Standardization of a Re sodium perrhenate radiochemical solution using the TDCR method in liquid scintillation counting

Rhenium-186 has several current and potential applications in nuclear medicine. It decays by beta minus emissions mainly to the fundamental and the 137 keV excited levels of ¹⁸⁶Os and by electron capture to ¹⁸⁶W. This paper describes the standardization of this radionuclide using the Triple to Double Coincidence Ratio model (TDCR) method. This is done by the calculation of the energy transferred to the scintillator by considering the various decay/de-excitation paths following the disintegration of the nuclide. The uncertainty on the detection efficiency is evaluated by stochastic methods by considering statistical distribution of theoretical and experimental parameters used in the calculation model. The detection efficiency was found to be higher than 97%, allowing a relative standard uncertainty on the activity determination of about 0.3%.