The Technetium Generator
A technetium-99m generator, often called a moly cow is a device used to extract the metastable isotope
of technetium from a source of decaying molybdenum-99.
has a half-life of 66 hours and can be easily transported over long distances to hospitals where its decay product technetium-99m (with a half-life of only 6 hours, inconvenient for transport) is extracted and used for a variety of medical purposes where its short half-life is very useful.. It decays with emission of a
- ray. The half life of 6 hours is extremely long for an electromagnetic decay - more typical is 10-16 seconds. Technetium-99m is employed in about 80% of all nuclear medicine procedures. This is because it has almost ideal characteristics for a nuclear medicine scan:
The half life is long enough to examine metabolic processes, yet short enough to minimize the radiation dose to the patient.
The energy of the gamma ray it emits is low, enabling easy imaging.
The chemistry of technetium is so versatile that it can be chemically bound to many different types of biologically active molecule for tracer work.
For medical purposes, 99mTc is used in the form of pertechnate (alias pertechnetate),
an anion similar in size to the iodide anion. As a result it is taken up by the thyroid, but is not bound to the organic structures into which iodine is incorporated to produce thyroxin and the other thyroid hormones.
Technetium-99m is used to image the skeleton, heart muscle, brain, thyroid, lungs, liver, spleen, kidney, gall bladder, bone marrow, salivary and lachrymal glands, heart blood pool, infection and numerous specialized medical studies.