Technetium-99m generator

Encyclopedia : T : TE : TEC : Technetium-99m generator

The first "technetium cow" (a device for separating Tc-99m from its parent isotope, Mo-99) at Brookhaven National Laboratory.

A technetium-99m generator, or colloquially a technetium cow is a device used to extract the metastable isotope ^99mTc of technetium from a source of decaying molybdenum-99. ⁹⁹Mo has a half-life of 66 hours and can be easily transported over long distances to hospitals where its decay product technetium-99m (with an inconvenient half-life of only 6 hours for transport) is extracted and used for a variety of nuclear medicine diagnostic procedures, where its low half-life is very useful.

Mechanism

The half-life of the mother nuclide (Mo-99) is much longer than that of the daughter nuclide (Tc-99). 50% of equilibrium activity is reached within one daughter half-life, 75% within two daughter half-lives. Hence, removing the daughter nuclide (elution process)from the generator ("milking" the generator) is reasonably done every 6 hours or, at most, twice daily in a Mo-99/Tc-99m generator. Most commercial Mo-99/Tc-99m generators use column chromatography, in which Mo-99 is adsorbed onto acid alumina. Pulling normal saline solution through the column of immobilized Mo-99 elutes the soluble Tc-99m, resulting in a saline solution containing the Tc-99m which is then added to an appropriate concentration to the organ-specific pharmaceutical to be used. The Isotope can also be used without pharmaceutical tagging for specific procedures requiring only the Tc-99m as the primary radiopharmaceutical. The useful life of a Mo-99/Tc-99m generator is about 3 half lifes or approximately one week. Hence, any clinical nuclear medicine units purchase at least one such generator per week or order several in a staggered fashion.

^{99Mo can be obtained by the neutron activation (nγ reaction) of 98Mo in a high neutron flux reactor. The most used method require a uranium target with high enriched uranium (up to 90% U-235) or low enriched uranium (less than 20% U-235). The target should be irradated with neutrons to form 99Mo as a fission product [link].}

External links

• [Brookhaven National Laboratory site on the history of the technetium cow.]

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.