68Ga-fibroblast activating protein inhibitors(FAPI) has been developed as a tumor-targeting agent as fibroblast activation protein is overexpressed in cancer-associated fibroblasts and some inflammation,such as inflammatory bowel 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 Pulmonary fibrosis than 18F-FDG PET/CT.

Pulmonary fibrosis is a prototype of chronic, progressive, and fibrotic lung disease.Healthy tissue is replaced by altered extracellular matrix and alveolar architecture is destroyed, which leads to decreased lung compliance, disrupted gas exchange, and ultimately respiratory failure and death.Pulmonary fibrosis is diagnosed by identification of a pattern of usual interstitial pneumonia on the basis of radiological or histological criteria in patients without evidence of an alternative cause. Activated fibroblasts are crucial for fibrotic processes in Pulmonary fibrosis. 68Ga-FAPI has been developed as a tumortargeting agent as fibroblast activation protein is overexpressed in cancerassociated fibroblasts and inflammation. Recently，a study shows that FAPI-PET/CT imaging is a promising new imaging modality for Pulmonary fibrosis.This head-to-head comparisons aims to evaluate the severity of pulmonary fibrosis and the therapy response of 68Ga-FAPI-04 compared with 18F-FDG in the same group of pulmonary fibrosis patients.

Inclusion Criteria:

• suspected or confirmed pulmonary fibrosis patients;
• 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