Spectral Doppler and resistive index. A promising tool in ultrasonographic evaluation of inflammation in rheumatoid arthritis

Abstract

Purpose: To evaluate the use of spectral Doppler in the longitudinal follow-up of inflammatory joint involvement in rheumatoid arthritis (RA) by comparing resistive index (RI) findings with color fraction and pain on a visual analog scale (VAS).

Material and methods: Five patients on unchanged disease modifying anti-rheumatic drugs (DMARD) treatment were followed after an intra-articular corticosteroids injection and received no further injections in the observation period. They were followed clinically and by ultrasound using color Doppler pixels and the spectral Doppler RI as indicators of inflammation. At 1, 6 and 12 months the measurements were repeated on the same joint.

Results: At 1-month follow-up after the corticosteroids injection, a marked decrease in the color fraction was seen in 4 out of 5 patients, while the fifth patient had a moderate decrease (Wilcoxon p < 0.05). The changes in RI showed correspondingly a marked increase in 4 out of 5 patients indicating a diminished flow to the synovium (Wilcoxon p < 0.05). The effect of the corticosteroid injection could still be seen after 1 year in 4 out of 5 patients. In RI, pixel fraction and VAS there was improvement compared with the baseline values; however, only the pixel fraction was statistically significant (Wilcoxon p < 0.05).

Conclusion: RI seems to be an objective alternative to pixel estimation of the degree of inflammation and treatment response in RA.