Microvascular imaging is superior to power doppler in synovitis vascular flow detection in rheumatoid arthritis using...

Superb Microvascular Imaging (SMI) uses an adaptive algorithm that improves the visualization of vessels with low-velocity blood flow. Power Doppler (PD) imaging is routinely used in clinical practice but includes a wall filter, resulting in signal loss from small blood vessels with low flow. A standardized EULAR-OMERACT scoring system exists for rheumatoid arthritis (RA), incorporating semi-quantitative grading for both synovitis on grey-scale (GS) and PD signals.  OBJECTIVE: To compare SMI and PD in the evaluation of synovitis in the hand and wrist joints of patients with RA.

Consecutive patients with an RA diagnosis, fulfilling the EULAR-ACR classification criteria and showing ultrasonographic synovitis in at least one joint, were recruited. Ultrasonographic assessments were performed using high-end machines equipped with high-frequency linear transducers for all metacarpophalangeal (MCP), proximal interphalangeal (PIP), and wrist joints (22 joints per patient), including GS, PD, and SMI grading. The existing EULAR-OMERACT score, which combines GS and PD signal, was compared with a proposed new version: the adapted EULAR-OMERACT score, which combines GS and SMI. A blinded real-time interrater agreement exercise between two ultrasonographers was conducted beforehand for GS, PD, and SMI, showing substantial agreement (squared-weighted κ = 0.729).  RESULTS: Fifty-eight RA patients were enrolled (74.1% female; mean age 63.4 ± 14.0 years), with a total of 1,276 joints scanned, of which 227 had GS grade ≥ 1. SMI detected intra-articular vascularization in 137 of 227 GS grade ≥ 1 joints (60.4%), compared to 58 of 227 joints (25.6%) with PD (p < 0.001, Chi-square test). SMI significantly improved the detection of vascular flow signals (χ² (9) = 1020.35, p = 0.001), with a large effect size (Cramer's V = 0.52): 79 joints (57.7%) increased vascular flow grading from PD grade 0 to SMI grade ≥ 1; 29 joints (74.4%) of PD grade 1 increased to SMI grade ≥ 2 and 9 joints (52.9%) of PD grade 2 increased to SMI grade 3. No joint had higher PD grade than corresponding SMI grade. Comparing the EULAR-OMERACT score with the adapted version, SMI led to an increase in the combined GS and vascular scores. No joint had a lower adapted EULAR-OMERACT score compared to the original (χ² (9) = 2076.09, p = 0.001), with a large effect size (Cramér's V = 0.86).

In RA patients, our study demonstrates that SMI has a higher sensitivity for detecting synovial vascular flow than PD across all grades. Negative findings are consistent, as no vascular flow was detected with PD in joints that showed no signal on SMI. This is the first study to adapt the EULAR-OMERACT scoring system for use with SMI, showing that SMI introduces statistically and ultrasonographically significant score changes.