Luo_2021_J.Nucl.Med_62_266

IgG4-related disease (RD) is characterized by lymphoplasmacytic infiltration enriched in IgG4-positive plasma cells and variable degrees of fibrosis with a characteristic storiform pattern. Since fibrosis is an important feature of IgG4-RD, we performed a prospective cohort study to evaluate the performance of (68)Ga-fibroblast activation protein inhibitor (FAPI), a recently introduced PET agent targeting fibroblast activation protein, in IgG4-RD. Methods: Twenty-six patients with IgG4-RD were recruited. All patients underwent both (68)Ga-FAPI and (18)F-FDG PET/CT. The positive rates of the PET/CT scans in the involved organs and the uptake values were compared. Results: In a total of 136 involved organs in the 26 patients, (68)Ga-FAPI PET/CT additionally detected 18 (13.2%) involved organs in 13 (50.0%) patients, compared with (18)F-FDG PET/CT. (68)Ga-FAPI PET/CT had a higher positive rate than (18)F-FDG PET/CT in detecting involvement in the pancreas, bile duct/liver, and lacrimal gland. (68)Ga-FAPI also demonstrated significantly higher uptake than (18)F-FDG in the matched disease in the pancreas, bile duct/liver, and salivary gland (P < 0.01). However, lymph node involvement with flip-flop uptake of (18)F-FDG did not accumulate (68)Ga-FAPI. Conclusion:(68)Ga-FAPI might be a promising imaging agent for the assessment of IgG4-RD.