Editing Radioactive tracer (section)

===Iodine===
{{main|Isotopes of iodine}}
[[Isotopes of iodine|<sup>123</sup>I]] is produced by proton irradiation of <sup>124</sup>[[xenon|Xe]]. The [[caesium]] isotope produced is unstable and decays to <sup>123</sup>I. The isotope is usually supplied as the iodide and hypoiodate in dilute sodium hydroxide solution, at high isotopic purity.<ref>[http://www.mds.nordion.com/documents/products/I-123_Solu_Can.pdf I-123 fact sheet]{{dead link|date=April 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> <sup>123</sup>I has also been produced at Oak Ridge National Laboratories by proton bombardment of [[tellurium|<sup>123</sup>Te]].<ref>{{cite journal | vauthors = Hupf HB, Eldridge JS, Beaver JE | title = Production of iodine-123 for medical applications | journal = The International Journal of Applied Radiation and Isotopes | volume = 19 | issue = 4 | pages = 345–51 | date = April 1968 | pmid = 5650883 | doi = 10.1016/0020-708X(68)90178-6 }}</ref>

<sup>123</sup>I decays by [[electron capture]] with a half-life of 13.22 hours. The emitted 159&nbsp;[[keV]] [[gamma radiation|gamma ray]] is used in [[single-photon emission computed tomography]] (SPECT). A 127&nbsp;keV gamma ray is also emitted.

[[Isotopes of iodine|<sup>125</sup>I]] is frequently used in [[radioimmunoassay]]s because of its relatively long half-life (59 days) and ability to be detected with high sensitivity by gamma counters.<ref>{{cite journal | vauthors = Gilby ED, Jeffcoate SL, Edwards R | title = 125-Iodine tracers for steroid radioimmunoassay | journal = The Journal of Endocrinology | volume = 58 | issue = 1 | pages = xx | date = July 1973 | pmid = 4578967 }}</ref>

[[Isotopes of iodine|<sup>129</sup>I]] is present in the environment as a result of the testing of [[nuclear weapons]] in the atmosphere. It was also produced in the [[Chernobyl disaster|Chernobyl]] and [[Fukushima Daiichi nuclear disaster|Fukushima]] disasters. <sup>129</sup>I decays with a [[half-life]] of 15.7 million years, with low-energy [[beta particle|beta]] and [[gamma ray|gamma]] emissions. It is not used as a tracer, though its presence in living organisms, including human beings, can be characterized by measurement of the gamma rays.