iód131

Iodine-131, often abbreviated as I-131, is a radioactive isotope of iodine used in medicine and nuclear science. It has an atomic number of 53 and a mass number of 131. I-131 decays by beta-minus emission to xenon-131 with a half-life of about 8.02 days and emits gamma photons of 364 keV, which makes it suitable for both therapeutic and diagnostic applications.

I-131 is produced in nuclear reactors by neutron irradiation of tellurium targets, typically Te-130 or Te-131, which yields Te-131 that subsequently decays to I-131. The radiochemical separation of the iodine from the target material is required to obtain medical-grade I-131 for clinical use.

Medical applications of I-131 focus on thyroid disorders. The isotope is used in radioiodine therapy to ablate hyperactive thyroid tissue in conditions such as hyperthyroidism and Graves’ disease, and to destroy residual thyroid tissue or metastases after thyroid cancer surgery. Diagnostic uses include small, controlled diagnostic doses to measure thyroid uptake and function, often preceding therapeutic treatment.

Administration and dosing depend on the condition being treated. Diagnostic doses are relatively small and used for imaging, while therapeutic doses are larger and delivered with radiation safety precautions. Patients may need guidance regarding pregnancy and breastfeeding due to radiation risk, and treatment typically occurs in facilities equipped for radioactive materials.

Safety and regulation are central to I-131 use. Radiation exposure to the patient, caregivers, and the environment is tightly controlled, with monitoring of thyroid function and potential side effects such as transient thyroiditis, sialadenitis, altered taste or dry mouth, and, at higher doses, hypothyroidism or bone marrow suppression. Proper handling, shielding, and disposal follow established radiopharmaceutical guidelines.