Performance Assessment of Motion Tracking Methods in Ultrasound-based Shear Wave Elastography

Ultrasound elastography is a modality that is uniquely suited to augment conventional B-mode ultrasound for various clinical applications. Motion tracking plays a critically important role during image formation for ultrasound elastography. In this study, the accuracy of four motion tracking methods tailored for acoustic radiation force-based elastography (e.g. acoustic radiation force imaging, shear wave elastography) is compared. In these elastography methods, external mechanical excitation results in small tissue displacements (i.e. 5-10 micrometers). This paper compares four published motion tracking methods: a quadratic sub-sample estimation method, a coupled sub-sample estimation method, a 2-D spline-based estimator, and a 2-D autocorrelation-based motion estimator. Those four methods are evaluated using computer-simulated and tissue-mimicking phantom data. Based on our preliminary data, we find that the autocorrelation-based method is the preferred estimator without considering the lateral displacement. Overall, the spline-based estimator is superior to the other two competitors when both axial and lateral displacements are estimated. Since the spline-based estimation algorithm is considerably time-intensive, the coupled sub-sample estimation method becomes a practical alternative.