Editing Radon (section)

==== Nuclear medicine ====
[[File:Radioactive Seeds (7845754328).jpg|thumb|{{sup|222}}Rn- and [[Iodine-125|{{sup|125}}I]]-containing seeds used in [[brachytherapy]]]]
Radon has been produced commercially for use in radiation therapy, but for the most part has been replaced by radionuclides made in [[particle accelerator]]s and [[nuclear reactor]]s. Radon has been used in implantable seeds, made of gold or glass, primarily used to treat cancers, known as [[brachytherapy]]. The gold seeds were produced by filling a long tube with radon pumped from a radium source, the tube being then divided into short sections by crimping and cutting. The gold layer keeps the radon within, and filters out the alpha and beta radiations, while allowing the [[gamma ray]]s to escape (which kill the diseased tissue). The activities might range from 0.05 to 5 millicuries per seed (2 to 200&nbsp;MBq).<ref name="Radon seeds" /> The gamma rays are produced by radon and the first short-lived elements of its decay chain (<sup>218</sup>Po, <sup>214</sup>Pb, <sup>214</sup>Bi, <sup>214</sup>Po).

After 11 half-lives (42 days), radon radioactivity is at 1/2,048 of its original level. At this stage, the predominant residual activity of the seed originates from the radon decay product <sup>210</sup>Pb, whose half-life (22.3 years) is 2,000 times that of radon and its descendants <sup>210</sup>Bi and <sup>210</sup>Po.{{cn|date=October 2022}}

<sup>211</sup>Rn can be used to generate <sup>211</sup>At, which has uses in [[targeted alpha therapy]].<ref>{{cite journal | last1=Crawford | first1=Jason R | last2=Kunz | first2=Peter | last3=Yang | first3=Hua | last4=Schaffer | first4=Paul | last5=Ruth | first5=Thomas J | title=<sup>211</sup>Rn/<sup>211</sup>At and <sup>209</sup>At production with intense mass separated Fr ion beams for preclinical <sup>211</sup>At-based α-therapy research | journal=Applied Radiation and Isotopes | publisher=Elsevier BV | volume=122 | year=2017 | issn=0969-8043 | doi=10.1016/j.apradiso.2017.01.035 | pages=222–228| pmid=28189025 | bibcode=2017AppRI.122..222C }}</ref>