This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fundamentals in Radiology, Subject name: Radiology
[{'content': 'What is meant by PET scan ? \nSelect and explain. \nA. Positive Emission Tomography, B. Positron Emission Tomography, C. Positron Energy Tomography, D. Positive Energy Tomography', 'role': 'user'}, {'content': 'Answer: B \nExplanation: PET stands for positron emission tomography', 'role': 'assistant'}]