Ultra low-level gamma ray spectrometry of thorium in human bone samples

Abstract

Following the use of in vivo measurements of Pb-210 to estimate retrospectively radon exposure, interest has been expressed in the use of in vivo measurements of (TI)-T-208 to estimate thorium intake, To aid with calibration and to determine the Optimum part of the body on which in vivo measurements should be made, the distribution of (TI)-T-208 and Ac-228 amongst different human bones was measured in the underground laboratory HADES, The (TI)-T-208 activity was determined by the 2614.5 keV and the 583.2 keV gamma ray lines, The Ac-228 activity was determined by the 911.2 keV and the 969.0 keV gamma ray lines, The back-round under those peaks when measured on the 106% relative efficiency coaxial HPGe detector in HADES is of the order of 1 d(-1), resulting in detection limits in the order of 1 mBq for both radionuclides for a typical 10 g bone sample and for a measuring time of 1 week.