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

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