Maximum intensity projection with magnetic resonance imaging for evaluating synovitis of the hand in rheumatoid arthritis: comparison with clinical and ultrasound findings

Magnetic resonance imaging (MRI) with maximum intensity projection (MIP) is used to evaluate the hand in rheumatoid arthritis (RA). MIP yields clear visualization of synovitis over the entirety of the bilateral hands with a single image. In this study, we assessed synovitis with MIP images, clinical findings, and power Doppler (PD) findings to examine the clinical usefulness of MIP images for RA in the hand. Thirty RA patients were assessed for swelling and tenderness in the joints included in the DAS28, and both contrast-enhanced MRI for bilateral hands and ultrasonography for bilateral wrist and metacarpophalangeal (MCP) joints were performed. Articular synovitis was scored in MIP images, and the scores were compared with those for PD. The agreement on synovitis between MIP and conventional MR images was excellent. Palpation showed low sensitivity and high specificity compared with both MIP and PD images. There were joints that were positive in MIP images only, but there were no joints that were positive in PD images only. A statistically significant correlation between the scores of MIP and PD images was found. Furthermore, the agreement between grade 2 on MIP images and positive on PD images was 0.87 (kappa = 0.73) for the wrist and 0.92 (kappa = 0.57) for MCP joints. Using MIP images together with palpation makes detailed evaluation of synovitis of the hand in RA easy. MIP images may predict further joint damage, since they allow semiquantitative estimation of the degree of thickening of the synovial membrane.