iodine125

Iodine-125 is a radioactive isotope of iodine with a mass number of 125. It is produced in nuclear reactors or accelerator facilities by irradiating stable precursor isotopes and is subsequently chemically isolated as an iodide. The nucleus decays by electron capture to tellurium-125 with a half-life of about 59.4 days, emitting low-energy gamma photons, primarily around 35 kiloelectronvolts, along with Auger electrons.

Due to its relatively low gamma energy and moderate half-life, iodine-125 is used as a sealed radioactive source in medical and research applications. In medicine, it is widely used in brachytherapy, where small capsules or seeds containing 125I are implanted near or within tumors to deliver localized radiation. It is also used in radiolabeling and various biochemical assays, where 125I-labelled compounds serve as tracers in research and diagnostic workflows. Additionally, 125I sources are employed as calibration and reference standards for gamma cameras and dosimetry equipment.

Production and handling: Iodine-125 is prepared in controlled environments, typically as sealed sources for safety and containment. Its low-energy emissions require appropriate shielding and radiological controls to limit external exposure. Handling, storage, transport, and disposal are subject to strict regulatory oversight and licensing by national authorities.

Safety considerations: Because 125I emits gamma rays and can be hazardous if ingested or inhaled, facilities using it implement radiation protection programs, including dose monitoring, shielding, containment, and leak tests for sealed sources. Accidental release or improper disposal can pose environmental and occupational health risks, so standardized procedures govern its use and accountability.