Rheumatoid arthritis (RA) is an autoimmune disease, which is associated with systemic and chronic inflammation of the joints, resulting in synovitis and pannus formation. For several decades, the assessment of RA has been limited to conventional radiography, assisting in the diagnosis and monitoring of disease. Nevertheless, conventional radiography has poor sensitivity in the detection of the inflammatory process that happens in the initial stages of RA. In the past years, new drugs that significantly decrease the progression of RA have allowed a more efficient treatment. Nuclear Medicine provides functional assessment of physiological processes and therefore has significant potential for timely diagnosis and adequate follow-up of RA. Several single photon emission computed tomography (SPECT) and positron emission tomography (PET) radiopharmaceuticals have been developed and applied in this field. The use of hybrid imaging, which permits computed tomography (CT) and nuclear medicine data to be acquired and fused, has increased even more the diagnostic accuracy of Nuclear Medicine by providing anatomical localization in SPECT/CT and PET/CT studies. More recently, fusion of PET with magnetic resonance imaging (PET/MRI) was introduced in some centers and demonstrated great potential. In this article, we will review studies that have been published using Nuclear Medicine for RA and examine key topics in the area.

Objective Tumor necrosis factor-alpha (TNF-α) is an important inflammatory cytokine. 99mTc-anti-TNF-α antibody scintigraphy has proven to be a viable alternative to MRI in specific cases. The objective of this study was to evaluate the performance of scintigraphy with 99mTc-anti-TNF-α in the identification of inflammatory foci in individuals diagnosed with rheumatoid arthritis using MRI as the gold standard. Methods This cross-sectional, descriptive and analytical-qualitative clinical study compared the performance of 99mTc-anti-TNF-α scintigraphy with that of MRI with intravenous administration of gadolinium (used as the gold standard) and a clinical examination (Disease Activity Score 28) in 220 joints of 20 patients with a diagnosis of rheumatoid arthritis and one healthy control. Results The concordance of scintigraphy with MRI in individuals with a diagnosis of rheumatoid arthritis was 79%. The accuracy, sensitivity and specificity of scintigraphy for distinguishing between inflammatory and noninflammatory sites were 92, 89, and 93%, respectively. No adverse reactions to the examinations were reported. Conclusions Scintigraphy with 99mTc-anti-TNF-α was well-tolerated and had a good ability to distinguish between inflammatory and noninflammatory lesions in patients with rheumatoid arthritis.