Objective To develop a promising type of radiation dosimeter based on doped hydroxyapatite,and to study the stability of dosimetric characteristics indepth.Methods The samples prepared by stereotyping techniques were stored under different temperatures,humidity and illumination conditions after 60Co γ-ray irradiation.Electron spin resonance (ESR) technique was used to quantitatively measure the radiation-induced free radical signal.Results The signal change was less than 3% when the dosimeter was preserved at 4℃ or room temperature within 3 months in the experiment.At 40℃,the signal changed by about 13%,but at room temperature with the humidity less than 36%,the signal changed less than 2%.The change rose to about 8% when humidity was 76%.However,no significant decay of signal strength occurred at relatively high temperatures and under high humidity conditions.When the samples were stored under average illumination of 1600 lux or in a light-resistant container,the signal changes were less than 3.8% or 3.4% respectively.Long-term stability inspection at room temperature suggested a signal change within 4.8%.Conclusion The dosimetric properties of the material don't change significantly below room temperature in a natural environment and exhibit good stability over long-term storage.The free radical signal is not influenced drastically by relatively strong light exposure.However,a high temperature or a highly humid environment may have some effect on the measurement process,which should be taken into consideration in further applications.

Objective To explore the feasibility of EPR in vivo fingernail dosimetry to address the difficulty in separating mechanically induced signals from fingernail EPR dosimetry for need of nuclear medical emergency aid.Methods Using the specially designed EPR in vivo measurement system,uncut fingernails were measured to obtain the characteristics of EPR signal without mechanically induced signals.The in vivo fingernail experiment was carried out to evaluate the impact of in vivo condition on the spectra.Actual in vivo measurement experiment was conducted to evaluate the interference of the in vivo condition on EPR spectra.Results The background signal distribution of uncut fingernails was obtained and background signals had no significant difference between male and female(P＞0.05).The dose response curve in the range of 2-10 Gy was established,and the half-life of the fingernail radiation-induced signal was approximately 5 d.The water treatment combined with temperature-changing was established for restoring the background signal.EPR signal obtained after restoring treatment has no significant difference with background signal (P＞ 0.05).The EPR spectra of in vivo fingernails were obtained.Conclusions The EPR spectra without mechanically induced signals can be acquired by this method.The feasibility of the in vivo fingernail EPR dosimetry is preliminarily verified.