Hydroxyapatite-based 99Mo/99mTc and 188W/188Re generator systems

Radioisotope generator systems have traditionally played a central role in nuclear medicine in providing short-lived radioisotopes for research and clinical applications. Techenitum-99m (half-life 6 h) is the most widely used radionuclide in diagnosis, and rhenium-188 (16.9 h) is a particularly attractive candidate for therapeutic applications. These daughter radioisotopes are provided by the 99Mo/99mTc and 188w/188Re generator systems in which 99Mo and 188w are adsorbed onto an alumina chromatographic column and the less strongly bound 99mTcO4- and 188ReO4- are eluted with isotonic saline solutions. This work proposes to use hydroxyapatite as the adsorbent material for both 99Mo/99mTc and 188w/188Re generator systems. Hydroxyapatite is an insoluble solid with anion exchange properties. A study of the adsorbent behaviour of 99Mo, 99mTc, 188w and 188Re on hydroxyapatite in NaCl and CaCl2 media was evaluated with batch experiments. Our results demonstrated that while 99Mo, 99mTc, 188w and 188Re are not adsorbed by the hydroxyapatite in NaCl solutions (Kd<5), use of CaCl2 solutions results in strong adsorption of 99Mo and 188w (Kd>500) whereas 99mTc and 188Re are weakly adsorbed (kd<5). Based on these measurements, hydroxyapatite 99Mo/99mTc and 188w/188Re generator systems were then constructed and eluted in CaCl2 solutions. The generator performances are presented and a method to modify the media of 99mTcO4- and 188ReO4- solutions is also proposed