FDG PET for rheumatoid arthritis: basic considerations and whole-body PET/CT

[(18) F]Fluorodeoxyglucose (FDG) is a tracer for glucose metabolism. Its distribution is not specific to cancer cells but is also observed in inflammatory tissue, including macrophages, capillaries, and fibroblasts. Rheumatoid arthritis (RA) is a systemic, chronic inflammation of the joints resulting in synovitis. The disease is characterized by fibrovascular proliferation leading to the formation of a pannus and causing high FDG uptake. Several clinical studies of RA have demonstrated that FDG uptake in affected joints reflects the disease activity of RA, with strong correlations between uptake and various clinical parameters having been noted. Furthermore, the use of FDG PET for the sensitive detection and monitoring of the response to RA therapy has been reported. FDG PET/computed tomography (CT) enables the detailed evaluation of disease in large joints throughout the whole body, which is a unique advantage of PET/CT. FDG PET/CT can also be used to detect high-risk disease complications, such as atlanto-axial joint involvement, at an early stage. The possible contribution of FDG PET to the management of patients with RA remains to be studied in detail.