Accurate Activity Measurement of Lu-177 (Liquid Scintillation 4 𝝅𝜷-𝜸 Coincidence Counting Technique)

B.R.S. Simpson n, M.J. van Staden, J. Lubbe, W.M. van Wyngaardt

National Metrology Institute of South Africa, 15 Lower Hope Road, Rosebank, 7700 Cape Town, South Africa

ABSTACT

This paper reports on absolute measurements made at the NMISA by the 4𝜋[LS]𝛽-𝛾 coincidence extrapolation technique, which formed part of a key comparison of activity measurements of the radionuclide lutetium-177, a beta–gamma emitter. A detection efficiency analysis based on the decay scheme indicated that the coincidence extrapolation method is feasible for extracting the source disintegration rate of 177Lu. A simulation was undertaken utilizing the efficiency equations to give an indication of the expected variation of the source count rate with efficiency for different gamma-ray windows. Both the simulation and experiment indicated that the window giving the highest counting efficiency was centered about the 208.4 keV photopeak, with the data showing linear variation in the upper efficiency range. The extracted activity concentration of the 177Lu solution proved to be highly accurate, being higher than the proposed comparison reference value by 0.15%, well within one standard uncertainty (s.0.26%) as specified by the NMISA.

VALIDATION

This article is validated for 0.1 CPD Credits in Category 1