Rhenium-188: Availability from the W-188/(188) Re Generator and Status of Current Applications

Rhenium-188 is one of the most readily available generator derived and useful radionuclides for therapy emitting beta(-) particles (2.12 MeV, 71.1% and 1.965 MeV, 25.6%) and imageable gammas (155 keV, 15.1%). The W-188/(188) Re generator is an ideal source for the long term (4-6 months) continuous availability of no carrier added (nca) Re-188 suitable for the preparation of radiopharmaceuticals for radionuclide therapy. The challenges associated with the double neutron capture route of production of the parent W-188 radionuclide have been a major impediment in the progress of application of Re-188. Tungsten-188 of adequate specific activity can be prepared only in 2-3 of the high flux reactors operating in the World. Several useful technologies have been developed for the preparation of clinical grade 188 W/188 Re generators. Since the specific activity of W-188 used in the generator is relatively low 185 GBq(< 5 Ci)/g], the eluted 188 ReO(4)(-)can have low radioactive concentration often insufficient for radiopharmaceutical preparation. However, several efficient post elution concentration techniques have been developed that yield clinically useful (ReO4-)-Re-188 solutions. Rhenium-188 has been used for the preparation of therapeutic radiopharmaceuticals for the management of diseases such as bone metastasis, rheumatoid arthritis and primary cancers. Several early phase clinical studies using radiopharmaceuticals based on Re-188-labeled phosphonates, antibodies, peptides, lipiodol and particulates have been reported. This article reviews the availability and use of Re-188 including a discussion of why broader use of Re-188 has not progressed as expected as a popular radionuclide for therapy.