Measurement of alpha-emitting therapeutic radiopharmaceutical Ra-223 dichloride injection by close/far S-D [gamma]-spectrum method

To accurately measure .sup.223Ra dichloride injection by HPGe [gamma] spectrometry, three calibration sources, including mixed mono-energy [gamma] nuclide, .sup.133Ba, and .sup.226Ra, were used to calibrate efficiency at close/far source/sample-detector (S-D) distance. The results show that the efficiency calibration at a far S-D distance can reduce the coincidence effect of the .sup.133Ba and .sup.223Ra simulation source, both far and close S-D are applicable to the .sup.226Ra simulation source; Using 269.48 keV, 271.23 keV and 351.03 keV [gamma]-ray full energy peaks for analysis, the deviation of the results between the simulation sources method and the mono-energy [gamma] nuclide source method is less than 1%. The influence of [gamma]-ray emission probabilities, the selection of full energy peak, and coincidence effect and other factors on the .sup.223Ra measurement results was also studied, the [gamma]-ray emission probabilities from different nuclear databases can cause up to 30% deviation in the measurement results.