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': 'A PET scan uses which of the following tracer materials? \nSelect and explain. \nA. FDG, B. CDF, C. ADP, D. MIBG', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A PET scan uses a small amount of a radioactive drug, or tracer, to show differences between healthy tissue and diseased tissue. The most commonly used tracer is called FDG (fluorodeoxyglucose), so the test is sometimes called an FDG-PET scan. Before the PET scan, a small amount of FDG is injected into the patient. Because cancer grows at a faster rate than healthy tissue, cancer cells absorb more of the FDG. The PET scanner detects the radiation given off by the FDG and produces color-coded images of the body that show both normal and cancerous tissue.', 'role': 'assistant'}]