Synovial volume--a marker of disease severity in rheumatoid arthritis? Quantification by MRI.

Volumes of synovial membrane and joint effusion were determined by magnetic resonance imaging (MRI) in patients with inflammatory gonarthritis. Volumes were calculated by adding the outlined areas of synovium/effusion from a continuous series of gadolinium-DTPA-enhanced 5 mm transversal T1-weighted MR-images. Ten knees with clinically active gonarthritis (CAG), 8 knees with clinically inactive gonarthritis (CIG) and 5 healthy controls (HC) were examined. The synovial volume of CAG-, CIG- and HC-knees were significantly different. The median volumes were 79 ml, 21 ml and 3 ml, respectively. Synovial and effusion volumes were highly correlated. A selected sagittal one-slice volume showed a high correlation to the total volumes. The reliable quantification of synovial and effusion volumes could be useful in the assessment of disease severity and as an outcome measure to treatment.