18F Half-life measurement using 2-γ coincidence method

Abstract

The accuracy of the half-life measurement of short-lived radioisotopes such as positron-emitting 18F (τ1/2≈100min) is limited mainly by inaccuracies in the detector counting statistics. Gamma-ray measurement with a high-activity 18F source requires counting-loss corrections to compensate for random summing effects and the detector׳s dead time. In this study, we measure the half-life of 18F with two 511-keV γ-rays using two high-purity germanium (HPGe) detectors. The counting-loss corrections are performed via two approaches to address the problems of random coincidence summing and dead time: a half-life measurement with a 22Na source and a Geant4 simulation of the detector response. Variations in the full-width at half maximum (FWHM) of the 511-keV peak are found to show good correlation with the random summing effect. The half-life of 18F is estimated as 109.73±0.14min.