Iodine123

Iodine-123 (I-123) is a radioactive isotope of the element iodine (atomic number 53) with a mass number of 123. It is used primarily in nuclear medicine for diagnostic imaging of the thyroid gland and related uptake studies.

Physical properties: The half-life is about 13.2 hours. It decays by electron capture to tellurium-123 and emits gamma radiation, most notably a 159 keV photon, which is well-suited for gamma cameras and SPECT imaging. It does not emit significant beta radiation, which helps keep patient radiation dose relatively low compared with beta-emitting alternatives.

Medical applications: I-123 is used in thyroid scintigraphy to visualize thyroid anatomy and function, and in uptake studies to measure how efficiently the thyroid absorbs iodine. It aids in the evaluation of nodules, Graves’ disease, and other thyroid disorders, and can help monitor treatment. Administration is commonly oral, as a sodium iodide preparation, followed by imaging at specified times after administration.

Production and supply: I-123 is produced in nuclear reactors or accelerators, typically via neutron or charged-particle induced reactions in precursors such as tellurium or xenon targets, followed by chemical separation to isolate iodide. Availability depends on radiopharmacy infrastructure and regulatory approvals, with the material supplied to licensed facilities for clinical use.

Safety and regulation: As a radiopharmaceutical, I-123 requires handling by trained personnel in licensed facilities. Its relatively short half-life minimizes long-term radiation exposure, but standard radiation safety practices, dosing controls, and regulatory guidelines govern its use, storage, transport, and waste disposal.