@article{91b6040901db4c359b3b4c53365f61f0,
title = "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.",
keywords = "Quantitative Imaging Biomarker Alliance, acoustic radiation force, elasticity, phantom, shear wave, viscoelasticity",
author = "Palmeri, \{Mark L.\} and Andy Milkowski and Richard Barr and Paul Carson and Mathieu Couade and Jun Chen and Shigao Chen and Manish Dhyani and Richard Ehman and Brian Garra and Albert Gee and Gilles Guenette and Zaegyoo Hah and Ted Lynch and Michael Macdonald and Ravi Managuli and Veronique Miette and Nightingale, \{Kathryn R.\} and Nancy Obuchowski and Rouze, \{Ned C.\} and Morris, \{D. Cody\} and Shana Fielding and Yufeng Deng and Derek Chan and Kingshuk Choudhury and Siyun Yang and Samir, \{Anthony E.\} and Vijay Shamdasani and Matthew Urban and Keith Wear and Hua Xie and Arinc Ozturk and Bo Qiang and Pengfei Song and Stephen McAleavey and Stephen Rosenzweig and Michael Wang and Yoko Okamura and Glen McLaughlin and Yuling Chen and David Napolitano and Lindsey Carlson and Todd Erpelding and Hall, \{Timothy J.\}",
note = "The Radiological Society of North America (RSNA) created the Quantitative Imaging Biomarker Alliance (QIBA) with imaging system manufacturers, academics, clinicians, and representatives from the United States federal government (eg, Food and Drug Administration, National Institutes of Health, and National Institute of Standards and Technology) to advance the concept of converting {\textquotedblleft}imaging systems{\textquotedblright} to {\textquotedblleft}measurement systems.{\textquotedblright} Quantitative Imaging Biomarker Alliance profiles are developed for each measurement system that provide specific claims of what biomarker performance is possible when following the QIBA protocol, with the ultimate intent being to validate the profile across imaging systems with phantoms. The ultrasonic shear wave speed (SWS) biomarker committee was formed in 2012, with the purpose of developing a protocol and data analysis methods to allow direct comparison of SWS measurements made with different commercial systems, with the current clinical application being to estimate liver fibrosis. Several systems that measure SWS in the liver are commercially available, and many articles report that these measurements can differentiate fibrosis stages.1,2 Shear wave elasticity imaging3 methods implemented by several manufacturers, including both point SWS measurements and 2-dimensional shear wave elastography,4 have been cleared by the Food and Drug Administration, and the technology has already reduced the number of liver biopsy procedures performed in Asia and Europe, as reflected in the National Institute for Health and Care Excellence guidelines for the management of viral hepatitis and the role of shear wave elasticity imaging in diagnosing and following disease progression in these patient populations.5 Literature suggests that SWS measurements depend on the measurement system.1,2,6,7,8 These system differences cause clinical uncertainty and slow the adoption of this technology by the clinical community. Given the need for serial assessments of liver fibrosis and the impracticality of serial liver biopsy, providing a consistent SWS measurement that is system agnostic would improve the impact of this technology to noninvasively stage liver fibrosis. A crucial step toward understanding sources of bias in SWS estimates is performing parametric studies in calibrated phantoms across all of the different manufacturer systems to study potential confounding factors, including the focal depth, material stiffness and viscosity, and appraiser. Phantoms may be elastic, which are relatively easy to fabricate, or viscoelastic, which are more difficult to fabricate but more closely mimic human liver. The SWS is independent of the shear wave frequency content in elastic media, but it depends on the frequency in viscoelastic media. Viscosity causes dispersion in the propagating shear waves, which means that the resultant SWS is dependent on the frequency content of the shear wave, with higher-frequency components of the shear wave propagating faster than lower-frequency components.9 The frequency content of the generated shear wave can be affected by the spatial and temporal acoustic radiation force focal configurations used to generate the shear waves and the stiffness of the tissue and is also dependent on the how the shear wave displacements are estimated by using echoes from tracking beams.10 Some commercial systems use tissue displacement data acquired from a single reference in the tissue before the acoustic radiation force is applied, whereas other systems estimate tissue velocity data using a progressive referencing sequence after the acoustic radiation force generates the shear wave.4 Velocity data represent the first time derivative of the displacement data and therefore inherently have higher appreciable frequency content than the displacement data, making them a potential source of SWS differences between systems in viscoelastic media.9 In these studies, we have calculated both the group SWS, which refers to the speed of a broadband pulse containing many frequencies, and the phase SWS, which refers to the speed of monochromatic waves as a function of frequency. We first conducted an elastic phantom study (phase I) to evaluate first-order intersystem measurement differences in the absence of material viscosity.11 We then conducted a viscoelastic phantom study (phase II) to evaluate how systems performed in materials with viscosity, which more realistically match the material properties of human liver tissue. For both phase I and II studies, comparative measurements were made with a research magnetic resonance elastography (MRE) system as a nonultrasonic modality that can also independently characterize stiffness and dispersion and is used clinically to characterize liver fibrosis.12 Additionally, MRE allows for multiple discrete excitation frequencies to be used to generate shear waves in the phantoms, which is not possible with the clinical ultrasound systems and allows for more direct characterization of the dispersive properties of these phantoms. The phase I and II studies allowed us to quantify the bias of SWS measurements between different commercial ultrasonic shear wave elasticity imaging systems and an MRE system in elastic and viscoelastic phantoms. These analyses serve as a foundation for the claims and protocols in the first QIBA ultrasonic SWS profile.13",
year = "2021",
month = mar,
doi = "10.1002/jum.15609",
language = "English (US)",
volume = "40",
pages = "569--581",
journal = "Journal of Ultrasound in Medicine",
issn = "0278-4297",
publisher = "John Wiley \& Sons, Ltd.",
number = "3",
}