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
Isotope used in RAIU – 
Select and explain. 
A. I131, B. I123, C. I125, D. I127
B: I123
Answer: B: I123 
Explanation: RAIU stands for radioactive iodine uptake. It is a thyroid imaging method that measures the fraction of orally administered iodine isotope taken up by thyroid. 1123 is the agent of choice for RAIU.