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a chemical element, atomic number 53, atomic weight 126.904. (See Appendix 6.) Iodine is essential in nutrition, being especially prevalent in the colloid of the thyroid gland. It is used in the treatment of hypothyroidism and as a topical antiseptic. Iodine is a frequent cause of poisoning (see iodism). Deficiency of iodine causes goiter. Since iodine salts are opaque to x-rays, they can be combined with other compounds and used as contrast media in diagnostic x-ray examinations of the gallbladder and kidneys.
iodine 123 a radioactive isotope of iodine having a half-life of 13.2 hours and emitting gamma rays and x-rays. It is used in diagnostic imaging and as radiation sources in radiation therapy. Symbol 123I.
iodine 125 a radioisotope of iodine having a half-life of 60.14 days and emitting gamma rays; used as a label in radioimmunoassays and other in vitro tests, and also for thyroid imaging. Symbol 125I.
iodine 131 a radioactive isotope of iodine having a half-life of 8.04 days and emitting beta particles and gamma rays. It is used as a tracer in diagnostic imaging and as a radiation source in radiation therapy. Symbol 131I.
radioactive iodine radioiodine.
iodine solution a transparent, reddish brown liquid, each 100 ml of which contains 1.8 to 2.2 g of iodine and 2.1 to 2.6 g of sodium iodide; a local antiinfective agent.
strong iodine solution Lugol's solution.
A radioisotope of iodine with a 159-keV gamma emission and a half-life of 13.2 h, used for studies of thyroid disease and of renal function.