Reactor production and electrochemical purification of169 Er: A potential step forward for its utilization in in vivo therapeutic applications

• Published in: Nuclear medicine and biology 2014, Vol.41 (2), p.163-170
• Main Authors: Chakravarty, Rubel, Chakraborty, Sudipta, Chirayil, Viju, Dash, Ashutosh
• Format: Article
• Language: English
• Subjects: Radiology
• ISSN: 0969-8051
• DOI: 10.1016/j.nucmedbio.2013.11.009

Abstract Introduction The aim of the present study was to develop and demonstrate a viable method for the reactor production of169 Er with acceptable specific activity using moderate flux reactor and its purification from169 Yb following electrochemical pathway based on mercury-pool cathode to avail169 Er in radionuclidically pure form essential for its therapeutic use. Methods Erbium-169 was produced in reactor by neutron bombardment of isotopically enriched (98.2% in168 Er) erbium target at a thermal neutron flux of ~ 8 × 1013 n.cm - 2 .s - 1 for 21 d. A thorough optimization of irradiation parameters including neutron flux, irradiation time and target cooling time was carried out. The influence of different experimental parameters for the quantitative removal169 Yb from169 Er was investigated, optimized and based on the results; a two-cycle electrochemical separation procedure was adopted. The suitablility of purified169 Er for application in radiation synovectomy and bone pain palliation was ascertained by carrying out radiolabeling studies with hydroxypaptite (HA) particles and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaminomethylene phosphonic acid (DOTMP), respectively. Results Thermal neutron irradiation of 10 mg of isotopically enriched (98.2% in168 Er) erbium target at a flux of ~ 8 × 1013 n.cm - 2 .s - 1 for 21 d followed by a two-step electrochemical separation of169 Yb impurity yielded ~ 3.7 GBq (100 mCi) of169 Er with a specific activity of ~ 370 MBq/mg (10 mCi/mg) and radionuclidic purity of > 99.99%. The reliability of this approach was amply demonstrated by performing several production batches, where the performance of each batch remained consistent. The utility of the purified169 Er was demonstrated in the radiolabeling studies with HA particles and DOTMP, wherein both the radiolabeled products were obtained with high radiolabeling yield (> 99%). Conclusions A viable strategy for the batch production and purification of169 Er, suitable for therapeutic applications, has been developed and demonstrated.