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. Tc – Thallium substraction scan', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Presently, Tc - 99m sestamibi is the best available agent for parathyroid scanning. Therefore, Technetium - sestamibi (Tc - 99m MIBI) is the investigation of choice in the localization of parathyroid tumor.\nTc - 99m thallium subtraction scan is the second choice.', 'role': 'assistant'}]