Brandon Reed Welker DO, Abstract Co-Author: Nothing to Disclose

Cathryn Peltz PhD, Abstract Co-Author: Nothing to Disclose

Daniel Scott Siegal MD, Presenter: Nothing to Disclose

Michael Bey PhD, Abstract Co-Author: Nothing to Disclose

Marnix T. van Holsbeeck MD, Abstract Co-Author: Consultant, General Electric Company Consultant, Koninklijke Philips Electronics NV Stockholder, Koninklijke Philips Electronics NV Stockholder, General Electric Company Grant, Reed Elsevier

Shear wave elastography is a novel ultrasound-based technique for real-time visualization of soft tissue stiffness. The purpose of this study was to determine the repeatability of this method for measurements of tendon stiffness.

Measurements of tendon stiffness were obtained for 12 subjects (6 male, 6 female, avg age 32 +/- 9) using the Aixplorer system (Supersonic Imagine). All measurements were performed by a single user. Measurements were obtained at four time points for each subject (twice a day at least 4 hours apart on 2 days at least one day apart). Four tendons (Achilles, patellar, quadriceps, and flexor pollicis longus) were evaluated for each subject at each time point on both the left and right sides. Two trials were obtained for each tendon at each time point. As a measure of repeatability, the intra-class correlation coefficient (ICC) was calculated across the two trials for each tendon on each side at each of the four time points. These values were then averaged to obtain a global ICC value for each tendon.

The ICC varied across tendons as well as between the right and left sides of the same tendon. The Achilles tendon had a poor ICC value (0.17) on the right side, but a moderate value (0.58) on the left. The patellar tendon also varied between its right and left sides (0.42 and 0.62, respectively) but showed better repeatability than the Achilles. The quadriceps and flexor policis longus tendons had the most consistent ICC values between the right and left sides as well as the highest ICC values (best repeatability) measured in the study (range 0.62-0.77).   

The finding that ICC varies across tendon type implies that repeatability may be affected by differences in tendon anatomy, as the Achilles tendon was the least repeatable and has a much more complex insertion than the quadriceps, which was the most repeatable. While the inconsistency between the right and left sides was unexpected, it may be in part a function of technique, as differences in applied pressure can result in different stiffness values. Overall, the repeatability of the system is promising and warrants further study.

Shear wave elastography is a promising new tool to measure soft-tissue stiffness in-vivo. Further investigation is needed to determine if clinically relevant changes can be consistently detected.

Welker, B, Peltz, C, Siegal, D, Bey, M, van Holsbeeck, M, Repeatability of Ultrasound Shear Wave Elastography Measurement of Tendon Stiffness.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043386.html