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': 'Best imaging study for the earliest diagnosis of cerebral infarct- \nSelect and explain. \nA. FLAIR MRI, B. Non-contrast CT, C. CECT, D. Diffusion-weighted MRI', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Diffusion-weighted MRIDiffusion-weighted MRI detects cytotoxic edema in just a few hours of infarction.', 'role': 'assistant'}]