Radiological Society of North America/Quantitative Imaging Biomarker Alliance Shear Wave Speed Bias Quantification in Elastic and Viscoelastic Phantoms

Abstract

Objectives To quantify the bias of shear wave speed (SWS) measurements between different commercial ultrasonic shear elasticity systems and a magnetic resonance elastography (MRE) system in elastic and viscoelastic phantoms. Methods Two elastic phantoms, representing healthy through fibrotic liver, were measured with 5 different ultrasound platforms, and 3 viscoelastic phantoms, representing healthy through fibrotic liver tissue, were measured with 12 different ultrasound platforms. Measurements were performed with different systems at different sites, at 3 focal depths, and with different appraisers. The SWS bias across the systems was quantified as a function of the system, site, focal depth, and appraiser. A single MRE research system was also used to characterize these phantoms using discrete frequencies from 60 to 500 Hz. Results The SWS from different systems had mean difference 95% confidence intervals of ±0.145 m/s (±9.6%) across both elastic phantoms and ± 0.340 m/s (±15.3%) across the viscoelastic phantoms. The focal depth and appraiser were less significant sources of SWS variability than the system and site. Magnetic resonance elastography best matched the ultrasonic SWS in the viscoelastic phantoms using a 140 Hz source but had a − 0.27 ± 0.027‐m/s (−12.2% ± 1.2%) bias when using the clinically implemented 60‐Hz vibration source. Conclusions Shear wave speed reconstruction across different manufacturer systems is more consistent in elastic than viscoelastic phantoms, with a mean difference bias of < ±10% in all cases. Magnetic resonance elastographic measurements in the elastic and viscoelastic phantoms best match the ultrasound systems with a 140‐Hz excitation but have a significant negative bias operating at 60 Hz. This study establishes a foundation for meaningful comparison of SWS measurements made with different platforms.

Full Characterization of in vivo Muscle as an Elastic, Incompressible, Transversely Isotropic Material Using Ultrasonic Rotational 3D Shear Wave Elasticity Imaging

“…A notable limitation of this work is that it neglects viscosity. Viscosity introduces dispersion and attenuation in shear wave elastography data, which has been shown to bias estimated parameters based upon group speeds [60]. We have observed some dispersion in vastus lateralis data, primarily across the fibers with less dispersion along the fibers [61], which is consistent with reports from the literature [45].…”

Sources of Variability in Shear Wave Speed and Dispersion Quantification with Ultrasound Elastography: A Phantom Study

“…2b). These values cover the range of depths relevant to liver assessment, consistent with similar studies analyzing depth-dependent biases (Chang et al 2013;Hall et al 2013;Wang et al 2014;Dhyani et al 2018;Palmeri et al 2021). For the third group of measurements, the acquisition box was fixed at 20 mm below the US probe, and the ROI was placed in the center of the box.…”

“…A decay in SWD can be caused only by frequency-dependent effects, that is, by effects that influence each phase velocity differently. As discussed, in viscoelastic media, attenuation depends on the frequency and lowers the SNR of higher-frequency components (Palmeri et al 2021). This may affect the estimations of high-frequency phase velocities (Deffieux et al 2009) and introduce biases in the computation of the dispersion slope.…”

“…The UL location was more robust to inaccurate coupling conditions. especially for higher-frequency components (Deffieux et al 2009;Palmeri et al 2021). If the variability in phase velocity estimations increases with frequency, the dispersion curve slope (SWD) may become very sensitive to noise-related errors.…”

Novel Uses of Ultrasound to Assess Kidney Mechanical Properties

“…Validation of mechanical properties against specific microstructural findings on histology and prognostic utility beyond common clinical tests (eGFR and proteinuria) are also necessary steps for establishing clinical utility. Reconciling the results from ultrasound-based methods implemented by different vendors is an important step as well as further exploring the role of evaluating the viscoelastic properties of the renal tissue 88 .…”