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: Unknown
[{'content': 'Which of the following is used to differentiate tumour recurrence and radiation necrosis? \nSelect and explain. \nA. PET scan, B. MRI, C. 3D CT, D. USG', 'role': 'user'}, {'content': 'Answer: A \nExplanation: ANSWER: (A) PET scanREF: Devita oncology 6th ed chapter 27PET may be used in therapeutic monitoring after chemotherapy or radiotherapy, with a classic indication being assessment for recurrent tumor versus radiation necrosis. Conventional imaging can not differentiate recurrent tumor from radiation necrosis', 'role': 'assistant'}]