232Th-Spallation-Produced 225AC with Reduced 227AC Content

Recent clinical results have demonstrated remarkable treatment responses of late -stage cancer patients when treated with alpha-emitting radionuclides such as actinium-225 (22sAc). The resulting intense global effort to produce greater quantities of 22sAc has triggered a number of emerging technologies to produce this rare, yet important, radionuclide. Accelerator -based methods for increasing global225Ac production capacity have focused on the high energy (>100 MeV) proton irradiation of thorium,;despite the coproduction_ of the undesirable 217Ac byproduct at 0.1-0.3% of the 22sAc activity. We at TRIUMF have developed a process for the 225,-. /225 A rproduction of a Tsai Ac generator from irradiated thorium 'that results in an22Ac product with reduced227Ac content. 22SAC was separated from irradiated thorium and coprodticed radioactive neutrons s- a ation and fission. r 0d CtS using s in g a thoriumi um peroxide er o xide pr ecipit atio n methodeth od followed b) y cation e xc han ge andnd ext r ac io nchrematograpStableand radioactive tracer studies dem nsttatedtheabilitY fthis methodtoseparateAcfom most other elements, providing a directly produced Ac product with measured 227Ac content of (0.15 0.04)0o. A second, indirectly produced Ac product with2'Ac content of <7.5 x 10- s% is obtainedbYrePea ing the fin l extraction chromatography step with the 22Ra containingfract n.The 21sRa- derived 22sAcshowed similar orimaiovedqtgity compared to the directly produced Product in terms of chemicai purity and radio-a eling capability, the latter of which wascomparableth other 225Ac sources reported in the literature.