Intraindividual comparison of 6 patients with IgG4-RD undergoing 18F-FDG and 68 Ga-FAPI-04 PET/CT. Examples show superiority of 68 Ga-FAPI-04 to 18F-FDG in depicting involvement of IgG4-RD in the pancreas (patients 13, 15, 17, and 18), bile duct/liver (patients 13, 15, and 17), retroperitoneal fibrosis (patient 21), lung/pleura (patient 25), and salivary gland (patients 13 and 17). Hypermetabolic lymph nodes in 18F-FDG-PET/CT did not show uptake of 68 Ga-FAPI-04 (patients 15 and 17). Renal involvement (patients 15 and 18) was both 18F-FDG-avid and 68 Ga-FAPI-04-avid. There was also unspecific 68 Ga-FAPI-04 uptake in the uterus (patients 21 and 25). Figure adapted from Luo et al. [97]