Standardization of 67Ga using a 4π(LS)β–γ anti-coincidence system

67Ga is an interesting radionuclide as it is widely used in nuclear medicine. The meta-stable level related to the 93.3 keV γ-transition represents the main difficulty when using the coincidence method to standardize this radionuclide. The 4π(LS)β–γ anti-coincidence system implemented at LNHB is based on the use of electronic modules specifically designed for radioactivity metrology. On the contrary to classical coincidence systems, activity measurements of 67Ga are carried out as for prompt β–γ emitters; indeed, when using a live-timed anti-coincidence system with extendable dead times, the problem due to the excess of counting generated by the meta-stable level is avoided. Considering that the standardization of 67Ga does not depend on the decay scheme parameters (except for the half-life), the measurement of the γ-emission intensities has been performed. The standardization of this radionuclide was also a good opportunity for a new participation of our laboratory in the SIR of 67Ga (International Reference System); the result obtained with the 4π(LS)β–γ anti-coincidence system is compared with those submitted by other National Metrology Institutes (NMIs). The non-extendable dead times used in most of the participations could be one of the causes responsible for the abnormal dispersion of the results. The optimization of the standard solution of 67Ga for the radioactive source preparation is also discussed.