In the present study the feasibility of using whole, naturally loose deciduous incisors for dose reconstruction with electron paramagnetic resonance (EPR) spectroscopy was investigated. The properties of EPR signals were analysed before and after laboratory irradiation. The parameters of the native EPR signal of deciduous incisors was found to be different from those from enamel of permanent molars. The native EPR signal of deciduous incisors with peak-to-peak line width of 0.65 mT was located at g = 2.0050. The evaluated parameters of the dosimetric EPR signal (CO2-) of deciduous incisors were in agreement with those for enamel of permanent molars. A detection threshold for absorbed dose of about 100 mGy was estimated.

Regarding in vivo L-band dosimetry with human teeth, a number of preliminary experiments were carried out that were linked to the resonators response and the relative contribution of enamel to the EPR signal intensity of irradiated whole teeth. The sensitivity of the extended loop resonator varies in the antenna plane, but this variation tends to vanish when the sample is moved away from this plane. When the loop antenna is placed just above the highly irradiated molar, around 88% of the dosimetric signal is due to the crown enamel. The sensitivity inside a birdcage cavity is approximately equal over the volume of a molar; only 30% of the molar's total dosimetric signal results from enamel. Some decrease in the intensity of the dosimetric signal from enamel is observed after irradiation. At room temperature, the signal is reduced by about 20% within 90 days and approaches a plateau with a time constant of about 35 days.

The use of electron paramagnetic resonance (EPR) tooth dosimetry for calculation of organ doses requires conversion of the measured absorbed dose in enamel. Before deriving conversion factors from simulation calculations with a realistic anthropomorphic human phantom, in the current study a simplified phantom was chosen to compare EPR measurement and Monte Carlo calculation. The dose response of tooth enamel of molars at various positions inside a cylindrical Plexiglas phantom of head-size was calculated hy Monte Carlo modelling in parallel photon beams of X rays of 63 keV equivalent energy and 60Co gamma rays (1.25 Mev). For X ray exposure, preliminary results of EPR dosimetry with tooth enamel samples prepared from molars irradiated in the phantom were in agreement with calculation. The mean value of the ratio of the measured to the calculated dose was 0.93 +/- 0.08.

No abstract

The current study characterizes and analyzes glow curves obtained from phosphate glass doped with different concentrations of lanthanum. Kinetic parameters of the glow curves obtained from beta-irradiated phosphate glass samples doped with lanthanum were determined using a newly designed deconvoluted software. The obtained results from the analyses indicated that the glow curves of the phosphate glass samples were composed of five overlapping peaks. The activation energies of the five electron traps were located between 0.622 and 1.133 eV. The obtained kinetic parameters were evaluated using the designed software and another two methods and all revealed good agreement. The first three traps displayed non-firstorder behaviour, while the two deep traps obeyed nearly first-order kinetics.

No abstract

No abstract

Nanocrystalline boehmite material was synthesized using the hydrothermal method. Different annealing temperatures have been used to transform boehmite into different alumina phases to study the effect of different phase transitions on the thermoluminescence properties of alumina. XRD analysis was carried out to investigate the crystal structure of the different alumina phases. The thermoluminescence glow curves for different alumina phases showed different structures; however, the sensitivity was almost constant for all the phase transitions of alumina over the applied dose ranging from 0.55 to 330 Gy.