Effective production of 65Zn with a PET cyclotron

Abstract

Cyclotrons dedicated to the production of PET radiopharmaceuticals for clinical use can be a resource also for research in other fields of science. In the present study we assessed the feasibility of 65Zn production via the 65Cu(p,n)65Zn reaction using a 16.5MeV GE-PETtrace biomedical cyclotron. The radioisotope 65Zn (t1/2=244.26zd; decay mode: EC 98.3%, β+ 1.7%) has a wide range of applications, especially in botany and agriculture; its long half life allows storage and delivery to research centers without a cyclotron on site.Natural copper foils (thickness: 100μm; purity: >99.9%) were irradiated in a solid target station developed in our institution. The EXFOR and IAEA cross sections databases were carefully studied to optimize the irradiation setup in order to maximize the yield of the radionuclide of interest and minimize the production of isotopic impurities. We performed production runs at 20μA for 30min. Activity was measured using a calibrated HPGe gamma ray detector and an ionization chamber radionuclide activity meter. These measures showed the presence of two main contaminants: 63Zn (t1/2=38.47min) and 64Cu (t1/2=12.7h); we produced 65Zn with a saturation yield of (1.06±0.07) GBq/μA (Ep=12.65→10.48MeV). The irradiated target was dissolved in 1ml of 6N HNO3 at the temperature of 90°C and then purified through anion exchange chromatography with BIO RAD AG 1×8 resin. The radionuclidic purity of the final solution of 65Zn in HCl 0.005N, expressed in activity, resulted superior to (99.921±0.003) %.