Evaluation of Robustness of Local Phase Velocity Imaging in Homogenous Tissue-Mimicking Phantoms

Shear wave elastography (SWE) is a method of evaluating mechanical properties of soft tissues. Most current implementations of SWE report the group velocity for shear wave velocity, which assumes an elastic, isotropic, homogenous and incompressible tissue. Local Phase Velocity Imaging (LPVI) is a novel method of phase velocity reconstruction that allows for accurate evaluation of shear wave velocity at specified frequencies. This method’s robustness was evaluated in 11 elastic and 8 viscoelastic phantoms using linear and curvilinear arrays. We acquired data with acoustic radiation force push beams with different focal depths and F-numbers and reconstructed phase velocity images over a wide range of frequencies. Regardless of phantom, push beam focal depth, and reconstruction frequency, using an F-number around 3.0 was found to produce the largest usable area in the phase velocity reconstructions. For elastic phantoms scanned with a linear array, the optimal focal depth, frequency range, and maximum region-of interest (ROI) were 20–30 mm, 100–400 Hz, and 2.70 cm(2), respectively. For viscoelastic phantoms scanned with a linear array, the optimal focal depth, frequency, and maximum ROI were 20–30 mm, 100–300 Hz, 1.54 cm(2), respectively. For the curvilinear array in the same phantoms; optimal focal depth, frequency range, and maximum ROIs were 45–60 mm, 100–400 Hz and 100–300 Hz, and 1.54 cm(2), respectively. Further work will be done to evaluate LPVI reconstructions from inclusion phantoms to simulate nonhomogeneous tissues. Additionally, LPVI will be evaluated in larger volume phantoms to account for wave reflection from the containers when using the curvilinear array.