This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Rectum, Subject name: Surgery
[{'content': 'Which of the following is the investigation of choice for assessment of depth of penetration and perirectal nodes in rectal cancer? \nSelect and explain. \nA. Trans rectal ultrasound, B. CT scan, C. Double contrast barium enema, D. MRI scan', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. (d) MRI ScanRef: Sabiston 19th Edition, Pages 1357-1358* Endo rectal MRI is the standard investigation to do T and N staging of cancer rectum* It's also good for overall staging** Even endorectal MRI is replaced now by surface coil MRI", 'role': 'assistant'}]