The goal of this observational study is to examine clinical utility of 18F-FAPI-RGD PET/CT imaging in evaluating connective tissue disease-associated interstitial lung disease. Participants will undergo clinical evaluation and 18F-FAPI-RGD PET/CT examination.

Interstitial lung disease is an overarching term for a wide range of disorders characterized by inflammation and/ or fibrosis in the lungs. Interstitial lung disease associated connective tissue diseases(CTD-ILD) is one of the most common types.The goal of this study is to explore the feasibility of using 18F-FAPI-RGD, a dual-targeting heterodimeric PET tracer that recognizes both fibroblast activation protein (FAP) and integrin αvβ3 for detecting connective tissue disease associated interstitial lung disease (CTD-ILD), and analyze the relationship between 18F- FAPI-RGD PET/CT images and related parameters of lung function, clinical laboratory indicators and HRCT scores.

Inclusion Criteria:

• Age 18 and above
• Patients who have been diagnosed with, or are clinically highly suspected of ILD
• Patients who have been diagnosed with, or are clinically highly suspected of CTD-ILD

Exclusion Criteria:

• Pregnant or breastfeeding
• Patients with tumor, other respiratory diseases, and lung surgery
• Abnormal cardiopulmonary function or mental state, unable tolerate PET/CT

Patients with clinically suspected or diagnosed connective tissue disease-associated interstitial lung disease