

SCOPUSTM   
Citations

2
checked on Dec 12, 2018

WEB OF SCIENCETM
Citations

1
checked on Dec 12, 2018

Page view(s)

17
checked on Oct 19, 2018

Google ScholarTM

Check

Altmetric


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.