Production of Ga-66 from natural zinc

ABSTRACT

In this study, production of Gallium-66 by irradiation of natural zinc target with 15 MeV protons was verified.Gallium-66 is an intermediate-lived radioisotope that has potential for positron emission tomography (PET), along study of the biological processes with intermediate to slow target tissue uptake. 66Ga [t1/2 = 9.49 h; ß+ (56.5 percent), EC(43.5 percent)] can be used in a large number of labeled proteins, peptides, and small molecules. We have produced 66Ga by irradiation of natural Zinc with 15 MeV proton beam, using the cyclotron -30Cyclon- at nuclear research center for agriculture and medicine. A 400µm Zinc target with copper backing substrate was irradiated for 1.5 hours with total integrated current 250µAh. Gallium has been purified from irradiated targets by passing through the cation exchange column and diisopropyl ether extraction. The concentration of zinc and copper in 0.1 and 0.5 ppm were respectively measured by polarography. In order to detect impurities, gallium radioisotopes were detected by a Canberra HPGe gamma spectrometer. The production yield at EOB was 7mCi/µAh with total activity of 1.75 Ci for Gallium-66. The ratio of activity at 9 hours after the EOB for 66Ga(t 1/2=9.5h), 68Ga(t1/2=1.1h) and 67Ga(t1/2=78h) was 98.63 percent, 1.12 percent and 0.25 percent respectively. The amount of 64Ga(t1/2=0.04h), and 70Ga(t1/2=0.35h) was not detectable. Due to using natural zinc, this method could be considered as an inexpensive method for laboratories studies. The production process comparing the irradiation of natural copper has no impurity such as copper-61, 64 and 67. The purification including cation-exchange and ether extraction afforded high yield beside negligible concentrations of copper and stable zinc as chemical impurity.