Source:http://linkedlifedata.com/resource/umls/id/C0303024
NCI: A radioactive isotope of iodine, a nonmetallic element of the halogen group, with an atomic mass of 124 and a half-life of 4.18 days with radioisotopic activity. Selectively accumulating in thyroid tissue, iodine I 124 emits positrons that can be detected by positron emission tomography (PET), allowing localization of thyroid tissue. This radioisotope also emits gamma rays.