Prospective Evaluation of 68Ga-FAPI PET in Biliary Cancers

The goal of this prospective observational study is to evaluate whether Gallium-68 Fibroblast Activation Protein Inhibitor (FAPI) PET/CT can improve detection, staging, and recurrence assessment in adult patients (≥18 years) with suspected or confirmed biliary tract cancers, including gallbladder cancer, cholangiocarcinoma, and post-treatment suspected recurrence. The main question(s) this study aims to answer are: Can FAPI PET/CT provide greater sensitivity, specificity and diagnostic accuracy for primary tumors, nodal disease, and metastatic lesions compared to standard FDG PET/CT? Does FAPI PET/CT offer additional diagnostic yield that may affect clinical decision-making and staging, potentially reducing need for invasive staging procedures? Researchers will compare FAPI PET/CT with FDG PET/CT to see if FAPI improves detection of metastatic or recurrent disease, especially peritoneal or liver metastasis and lymph node involvement. Participants will: Provide written informed consent. Undergo FAPI PET/CT imaging (baseline and/or at suspected biochemical or radiologic recurrence). Have quantitative imaging parameters evaluated (SUVmax, tumor-to-liver ratios, metabolic volume). May undergo comparison with FDG PET/CT and/or follow-up imaging or histopathology as gold standard.