Andy Milkowski MS, Presenter: Employee, Siemens AG

Timothy J. Hall PhD, Abstract Co-Author: Equipment support, Siemens AG

Michael Paul Andre PhD, Abstract Co-Author: Research Consultant, Almen Laboratories, Inc

Paul L. Carson PhD, Abstract Co-Author: Research collaboration, General Electric Company Research collaboration, Sonetics Ultrasound, Inc Research collaboration, ZONARE Medical Systems, Inc Research collaboration, Light Age, Inc

Shigao Chen PhD, Abstract Co-Author: Nothing to Disclose

Claude Cohen-Bacrie, Abstract Co-Author: Executive Vice President, SuperSonic Imagine Officer, SuperSonic Imagine

Stephanie Franchi-Abella MD, Abstract Co-Author: Nothing to Disclose

Brian Stephen Garra MD, Abstract Co-Author: Nothing to Disclose

Stephen McAleavey PhD, Abstract Co-Author: Research collaboration, General Electric Company

Steve Metz, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

Kathryn Nightingale PhD, Abstract Co-Author: Research support, Siemens AG

Mark Palmeri MD, PhD, Abstract Co-Author: Nothing to Disclose

Anthony Edward Samir MD, Abstract Co-Author: Nothing to Disclose

Laurent Sandrin PhD, Abstract Co-Author: Director, Echosens Employee, Echosens

Mickael Tanter PhD, Abstract Co-Author: Co-founder, SuperSonic Imagine

To test commercial and research ultrasound SWS systems to identify the sources and magnitude of bias and variability in SWS measurements.

Eleven phantom pairs were built from stiff and soft batches of Zerdine® by CIRS. Larger phantoms were also prepared for correlative testing using magnetic resonance elastography. All phantoms were initially tested by one lab to determine manufacturing variation and were then shipped to 11 different labs for SWS measurements. At each site, 3-5 operators measure each phantom at three times at each of three depths according to a randomized schedule. Each measurement consists of the average of ten valid SWS acquisitions as has been reported in the clinical literature. The data are analyzed using crossed Gage R & R methodology with ANOVA. Bias is estimated by comparing the results with known values of elastic modulus (converted to SWS) from the manufacturer and from mechanical testing performed across a broad range of shear wave frequencies at two sites. Estimates of linearity can also be obtained since stiff and soft phantoms are tested at each site.

Mechanical test results from the two sites performing those measurements were in excellent agreement. Initial analysis of US SWS measurements shows overall variability of 5-7% in SWS mean values for several sites. ANOVA shows that site and measurement depth are the dominant sources of variation with operator variability being a minor component. Variation in SWS for all phantoms was 3-5% on initial testing of all phantoms. A 5-10% depth dependence (lower SWS at deeper depths) was also seen. Also, a small bias in SWS estimates of 5-6% was seen. Similar variability and bias are seen for both stiff and soft phantoms.

Initial results show a relatively small amount of variability in SWS estimates and also show that operator variability contributes little to total measurement variation. Phantom variation may be a significant source of the variability in measurements. Given these encouraging results, we will add measurements from additional sites, explore the causes of the depth dependence of SWS, and extend our work to lossy (viscoelastic) phantoms which more closely mimic human liver tissue.

This work by QIBA is the first step in development of a protocol for US SWS measurement that gives accurate & repeatable results across a range of instruments for drug testing, clinical & research use

Milkowski, A, Hall, T, Andre, M, Carson, P, Chen, S, Cohen-Bacrie, C, Franchi-Abella, S, Garra, B, McAleavey, S, Metz, S, Nightingale, K, Palmeri, M, Samir, A, Sandrin, L, Tanter, M, Ultrasound Shear Wave Speed Estimation in Elastic Phantoms: Sources and Magnitude of Variability in a QIBA Multicenter Study.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13019231.html