Editing Radioactive tracer (section)

===Technetium===
{{main|technetium-99m}}
[[Technetium-99m|<sup>99m</sup>Tc]] is a very versatile radioisotope, and is the most commonly used radioisotope tracer in medicine. It is easy to produce in a [[technetium-99m generator]], by decay of [[molybdenum|<sup>99</sup>Mo]].
:<sup>99</sup>Mo → <sup>99m</sup>Tc + {{Subatomic particle|Electron-}} + {{Subatomic particle|Electron antineutrino}}
The molybdenum isotope has a half-life of approximately 66 hours (2.75 days), so the generator has a useful life of about two weeks. Most commercial <sup>99m</sup>Tc generators use [[column chromatography]], in which <sup>99</sup>Mo in the form of molybdate, MoO<sub>4</sub><sup>2−</sup> is adsorbed onto acid alumina (Al<sub>2</sub>O<sub>3</sub>). When the <sup>99</sup>Mo decays it forms [[pertechnetate]] TcO<sub>4</sub><sup>−</sup>, which because of its single charge is less tightly bound to the alumina. Pulling normal saline solution through the column of immobilized <sup>99</sup>Mo elutes the soluble <sup>99m</sup>Tc, resulting in a saline solution containing the <sup>99m</sup>Tc as the dissolved sodium salt of the pertechnetate. The pertechnetate is treated with a [[reducing agent]] such as [[tin|Sn<sup>2+</sup>]] and a [[ligand]]. Different ligands form [[coordination complex]]es which give the technetium enhanced affinity for particular sites in the human body.

<sup>99m</sup>Tc decays by gamma emission, with a half-life: 6.01 hours. The short half-life ensures that the body-concentration of the radioisotope falls effectively to zero in a few days.