Abstract
The β+-emitting radionuclide 86gY (t1/2 = 14.7 h) forms a matched-pair with the β−-emitting therapeutic radionuclide 90Y (t1/2 = 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 86gY. In this work, an 86gY 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 γ-ray spectroscopy. The electron capture intensity was also determined as an additional check by measuring the Kα and Kβ 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 β+-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.
Highlights
Among the various imaging techniques used in diagnostic medicine, the positron emission tomography (PET) occupies a unique position
X-ray Spectroscopy After the γ-ray spectroscopic measurements on the 86SrCO3 enriched sample, irradiated with 8- or 7-MeV protons, in which 86Y was formed through the 86Sr(p,n)-reaction, X-ray spectroscopy was carried out using a special high-purity germanium (HPGe) detector with a thin Be-window of 300-μm thickness, supplied by ORTEC
The peak area under a characteristic γ-ray as well as an X-ray emitted in the decay of 86gY was converted to count rate and normalized to the end of bombardment (EOB)
Summary
Among the various imaging techniques used in diagnostic medicine, the positron emission tomography (PET) occupies a unique position. The decay data of the so called “standard” positron emitters, i.e., 11C (t1/2 = 20.4 min), 15O (t1/2 = 2.0 min), 18F (t1/2 = 1.83 h), 68Ga (t1/2 = 1.13 h), and 82Rb (t1/2 = 1.3 min) are known well: their positron emission intensity is high, the positron endpoint energy is low and the accompanying γ-rays, if any, do not interfere in the measurement of the annihilation radiation. We concentrated on the measurement of the positron emission intensity of the non-standard positron emitter 86gY (t1/2 = 14.7 h) by determining the ratio of the intensity of the annihilation radiation and of the K X-rays to the decay rate of 86gY The latter was deduced through a spectroscopic analysis of its four strong γ-rays of wellestablished intensities. The salient features of the techniques applied in this work are described
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