Iodine-123

Iodine-123 (also known as I-123) is a radioisotope of iodine used in nuclear medicine for diagnostic purposes. It is produced by the proton bombardment of xenon in a cyclotron, a type of particle accelerator.

Physical Characteristics

Iodine-123 has a half-life of approximately 13.2 hours. It decays by electron capture to stable tellurium-123, emitting gamma radiation with a primary energy of 159 keV, which is ideal for detection by a gamma camera.

Medical Uses

In nuclear medicine, Iodine-123 is used primarily for the evaluation of thyroid function. It is the preferred isotope for such studies, as it does not cause damage to the thyroid gland unlike Iodine-131, which is a beta particle emitter. Iodine-123 is also used in single photon emission computed tomography (SPECT) imaging of the brain to study blood flow and neurotransmitter activity.

Production and Availability

Iodine-123 is produced in a cyclotron by proton bombardment of xenon. The resulting xenon-123 undergoes beta decay to produce Iodine-123. The isotope is then purified and made available for medical use. Due to its short half-life, Iodine-123 must be used shortly after production.

Safety and Precautions

While Iodine-123 is less harmful than other iodine isotopes, precautions must still be taken when handling and administering it. Patients undergoing tests with Iodine-123 are exposed to radiation, and the risks must be weighed against the benefits of the diagnostic information obtained.

See Also

• Nuclear medicine
• Radioisotope
• Iodine-131
• Cyclotron
• Gamma camera
• Single photon emission computed tomography