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Background: Prompt gamma neutron activation analysis (PGNAA) is known as a non-invasive technique capable of measuring elemental concentration in voluminous samples in a short period of time. Also it is a valuable diagnostic tool for total body elemental measurements. 252Cf and 241Am-Be sources which are usually used in this method, generate not only neutrons, but also emit high-energy and unwanted gamma-rays. Because the patient must be located against the neutron source, patient dose during an analysis is an important concern when using this technique.

Materials and Methods: Gamma-rays were attenuated without losing the neutron flux or significant alteration in the neutron spectrum. A relatively safe body chemical composition analyzer was designed with an optimal spherical gamma-ray shield, enclosed to the neutron source. Effects of gamma-ray shielding and optimum radius of spherical Pb shield was investigated and compared with the unfiltered bare source, using MCNP4C code. Then, the gamma ray dose equivalent per source neutron rate (user defined parameter) in the soft tissue is calculated for different radiuses of spherical Pb shield, for both neutron sources.

Results: A decreasing flux of gamma-ray was observed when the radius of the spherical Pb shields increased. The value of this reduction was about 94% for 252Cf source when a lead spherical shield of radius 4 cm was used while the reduction was about 50% for 241Am-Be source with the same spherical shield. For a spherical Pb shield of radius 4 cm, reduction of the gamma dose equivalent per source neutron rate was about 8.44×10-17 Sv when the neutron source was 252Cf and about 1.24×10-16 Sv when the neutron source was 241Am-Be.

Conclusion: Results show using optimum gamma-ray shield geometry can reduce the patient absorbed dose per incident neutron in a body chemical composition analyzer.

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Background: Several landmine detection methods, based on nuclear techniques, have been suggested up to now. Neutron-induced gamma emission, neutron and gamma attenuation, and fast neutron backscattering are the nuclear methods used for landmine detection. In this paper an optimized (safe and effective) moderating structure using an 241Am-Be neutron source for detecting landmines has been investigated by experiment and MCNP simulation. Materials and Methods: The experimental set up was composed of a lead (Pb) cylindrical shell enclosing the neutron source, embedded in a fixed size high-density polyethylene (HDPe) cylinder with the variable thickness of the upper and lower moderator/reflector. Some experimental groups were used to measure several moderator configurations' responses by replacing a thermal neutron detector with the mine and counting the neutron capture events. Results: the total experimental results led to the introduction of optimum moderator geometry for landmine detection. A safe landmine detection system was obtained which enabled the operator to use it for 950 h/year, regarding the dose limit recommended by ICRP. Conclusion: The novel method for optimization applied in this work is more applicable than the usual approach that is based on measuring the prompt gamma rays emitted by the landmine. Results showed that the method can be optimized in short time, without the usual difficulties of the other methods.

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Background: Since 1996 the assessment of environmental gamma radiation dose in residential areas of Iranian towns and cities has been accomplished for 10 counties. As a practical method and based on the results of a pilot study, in order to attribute the final results to the whole residential area of a town five stations were selected for every town. The location of individual station was studied closely to comply with recommended conditions in the literature. Materials and Methods: RDS-110 was employed to measure gamma dose rate for one hour. Average annual dose rates plus conversion coefficients were employed to estimate gonad, bone marrow, equivalent and effective dose. Result: Minimum and maximum annual bone marrow and gonad dose equivalent attributed to environmental gamma are 0.24 mSvy-1 (for both tissues) and 1.44 and 1.46 mSvy-1, respectively. Conclusion: Average gonad and bone marrow doses for North Khorasan, Boshehr and Hormozgan provinces were less than the corresponding values for normal area. Iran. J. Radiat. Res., 2009 7 (1): 41-47

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Background: Microwave Thermotherapy has been gradually used in radiotherapy and it is reported that microwave radiation increases bone demineralization rate independently of temperature. Furthermore, it becomes more and more widespread that the damage caused by the synergistic effect of microwave radiation and hypergravity. The experiment was designed to investigate the effect of microwave radiation on osteogenesis and osteolysis of rats in the hypergravity condition and to observe the role of Rana sylvatica Le conte oil as a radioprotector. Materials and Methods: Wistar rats were exposed to microwave radiation of 200mW/cm2 power density and +6G hypergravity, and the concentrations of osteocalcin, calcitionin, calcium, phosphorus, and hydroxyproline and the activity of alkaline phosphatase were detected in serum. Results: The serum concentrations of osteocalcin and calcitionin and the activity of alkaline phosphatase decreased, while the calcium, phosphorus and hydroxyproline concentrations increased after the synergistic effect of microwave radiation and hypergravity. Rana sylvatica Le conte oil intervention inhibited significantly the decrease of osteocalcin concentration and restrained significantly the increases of hydroxyproline and calcium concentrations in serum. Conclusion: These results imply that the synergistic effect of microwave radiation and hypergravity inhibits osteogenesis and enhances osteolysis in rats causing bone metabolic disturbance, while the injury resulted from microwave radiation and hypergravity could be protected by intervention with Rana sylvatica Le conte oil and it provides an original direction in the investigation of radioprotectors. Iran. J. Radiat. Res., 2011 9(1): 1-8

