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Pesquisa : G01.249.660.250.368 [Categoria DeCS]
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  1 / 1945 MEDLINE  
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PMID:28809605
Autor:Imaoka T; Nishimura M; Daino K; Hosoki A; Takabatake M; Kokubo T; Doi K; Showler K; Nishimura Y; Moriyama H; Morioka T; Shimada Y; Kakinuma S
Endereço:a Department of Radiation Effects Research, National Institute of Radiological Sciences (NIRS), National Institutes for Quantum and Radiological Science and Technology (QST), Chiba 263-8555, Japan.
Título:Age Modifies the Effect of 2-MeV Fast Neutrons on Rat Mammary Carcinogenesis.
Fonte:Radiat Res; 188(4):419-425, 2017 Oct.
ISSN:1938-5404
País de publicação:United States
Idioma:eng
Resumo:The relative biological effectiveness (RBE) of neutrons depends on their physical nature (e.g., energy) and the biological context (e.g., end points, materials). From the perspective of radiological protection, age is an important biological context that influences radiation-related cancer risk, but very few studies have addressed its potential impact on neutron effects. We therefore investigated the influence of age on the effect of accelerator-generated fast neutrons (mean energy, ∼2 MeV) in an animal model of breast carcinogenesis. Female Sprague-Dawley rats at 1, 3 and 7 weeks of age were irradiated with fast neutrons at absorbed doses of 0.0485-0.97 Gy. All animals were kept under specific pathogen-free conditions and screened weekly for mammary tumors by palpation until they were 90 weeks old. Tumors were diagnosed based on histology. Mathematical modeling was used to analyze mammary cancer incidence, collectively using data from this study and a previously reported experiment on Cs gamma rays. The results indicate that neutron irradiation elevated the risk of palpable mammary carcinoma with a linear dose response, the slope of which depended on age at time of irradiation. The RBE of neutron radiation was 7.5 ± 3.4, 9.3 ± 3.5 and 26.1 ± 8.9 (mean ± SE) for animals exposed at 1, 3 and 7 weeks of age, respectively. Our results indicate that age of the animal is an important factor influencing the effect of fast neutrons on breast cancer risk.
Tipo de publicação: JOURNAL ARTICLE


  2 / 1945 MEDLINE  
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PMID:28192285
Autor:Arbor N; Higueret S; Elazhar H; Combe R; Meyer P; Dehaynin N; Taupin F; Husson D
Endereço:Université de Strasbourg, IPHC, 23 rue du Loess 67037 Strasbourg, France. CNRS, UMR7178, 67037 Strasbourg, France.
Título:Real-time detection of fast and thermal neutrons in radiotherapy with CMOS sensors.
Fonte:Phys Med Biol; 62(5):1920-1934, 2017 Mar 07.
ISSN:1361-6560
País de publicação:England
Idioma:eng
Resumo:The peripheral dose distribution is a growing concern for the improvement of new external radiation modalities. Secondary particles, especially photo-neutrons produced by the accelerator, irradiate the patient more than tens of centimeters away from the tumor volume. However the out-of-field dose is still not estimated accurately by the treatment planning softwares. This study demonstrates the possibility of using a specially designed CMOS sensor for fast and thermal neutron monitoring in radiotherapy. The 14 microns-thick sensitive layer and the integrated electronic chain of the CMOS are particularly suitable for real-time measurements in γ/n mixed fields. An experimental field size dependency of the fast neutron production rate, supported by Monte Carlo simulations and CR-39 data, has been observed. This dependency points out the potential benefits of a real-time monitoring of fast and thermal neutron during beam intensity modulated radiation therapies.
Tipo de publicação: JOURNAL ARTICLE


