<prompt> Radioisotope used for thyroid treatment of metastasis ablation:I-123I-131I-83I-90  <response>: Ans. B. I-131 Iodine-131 has a radioactive decay half-life of about eight days. Iodine-131 exhibits a beta mode of decay and leads to death in cells that it penetrates up to several millimeters and hence is useful for thyroid ablation. I-123 has a half-life of 13.22 hours and is a radioactive isotope of iodine used in nuclear medicine imaging, including single photon emission computed tomography. 