# Measurement of the frequency dependent phase velocity and attenuation from the Fourier description of shear wave propagation: Addressing geometric spreading arising from spatially asymmetric Gaussian excitations

Conference Paper

© 2015 IEEE. Observations of shear wave propagation in a viscoelastic (VE) tissue are typically analyzed by assuming the wave is described as a plane wave, or as the asymptotic form of a wave expanding radially from a cylindrically symmetric source. In this study we present an exact expression for the two dimensional Fourier transform (2D-FT) description of shear wave propagation in a VE material following an asymmetric Gaussian excitation. This expression is used to evaluate the bias in 2D-FT measurements obtained using the plane or cylindrical wave assumptions. A wide range of biases are observed depending on specific values of frequency and aspect ratio R of the source asymmetry. These biases can be reduced significantly by weighting the shear wave signal in the spatial domain to correct for the geometric spreading of the shear wavefront using a factor of x p . The optimal weighting power p is found to be near the theoretical value of 0.5 for the case of a cylindrical source with R = 1, and decreases for asymmetric sources with R > 1.

### Full Text

### Duke Authors

### Cited Authors

- Rouze, NC; Palmeri, ML; Nightingale, KR

### Published Date

- November 13, 2015

### Published In

- 2015 IEEE International Ultrasonics Symposium, IUS 2015

### International Standard Book Number 13 (ISBN-13)

- 9781479981823

### Digital Object Identifier (DOI)

- 10.1109/ULTSYM.2015.0199

### Citation Source

- Scopus