Activity standardization of 99mTc by digitizer-based 4ce(LS)- and 4ce(PC)- coincidence counting

An aqueous solution of 99mTc was standardized by means of 4 & pi;ce(LS)-& gamma; and 4 & pi;ce(PC)-& gamma; coincidence counting. The activity concentration was obtained by efficiency extrapolation relying on four different variation techniques. In both setups, fast digitizers were used for data acquisition. Detected events were recorded in list mode format, and their coincidence relationship was analyzed in the subsequent offline analysis. The combined result was used to participate in an international comparison using the Transfer Instrument of the International Reference System.