Abstract
The development of new dosimeters with good dosimetric properties is important for quality control in radiation applications. A new practical electron spin resonance (ESR) dosimeter based on carbonated hydroxyapatite that simulated the composition and structure of tooth enamel was specially synthesized. The synthesized material was investigated by transmission electron microscope, X-ray diffraction, fourier transform infrared spectroscopy and X-ray photo electron spectroscopy to confirm to the main composition of carbonated hydroxyapatite with CO32- successfully doped into the crystal lattice through optimizing the synthesis process of C/P molar ratio, pH value dynamical adjustment, annealing temperature and time. The dosimetric properties were systematically investigated by ESR spectroscopy. The results indicated that the radiation induced signal had a good dose response within a relatively wide dose range. The dose response was linear in the dose range of 0–400 Gy with a correlation coefficient of 0.9999 and had dose accumulative effect in the experimental dose range of 0–100 Gy. In a wider dose range up to 30 kGy, the dose response also presented linear feature in double-logarithmic coordinate system with a correlation coefficient of 0.9970. The dose detection limit was about 0.34Gy with a given probability of 95% confidence level depending upon a rigid calculation algorithm. The signal was extremely stable in the observation time of 360 days with a variation coefficient of 3.8%. The radiation sensitivity of the material showed no remarkable variation against photon energy from 662 KeV to 1.25 MeV and dose rate from 0.86 Gy/min to 12.17 Gy/min. The material showed more sensitive in lower photon energy range below 662 keV, which hint additional calibration may need when using in special photon energy condition. The preliminary results suggested that this newly developed dosimeter was potential to become a practical dosimeter that would expand the application fields of ESR dosimetry.
Highlights
Ionizing radiation has been widely used in many fields
The X-ray diffraction (XRD) spectrum demonstrated that the dosimeter was mainly consisted of carbonated hydroxyapatite and this conclusion was further verified by the Fourier Transform infrared spectroscopy (FTIR) spectra which indicated that CO32- had been invaded into CHAP intracell successfully because the vibrating peak of CO32- was singlet
The X-ray photo electron spectroscopy (XPS) spectra showed that CHAP sample were consisted of Ca, P, O, C and a small quantity of N, and CO32- was successfully doped into the material (Fig 3D)
Summary
The development of new dosimeters with good dosimetric performance properties is important for quality control in radiation. Alanine ESR dosimeter has become a standard method which has been applied in radiation process applications. To develop dosimeters that have better dosimetric properties, such as with lower dose detection limit and wider dose response range, more stable, good tissue equivalent etc., has always been a valuable attempt especially for the usage of quality control in clinical radiation applications. Distribution of background signals was got by ESR measurements of twenty unirradiated samples from different batches. We calculated the relative signal intensity in the same spectrum position as that of the RIS and got the background signal distribution was 2.03±0.16 with coefficient of variation of 7.9%.
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