This is a prospective, single-center, diagnostic study designed to compare the accuracy of \[68Ga\]Ga-CTR-FAPI PET/MRI and \[18\]F-FDG PET/MRI for the detection of lymph node metastasis in patients with initially untreated, resectable middle to high rectal cancer. The study aims to evaluate whether \[68Ga\]Ga-CTR-FAPI PET/MRI provides higher sensitivity and specificity than traditional 18F-FDG PET/MRI at both the patient level and the lymph node level.
Confirmed rectal adenocarcinoma by pathological biopsy.
Lower margin of the tumor is ≥ 5 cm and ≤15 cm from the anal verge.
Planned to undergo radical surgery.
ECOG performance status score ≤ 2.
History of pelvic radiotherapy or chemotherapy.
Concurrent with other malignant tumors or active infections.
Pregnant or unable to sign the informed consent form.
Claustrophobia or inability to tolerate MRI examinations due to other reasons.