Abstract
2670
Introduction: To compare the roles of FDG- and NaF-PET/CT in rheumatoid arthritis (RA) and osteoarthritis (OA) and identify the utility of each.
Methods: Several databases, including PubMed, Google Scholar, and Web of Science were used to compile original studies and reviews discussing clinical PET/CT and PET/MRI practices in musculoskeletal (MSK) disorders. Search terms included FDG, NaF, fluoride, PET, CT, MRI, rheumatoid arthritis, osteoarthritis, and degenerative joint disease. The scoping review was conducted following PRISMA-ScR guidelines and eligibility criteria of the studies was based on number of patients, quality of methods, and recency of publications.
Results: 18F-sodium fluoride (NaF) and 18F-FDG are two of the PET/CT tracers used to study disorders like RA and OA. Here we will be comparing the utility of these two tracers in RA and OA. NaF is an indicator of bone turnover while FDG is an indicator of inflammation, and as many studies showed, NaF uptake is mostly located in bone while FDG is mostly located in surrounding tissue. In these studies, NaF PET was often determined to be an objective measurement of bone metabolism that can complement MRI assessment of structural abnormalities. Studies also showed a positive association between inflammation (FDG) and the degree of new bone formation (NaF), suggesting that both tracers were related and associated with both RA and OA affected joints. However, most studies looking at OA more commonly used NaF PET/CT, while most studies on RA used FDG PET/CT, indicating that these modalities had higher value in these respective disorders.
Conclusions: Overall NaF PET/CT seemed to be more effective in OA, where bone activity is more relevant, while FDG PET/CT was an accurate marker in RA, where inflammation is more relevant. Possible explanations include the autoimmune etiology of RA as compared to the physical insult seen in OA, as well as the synovial/periarticular involvement of RA compared to the articular involvement of OA. Both imaging techniques have proved themselves as feasible and non-invasive assessments of inflammation and bone metabolism in varying MSK disorders. However, the usefulness of each tracer differs based on the disorder so it is important to adjust imaging protocol for early detection of different disorders. There is a need for larger longitudinal and prospective data that evaluates the use of FDG- and NaF- PET/CT in RA and OA but the literature does suggest these imaging techniques to be highly valuable tools.