EFFICIENT PRODUCTION OF HIGH SPECIFIC ACTIVITY CU-64 USING A BIOMEDICAL CYCLOTRON

Copper-64 (T-1/2 = 12.7 h) is an intermediate lived positron emitting radionuclide that is a useful radiotracer for positron emission tomogr aphy (PET) as well as a promising radiotherapy agent for the treatment for cancer. Currently, copper-64 suitable for biomedical studies is p roduced in the fast neutron flux trap (irradiation of zinc with fast n eutrons) at the Missouri University Research Reactor. Access to the fa st neutron flux trap is only possible on a weekly basis, making the av ailability of this tracer very limited. In order to significantly incr ease the availability of this intermediate-lived radiotracer, we have investigated and developed a method for the efficient production of hi gh specific activity Cu-64 using a small biomedical cyclotron. It has been suggested that it may be possible to produce Cu-64 on a small bio medical cyclotron utilizing the Ni-64(p,n)(CU)-C-64 nuclear reaction. We have irradiated both natural nickel and enriched (95% and 98%) Ni-6 4 plated on gold disks. Nickel has been electroplated successfully at thicknesses of similar to 20-300 mm and bombarded with proton currents of 15-45 mu A A Special water-cooled target had been designed to faci litate the irradiations on a biomedical cyclotron up to 60 mu A. We ha ve shown that it is possible to separate Cu-64 from Ni-64 and other re action byproducts rapidly and efficiently by using ion exchange chroma tography. Production runs using 19-55 mg of 95% enriched Ni-64 have yi elded 150-600 mCi of Cu-64 (2.3-5.0 mCi/mu Ah) with specific activitie s of 94-310 mCi/mu g Cu. The cyclotron produced Cu-64 had been used to radiolabel PTSM [pyruvaldehyde bis-(N-4- methylthiosemicarbazone), us ed to quantify myocardial, cerebral, renal, and tumor blood flow], MAb 1A3 [monoclonal antibody MAb to colon cancer], and octreotide. A recy cling technique for the costly Ni-64 target material has been develope d. This technique allows the nickel eluted off the column to be recove red and reused in the electroplating of new targets with an overall ef ficiency of greater than 90%. Copyright (C) 1997 Elsevire Science Inc.