Production, radiochemical separation and electrochemical concentration of No-carrier-added Mn: An emerging PET radiometal.

Recently, there has been significant interest in Mn (T = 5.6 d) as a relatively long lived radiometal for PET imaging of cancer. In this study, we have produced Mn from natural Cr metallic powder target via Cr (p, n) Mn reaction in a particle accelerator. An efficient radiochemical separation method based on selective precipitation of Cr as Cr(OH) followed by electrochemical purification and concentration of Mn was developed for isolation of no-carrier-added (nca) Mn from the irradiated target. The overall radiochemical separation yield of the process was >75 %. After separation, Mn was obtained with >99.5 % radionuclidic purity and >97 % radiochemical purity. The apparent molar activity of Mn was determined to be 2.2 ± 0.1 MBq/nmol and it was found suitable for preparation of radiopharmaceuticals. As a proof of concept, [Mn]Mn-DOTA-E[c(RGDfK)] was prepared with 98.8 ± 0.4 % radiolabeling yield and the radiochemical stability of the formulation was maintained over a period of 7 days under physiological conditions. Overall, this strategy is viable for obtaining nca Mn in a suitable form for radiopharmaceutical preparation and would potentially increase the availability of this radiometal for clinical PET imaging in foreseeable future.