MEASUREMENT OF THE RATIO OF ~(99m)Tc AND ~(99)Mo INTENSITY IN ~(99)Mo-~(99m)TC BALANCED SOURCE

The measurement of the total β intensity of a ~(99)Mo-~(99m)Tc balanced source byextrapolation absorption method of 4πβ-γ coincidence and the measurement ofabsolute intensity of ~(99m)Tc in the balanced source by a S--80 MCA HPGE γspectrometer with the efficiency calibrated by an accurately standardized sourceof ~(99m)Tc are described. The ~(99m)Tc/~(99)Mo intensity ratio is found to be 0.974±0.023. This result is compared with the compilation value. Thus a experimentallymeasured correction factor of ~(99m)Tc is 0.1088±0.0023 for the absolute standar--dization of ~(99)Mo.