A radionuclide generator is a device which provides a local supply of a short-lived radioactive substance from the decay of a longer-lived parent radionuclide.
[2][3] Use of a generator avoids the challenge of distributing short-lived radionuclides from the original production site (typically a nuclear reactor) to individual users; the loss of activity due to decay in transit can result in too little being supplied or the need for much larger initial quantities to be sent out (incurring additional production and transport costs).
It is feasible to have cyclotrons at larger centres, but they are much more expensive and complex than generators.
In some cases a cyclotron is used to produce the parent radionuclide for a generator.
[5] Long-lived radionuclides which are administered to a patient with a view to utilising useful properties of a daughter product have been termed in-vivo generators, though they are not routinely used clinically.