The aim of this work was to develop some X-ray qualities recommended by the International Standardization Organization (ISO) in its standard ISO 4037-1. X-ray qualities corresponding to narrow-spectrum series were established, determined their characteristics and found good agreement with those of reference X-ray beam qualities [difference between first half-value layer (HVL1) < 5% for all qualities]. Acceptable results have also been obtained for second half-value layer (HVL2). The production of X-ray spectra corresponding to developed X-ray qualities with Monte Carlo code PENELOPE (PENetration and Energy Loss Of Positrons and Electrons) was simulated. The characteristics [HVL1, HVL2, homogeneity coefficient (HC) and mean energy (Emean)] of simulated spectra have been calculated and compared to those of measured spectra at Physikalisch-Technische Bundesanstalt taken as reference spectra. The obtained results showed a good agreement between simulated and measured spectra (differences in HVL1, HVL2, HC and Emean were 1.7, 1.44, 0.44 and 1.3%, respectively). The comparison between simulated and measured spectra by calculating the conversion coefficients from air kerma to the personal dose equivalent, hpk(10), and to the ambient dose equivalent, hk*(10), was supplemented. The comparison between the calculated quantities (hpk(10) and hk*(10)) for the two X-ray spectra series showed a good agreement (the maximum difference was <0.4% for hpk(10) and <0.3% for hk*(10)). Furthermore, the percentage depth dose produced in water by simulated and measured spectra was investigated and a good agreement was found between the obtained curves. The established X-ray qualities have been fully characterised (measurement and Monte Carlo simulation). These X-ray beams can be used for calibration of radiation protection instruments and for reference irradiations.
Abstract:The aim of this work is to study the energy dependence of thermoluminescent dosimeter (TLD-700) for low energy X-ray beams encountered in conventional diagnostic radiology. In the rst step, we studied some characteristics (reproducibility and linearity) of TLD-700 chips using a Cs source, and selected TLD chips with reproducibility better than 2.5%. Then we determined TLD-700 energy response for diagnostic radiology X-ray qualities, and investigated its in uence on air kerma estimate. A maximum deviation of 60% can be obtained if TLDs are calibrated for Cs radiation source and used in diagnostic radiology elds. However, this deviation became less than 20% if TLDs chips are calibrated for the reference x-ray radiation quality RQR5 (recommended by the IEC 61267 standard). Consequently, we recommend calibrating this kind of TLD detector with RQR5 diagnostic radiology X-ray quality. This method permits to obtain a good accuracy when assessing the entrance dose in diagnostic radiology procedures.
An intercomparison exercise on the measurement of personal dose equivalent Hp(10) was jointly organised by the International Atomic Energy Agency and the Nuclear Research Centre of Algiers through its Secondary Standard Dosimetry Laboratory in the African region. This intercomparison exercise was aimed at verifying the performance of the individual monitoring services of the participants in order to assess their capabilities to measure the quantity Hp(10) in photon (gamma and X ray) fields helping them to comply with dose limitation requirements. The scope of this intercomparison was aimed at passive dosemeters, which determine the personal dose equivalent in photon radiation fields, mainly for thermoluminescence and optically stimulated luminescence dosemeters. Twenty-seven countries from the Africa region and from outside Africa participated in this exercise. The intercomparison protocol, including the preparation of the dosemeters and the irradiation procedures, is described and the results are presented, analysed and discussed.
As part of the intercomparison on the measurement of personal dose equivalent Hp(10), jointly organised by the International Atomic Energy Agency and the Algerian Secondary Standard Dosimetry Laboratory, for the African region, up to 12 dosemeters were added to the packages of the 28 participants to evaluate the background and transport dose (BGTD), received by the dosemeters before and after their irradiation at the SSDL (environmental irradiations, scanning process at the airports, etc.). Out of the 28 participants, only 17 reported the corresponding BGTD measured values, which lied between 0.03 and 0.8 mSv. The mean measured value of BG was (0.25±0.14) mSv, which is significantly high compared with the lowest dose value used in the intercomparison exercise. The BGTD correction shifted the overall results of the intercomparison from an overestimation of dose (∼8 % before applying BGT dose correction) to an underestimation of dose (-9 % after correction). The measurement protocol and the detailed analysis of the results and applied corrections are discussed in this paper.
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