Background/Purpose: Many imaging modalities, including ultrasound (US) have been used in evaluating rheumatoid arthritis (RA). Previous literatures revealed that US using power doppler imaging (PDI) may be correlated with the degree of synovitis and represent the disease activity in clinical course. The superb microvascular imaging (SMI) is a new software introduced by Toshiba, which can show a vascularity more sensitively excluding artifacts. Therefore, this prospective study was aimed to evaluate the clinical usefulness of the SMI technology for detection of active synovitis in patients with with RA, compared to power doppler imaging (PDI).

Methods: This prospective observational study includes 39 patients with RA (29 females; range of age, 18-83 years; mean age, 52.9 ± 18.1 years), from June, 2015 to May, 2016. All the included patients underwent ultrasound about both wrists and hands (radiocarpal or ulnaocarpal, metacarpophalangeal, and proximal interphalangeal joints; total 22 joints). All the ultrasound examinations were performed at volar side of wrists and hands, using both PDI and SMI using Aplio TM 500 Ultrasound (Toshiba Medical Systems Corporation), and their results were scored for each joint from grade 0 to grade 3 according to the vascularity (grade 0, no vascularity; grade 1, single vessel; grade 2, vascular flow less than 50% in field of view; grade 3, equal to 50% or more). The sum of grades for 22 joints was compared between PDI (PDI-sum) and SMI (SMI-sum). We also evaluated the correlation between the sum of grades values and inflammatory laboratory parameters including the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and disease activity score 28 (DAS28).

Results: The mean values of ESR, CRP and DAS28 were 31.0 ± 18.1 mm/hr, 8.17 ± 8.47 mg/L and 3.72 ± 1.08, respectively. The number of clinical remission (DAS28 score below 2.6) was 7 (17.9%). The positive rates of rheumatoid factor and anti-cyclic citrullinated antibody were 82.1% and 76.9%, respectively. The sum of grades 22 joints was significantly higher in SMI-sum compared to PDI-sum (14.33 ± 8.76 vs. 7.56 ± 5.71, p < 0.001). The SMI-sum score was highly correlated with the PDI-sum score (γ = 0.789, p < 0.001). The SMI-sum score and PDI-sum score were correlated with CRP value (γ = 0.365, p = 0.026; γ = 0.473, p = 0.002, respectively). All of the patients with clinical remission showed active synovitis at more than one joint in both SMI and PDI.

Conclusion: SMI can show more sensitive vascularity than PDI in RA patients. We can detect active synovitis in the RA patients with clinical remission through SMI. SMI could be a useful technology for evaluation of active synovitis in RA patients, especially for detection of clinically subtle, but active synovitis in the RA patients with remission.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-usefulness-of-smi-technology-on-ultrasound-for-the-evaluation-of-active-synovitis-in-patients-with-rheumatoid-arthritis/