Positron Emission Intensity in the Decay of Y-86g for Use in Dosimetry Studies

The beta(+)-emitting radionuclide Y-86g (t(1/2) = 14.7 h) forms a matched-pair with the beta(-)-emitting therapeutic radionuclide Y-90 (t(1/2) = 2.7 d) for theranostic application in medicine. This approach demands a precise knowledge of the positron emission probability of the PET nuclide which was until recently rather uncertain for Y-86g. In this work, an Y-86g source of high radionuclidic purity was prepared and a direct measurement of the positron emission intensity per 100 decay of the parent (hereafter "positron emission intensity") was performed using high-resolution HPGe detector gamma-ray spectroscopy. The electron capture intensity was also determined as an additional check by measuring the K-alpha and K-beta X-rays of energies 14.1 and 15.8 keV, respectively, using a low energy HPGe detector. From those measurements, normalized values of 27.2 +/- 2.0% for beta(+)-emission and 72.8 +/- 2.0% for EC were obtained. These results are in excellent agreement with values recently reported in the literature based on a detailed decay scheme study.