Cyclotron production of high purity 44m,44Sc with deuterons from 44CaCO3 targets

Introduction: Due to its longer half-life, Sc-44 (T-1/2 = 3.97 h) as a positron emitter can be an interesting alternative to Ga-68 (T-1/2 = 67.71 min). It has been already proposed as a PET radionuclide for scouting bone disease and is already available as a Ti-44/Sc-44 generator. Sc-44 has an isomeric state, (SC)-S-44m (T-1/2 = 58.6 h), which can be co-produced with Sc-44 and that has been proved to be considered as an in-vivo PET generator Sc-44m/Sc-44. This work presents the production route of Sc-44m/Sc-44 generator from Ca-44(d,2n), its extraction/purification process and the evaluation of its performances. Methods: Irradiation was performed in a low activity target station using a deuteron beam of 16 MeV, which favors the number of (SC)-S-44m atoms produced simultaneously to Sc-44. Typical irradiation conditions were 60 min at 02 mu A producing 44 MBq of Sc-44 with a (SC)-S-44/(SC)-S-44m activity ratio of 50 at end of irradiation. Separations of the radionuclides were performed by means of cation exchange chromatography using a DGA (R) resin (Triskem). Then, the developed process was applied with bigger targets, and could be used for preclinical studies. Results: The extraction/purification process leads to a radionucleidic purity higher than 99.99% (Sc-43, Sc-46, Sc-48 < DL). Sc-44m/Sc-44 labeling towards DOTA moiety was performed in order to get an evaluation of the specific activities that could be reached with regard to all metallic impurities from the resulting source. Reaction parameters of radiolabeling were optimized, reaching yields over 95%, and leading to a specific activity of about 10-20 MBq/nmol for DOTA. A recycling process for the enriched Ca-44 target was developed and optimized. Conclusion: The quality of the final batch with regard to radionucleidic purity, specific activity and metal impurities allowed a right away use for further radiopharmaceutical evaluation. This radionucleidic pair of (SC)-S-44m/(SC)-S-44 offers a quite interesting PET radionuclide for being further evaluated as an in-vivo generator. (C) 2015 Elsevier Inc. All rights reserved.