The influence of unstable signals for electron spin resonance dosimetry with synthetic A-type carbonated apatite

Synthetic A-type carbonated apatite prepared in reproducible conditions was irradiated at room temperature with 60Co gamma rays. The ESR spectrum is associated to axial CO2- and orthorhombic CO3- species. Radicals used as dose markers in biological apatites are long-lived paramagnetic species. The stability of the post-irradiation signal of A-type apatite was investigated for more than one year. Measurements showed variations in the spectra attributed to unstable CO3- species, which can be eliminated by thermal treatments at 100 deg. C for 24 h. The CO2-spectrum can be identified in samples irradiated up to 0.2 Gy. All results indicate that the A-type apatite is an appropriate materials for radiotherapy dosimetry. (author)