<prompt> Iodine isotope used for radio ablation of thyroid in Graves disease is:I-125I-123I-131I-124  <response>: Radio-isotopes Half-life Uses I-131 8 days Radio ablation of thyroid gland Systemic radiotherapy of thyroid metastasis I-125 60 days Brachytherapy prostate cancer Radio-immunoassay I-124 4 days Positron emitter PET I-123 13 hours Functional scanning of thyroid gland Thyroid scintigraphy Radio-active Iodine Uptake RAIU 