Accurate activity measurement of Lu-177 by the liquid scintillation 4πβ-γ coincidence counting technique

► Activity of lutetium-177 was determined by liquid scintillation coincidence counting. ► The measurements formed part of a key comparison of absolute activity measurements. ► A source rate simulation utilizing detection efficiency equations was undertaken. ► The simulation indicated the expected variation of rate with counting efficiency. ► The extracted activity concentration of the solution proved to be highly accurate.