Speaker
Description
Authors (affiliation): 1. Agung Agusbudiman (UST, South Korea), 2. Kyoung Beom Lee (KRISS, South Korea), 3. Jong Man Lee (KRISS, South Korea), 4. Sang Hoon Hwang (KRISS, South Korea), 5. Byoung Chul Kim (KRISS, South Korea).
The copper-64 (64Cu) is one of the important radiopharmaceuticals used in nuclear medicine. The nature of its decay through three different modes, β+, β-, and electron capture, makes this radionuclide useful for both imaging and radionuclide therapy purposes. On the other hand, this decay scheme makes the activity standardization of 64Cu become challenging. We present the activity standardization of 64Cu performed at the Korea Research Institute of Standards and Science (KRISS). The standardization was mainly performed based on the 4πβ(LS)-γ coincidence counting method with the TDCR counting method used for confirmatory measurement purposes. Two analysis techniques were used in the activity determination by the coincidence counting method. The first technique uses the general extrapolation method based on coincidence events between the electron capture radiations and the low-probability of 1346 keV gamma radiations. This technique requires an ad-hoc correction to be applied to the extrapolated value because the detection efficiencies of beta plus and beta minus electrons are not able to be extrapolated to 100 % with the extrapolation range of electron capture radiations. The second technique uses two-dimensional extrapolation, which adds the contribution of coincidence events between the positron and the 511 keV annihilation gamma radiations to the first analysis; thus, no correction is required for the extrapolated value. The 4πβ(LS)-γ coincidence system was used in the experiments with a digital sampling technique that allowed us to perform both analysis techniques based on a single measurement data. For the TDCR method, an in-house code is developed based on the KLM shell model to calculate the efficiency for all 64Cu decay paths. The energy transfer probability in the liquid scintillator was calculated using the PENELOPE simulation code (version 2018). We compared the three results of activity value and investigated the measurement comparability between the results, and found that they still agree within the uncertainty range.
