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Germanium-68

General information

For PET imaging, fluorine-18 is certainly the radioisotope of choice due to its favorable radiophysical characteristics. Many new vectors, including FLT, F-MISO, the F-Choline, the FES and F-DOPA, were clinically evaluated and some have obtained (F-DOPA, NaF, and F-choline), or could get in the coming years, a market authorization for routine use. However, the short half life of 110 minutes of fluorine-18 requires a cyclotron located at close distance of each user center. This is why there are more and more interest in Gallium-68, which has a physical half-life of 68 minutes. It can be obtained through its Father decay, the Germanium-68 whose physical period is long, 271 days.
Such a generator has the great advantage to be usable for several months in a nuclear medicine department. Gallium-68 also presents the interest of being a metal and thus provide opportunities for different complexation of fluoride which makes it more versatile.

The production of Germanium-68 requires a highly intense intermediate proton energy beams and long irradiation times.
Some manufacturers produce it using 30 MeV accelerators, others use a stack of targets irradiated by high energy protons. They can produce several isotopes of interest at the same time. This is the case for the production of Strontium-82 which is sometimes produced jointly with Germanium-68. (LANL, ithemba labs).

Production at ARRONAX

We decided to implement this latter method of production. The development of an Ni / Ga alloy as target for the production of Germanium-68 has been made. The use of such alloy makes possible, if proportions of atoms are chosen correctly, to increase the melting temperature of the target. Indeed, gallium has a low melting temperature (30 ° C) and is highly corrosive in the liquid state. A dedicated hot cell is now commissioned for production of Ge-68.

The next step will be to develop:

  • an irradiation device to accomodate our targets with adequate cooling
  • the chemical protocol for extraction and purification of Germanium-68.