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Iodine is an essential trace element, found in many foods and an essential part of thyroid biology. Iodine-124 is a synthetic, proton-rich radioisotope produced for imaging, with a half-life of about 4.2 days.
Iodine-124 decays partly by positron emission, which makes it suitable for high-resolution PET imaging, and its relatively long half-life is unusual among PET isotopes. That longevity allows it to track molecules with slow kinetics, such as antibodies, over several days, supporting quantitative imaging that shorter-lived tracers cannot.
It is used in immuno-PET to image radiolabelled antibodies, in thyroid cancer imaging and dosimetry, and in quantitative physiological studies where its long half-life and positron emission are advantageous. It holds a key position for dosimetry of next-generation astatine-211 radiopharmaceuticals.
Iodine-124 is produced in a cyclotron, but challenges in achieving sufficient yield and high radionuclidic purity while limiting co-produced iodine impurities limit production to relatively few specialist suppliers.
StandardX is developing accelerator-based production to deliver high-purity iodine-124 at greater scale.