iodine123I

Iodine-123 (123I) is a radioactive isotope of iodine used in diagnostic nuclear medicine. It decays by electron capture to tellurium-123 with a half-life of 13.2 hours. Its decay produces gamma photons with an energy of 159 keV, suitable for detection by standard gamma cameras and SPECT systems. The relatively low energy and short half-life provide good image quality while minimizing radiation dose with higher-energy isotopes.

Production and handling: 123I is produced in nuclear reactors or cyclotrons. It is typically manufactured by irradiation of tellurium or xenon targets and subsequently separated chemically to obtain iodide. The production route depends on facility capabilities and regulatory constraints. Commercial 123I radiopharmaceuticals are provided in ready-to-use formulations for clinical imaging.

Clinical uses: The most common application is thyroid imaging and uptake studies to assess thyroid function and morphology, using sodium iodide labeled compounds. It is also used in radiopharmaceuticals for brain imaging, notably iodine-123-labeled ioflupane (FP-CIT) for dopamine transporter imaging (DaTSCAN), aiding in the evaluation of Parkinsonian syndromes. Another major use is iodine-123 metaiodobenzylguanidine (MIBG) for imaging of adrenergic tissue, such as pheochromocytoma and neuroblastoma, or cardiomyopathy evaluation.

Safety and regulation: As with other radiopharmaceuticals, 123I requires handling in specialized facilities. Typical diagnostic activities range widely but aim to keep radiation exposure as low as reasonably achievable. Waste management and patient-specific factors (age, pregnancy status) are considered during imaging protocols.