Incorporating Gradient Similarity for Robust Time Delay Estimation in Ultrasound Elastography

TL;DR

This paper introduces rGLUE, a robust ultrasound elastography method that combines amplitude and gradient similarity constraints to improve displacement estimation accuracy, especially in the presence of outliers.

Contribution

The authors propose a novel data term formulation using combined amplitude and gradient similarities with an adaptive weighting scheme for enhanced robustness in elastography.

Findings

rGLUE outperforms recent methods in SNR and CNR across datasets.

Achieves significant improvements in image quality metrics.

Validated on simulation, phantom, and in vivo data.

Abstract

Energy-based ultrasound elastography techniques minimize a regularized cost function consisting of data and continuity terms to obtain local displacement estimates based on the local time-delay estimation (TDE) between radio-frequency (RF) frames. The data term associated with the existing techniques takes only the amplitude similarity into account and hence is not sufficiently robust to the outlier samples present in the RF frames under consideration. This drawback creates noticeable artifacts in the strain image. To resolve this issue, we propose to formulate the data function as a linear combination of the amplitude and gradient similarity constraints. We estimate the adaptive weight concerning each similarity term following an iterative scheme. Finally, we optimize the non-linear cost function in an efficient manner to convert the problem to a sparse system of linear equations which are solved for millions of variables. We call our technique rGLUE: robust data term in GLobal Ultrasound Elastography. rGLUE has been validated using simulation, phantom, in vivo liver, and breast datasets. In all of our experiments, rGLUE substantially outperforms the recent elastography methods both visually and quantitatively. For simulated, phantom, and in vivo datasets, respectively, rGLUE achieves 107%, 18%, and 23% improvements of signal-to-noise ratio (SNR) and 61%, 19%, and 25% improvements of contrast-to-noise ratio (CNR) over GLUE, a recently-published elastography algorithm.