This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
[{'content': 'The investigation of choice in aoic dissection is: \nSelect and explain. \nA. USG, B. CT, C. MRI, D. Digital segmental angiography', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. CT', 'role': 'assistant'}]