Standardization of 67Ga by 4πγ (NaI) and 4πβ–γ coincidence methods

The nuclide 67Ga is widely used in nuclear medicine for diagnostic purposes. It decays with a half-life of 3.259 days to 67Zn, a stable nuclide. The decay mode is electron capture with several branches followed by γ- de-excitation. One of the excited levels of 67Zn with energy 93 keV has a half-life of 9.1 μs, which makes its absolute standardization by coincidence methods difficult. Two methods were used to standardize a solution of this nuclide: (a) 4π–EC(PPC)–γ(NaI) coincidence counting with efficiency extrapolation to infinite dead time and (b) high-efficiency 4πγ counting with a well-type NaI detector.