Shear wave speed measurement bias in a viscoelastic phantom across six ultrasound elastography systems: a comparative study with transient elastography and magnetic resonance elastography

Riwa Kishimoto,Mikio Suga,Kei Konno,Tsuyoshi Shiina,Masahiro Yoshida,Takayuki Obata,Tadashi Yamaguchi,Makoto Yamakawa,Hiroyuki Hachiya,Masashi Usumura,Hiroko Iijima

doi:10.1007/s10396-022-01190-x

Abstract

PurposeTo quantify the bias of shear wave speed (SWS) measurements in a viscoelastic phantom across six different ultrasound (US) systems and to compare the SWS with those from transient elastography (TE) and magnetic resonance elastography (MRE).MethodsA viscoelastic phantom of stiffness representing fibrotic liver or healthy thyroid was measured with nine (linear probe) and 10 (convex probe) modes of six different US-based shear wave elastography (SWE) systems using linear and convex probes. SWS measurements of three regions of interest were repeated thrice at two focal depths, coupling the probe to the phantom using a jig. An MRE system using three motion-encoding gradient frequencies of 60, 90, and 120 Hz and TE were also used to measure the stiffness of the phantom.ResultsThe SWS from different SWE systems had mean coefficients of variation of 9.0–9.2% and 5.4–5.6% with linear and convex probes, respectively, in viscoelastic phantom measurement. The focal depth was a less significant source of SWS variability than the system. The total average SWS obtained with US-SWE systems was 19.9% higher than that obtained with MRE at 60 Hz, which is commonly used in clinical practice, and 31.5% higher than that obtained with TE using the M probe.ConclusionsDespite the measurement biases associated with the SWE systems, biases were not necessarily consistent, and they changed with the probes used and depth measured. The SWS of the viscoelastic phantom obtained using different modalities increased according to the shear wave frequency used.

Highlights

Quantitative elastography has been widely used to evaluate liver fibrosis or differentiate malignant from benign lesions in various organs
The median and interquartile range (IQR) of the shear wave speed (SWS) obtained from the shear wave elastography (SWE) systems, transient elastography (TE), and magnetic resonance elastography (MRE) are summarized in Fig. 4 and Fig. 5
Among the three different modalities, the SWS obtained with US-based SWE (US-SWE) was the highest, followed by the SWS with MRE, which was higher for higher frequencies among the three MEG frequencies, and the SWS with TE was the lowest

Summary

Introduction

Quantitative elastography has been widely used to evaluate liver fibrosis or differentiate malignant from benign lesions in various organs. Journal of Medical Ultrasonics gold standard for the measurement of liver stiffness, shear wave elastography (SWE), including point SWE (pSWE) and two-dimensional color-coded SWE (2DSWE), which can be performed with a standard ultrasonography device, is more often performed clinically to evaluate the stiffness of various organs other than the liver. Many studies have evaluated the diagnostic performance of US-based SWE (US-SWE) technology for the assessment of liver fibrosis or tumor malignancy and showed that US-SWE is a valid imaging biomarker for detection and, to some degree, staging of fibrosis [7] and differentiating between malignant and benign tumors [8, 9]. The major factor that causes bias is that the method of setting the region of interest (ROI) and the conditions for applying push pulses in SWS measurement vary among different SWE systems or among the software versions even in the same system

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