A PSF-Shape-Based Beamforming Strategy for Robust 2D Motion Estimation in Ultrafast Data

Anne Saris,Stein Fekkes,Maartje Nillesen,Hendrik Hansen,Chris De Korte

doi:10.3390/app8030429

Abstract

This paper presents a framework for motion estimation in ultrafast ultrasound data. It describes a novel approach for determining the sampling grid for ultrafast data based on the system’s point-spread-function (PSF). As a consequence, the cross-correlation functions (CCF) used in the speckle tracking (ST) algorithm will have circular-shaped peaks, which can be interpolated using a 2D interpolation method to estimate subsample displacements. Carotid artery wall motion and parabolic blood flow simulations together with rotating disk experiments using a Verasonics Vantage 256 are used for performance evaluation. Zero-degree plane wave data were acquired using an ATL L5-12 (fc = 9 MHz) transducer for a range of pulse repetition frequencies (PRFs), resulting in 0–600 µm inter-frame displacements. The proposed methodology was compared to data beamformed on a conventionally spaced grid, combined with the commonly used 1D parabolic interpolation. The PSF-shape-based beamforming grid combined with 2D cubic interpolation showed the most accurate and stable performance with respect to the full range of inter-frame displacements, both for the assessment of blood flow and vessel wall dynamics. The proposed methodology can be used as a protocolled way to beamform ultrafast data and obtain accurate estimates of tissue motion.

Highlights

Ultrasound imaging is often used to visualize and estimate motion in our body [1,2,3,4,5,6,7,8,9,10]
We investigate whether standardization of the shape, or sampling, of the peak combined with 2D cubic interpolation increases the accuracy and precision of multi-step Speckle tracking (ST)-based displacement estimation
The statistics were calculated while taking into account all simulated with N theangles

Summary

Introduction

Ultrasound imaging is often used to visualize and estimate motion in our body [1,2,3,4,5,6,7,8,9,10]. Stiff regions in breasts are often related to cancers [11,12], the assessment of local arterial deformation provides information about the atherosclerotic progression and vulnerability of lesions [13,14,15,16], increased blood velocities indicate the presence of a stenosis in the vessel [17,18,19], and infarcted myocardial tissue shows changed deformation patterns as compared to healthy tissue [20]. Speckle tracking (ST), first introduced by Trahey et al [21,22], is one of the motion estimation methods which is frequently utilized. Speckle patterns are tracked to find the displacement of the underlying tissue. The location of the best match defines the displacement of the kernel region and the displacement of the underlying

Methods

Results

Discussion

Conclusion