Shear wave elastography imaging of carotid plaques: feasible, reproducible and of clinical potential.

Kumar V Ramnarine,Timothy C Hartshorne,Sarah Nduwayo,Thompson G Robinson,James W Garrard,Baris Kanber

doi:10.1186/1476-7120-12-49

Abstract

BackgroundShear Wave Elastography (SWE) imaging is a novel ultrasound technique for quantifying tissue elasticity. Studies have demonstrated that SWE is able to differentiate between diseased and normal tissue in a wide range clinical applications. However its applicability to atherosclerotic carotid disease has not been established. The aim of this study was to assess the feasibility and potential clinical benefit of using SWE imaging for the assessment of carotid plaques.MethodsEighty-one patients (mean age 76 years, 51 male) underwent greyscale and SWE imaging. Elasticity was quantified by measuring mean Young’s Modulus (YM) within the plaque and within the vessel wall. Echogenicity was assessed using the Gray-Weale classification scale and the greyscale median (GSM).ResultsFifty four plaques with stenosis greater than 30% were assessed. Reproducibility of YM measurements, quantified by the inter-frame coefficient of variation, was 22% within the vessel wall and 19% within the carotid plaque. Correlation with percentage stenosis was significant for plaque YM (p = 0.003), but insignificant for plaque GSM (p = 0.46). Plaques associated with focal neurological symptoms had significantly lower mean YM than plaques in asymptomatic patients (62 kPa vs 88 kPa; p = 0.01). Logistic regression and Receiver Operating Characteristic (ROC) analysis showed improvements in sensitivity and specificity when percentage stenosis was combined with the YM (area under ROC = 0.78).ConclusionsOur study showed SWE is able to quantify carotid plaque elasticity and provide additional information that may be of clinical benefit to help identify the unstable carotid plaque.Electronic supplementary materialThe online version of this article (doi:10.1186/1476-7120-12-49) contains supplementary material, which is available to authorized users.

Highlights

Shear Wave Elastography (SWE) imaging is a novel ultrasound technique for quantifying tissue elasticity
Greyscale imaging demonstrates apparently large fibrous and calcified plaque corresponding to relatively high Young’s Modulus (YM) in the SWE image
Greyscale imaging demonstrates a predominately anechoic type 1 plaque on the posterior wall corresponding to relatively low YM in the SWE image

Summary

Introduction

Shear Wave Elastography (SWE) imaging is a novel ultrasound technique for quantifying tissue elasticity. Studies have demonstrated that SWE is able to differentiate between diseased and normal tissue in a wide range clinical applications. For a severe stenosis (≥70%), Shear Wave Elastography (SWE) is a novel imaging technique developed to assess tissue elasticity and to differentiate diseased tissue from normal tissue. Application of SWE for imaging carotid plaques is challenging as the carotid plaque is often small, of variable morphology, subject to arterial pulsatile motion, with heterogeneous surrounding tissue. Despite these challenges, we have previously shown that SWE estimates of YM using invitro vessel stenosis phantom models are feasible, and able to distinguish soft and hard regions with good reproducibility [7]. Our case study demonstrated the clinical application of SWE for imaging carotid plaques in comparison with the greyscale median (GSM) and histological assessment [6]

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