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Introduction to radionuclide generators

Radionuclide generators are a source of radionuclides for the production of radiopharmaceuticals. The other major sources of radionuclides are the cyclotron and the nuclear reactor (fission products, neutron activation products). By far the most important radionuclide generator for radiopharmaceutical preparation is the 99Mo → 99mTc generator often referred to as a technetium generator.

The generator sometimes seems like a magical device since it is able to provide short-lived radionuclides (short half-lives) over a time period much longer than this short half-life. The "magic" is really a unique equilibrium that is established between a long-lived "parent" radionuclide and its short-lived radioactive daughter. The second part of this magic is the ability to physically separate the parent and daughter radionuclides allowing the daughter to be used for the preparation of short-lived radiopharmaceuticals. In the 99Mo → 99mTc generator the parent is 99Mo with a half-life of 66 hours, which decays to produce the radioactive daughter 99mTc with a half-life of 6 hours. The separation of the parent and daughter is accomplished by simply washing the daughter from the generator with sterile saline.

The generators for this process are supplied commercially in a variety of configurations although the design features and separation and collection of the product 99mTc are similar in most cases.

More details of the 99Mo → 99mTc generator and general generator principles are provided under the following headings:

1. Design principles of the 99Mo → 99mTc generator.

2. Radionuclide principles of the 99Mo → 99mTc generator.

3. Elution methods.

4. Generator set-up.