TH‐A‐207B‐01: Basics and Current Implementations of Ultrasound Imaging of Shear Wave Speed and Elasticity

Imaging of tissue elastic properties is a relatively new and powerful approach to one of the oldest and most important diagnostic tools. Imaging of shear wave speed with ultrasound is has been added to most high-end ultrasound systems. Understanding this exciting imaging mode aiding its most effective use in medicine can be a rewarding effort for medical physicists and other medical imaging and treatment professionals. Assuring consistent, quantitative measurements across the many ultrasound systems in a typical imaging department will constitute a major step toward realizing the great potential of this technique and other quantitative imaging. This session will target these two goals with two presentations. A. Basics and Current Implementations of Ultrasound Imaging of Shear Wave Speed and Elasticity - Shigao Chen, Ph.D. Learning objectives-To understand: 1.Introduction: •Importance of tissue elasticity measurement •Strain vs. shear wave elastography (SWE), beneficial features of SWE •The link between shear wave speed and material properties, influence of viscosity 2.Generation of shear waves •External vibration (Fibroscan) •ultrasound radiation force •Point push •Supersonic push (Aixplorer) •Comb push (GE Logiq E9) 3.Detection of shear waves •Motion detection from pulse-echo ultrasound •Importance of frame rate for shear wave imaging •Plane wave imaging detection •How to achieve high effective frame rate using line-by-line scanners 4.Shear wave speed calculation •Time to peak •Random sample consensus (RANSAC) •Cross correlation 5.Sources of bias and variation in SWE •Tissue viscosity •Transducer compression or internal pressure of organ •Reflection of shear waves at boundaries B. Elasticity Imaging System Biomarker Qualification and User Testing of Systems – Brian Garra, M.D. Learning objectives-To understand: 1.Goals •Review the need for quantitative medical imaging •Provide examples of quantitative imaging biomarkers •Acquaint the participant with the purpose of the RSNA Quantitative Imaging Biomarker Alliance and the need for such an organization •Review the QIBA process for creating a quantitative biomarker •Summarize steps needed to verify adherence of site, operators, and imaging systems to a QIBA profile 2.Underlying Premise and Assumptions •Objective, quantifiable results are needed to enhance the value of diagnostic imaging in clinical practice •Reasons for quantification i.Evidence based medicine requires objective, not subjective observer data ii.Computerized decision support tools (eg CAD) generally require quantitative input. iii.Quantitative, reproducible measures are more easily used to develop personalized molecular medical diagnostic and treatment systems 3.What is quantitative imaging? •Definition from Imaging Metrology Workshop 4.The Quantitative Imaging Biomarker Alliance •Formation 2008 •Mission •Structure •Example Imaging Biomarkers Being Explored •Biomarker Selection •Groundwork •Draft Protocol for imaging and data evaluation •QIBA Profile Drafting •Equipment and Site Validation i.Technical ii.Clinical •Site and Equipment QA and Compliance Checking 5.Ultrasound Elasticity Estimation Biomarker •US Elasticity Estimation Background •Current Status and Problems •Biomarker Selection-process and outcome 6.US SWS for Liver Fibrosis Biomarker Work •Groundwork i.Literature search and analysis results ii.Phase I phantom testing-Elastic phantoms iii.Phase II phantom testing-Viscoelastic phantoms iv.Digital Simulated Data •Protocol and Profile Drafting iProtocol: based on UPICT and existing literature and standards bodies protocols ii.Profile-Current claims, Manufacturer specific appendices 7.What comes after the profile •Profile Validation iTechnical validation ii.Clinical validation •QA and Compliance i.Possible approaches 1.Site a.Operator testing b.Site protocol re-evaluation 2.Imaging system a.Manufacturer testing and attestation b.User acceptance testing and periodic QA i.Phantom Tests ii.Digital Phantom Based Testing iii.Standard QA Testing iv.Remediation Schemes 8.Profile Evolution •Towards additional applications •Towards higher accuracy and precision Supported in part by NIH contract HHSN268201300071C from NIBIB. Collaboration with GE Global Research, no personal support.; S. Chen, Some technologies described in this presentation have been licensed. Mayo Clinic and Dr. Chen have financial interests these technologies.