188W/188Re Generator System and Its Therapeutic Applications

Abstract

The 188Re radioisotope represents a useful radioisotope for the preparation of radiopharmaceuticals for therapeutic applications, particularly because of its favorable nuclear properties. The nuclide decay pattern is through the emission of a principle beta particle having 2.12 MeV maximum energy, which is enough to penetrate and destroy abnormal tissues, and principle gamma rays (Eγ=155 keV), which can efficiently be used for imaging and calculations of radiation dose. 188Re may be conveniently produced by 188W/188Re generator systems. The challenges related to the double neutron capture reaction route to provide only modest yield of the parent 188W radionuclide indeed have been one of the major issues about the use of 188Re in nuclear medicine. Since the specific activity of 188W used in the generator is relatively low (<185 GBq/g), the eluted Re188O4- can have a low radioactive concentration, often ineffective for radiopharmaceutical preparation. However, several efficient postelution concentration techniques have been developed, which yield clinically useful Re188O4- solutions. This review summarizes the technologies developed for the preparation of 188W/188Re generators, postelution concentration of the 188Re perrhenate eluate, and a brief discussion of new chemical strategies available for the very high yield preparation of 188Re radiopharmaceuticals.