Phase Velocity Estimation With Expanded Bandwidth in Viscoelastic Phantoms and Tissues

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Acoustics

Background:

• Ultrasound shear wave elastography (SWE) assesses soft tissue mechanical properties using acoustic radiation force (ARF) to generate shear waves.
• Tissue viscoelasticity is analyzed via shear wave phase velocity dispersion, but current methods have limitations in resolution, variance, and frequency bandwidth.
• Existing dispersion estimation techniques often reconstruct curves for a restricted frequency range.

Purpose of the Study:

• To introduce and evaluate a novel method for calculating shear wave elastography dispersion curves.
• To enhance the accuracy and frequency bandwidth of dispersion estimation in viscoelastic tissues.
• To compare the proposed method against established techniques for shear wave velocity estimation.

Main Methods:

• A novel method combining generalized Stockwell transformation and slant frequency-wavenumber analysis (GST-SFK) was developed for dispersion curve calculation.
• The GST-SFK method was validated using numerical phantom data, noisy shear wave motion data, and experimental data from tissue-mimicking phantoms, ex vivo porcine liver, and in vivo liver.
• Performance was compared against the two-dimensional Fourier transform (2D-FT) and eigenvector (EV) methods.

Main Results:

• The GST-SFK method demonstrated lower errors in dispersion curve estimation compared to 2D-FT and EV methods.
• GST-SFK achieved significantly wider frequency bandwidths (at least double) for phase velocity estimation.
• The method proved effective across numerical simulations and various experimental phantom and tissue measurements.

Conclusions:

• The proposed GST-SFK method offers a superior approach for calculating shear wave elastography dispersion curves.
• Its ability to provide more accurate estimates over a broader frequency range is crucial for in vivo tissue dispersion analysis.
• GST-SFK represents a significant advancement for evaluating the mechanical properties of biological tissues using ultrasound.