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Background: The South-west coast of India is known to have very high levels of natural background radiation due to the monazite beach sand. Uranium is the heaviest trace element found in all terrestrial substances at varying levels with chemical and radio toxicities. It supports several short-lived radioisotopes in its decay series including radium. Uranium in drinking water is important in terms of the ingestion dose. Materials and Methods: The present study reports the results of uranium analysis of 346 drinking water samples from the three costal districts of Kerala using fission track registration technique. Results: Results obtained show that uranium concentrations vary from 0.31 μg/l to 4.92 μg/l equivalent to the specific activity of 3.9 Bq/m3 and 62 Bq/m³, respectively. Conclusion: The estimated daily intake of uranium through drinking water is lower than the recommended limits. The distribution of uranium in water bodies shows a heterogeneous nature of distribution. Iran. J. Radiat. Res., 2012 10(1): 31-36

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Background: To determine which radiotherapy parameters are associated with the tumor response of locally advanced non-small cell lung cancer (NSCLC) patients undergoing concurrent chemoradiotherapy. Materials and Methods: Thirty one patients with IIIA/IIIB NSCLC underwent chemoradiotherapy with a median dose of 63 Gy. On our actual treatments, we made radiotherapy planning to cover the planning target volume (PTV) with 95% of the prescribed dose, and checked the second CT simulation when a cumulative dose was about 36 Gy. For this study, each PTV of primary tumor was re-defined with even margins from the gross target volume (GTV), and the actual plan overlaid the re-defined PTV. The correlations between the tumor response rate during chemoradiotherapy and after chemoradiotherapy, and the dose distribution parameters (D95, V95, mean tumor dose and homogeneity index), total dose and GTV, were evaluated. Results: Median overall survival was 15.5 months and the two-year survival 42.3%. At first recurrence, radiation-field recurrence, distant metastases and simultaneous recurrence were developed in 35.5%, 41.9% and 9.7% of the cases, respectively. The dose distribution parameters were generally favorable and were not related with tumor response rate. The tumor response rate after chemoradiotherapy was correlated with the residual GTV at second simulation (&gamma=-0.627, p<0.001) and the tumor response rate during chemoradiotherapy (&gamma=0.541, p=0.003). Conclusion: Minimal correlation was found between the dose distribution parameters that were over the minimal dose requirement and tumor response in NSCLC with concurrent chemoradiotherapy. The small residual volume during chemoradiotherapy could indicate good tumor response after chemoradiotherapy.

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Background: The trabecular bone changes in the tibia of C₃H/HeN mice were measured 12 weeks after whole body irradiation with various doses of fast neutrons (0-2.4 Gy) or ¹³⁷Cs-generated gamma-rays (0-6 Gy). Materials and Methods: Serum calcium, phosphorus, estradiol concentration and alkaline phosphatase activity were measured. Tibiae were analyzed using microcomputed tomography. Biomechanical property and osteoclast surface level were measured. Results: There was a significant relationship between the loss of bone architecture and the radiation dose, and the best-fitting dose-response curves were linear-quadratic. Mean relative biological effectiveness (RBE) values (Ref. gamma) of 2.05 and 2.33 were estimated for fast neutron irradiation in trabecular bone volume fraction and bone mineral density, respectively. There was a substantial reduction in osteoclast surface level in tartrate-resistant acid phosphatase-stained histological sections of tibial metaphyses in irradiated mice with high dose of neutrons. Conclusion: There was a significant relationship between the loss of bone architecture and the radiation dose. The difference of osteoclastic bone resorption may represent a contributor to the low RBE in high dose of irradiation level relative to that of low dose level.

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Background: The variation of the radon progeny concentration in outdoor environment and meteorological parameters at fine resolution were studied for one year at a continental location, National Atmospheric Research Laboratory, Gadanki, India.  Materials and Methods: The concentrations were measured using Alpha Progeny Meter by collecting air samples at a height of 1 m above the Earth’s surface at a known flow rate. Results: Radon progeny concentration shows temporal variations on diurnal and monthly scales, and is due to mixing in the atmosphere. Peak in the early morning hours and low values during afternoon compared to nighttime are due to differential heat contrast between earth’s surface and its atmosphere. However, the activity during February shows maximum compared to June/July months.  The diurnal variation of radon progeny shows positive correlation with the relative humidity and negative correlation with ambient temperature.  The monthly mean activity of radon progeny for the year 2012 was found to be 4.76 ± 0.73 mWL. Conclusion: The mean concentration of radon progeny in the study region is relatively high compared to the other locations in India and may be due to the rocky terrains and trapping of air-masses near the observation site due to its topography.    

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Background: To evaluate the risk involved, there is need to know the quantum of personnel exposures in whole service. Dose reports from an Oncology Centre over 7 block periods, 5 years each from 1979 till 2013 are analyzed. Materials and Methods: Personnel monitoring (PM) reports till 1990s with film badges and later thermoluminescent (TL) badges (CaSo₄.Dy) were evaluated. 35 years total service was taken to represent total professional service of staff superannuating at age 60 years. Results: Mean personnel equivalent dose for 5 year block period is 3.30±0.43 mSv (n=7 blocks). Maximum dose in any block period was 30-60 mSv. Equivalent doses 22% were zero, 64.3% within 5 mSv. 2.1% were above 30 mSv in 5 year periods. Doses were decreasing order 11.8 mSv (radiopharmaceutical preparation), 4.3 mSv (nuclear medicine), 4.1 mSv (medical physics), 2.2 mSv(brachytherapy); 1.2 mSv (radiodiagnosis), 1.1 mSv (external beam radiotherapy) and 0.73 mSv (radiation sterilization plant). Conclusion: The whole body personnel dose in are much lower than recommended annual dose equivalent limits of 100 mSv/ 5 years. The magnitude of recorded doses to staff show that the risk is negligible and the principle of ALARA is being practiced in the work areas.

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