Ra-223 for endoradiotherapeutic applications prepared from an immobilized Ac-227/Th-227 source

A method is described for the production of Ra-223 (t(1/2) = 11.4 d) in a q uality useful for endoradiotherapeutic applications. The method is based on a long term operating generator with a source of Ac-227 (t(1/2) = 21.7 yea rs), from which Ra-223 is eluted. The Ac-227 was isolated from a Pa-231 sou rce using the f-element selective extraction chromatographic material TRU-r esin. The purified Ac-227/Th-227 source was subsequently applied to another extraction chromatographic resin, containing the extractant P,P'-di(2-ethy lhexyl)methanediphosphonic acid on silica (Dipex-2) and used as a generator for Ra-223. From the generator column, the yield of Ra-223 was about 60 kB q per 100 kBq of Ac-227 with a highly effective separation of Ra-223 from t he precursors. In production runs, the activity of Ac-227 was found to be 6 x 10(-6) relative to the eluted activity of Ra-223. By using a second colu mn of Dipex-2 for additional purification, the activity of Ac was reduced t o below 7 x 10(-8) relative to Ra-223 with nearly quantitative recovery of Ra-221. The described procedure resulted in a high purity Ra-223 preparatio n, potentially useful in, e.g., targeted radiotherapy of tumors.