Standardization of 99mTc and 99Mo by the use of a 4πβ−4πγ counter

Technetium-99m is widely used for many diagnostic investigations in nuclear medicine, thus the standardization of this nuclide is important. In classical 4πβ−γ coincidence counting of 99mTc, the steep slope of the efficiency function and the large extrapolation range may cause a large measurement uncertainty. In order to overcome these difficulties, we apply the 4πβ+4πγ sum counting technique for the standardization. Furthermore, we adopt both the 4πβ−4πγ coincidence counting method and the 4πβ+4πγ sum counting technique for the standardization of its parent nuclide 99Mo. High efficiencies for both nuclides were easily achieved by the use of our 4πβ−4πγ counter. All the results were consistent with the reference value obtained by the conventional method obtained by NMIJ.