Use of magnetic resonance imaging and positron emission tomography in the assessment of synovial volume and glucose metabolism in patients with rheumatoid arthritis.

Objective: To measure the anatomic and physiologic changes in the synovium of patients with active rheumatoid arthritis (RA) before and after the initiation of treatment with low-dose systemic glucocorticoids and methotrexate (MTX).

Methods: Two patients with RA with active synovitis involving the carpus were evaluated by imaging parameters at baseline and again after 14 weeks (of treatment with low-dose prednisone and MTX). Standard clinical parameters, laboratory measurements, and contrast-enhanced magnetic resonance imaging (MRI) (synovial volume estimate) and positron emission tomography (PET) with 18F-fluoro-2-deoxyglucose (18-FDG) (synovial metabolism estimate) were performed.

Results: Compared with baseline, standard clinical parameters (i.e., joint count, joint index, morning stiffness, global assessments of arthritis activity, and erythrocyte sedimentation rate) improved dramatically in both patients after treatment with low-dose prednisone and MTX. In concert with this trend, the synovial volume of the affected wrist was reduced by 60%, and 76% and the metabolism of 18-FDG was reduced by 66% and 69% in the 2 patients.

Conclusion: These preliminary observations indicate that a volumetric estimate of inflamed synovium (using contrast-enhanced MRI) and quantification of synovial deoxyglucose metabolism (using PET) are technically feasible and, in the 2 reported cases, correlate well with standard outcome measures. These imaging modalities may provide new objective parameters to determine RA disease activity and effectiveness of antirheumatic medications; however, the potential clinical utility of these measures remains to be defined.