223Ra for endoradiotherapeutic applications prepared from an immobilized227Ac/227Th source

A method is described for the production of 223 Ra ( t 1/2 =11.4 d) in a quality useful for endoradiotherapeutic applications. The method is based on a long term operating generator with a source of 227 Ac ( t 1/2 =21.7 years), from which 223 Ra is eluted. The 227 Ac was isolated from a 231 Pa source using the f-element selective extraction chromatographic material TRU-resin. The purified 227 Ac/ 227 Th source was subsequently applied to another extraction chromatographic resin, containing the extractant P,P ′ -di(2-ethylhexyl)methanediphosphonic acid on silica (Dipex-2) and used as a generator for 223 Ra. From the generator column, the yield of 223 Ra was about 60 kBq per 100 kBq of 227 Ac with a highly effective separation of 223 Ra from the precursors. In production runs, the activity of 227 Ac was found to be 6×10 -6 relative to the eluted activity of 223 Ra. By using a second column of Dipex-2 for additional purification, the activity of Ac was reduced to below 7×10 -8 relative to 223 Ra with nearly quantitative recovery of 223 Ra. The described procedure resulted in a high purity 223 Ra preparation, potentially useful in, e.g ., targeted radiotherapy of tumors.