Characterizing IgG4-RD With 68Ga-FAPI PET/CT

68Ga-FAPI has been developed as a tumor-targeting agent as fibroblast activation protein is overexpressed in cancer-associated fibroblasts and some inflammation,such as IgG4-related disease.And it might be more sensitive than FDG in detecting a certain type of inflammations according to our preliminary research.Thus this prospective study is going to investigate whether 68Ga-FAPI PET/CT may be superior for diagnosis, therapy response assessment and follow-up of IgG4-related disease.

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory condition that is capable of affecting multiple organs. Common forms of presentation include:Type 1 (IgG4-related) autoimmune pancreatitis (AIP)，IgG4-related sclerosing cholangitis, major salivary gland enlargement or sclerosing sialadenitis; Orbital disease, often with proptosis and retroperitoneal fibrosis. The involved organs share a number of core pathologic features and striking clinical and serologic similarities, including tumor-like swelling of involved organs, a lymphoplasmacytic infiltrate enriched in IgG4-positive plasma cells, and a variable degree of fibrosis that has a characteristic "storiform" pattern. 68Ga-FAPI has been developed as a tumor-targeting agent as fibroblast activation protein is overexpressed in cancer-associated fibroblasts and it might be a pan-tumor PET agent. Recently we have reported a case of IgG4-related disease revealed by 68Ga-FAPI and 18F-FDG PET/CT which showed FAPI was not more tumor-specific than FDG, furthermore,it might be more sensitive than FDG in detecting a certain type of inflammations-like the pancreatic lesion. Thus this prospective study is going to investigate whether 68Ga-FAPI PET/CT may be superior for diagnosis, therapy response assessment and follow-up of IgG4-related disease.

Intravenous injection of one dosage of 74-148 MBq (2-4 mCi) 68Ga-FAPI. Tracer doses of 68Ga-FAPI will be used to image lesions of IgG4-RD by PET/CT.

Inclusion Criteria: suspected or confirmed untreated IgG4-RD patients; 18F-FDG PET/CT within two weeks; signed written consent. Exclusion Criteria: pregnancy; breastfeeding; known allergy against FAPI any medical condition that in the opinion of the investigator may significantly interfere with study compliance.