RSNA/QIBA efforts to standardize shear wave speed as a biomarker for liver fibrosis staging

Abstract

Commercial shear elasticity systems have been available to clinicians for several years for characterizing liver stiffness. The Radiological Society of North America (RSNA) established a Quantitative Imaging Biomarker Alliance (QIBA) committee on Ultrasound Shear Wave Speed to help achieve better consistency between the shear wave speed and elastic modulus values reported by different manufacturer systems. An inter-laboratory study of shear wave speed estimation was conducted at academic, industry and clinical laboratories using commercial ultrasound and magnetic resonance elastography systems in elastic (Phase I) and viscoelastic (Phase II) homogeneous, isotropic tissue-mimicking phantoms. In the elastic phantoms, shear wave speeds from different systems were within ±5% of the grand mean of all system measurements. Different appraisers and replicate measurements at a given site were not sources of significant variability in shear wave speed measurements. In the viscoelastic phantoms, shear wave speeds from different systems were within ±15% of the grand mean of all systems, with the stiffest phantoms at the deepest focal depth (7 cm) having the greatest measurement variance. Magnetic resonance elastography measurements at 140 Hz in the viscoelastic phantoms were consistent to within ±5% of thosemade with the ultrasound shear elasticity systems, while measurements made at 60 Hz had a mean bias of -2.6% relative to ultrasound systems. A method for reporting group shear wave velocities using both displacement and velocity data, along with shear wave phase velocity analysis, has been developed as a common calibration approach for the phantoms. An open-source repository of research scanner shear wave sequences and processing code has been created to allow manufacturers to have a calibration standard to assess compliance with the QIBA US shear wave speed profile and to achieve more consistent results to facilitate more rapid clinical adoption of this technology to evaluate liver fibrosis.