Standardization of Ga-68 by coincidence measurements, liquid scintillation counting and 4πγ counting

The radionuclide Ga-68 is one of the few positron emitters that can be prepared in-house without the use of a cyclotron. It disintegrates to the ground state of Zn-68 partially by positron emission (89.1%) with a maximum energy of 1899.1 keV, and partially by electron capture (10.9%). This nuclide has been standardized in the frame of a cooperation project between the Radionuclide Metrology laboratories from CIEMAT (Spain) and CNEA (Argentina). Measurements involved several techniques: 4 pi beta-gamma coincidences, integral gamma counting and Liquid Scintillation Counting using the triple to double coincidence ratio and the CIEMAT/NIST methods. Given the short half-life of the radionuclide assayed, a direct comparison between results from both laboratories was excluded and a comparison of experimental efficiencies of similar Nal detectors was used instead. (C) 2012 Elsevier Ltd. All rights reserved.