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': 'Time of Flight technique is employed in – \nSelect and explain. \nA. Spiral CT, B. MR imaging, C. CT angiography, D. Digital radiography', 'role': 'user'}, {'content': "Answer: B \nExplanation: 'Time of flight (TOF)' technique is employed in magnetic resonance angiography (MR angiography).", 'role': 'assistant'}]