Purpose: To investigate the reliability, validity and feasibility of a computer-assisted manual segmentation method for determining the synovial membrane volume as a surrogate measure for synovitis in patients with rheumatoid arthritis (RA). Materials and Methods:The 3 Tesla (T) MRI scans were acquired in 22 early RA and 16 established RA patients. Synovial membrane volumes in postcontrast T1w axial images at three wrist joint regions were determined by two nonradiologist observers using a computer-assisted manual segmentation method. Conclusion: Measurement of MRI synovitis using a computer-assisted manual segmentation method demonstrated excellent intraobserver and very good interobserver reliability, content validity (represented by its strong correlation with RAMRIS synovitis), and moderate feasibility.

IntroductionCartilage damage impacts on patient disability in rheumatoid arthritis (RA). The aims of this magnetic resonance imaging (MRI) study were to investigate cartilage damage over three years and determine predictive factors.MethodsA total of 38 RA patients and 22 controls were enrolled at t = 0 (2009). After 3 years, clinical and MRI data were available in 28 patients and 15 controls. 3T MRI scans were scored for cartilage damage, bone erosion, synovitis and osteitis. A model was developed to predict cartilage damage from baseline parameters.ResultsInter-reader reliability for the Auckland MRI cartilage score (AMRICS) was high for status scores; intraclass correlation coefficient (ICC), 0.90 (0.81 to 0.95) and moderate for change scores (ICC 0.58 (0.24 to 0.77)). AMRICS scores correlated with the Outcome MEasures in Rheumatoid Arthritis Clinical Trials (OMERACT) MRI joint space narrowing (jsn) and X-Ray (XR) jsn scores (r =0.96, P < 0.0001 and 0.80, P < 0.0001, respectively). AMRICS change scores were greater for RA patients than controls (P = 0.06 and P = 0.04 for the two readers). Using linear regression, baseline MRI cartilage, synovitis and osteitis scores predicted the three-year AMRICS (R2 = 0.67, 0.37 and 0.39, respectively). A multiple linear regression model predicted the three-year AMRICS (R2 = 0.78). Baseline radial osteitis predicted increased cartilage scores at the radiolunate and radioscaphoid joints, P = 0.0001 and 0.0012, respectively and synovitis at radioulnar, radiocarpal and intercarpal-carpometacarpal joints also influenced three-year cartilage scores (P-values of 0.001, 0.04 and 0.01, respectively).ConclusionsMRI cartilage damage progression is preceded by osteitis and synovitis but is most influenced by pre-existing cartilage damage suggesting primacy of the cartilage damage pathway in certain patients.

Cartilage damage is less severe in gout than in RA, with fewer sites affected and lower overall scores. It is associated with synovitis in both diseases, likely indicating an effect of pro-inflammatory cytokine production on cartilage integrity. However, the strong association between cartilage damage and BME observed in RA was not identified in gout. This emphasizes differences in the underlying pathophysiology of joint damage in these two conditions.