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Shear wave (SW) propagation in viscoelastic materials is characterized by a complex, frequency-dependent shear modulus μ(f). Measurements of μ(f) typically require Fourier transform techniques to decompose an observed SW signal into discrete frequency components and two independent measurements such as the phase velocity c(f) and attenuation α(f) to determine the real and imaginary parts of μ(f).
We are studying shear wave speed (SWS) as a biomarker to detect abnormal cervical softening that could lead to spontaneous preterm birth. Elucidating factors affecting the stiffness of the in vivo non-pregnant (NP) cervix is the first step to understand the pregnant cervix. Animal models with anatomy and physiology akin to humans, such as the Rhesus macaque, can help achieve this task. Here we investigate...
This study describes a new method to determine the stiffness µ0 and viscosity η of viscoelastic materials by observing shear wave propagation following localized, impulsive excitations and measuring the group shear wave speeds Vdisp and Vvel determined using the shear wave displacement and velocity signals, respectively. The stiffness and viscosity are found by analytically solving the equation of...
Acoustic radiation force impulse (ARFI) based elasticity imaging methods have been under development for the past 15 years, and both qualitative on-axis (ARFI imaging) and quantitative shear wave speed (SWEI) methods have been introduced into the commercial market. On-axis methods employ less processing and provide higher spatial resolution, whereas SWEI methods employ reconstruction algorithms that...
A 2D matrix array is used to monitor acoustic radiation force impulse (ARFI) induced shear wave propagation in 3D in excised canine muscle. From a single acquisition, both the shear wave phase and group velocity can be calculated within a plane of symmetry to estimate the shear wave speed (SWS) along and across the fibers, as well as the fiber orientation in 3D. The true fiber orientation found using...
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