Original Contribution
Assessing Liver Stiffness by 2-D Shear Wave Elastography in a Healthy Cohort

https://doi.org/10.1016/j.ultrasmedbio.2017.10.013Get rights and content

Abstract

The aim of this study was to assess the normal ranges of liver stiffness measurements (LSMs) in participants with healthy livers, using General Electric 2-D shear wave elastography (2-D-SWE-GE) compared with transient elastography (TE). We included 80 participants with healthy livers and without known liver disease, in whom liver stiffness was evaluated in the same session using two elastographic methods, TE and 2-D-SWE-GE. Reliable LSMs were defined for TE as the median of 10 measurements with a success rate of ≥60% and an interquartile range (IQR) < 30%, and for 2-D-SWE-GE, as the median of 10 measurements acquired in a homogenous area and an IQR < 30%. Participants with LSMs > 6.5 kPa by TE were excluded. Reliable LSMs were obtained in 79 participants (98.7%) by means of 2-D-SWE-GE and in 80 participants (100%) by means of TE (p = 0.9). The mean LSM obtained by 2-D-SWE-GE in our cohort of participants with healthy livers was 5.1 ± 1.3 kPa, which was significantly higher than the LSM assessed by TE (4.3 ± 0.9 kPa, p < 0.0001). In 2-D SWE-GE, mean LSMs were significantly higher for men than for women, 5.9 ± 1.2 kPa versus 4.7 ± 1.2 kPa (p = 0.0005). In conclusion, 2-D-SWE-GE has very good feasibility (98.7%) in healthy persons. The mean LSM determined by 2-D-SWE-GE in healthy participants was 5.1 ± 1.3 kPa. LSMs obtained by means of 2-D-SWE-GE were higher than those obtained by TE in participants with healthy livers.

Introduction

In recent years, several non-invasive methods for liver fibrosis evaluation have been introduced. These include biological tests (Castera et al. 2015) and elastographic methods (ultrasound-based elastography and magnetic resonance elastography).

Ultrasound-based elastography methods have been widely assessed for liver fibrosis in clinical practice. The European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) and the World Federation of Societies for Ultrasound in Medicine and Biology (WFUMB) have published guidelines and recommendations that describe these technologies and provide recommendations for their clinical use. According to these guidelines (Bamber et al, 2013, Cosgrove et al, 2013, Dietrich et al, 2017, Ferraioli et al, 2015), the ultrasound-based elastographic methods are divided into strain/displacement elastography and shear wave elastography (SWE) techniques. The latter include transient elastography (TE), point SWE (Virtual Touch Quantification [VTQ] and ElastPQ) and real-time SWE (including 2-D SWE and 3-D SWE). TE (Fibroscan, Echosens, Paris, France) is the older method and has been well studied with several meta-analyses published in this regard (Chon et al, 2012, Friedrich-Rust et al, 2008, Tsochatzis et al, 2011). Furthermore, several articles and meta-analyses have been published regarding point SWE using VTQ (Siemens) (Bota et al, 2013, Friedrich-Rust et al, 2012, Nierhoff et al, 2013) and 2-D SWE using the Aixplorer system (SuperSonic Imagine [SSI], Aix en Provence, France) (Ferraioli et al, 2012a, Ferraioli et al, 2012b, Herrmann et al, 2017 March 31, Leung et al, 2013, Sporea et al, 2014a). For other manufacturers who have launched SWE systems, the published data are still scarce. These include ElastPQ (Philips) (Ferraioli et al. 2014) and 2-D SWE-GE (2-D-SWE from General Electric) (Bende et al. 2017), among others.

Two-dimensional SWE is an imaging method that quantifies the elasticity of tissue by measuring the speed of shear waves induced in the tissue by acoustic push pulses, generating 2-D quantitative images of shear-wave speed. Two-dimensional SWE-GE displays 2-D color images of shear wave speed in a region of interest (ROI), which is overlaid on top of a B-mode image. The ROI can be adjusted in size and position, and the tissue stiffness can be obtained at any location within the ROI, as shear wave speed (m/s), or converted to Young's modulus (kPa). This differs from point SWE modules, which measure the average stiffness within a ROI without displaying a color image in the ROI representing the tissue stiffness.

To recognize pathologic LS measurements it is essential to establish the ranges of liver stiffness measurements (LSMs) in healthy livers and their normal variability. It is also important to determine whether LSMs change with gender, age and the method applied or factors associated with failure to obtain valid measurements of LS performed by 2-D-SWE-GE.

The aim of this study was to assess the normal ranges of LSMs in participants with healthy livers using 2-D SWE-GE, with TE as the reference method, and to determine the effects of gender, age and body mass index (BMI) on LSMs.

Section snippets

Methods

This prospective study was performed between November 2016 and February 2017 in the Department of Gastroenterology and Hepatology of the University Hospital of Timisoara.

The study population (Fig. 1) comprised 80 participants with healthy livers, both patients and staff members. Staff members (n = 34) were eligible for inclusion if they had no history of liver disease, had a normal abdominal ultrasound examination and previously tested negative for hepatitis B/C virus. Participants with

Results

Our study population consisted of 80 participants without known liver disease; 57.5% of these were hospitalized patients and the remaining 42.5% were staff members. Valid measurements were obtained by 2-D-SWE-GE in 79 participants (98.7%) and by TE in 80 participants (100%) (p = 0.9), using the M probe in 72 (90%) and the XL probe in 8 (10%). In one participant (1.2%) we could not obtain valid 2-D-SWE-GE measurements because of an inability to suspend breathing. Thus, 79 participants with valid

Discussion

Two-dimensional GE-SWE has recently been introduced into clinical practice, and published data on clinical application of the method are limited. To our knowledge, our study is the first to evaluate LSM in people with healthy livers using 2-D-SWE-GE. A study performed on liver fibrosis phantoms reported excellent inter-observer correlation in vitro (Mulabecirovic et al. 2016), and another study found that for the evaluation of liver fibrosis in a mixed cohort, 2-D-SWE-GE had areas under the

Conclusions

Two-dimensional SWE-GE had excellent feasibility (98.7%) when used for LSM in a cohort of people with healthy livers. The mean LSM determined by 2-D-SWE-GE in participants with healthy livers was 5.1 ± 1.3 kPa. Age > 40 y, but not gender or BMI > 30, was associated with significantly higher LSMs in this study. The mean LSM obtained in participants with healthy livers using 2-D-SWE-GE was significantly higher than that obtained using TE.

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