Production of no‐carrier‐added 64Cu from zinc metal irradiated under boron shielding

Abstract

Background. Positron emission tomography offers advantages for radioimmunodiagnosis of cancer but requires radionuclides of appropriate half‐life that have high specific activity and high radio‐purity. This work was designed to develop a viable method to produce and purify 64Cu, which has high specific activity, for positron emission tomography. Methods. 64Cu was produced at the University of Missouri Research Reactor by the nuclear reaction, 64Zn(n,p)64Cu. Highly pure zinc metal (99.9999%) was irradiated in a specially designed boron nitride lined container, which minimized thermal neutron reactions during irradiation. A new two‐step procedure was developed to chemically separate the no‐carrier‐added 64Cu from the zinc metal target. Results. 64Cu recovery for 24 runs averaged 0.393 (±0.007) mCi per milligram of zinc irradiated. The boron‐lined irradiation container reduced unwanted zinc radionuclides 14.3‐fold. Zinc radionuclides and non‐radioactive zinc were separated successfully from the 64Cu. The new separation technique was fast (2 hours total time) and highly efficient for removing the zinc. The zinc separation factor for this technique averaged 8.5 × 10−8, indicating less than 0.0000085% of the zinc remained after separation. Thus far, the highest 64Cu specific activity at end of irradiation was 683 Ci/mg Cu, with an average of 512 Ci/mg Cu for the last six analyzed runs. Conclusion. The boron‐lined irradiation container has sufficient capacity for 75‐fold larger‐sized zinc targets (up to 45 g). The new separation technique was excellent for separating 64Cu, which appears to be a radionuclide with great potential for positron emission tomography. Cancer 1994; 73:774–8. Copyright © 1994 American Cancer Society