[Application of 18F-FDG PET/CT in rheumatic diseases].

Objective: To explore the application of ¹⁸F-flurodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) in rheumatic diseases, to compare these different imaging features, and to describe the current PET/CT imaging status in clinical practice.

Methods: A total of 486 cases in our department from January 2012 to December 2018 were enrolled in this study, and ¹⁸F-FDG PET/CT examination was performed in all the patients. The clinical use of ¹⁸F-FDG PET/CT was retrospectively analyzed to discuss the clinical application and its imaging characteristics of rheumatic diseases. Categorical data were used to ascertain prevalence statistics, whereas continuous data were used to delineate means and standard deviations. Independent sample t test, Chi square test and Mann-Whitney U test were used for statistical analysis. A P-value of < 0.05 was considered significant.

Results: (1) From 2012 to 2018, totally 486 patients in the Department of Rheumatology and Immunology underwent ¹⁸F-FDG PET/CT examination, accounting for 5.30% of the total number of PET/CT examinations in the whole hospital. In this study, 304 of the 486 patient were female (62.55%), 182 of them were male (37.45%), the average age of the patients was (53.21±18.81) years, and the proportion of the patients aged 45-65 (227/486, 46.71%) was the highest group. (2) Three leading purposes of the PET/CT examination in our department were to exclude cancers (55.56%), assist in diagnosis (24.60%) and evaluate the disease activity (19.84%). (3) Of the 486 patients who underwent ¹⁸F-FDG PET/CT, 327 cases might indicate a differential diagnosis of rheumatic disease, of which, 292 cases were highly suggestive of diagnosis, including 61 cases of myositis, 60 cases of vasculitis, 37 cases of adult still's disease, 32 cases of IgG4 related diseases, 30 cases of rheumatoid arthritis, 22 cases of Sjögren's syndrome, 22 cases of systemic lupus erythematosus, and 9 cases of rheumatic polymyalgia; the remaining 35 cases only prompted the possibility of autoimmune disease. Of the 486 patients, 74 cases suggested the diagnosis of cancers, 25 cases indicated the diagnosis of infectious diseases, while 60 cases could not show any diagnostic values. Ten patients with rheumatic disease were followed up with a post-treatment repeat PET/CT, and the findings in remission showed reduced ¹⁸F-FDG metabolic activity as well as a reduction in the extent of metabolic hypertrophic lesions.

Conclusion: There are some typical sign of ¹⁸F-FDG PET/CT for diffuse connective tissue diseases, therefore ¹⁸F-FDG PET/CT has auxi-liary effect on the classification diagnosis of rheumatic diseases, especially for the exclusion of cancers.