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Background: Computed Tomography [CT] is main contributor of population dose from diagnostic X-ray examinations. Children are more radiosensitive than adults, thus optimization of CT examination in these patients is essential. The purpose of this study was to evaluate dose delivered to pediatric patients' undergoing CT examination of the common examinations and also establishing local Diagnostic Reference Levels [DRLs]. Materials and Methods: Questionnaires were designed for data collection at seven public hospitals and information about patient, protocol and CT system were recorded during 2013 and 2014. Dose measurement was performed in four age groups: 0-1, 1-5, 5-10 and 10-15 years old and two CT dose quantity including CTDIw and DLP were calculated. Results: Values of 40, 48, 59.5, 59.5 mGy; 16.9, 16.9, 17.14, 17.14 mGy; 17, 17, 17, 17 mGy; 17, 17, 19.2, 19.2 mGy in terms of CTDIw and 448, 538, 758, 758 mGy cm; 129, 129, 154, 167 mGy cm; 184, 225, 306, 315 mGy cm; 289, 408, 595, 670 mGy cm in terms of DLP as regional DRL for brain, sinus, chest, abdomen and pelvic examinations were obtained respectively. Conclusion: The variations in dose of some examination were considerable. As the role and usage of CT technology continues to expand, it is important that all practitioners adapt optimized protocols, especially for pediatrics scanning, following proposed reference levels
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The radiation doses resulting from diagnostic X-ray examinations are routinely measured in terms of entrance surface dose [ESD] and effective dose [ED]. In this study, for the purpose of radiation protection, the radiation doses received from Digital chest X-ray examination were evaluated in terms of ESD and ED. The ED was calculated by using the MCNP Monte Carlo code and an adult hermaphrodite mathematical phantom. The effects of both operating high voltage and projection geometry on the effective dose were investigated. The absolute values of the ED were calculated for digital and conventional Posterior-Anterior [PA] and Lateral [LAT] projections of chest radiography. The results show ED for PA projection in digital chest radiography in some major hospitals is higher than National Diagnostic Reference Level [NDRL]. Therefore optimization process should be considered seriously at national level to reduce patient exposure in digital chest radiography in Iran
RESUMO
The Poly-Allyl Diglycol Carbonate [PADC] detector is of particular interest for development of a fast neutron dosimeter. Fast neutrons interact with the constituents of the CR-39 detector and produce H, C and 0 recoils, as well as [n, a] reaction. These neutron- induced charged particles contribute towards the response of CR-39 detectors. Material and Electrochemical etching was used to enlarge track diameter which was made by low energy recoil protons. Before electrochemical etching, a chemical etching was performed for 1 hour. The responses were also calculated by Monte Carlo simulations, using MCNPX code in different energy bins considering H, C and O recoils. The total registered efficiency and partial contributions of the efficiency, due to interactions with each constituent of CR-39, were calculated. The optimized condition of etchant was obtained to be 6N KOH 15kV.cm[1], and 6 hours etching time. The obtained results show that track efficiency of CR-39 was a function of incident neutron energy. The tracks caused by O and C recoil nuclei were negligible for neutron energies lower than 1 MeV. At neutron energies lower than 1 MeV, only recoil protons would have sufficient energy to leave visible tracks. But, O and C recoils had important contributions in overall response of PADC at neutron energies of few MeV. The efficiency of a CR-39 based dosemeter could be calculated by MCNPX code and the results were in a good agreement with experimental results in energy range of [241]Am - Be bare source and [241]Am-Be was softened with a spherical polyethylene moderator of radius of 20 cm