Tantalum-178--A Short-Lived Nuclide for Nuclear Medicine: Production of the Parent W-178

The physical decay characteristics of the short-lived radionuclide Ta-178 (half-life 9.3 min) appear to be suitable for use in conjunction with low-energy detection systems such as the multiwire proportional camera. This camera is inefficient for emissions with energies greater than 100 keV. The gamma-ray spectrum of Ta-178 is dominated by the characteristic hafnium x-rays (55--65 keV), emitted as a result of electron-capture decay. The parent nuclide, W-178 (half-life 21.7 d), was produced in the Michigan State University cyclotron by proton bombardment of stacked natural tantalum-foil targets. Optimum production was found to occur with an incident proton energy of 34 MeV at an effective activity of 1.1 mCi/muA-hr per MeV of target thickness. Tungsten-178 was chemically separated from the Ta foils with a yield of 98%.