Application of PET/MRI in the Evaluation of the Efficacy of Neoadjuvant Therapy for Locally Advanced Rectal Cancer

This study plans to include LARC patients receiving neoadjuvant therapy at this center, conducting PET/CT and PET/MR examinations before treatment, and PET/MR examinations before surgery after neoadjuvant therapy. The changes in the lesion before and after treatment will be compared to evaluate the efficacy of neoadjuvant therapy, including: the relief situation of the rectal primary lesion ; lymph node metastasis; local infiltration around the tumor; peritoneal and other distant metastases , etc. The pathological relief diagnosed by surgical pathology is the gold standard, and the predictive efficacy of PET/MR will be evaluated, comparing the advantages and disadvantages of 18F-FDG and 68Ga-FAPI PET/MR, and comparing with traditional PET/CT and rectal MRI to explore the value of PET/MRI in predicting the efficacy of neoadjuvant therapy in LARC patients.