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

M.      R.A. Pillai; Ashutosh      Dash; F.      F. Knapp

Abstract

Rhenium-188 is one of the most readily available generator derived and useful radionuclides for therapy emitting β- particles (2.12 MeV, 71.1% and 1.965 MeV, 25.6%) and imageable gammas (155 keV, 15.1%). The 188W/188Re generator is an ideal source for the long term (4-6 months) continuous availability of no carrier added (nca) 188Re suitable for the preparation of radiopharmaceuticals for radionuclide therapy. The challenges associated with the double neutron capture route of production of the parent 188W radionuclide have been a major impediment in the progress of application of 188Re. 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 188W/188Re generators. Since the specific activity of 188W used in the generator is relatively low 185 GBq(<5 Ci)/g], the eluted 188ReO4 - can have low radioactive concentration often insufficient for radiopharmaceutical preparation. However, several efficient post elution concentration techniques have been developed that yield clinically useful 188ReO4 - 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 188Re-labeled phosphonates, antibodies, peptides, lipiodol and particulates have been reported. This article reviews the availability and use of188Re including a discussion of why broader use of 188Re has not progressed as expected as a popular radionuclide for therapy.

Keywords: Rhenium-188, 188W/188Re generator, Radionuclide therapy, Bone pain palliation, hepatocarcinoma, Rheumatoid arthritis, neutron flux, Gel Generator, biphasic system, Antibodies