The project aims to perform integrated PET/MR or PET/CT imaging in patients with histologically confirmed or clinically suspected gastric cancer, pancreatic cancer, cholangiocarcinoma, or other malignant tumors with high Claudin18.2 (CLDN18.2) expression, as well as healthy volunteers. This study utilizes a CLDN18.2-specific PET imaging probe (e.g., [^68Ga]Ga-labeled humanized antibody fragment) to evaluate the feasibility, accuracy, and clinical value of non-invasive, in vivo CLDN18.2 visualization.

For patients with malignant tumors, the study will assess the diagnostic performance of CLDN18.2-targeted PET in identifying tumor lesions, compare the imaging results with gold-standard histopathology, determine the location, extent, and metabolic features of CLDN18.2-positive lesions, and evaluate tumor burden and treatment stratification value compared with [^18F]FDG PET imaging. These results may assist in patient selection for CLDN18.2-targeted therapies (e.g., Zolbetuximab), guide clinical decision-making, and provide early prediction of therapeutic response.

For healthy volunteers, pharmacokinetic profiling will be conducted to investigate the biodistribution, clearance, and safety of the radiotracer in vivo.

Inclusion Criteria:

• Each participant must meet all inclusion criteria to be eligible to participate in the study:

  1. The participant or their legal representative is able to sign the informed consent form with signature and date;
  2. Commit to adhering to the research procedures and cooperating in the implementation of the entire research process;
  3. Adult patients or healthy volunteers (aged 18-70 years), male or female;
  4. Patients with malignant tumors such as gastric cancer, pancreatic cancer, bile duct cancer, esophageal cancer, etc., suspected or diagnosed clinically (supporting evidence includes serum tumor markers, ultrasound, CT, MRI, and other imaging data, as well as histopathological examination), and in good general condition;
  5. Meet specific laboratory test results;
  6. Women of childbearing age must use contraception for at least one month before screening and commit to using contraception throughout the study period and continuing it until the specified time after the study ends;
  7. Other set inclusion criteria.

Exclusion Criteria:

• All subjects who meet any exclusion criteria baseline will be excluded from the study:

  1. Those unable to complete PET/MR or PET/CT scans (including those unable to lie flat, claustrophobia, radiation phobia, etc.);
  2. Those with other comorbidities;
  3. Patients known to be allergic to the targeted CLDN18.2 PET imaging agent or synthetic excipients; fasting blood glucose level exceeding 11.0 mmol/L before injection of 18F-FDG;
  4. Those with a history of concomitant medication use;
  5. Patients considered to have poor compliance by the researcher.

Patients with suspected or confirmed malignant tumors such as gastric adenocarcinoma, pancreatic cancer, bile duct cancer, esophageal adenocarcinoma, etc. (supporting evidence includes serum tumor markers, ultrasound, CT, MRI, and histopathological examination of tissue, etc.), and in good general condition.