Three-Dimensional Mapping of Shear Wave Velocity in Human Tendon: A Proof of Concept Study.

Tobias Götschi,Jörg Spörri,Jess G Snedeker,Jonas Hanimann,Martino V Franchi,Nicole Schulz

doi:10.3390/s21051655

Abstract

Ultrasound-based shear wave elastography (SWE) provides the means to quantify tissue mechanical properties in vivo and has proven valuable in detecting degenerative processes in tendons. Its current mode of use is for two-dimensional rendering measurements, which are highly position-dependent. We therefore propose an approach to create a volumetric reconstruction of the mechano-acoustic properties of a structure of interest based on optically tracking the ultrasound probe during free-hand measurement sweeps. In the current work, we aimed (1) to assess the technical feasibility of the three-dimensional mapping of unidirectional shear wave velocity (SWV), (2) to evaluate the possible artefacts associated with hand-held image acquisition, (3) to investigate the reproducibility of the proposed technique, and (4) to study the potential of this method in detecting local adaptations in a longitudinal study setting. Operative and technical feasibility as well as potential artefacts associated with hand-held image acquisition were studied on a synthetic phantom containing discrete targets of known mechanical properties. Measurement reproducibility was assessed based on inter-day and inter-reader scans of the patellar, Achilles, and supraspinatus tendon of ten healthy volunteers and was compared to traditional two-dimensional image acquisition. The potential of this method in detecting local adaptations was studied by testing the effect of short-term voluntary isometric loading history on SWV along the tendon long axis. The suggested approach was technically feasible and reproducible, with a moderate to very good reliability and a standard error of measurement in the range of 0.300–0.591 m/s for the three assessed tendons at the two test-retest modalities. We found a consistent variation in SWV along the longitudinal axis of each tendon, and isometric loading resulted in regional increases in SWV in the patellar and Achilles tendons. The proposed method outperforms traditional two-dimensional measurement with regards to reproducibility and may prove valuable in the objective assessment of pathological tendon changes.

Highlights

This article is an open access articleTendon-related complaints, such as tendinopathy, are common in athletes, workers, and the general population [1], with the patellar, Achilles, and supraspinatus tendons being among the most frequently affected [2]
We propose a free-hand 3D ultrasound approach based on optical probe tracking on a shear wave elastography (SWE)-capable US device in order to obtain a 3D mapping of unidirectional shear wave velocity of human tendons in vivo, hereafter called 3D
The aims of the study were: (1) to assess the technical feasibility and validity of 3D SWVM by scanning an elastography tissue phantom and validating the acquired data with the reference values of the substructures in the phantom provided by the manufacturer; (2) to evaluate potential artefacts caused by out-of-plane transducer motion during image acquisition at varying transducer speeds; (3) to investigate the inter-operator- and inter-day reproducibility of 3D SWVM in patellar, supraspinatus, and Achilles tendons compared to traditional 2D SWVM; and (4) to assess the effect of isometric loading on local tendon

Summary

Introduction

Tendon-related complaints, such as tendinopathy, are common in athletes, workers, and the general population [1], with the patellar, Achilles, and supraspinatus tendons being among the most frequently affected [2]. Quantitative assessments of the elastic properties of tendon structures have proven valuable in identifying pathologic and traumatic conditions [3]. Degenerative processes of such conditions include an increase in collagen type III fibers, fibrocartilaginous changes caused by an upregulated production of glycosaminoglycans (GAGs), tenocyte rounding and proliferation, and neovascularization [4,5,6,7]. As a consequence of these adaptations, the stiffness of pathological tendons is reduced [10,11,12], favoring traumatic tendon injuries such as ruptures [13,14]

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