Using medical accelerators and photon activation to determine Sr/Ca concentration ratios in teeth

This paper describes a photon activation method, studied by using two medical accelerators (energies: 15 and 18 MeV) as photon sources, for determining Sr and Ca levels and Sr/Ca ratios in tooth samples. The radionuclides formed by various photonuclear reactions were measured and identified using a gamma-spectrometry with HPGe detection system. The yields of the corresponding photonuclear reactions and the detection sensitivities for the alkaline earth metals (e.g., Ca, Sr) were surveyed and estimated in relation to the radiation dose. The minimum detectable amount of Sr was estimated to be less than 1 μg g−1, allowing the Sr/Ca ratios in teeth to be determined conveniently. The Sr/Ca ratios in deciduous and permanent tooth samples obtained from local dental clinics were 0.390 and 0.565 mg g−1, respectively. This photon activation method of determining Sr/Ca ratio in bones and teeth using medical accelerators for cancer treatment is thought to be useful also in biological and archaeological studies.