The purpose of this study was to evaluate the diagnostic efficacy and prognostic value of 18F-FAPI PET/CT combined with multiparameter MRI in gastric cancer.

Evaluation of the diagnostic and staging efficacy of 18F-FAPI PET/CT combined with multiparametric MRI This study aims to evaluate the sensitivity, specificity, and accuracy of 18F-FAPI PET/CT combined with multiparametric MRI in gastric cancer patients, providing a basis for clinical application. By performing 18F-FAPI PET/CT and multiparametric MRI imaging on gastric cancer patients, relevant data were collected and analyzed to assess their performance in early diagnosis, staging, and recurrence monitoring. The goal is to provide a scientific basis for clinical physicians in the diagnosis, precise staging, and treatment decision-making of gastric cancer.

2.1.2 Comparative Study of 18F-FAPI PET/CT and Contrast-Enhanced MRI A comparative study of 18F-FAPI PET/CT and contrast-enhanced MRI in gastric cancer patients to evaluate the differences in tumor detection sensitivity, specificity, and accuracy among various imaging modalities. The study aims to clarify their advantages in clinical applications for gastric cancer. The research will focus on analyzing the differences in tumor size, location, metastasis, and pathological characteristics detected by each imaging technique, and explore the potential of 18F-FAPI PET/CT combined with multiparametric MRI in improving the diagnostic accuracy and early detection of gastric cancer.

2.1.3 Analysis of diagnostic differences in gastric cancer subgroups using 18F-FAP PET/CT combined with multiparametric MRI Subgroup analysis was performed based on pathological type, stage, and molecular subtype, stratified by disease pathological type, stage (early/progressive/advanced), and molecular subtype, to evaluate the differences in sensitivity and specificity of 18F-FAPI PET/CT combined with multiparameter MRI across different patient populations. This study will help identify which specific types of gastric cancer patients are more likely to benefit from 18F-FAPI PET/CT, thereby providing a basis for the development of individualized treatment plans.

2.1.4 Evaluation of Multimodal Imaging Combinations in Predicting Gastric Cancer Prognosis Based on TNM staging and PERCIST criteria, this study evaluates the post-treatment reassessment, efficacy prediction, and prognostic assessment (AUC comparison of PFS/OS) of 18F-FAPI PET/CT combined with multiparametric MRI in gastric cancer. The research aims to analyze the multimodal imaging combination's monitoring capability for tumor response post-treatment and its value in prognostic evaluation, providing clinicians with a more precise tool for therapeutic outcome assessment. It tracks the time from diagnosis to specific events (e.g., CR, PR, SD, PD, recurrence, death) in gastric cancer patients to identify influencing factors. Survival rates over time are plotted using Kaplan-Meier curves to visually compare survival differences across groups. Additionally, Cox proportional hazards model-based multivariate regression quantifies the contribution of factors such as age and pathological stage to survival risk, aiding clinical decision-making.

Inclusion Criteria:

1. Patients suspected or diagnosed with gastric cancer
2. 18F-FAPI PET/CT has been performed
3. Gastric MRI with both non-contrast and contrast-enhanced scans performed

Exclusion Criteria:

1. Concurrent presence of other active malignant tumors or a history of other malignant tumors within the past 5 years;
2. Severe uncontrollable diseases or active infections;
3. Ineligible participants who cannot provide informed consent for the study;
4. Patients with suboptimal image quality in 18F-FAPI PET/CT
5. Patients with suboptimal MRI image quality enhancement

The purpose of this study was to evaluate the diagnostic efficacy and prognostic value of 18F-FAPI PET/CT combined with multiparameter MRI in gastric cancer.

Primary endpoint: Diagnostic efficacy of 18F-FAPI PET/CT combined with multiparametric MRI in gastric cancer patients (sensitivity, specificity, accuracy) secondary end points:

• To compare the diagnostic performance differences between 18F-FAPI PET/CT and contrast-enhanced MRI in the clinical application of gastric cancer; ② Analysis of diagnostic differences in the subgroup (pathological, genetic, etc.) of patients using 18F-FAPI PET/CT combined with multiparameter MRI; ③ Evaluation of 18F-FAPI PET/CT combined with multiparameter MRI in predicting the prognosis of gastric cancer.