Introduction: Shear-wave elastographic ultrasound (SW-EUS) assesses the stiffness of human tissues. It is used in liver, thyroid and breast imaging but has not been studied in synovium. Soft tissues have a slower shear-wave velocity (SWV) than stiff tissues. We hypothesised that rheumatoid arthritis (RA) patients would have softer synovium than controls and this could be quantified with a slower SWV. We also assessed whether SWV varied with disease activity.
Methods: Nine patients with RA were consecutively recruited and matched with five controls. Participants underwent clinical assessment, blood sampling, grey scale ultrasound (GSUS), power Doppler ultrasound and SW-EUS of MCP joints 2-5 on the dominant hand.
Results: Average age was 60. Mean RA disease activity (DAS28-ESR) was moderate at 3.65. Patients with RA had lower maximum synovial SWV than controls (6.38 m/s vs. 6.99 m/s P = 0.042). Negative Pearson's correlation coefficients (PCC) were observed between maximum SWV and disease activity markers including GSUS graded synovial thickness (PCC = -0.57, P = 0.03) and ESR (PCC = -0.46, P = 0.095). Intra- and interobserver reliability was good with intraclass correlation coefficients (ICC) of 0.66 and 0.58, respectively, for quantitative maximum SWV and ICC > 0.80 for colour scale rated SWV.
Conclusion: This is the first pilot study of SW-EUS in synovium. Maximum synovial SWV was significantly lower in RA than controls. There was a negative correlation between maximum SWV and GSUS synovial thickening. Further study is warranted to confirm the role of SW-EUS in diagnosing and assessing disease activity in RA.
Keywords: elasticity imaging techniques; elastography; rheumatoid arthritis; synovium; ultrasonography.
© 2017 Australasian Society for Ultrasound in Medicine.