Technetium-99m-Generator

A technetium- 99m generator is a nuclide to extract the metastable isotope technetium- 99m from a source, the decaying molybdenum -99 contains. Technetium -99m is used for a variety of applications in nuclear medicine.

99Mo has a half-life of 66 hours and can be delivered to hospitals and practices over larger distances where the decay product technetium- 99m is extracted ( with the very unfavorable for the transport half-life of only 6 hours). In nuclear medicine, the short half-life, the favorable radiation quality ( gamma emitters ) and the favorable radiation energy ( 140.1 and 140.6 keV ) of technetium- 99m is greatly appreciated.

Mechanism

The half-life of the parent, 99Mo is much greater than that of the daughter nuclide of99m Tc with 6 hours of 66 hours. 50 % of the equilibrium activity is achieved within a half-life of the daughter, 75 % over two half-lives of the daughter. Therefore ( generator " milking " ) the removal of the daughter nuclide ( elution process ) from the generator is usefully carried out approximately every 6-12 hours.

Most commercial 99Mo/99mTc-Generatoren using 99mTc- chromatography columns, is applied in the 99Mo on acidic alumina. Pressing a normal saline solution through the columns with immobilized and soluble 99Mo 99mTc, results in a salt solution containing 99m Tc, with the subsequent specific for each member is placed in a pharmaceutical suitable concentration. The isotope can be (eg, thyroid scintigraphy ), used without pharmaceutical labeling for certain purposes that require pure 99mTc as ​​the primary radiopharmaceutical.

The useful life of a 99Mo/99mTc-Generators is about three half lives of the molybdenum, or about one week. Thereafter, the content of 99Mo is too low. Thus, a hospital or private practice for nuclear medicine buys least one such generator per week or more in a staggered form.

99Mo, by neutron activation ( N r reaction) of 98Mo are produced with a high neutron flux in a reactor. The most used method using a 235U target. By irradiation of the target with neutrons 99Mo formed as a breakdown product.

Decay process

The running in a technetium generator decomposition process can be described as follows:

This breaks down the 99Mo with 66.02 hours Half-life in excited states of 99Tc. About 14 % of the 99Mo decay by beta-minus decay to the ground state of 99Tc and about 86 % in the metastable state 99mTc. This in turn results in an excitation energy of 143 keV and decays with gamma emission and internal conversion with a half-life of 6.02 hours into the unstable state of the base 99Tc.