Quasi-Static Elastography and Ultrasound Plane-Wave Imaging: The Effect of Beam-Forming Strategies on the Accuracy of Displacement Estimations

Gijs Hendriks,Chuan Chen,Chris de Korte,Hendrik Hansen

doi:10.3390/app8030319

Abstract

Quasi-static elastography is an ultrasound method which is widely used to assess displacements and strain in tissue by correlating ultrasound data at different levels of deformation. Ultrafast plane-wave imaging allows us to obtain ultrasound data at frame rates over 10 kHz, permitting the quantification and visualization of fast deformations. Currently, mainly three beam-forming strategies are used to reconstruct radio frequency (RF) data from plane-wave acquisitions: delay-and-sum (DaS), and Lu’s-fk and Stolt’s-fk operating in the temporal-spatial and Fourier spaces, respectively. However, the effect of these strategies on elastography is unknown. This study investigates the effect of these beam-forming strategies on the accuracy of displacement estimation in four transducers (L7-4, 12L4VF, L12-5, MS250) for various reconstruction line densities and apodization/filtering settings. A method was developed to assess the accuracy experimentally using displacement gradients obtained in a rotating phantom. A line density with multiple lines per pitch resulted in increased accuracy compared to one line per pitch for all transducers and strategies. The impact on displacement accuracy of apodization/filtering varied per transducer. Overall, Lu’s-fk beam-forming resulted in the most accurate displacement estimates. Although DaS in some cases provided similar results, Lu’s-fk is more computationally efficient, leading to the conclusion that Lu’s-fk is most optimal for plane wave ultrasound-based elastography.

Highlights

In 1991, Ophir et al [1] proposed a new ultrasound technique, quasi-static elastography, to visualize and quantify deformation of tissue to detect abnormalities
These artifacts were visible for all beam-forming strategies and line densities
We investigated the effect of different beam-forming strategies on the accuracy of displacement estimates in four different transducers (L7-4, 12L4VF, L12-5 and MS250)

Summary

Introduction

In 1991, Ophir et al [1] proposed a new ultrasound technique, quasi-static elastography, to visualize and quantify deformation of tissue to detect abnormalities (e.g., through the relatively stiffer breast and prostate tumors). In this technique, ultrasound radio frequency (RF) data are obtained prior to and after deformation of the target tissue. The position of the cross-correlation peak indicates the displacement of the template. To cope with relatively large displacements, coarse-to-fine cross-correlation methods were developed [2]. In coarse-to-fine cross-correlation, multi-iterative cross-correlation is executed

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