  3 / 1945 MEDLINE  
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PMID:27347593
Autor:Vorozhtsova SV; Bulynina TM; Ivanov AA
Título:[CYTOGENETIC EFFECTS IN MICE BONE MARROW AFTER IRRADIATION BY FAST NEUTRONS].
Fonte:Aviakosm Ekolog Med; 50(1):55-60, 2016.
ISSN:0233-528X
País de publicação:Russia (Federation)
Idioma:rus
Resumo:Mechanisms of damaging mice bone marrow cells by 1.5 MeV neutrons at the dose of 25-250 cGy, dose rate of 23.9 cGy/s and γ-quants 6°Co as a standard radiation were studied. The mitotic index and aberrant mitoses in marrow preparations were counted in 24 and 72 hours after irradiation. Coefficients of relative biological effectiveness (RBE) of fast neutrons 24 and 72 hours post irradiation calculated from mitotic index reduction and aberrant mitoses formation were within the range from 4.1 ± 0.1 to 7.3 ± 0.1. Mean time of the existence of chromosomal aberrations in marrow cells was determined. For the specified doses from γ-rays, the period of aberrations existence was 1.4-1.1 cycles and for neutrons, 1.0-0.6 cycles. Morphologic analysis of neutron-induced damages and ratio of the most common breaks demonstrated a high production of bridges, which outnumbered cells with fragments in 3 to 4 times suggesting a more destructive effect on the genetic structures of cells. RBE of fast neutrons is a variable that grows with a radiation dose. Moreover, RBE estimated after 72 hours exceeded values it had 24 hours after irradiation.
Tipo de publicação: ENGLISH ABSTRACT; JOURNAL ARTICLE


  4 / 1945 MEDLINE  
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PMID:27282876
Autor:Campbell BW; Hofstad AN; Sreekanta S; Fu F; Kono TJ; O'Rourke JA; Vance CP; Muehlbauer GJ; Stupar RM
Endereço:Department of Agronomy and Plant Genetics, University of Minnesota, Saint Paul, MN, 55108, USA.
Título:Fast neutron-induced structural rearrangements at a soybean NAP1 locus result in gnarled trichomes.
Fonte:Theor Appl Genet; 129(9):1725-38, 2016 Sep.
ISSN:1432-2242
País de publicação:Germany
Idioma:eng
Resumo:KEY MESSAGE: Three adjacent and distinct sequence rearrangements were identified at a NAP1 locus in a soybean mutant. Genetic dissection and validation revealed the function of this gene in soybean trichome development. A soybean (Glycine max (L.) Merr.) gnarled trichome mutant, exhibiting stunted trichomes compared to wild-type, was identified in a fast neutron mutant population. Genetic mapping using whole genome sequencing-based bulked segregant analysis identified a 26.6 megabase interval on chromosome 20 that co-segregated with the phenotype. Comparative genomic hybridization analysis of the mutant indicated that the chromosome 20 interval included a small structural variant within the coding region of a soybean ortholog (Glyma.20G019300) of Arabidopsis Nck-Associated Protein 1 (NAP1), a regulator of actin nucleation during trichome morphogenesis. Sequence analysis of the candidate allele revealed multiple rearrangements within the coding region, including two deletions (approximately 1-2 kb each), a translocation, and an inversion. Further analyses revealed that the mutant allele perfectly co-segregated with the phenotype, and a wild-type soybean NAP1 transgene functionally complemented an Arabidopsis nap1 mutant. In addition, mapping and exon sequencing of NAP1 in a spontaneous soybean gnarled trichome mutant (T31) identified a frame shift mutation resulting in a truncation of the coding region. These data indicate that the soybean NAP1 gene is essential for proper trichome development and show the utility of the soybean fast neutron population for forward genetic approaches for identifying genes.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Plant Proteins); 0 (RNA, Plant)


  5 / 1945 MEDLINE  
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PMID:27150515
Autor:Takada M; Nunomiya T; Nakamura T; Matsumoto T; Masuda A
Endereço:National Defense Academy, Yokosuka 239-8686, Japan takada@nda.ac.jp.
Título:CHARACTERIZATION OF A THIN SILICON SENSOR FOR ACTIVE NEUTRON PERSONAL DOSEMETERS.
Fonte:Radiat Prot Dosimetry; 170(1-4):213-7, 2016 Sep.
ISSN:1742-3406
País de publicação:England
Idioma:eng
Resumo:A thin silicon sensor has been developed for active neutron personal dosemeters for use by aircrews and first responders. This thin silicon sensor is not affected by the funneling effect, which causes detection of cosmic protons and over-response to cosmic neutrons. There are several advantages to the thin silicon sensor: a decrease in sensitivity to gamma rays, an improvement of the energy detection limit for neutrons down to 0.8 MeV and an increase in the sensitivity to fast neutrons. Neutron response functions were experimentally obtained using 2.5 and 5 MeV monoenergy neutron beams and a (252)Cf neutron source. Simulation results using the Monte Carlo N-Particle transport code agree quite well with the experimental ones when an energy deposition region shaped like a circular truncated cone is used in place of a cylindrical region.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:9002-88-4 (Polyethylene); 975X05H15A (Californium); Z4152N8IUI (Silicon)


