A generator is a device that is used to extract one nuclide from another. For example, technetium-99m is recovered from technetium generators, which are shielded cartridges that contain molybdenum-99. Saline solutions can be passed through these generators (a process known as “milking”) to recover the technetium-99m.
The ability to access PET radionuclides without the use of onsite accelerators or reactors depends upon the availability of generator-produced radionuclides. Lawrence Berkeley National Laboratory developed the first practical generators for the germanium-68/gallium-68 and the strontium-82/rubidium-82 pairs. Strontium-82 is now being used with increasing frequency for clinical cardiac studies. It is presently supplied through a consortium of accelerators throughout the world that run parasitically and is not under the control of the user community. With the increasing demand for the strontium-82 generator, the current sources may not be sufficient in sustaining availability of this radionuclide.
ORNL developed the tungsten-188/carrier-free rhenium-188 perrhenic acid generator system. Rhenium isotopes have chemistry similar to that of technetium and thus are of interest for adapting the extensive labeling tools created for technetium-99m. Rhenium-188 in particular is attractive for certain therapy applications because it emits a high-energy beta particle and has a relatively short half-life.
The Department of Energy’s (DOE) national laboratories remain the primary source of less commonly used or exotic radionuclides, produced from their large reactor and accelerator facilities. These facilities include the High Flux Isotope Reactor (HFIR) at ORNL, Brookhaven Linac Isotope Producer (BLIP) at BNL, the Isotope Production Facility at Los Alamos Nuclear Science Center (LANSCE) at Los Alamos National Laboratory