Production of Zr-89 using sputtered yttrium coin targets

An increasing interest in zirconium-89 (89Zr) can be attributed to the isotope's half-life which is compatible with antibody imaging using positron emission tomography (PET). The goal of this work was to develop an efficient means of production for 89Zr that provides this isotope with high radionuclidic purity and specific activity. We investigated the irradiation of yttrium sputtered niobium coins and compared the yields and separation efficiency to solid yttrium coins. The sputtered coins were irradiated with an incident beam energy of 17.5 MeV or 17.8 MeV providing a degraded transmitted energy through an aluminum degrader of 12.5 MeV or 12.8 MeV, respectively, with various currents to determine optimal cyclotron conditions for 89Zr production. Dissolution of the solid yttrium coin took 2 h with 50 mL of 2 M HCl and dissolution of the sputtered coin took 15-30 min with 4 mL of 2 M HCl. During the separation of 89Zr from the solid yttrium coins, 77.9 ± 11.2% of the activity was eluted off in an average of 7.3 mL of 1 M oxalic acid whereas for the sputtered coins, 91 ± 6% was eluted off in an average of 1.2 mL of 1 M oxalic acid with 100% radionuclidic purity. The effective specific activity determined via DFO-SCN titration from the sputtered coins was 108 ± 7 mCi/μmol as compared to 20.3 mCi/μmol for the solid yttrium coin production. ICP-MS analysis of the yttrium coin and the sputtered coins showed 99.99% yttrium removed with 178 μg of yttrium in the final solution and 99.93-100% of yttrium removed with remaining range of 0-42 μg of yttrium in the final solution, respectively. The specific activity calculated for the solid coin and 3 different sputtered coins using the concentration of Zr found via ICP-MS was 140 ± 2 mCi/μmol, 300 ± 30 mCi/μmol, 410 ± 60 mCi/μmol and 1719 ± 5 mCi/μmol, respectively. Labeling yields of the 89Zr produced via sputtered targets for 89Zr- DFO-trastuzumab were >98%. Overall, these results show the irradiation of yttrium sputtered niobium coins is a highly effective means for the production of 89Zr.