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': 'Investigation of choice in parathyroid pathology is: \nSelect and explain. \nA. CT scan, B. Gallium scan, C. Thallium scan, D. Technetium-thallium subtraction scan', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. Technetium-thallium subtraction scan', 'role': 'assistant'}]