Contrast-enhanced power Doppler sonography of knee synovitis in rheumatoid arthritis: assessment of therapeutic response

The aim of this study was to evaluate the ability of power Doppler sonography (PDS) with ultrasound contrast agent to assess the synovial perfusion changes induced by intra-articular steroid injection therapy in the knee joints of patients with rheumatoid arthritis (RA). Eighteen RA patients (16 women, 2 men) with a history and signs of active knee synovitis were studied. Tenderness was evaluated using Thompson’s modified index of synovitis activity. All patients underwent joint aspiration followed by intra-articular injection of 40 mg of triamcinolone hexacetonide. Gray-scale ultrasonography and PDS with an intravenous ultrasound contrast agent (Levovist) examinations were carried out before and 3 weeks after the intra-articular steroid injection. The calculation of the time–intensity curves provided a quantitative estimation of the synovial perfusion. The median values of the index of synovitis activity decreased significantly from 7.0 (95% confidence interval (CI) 6.0–8.0) to 3.0 (95% CI 2.0–4.0) (p<0.01) 3 weeks after the intra-articular steroid injection. All patients showed a reduction of PDS signal after intra-articular steroid therapy and the baseline and follow up median values of the area underlying time–intensity curves were 7.48 (95% CI 5.79–8.73) and 2.45 (95% CI 1.92–3.61), respectively. The comparison between baseline and follow-up median values of the area under the curves showed a statistically significant reduction of PDS findings (p<0.01). At follow-up examinations the changes in the index score of the synovitis activity were significantly correlated to the changes in the values of the area underlying time–intensity curves (r=0.785; p<0.01). A significant correlation was also observed between baseline values of the area underlying time–intensity curves and C-reactive protein (CRP) (r=0.548; p=0.023). In conclusion, PDS with an intravenous ultrasound contrast agent has been shown to be able to detect changes in synovial perfusion after intra-articular steroid injection and may be an additional useful method in the evaluation of synovial inflammation and in the assessment of the therapeutic response.