radioactive iodine

Iodine-131 (131I), also called radioiodine, is a radioisotope of iodine.131I decays with a half-life of 8.0197 days with beta and gamma emissions. This nuclide of iodine atom has 78 neutrons in nucleus, the stable nuclide 127I has 74 neutrons. On decaying, 131I transforms into ¹³¹Xe: 131I is a fission product with a yield of 2.8336%, and was released in nuclear weapons tests and the Chernobyl accident. However, the short half-life means it is not present in cooled spent nuclear fuel, unlike iodine-129.
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Iodine that gives off radiation. See radioiodine.

[RAY-dee-o-AK-tiv EYE-uh-dine]
A radioactive form of iodine, often usedfor imaging tests or as a treatment for thyroid cancer and certain other cancers. For imaging tests, the patient takes a small dose of radioactive iodine that collects in thyroid cells and certain kinds of tumors and can be detected by a scanner. For treatment of thyroid cancer, the patient takes a large dose of radioactive iodine, which kills thyroid cells. Radioactive iodine is also used in internal radiation therapy for prostate cancer, intraocular (eye) melanoma, and carcinoid tumors. The radioactive iodine is given by infusion or sealed in seeds, which are placed in or near the tumor to kill cancer cells. radioactive palladium A radioactive form of palladium (a metallic element that resembles platinum). When used to treat prostate cancer, radioactive seeds (small pellets that contain radioactive palladium) are placed in the prostate. Cancer cells are killed by the energy given off as the radioactive material decays (breaks down).