Comparative Evaluation of (68)Ga-Citrate PET/CT and (18)F-FDG PET/CT in the Diagnosis of Type II Collagen-Induced Arthritis in Rats

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by systemic, symmetrical, and erosive synovitis. RA is one of the most common disabling diseases in the clinic. The main clinical intervention strategies are early diagnosis and early treatment. This study aims to predict the diagnostic value of (68)Ga-citrate and (18)F-FDG PET/CT in RA by comparing and analyzing the value of (68)Ga-citrate and (18)F-FDG PET/CT for diagnosing type II collagen-induced arthritis (CIA) in rats. Some CIA models were established. Normal rats were selected as the control group, and 23 days and 40 days were selected as the early and late time points of arthritis, respectively. The semiquantitative analysis of CIA rats was carried out with (68)Ga-citrate PET/CT and (18)F-FDG PET/CT, and the ratio of the maximum standardized uptake (SUV(max)) values in the regions of interest (ROIs) of the hind foot ankle joint and thigh muscle was calculated and statistically analyzed. The distribution of CIA rats in vivo at the (68)Ga-citrate 90 min time point was studied, and the ankle tissues were evaluated with hematoxylin and eosin (HE) staining. (68)Ga-citrate PET/CT is obviously superior to (18)F-FDG PET/CT for CIA imaging, and the statistical results show that the difference between the two examination methods is statistically significant (P < 0.001). The uptake of these two radiopharmaceuticals showed the same trend in arthritis rats with different scores. The distribution of (68)Ga-citrate at 90 min is consistent with the trend shown by (68)Ga-citrate PET/CT. (68)Ga-citrate PET/CT can reflect the inflammatory activity of affected joints in CIA rats earlier and more sensitively than (18)F-FDG PET/CT, and this imaging advantage continues until the later stage of inflammation. Therefore, (68)Ga-citrate PET/CT is worthy of further promotion and application in the clinical diagnosis of RA.