Establishment of MRI Model for pTRG in Rectal Cancer With Establishment of

they will received two pelvic MR examinations before and after neoadjvant therapy. The MRI before neoadjvant therapy is considered as baseline MRI, which is usually taken within 3 weeks before NAT. The MRI after neoadjvant therapy is considered as preoperative MRI, which is usually taken within 3-8 weeks before NAT.