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': 'All of the following radioisotopes are used as systemic radionuclides, EXCEPT: \nSelect and explain. \nA. Iridium192, B. Strontium89, C. Samarium153, D. Phosphorus32', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Systemic radionuclides are non sealed radio nuclides which are administered orally, intravenously or intracvitarily. Sodium iodide (I131), sodium phosphate (P32), samarium 153, strontium 89 chloride and rhenium are used as systemic radionuclides. Ref: Principles of Radiation Oncology By Carlos and Luther, 4th Edition, Pages 636-7', 'role': 'assistant'}]