  6 / 1945 MEDLINE  
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PMID:26773818
Autor:Kim HG; Jamil M; Rhee JT; Ahmad F; Jeon YJ
Endereço:IAP, High Energy Physics Lab, Konkuk University, Seoul 143-701, Republic of Korea.
Título:A simulation study on angular and micro pattern effects in GEM detectors.
Fonte:Appl Radiat Isot; 110:64-69, 2016 Apr.
ISSN:1872-9800
País de publicação:England
Idioma:eng
Resumo:A useful approach for the enhancement of thermal neutrons detection has been reported here. This technique, based on the angular and micro pattern effects, has been developed and applied to the boron-coated ((10)B) Gas Electron multiplier (GEM) detector. In the angular effect case, as a general rule, the detector device is turned at an angle which improves the device response per unit area of the detector. While for the latter case, a regular pattern in the form of micrometer deep grooves is fabricated onto the converter coating, consequently it enhances the capture probability of the detector. For the current study, both of these techniques using a (10)B-coated GEM detector have been simulated for low energy neutrons. For the evaluation of detector response thermal neutrons in the energy ranges from 25meV to 100meV were transported onto the detector surface. For this work, FLUKA MC code has been utilized. The output in both cases has been estimated as a function of incident thermal neutron energies. By employing both techniques, the angle and the micro pattern dependent efficiencies for (10)B-coated GEM detectors are presented, which indicate an improved efficiency response of the device. We anticipate that by using these modifications can lead a further forward step in the development and improvement of thermal neutron detection technology.
Tipo de publicação: JOURNAL ARTICLE


  7 / 1945 MEDLINE  
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PMID:26749562
Autor:Albright S; Seviour R
Endereço:West Building (W3/01), The University of Huddersfield, Huddersfield, West Yorkshire, England HD1 3DH, United Kingdom. Electronic address: simon.albright@hud.ac.uk.
Título:Radioisotopes produced by neutron irradiation of food.
Fonte:Appl Radiat Isot; 110:224-229, 2016 Apr.
ISSN:1872-9800
País de publicação:England
Idioma:eng
Resumo:The use of neutrons for cargo interrogation has the potential to drastically improve threat detection. Previous research has focussed on the production of (24)Na, based on the isotopes produced in pharmaceuticals and medical devices. For both the total activity and the ingestion dose we show that a variety of isotopes contribute and that (24)Na is only dominant under certain conditions. The composition of the foods has a strong influence on the resulting activity and ingestion dose suggesting that the pharmaceuticals and medical devices considered initially are not a viable analogue for foodstuffs. There is an energy dependence to the isotopes produced due to the cross-sections of different reactions varying with neutron energy. We show that this results in different isotopes dominating the ingestion dose at different energies, which has not been considered in the previous literature.
Tipo de publicação: JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
Nome de substância:0 (Radioisotopes); 0 (Sodium Radioisotopes)


  8 / 1945 MEDLINE  
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PMID:26745925
Autor:Young LA; Yang F; Woodworth D; McCormick Z; Sandison G
Endereço:Department of Radiation Oncology, University of Washington, Seattle, Washington 98115.
Título:Commissioning optically stimulated luminescence in vivo dosimeters for fast neutron therapy.
Fonte:Med Phys; 43(1):314, 2016 Jan.
ISSN:2473-4209
País de publicação:United States
Idioma:eng
Resumo:PURPOSE: Clinical in vivo dosimeters intended for use with photon and electron therapies have not been utilized for fast neutron therapy because they are highly susceptible to neutron damage. The objective of this work was to determine if a commercial optically stimulated luminescence (OSL) in vivo dosimetry system could be adapted for use in fast neutron therapy. METHODS: A 50.5 MeV fast neutron beam generated by a clinical neutron therapy cyclotron was used to irradiate carbon doped aluminum oxide (Al2O3:C) optically simulated luminescence dosimeters (OSLDs) in a solid water phantom under standard calibration conditions, 150 cm SAD, 1.7 cm depth, and 10.3 × 10.0 cm field size. OSLD fading and electron trap depletion studies were performed with the OSLDs irradiated with 20 and 50 cGy and monitored over a 24-h period to determine the optimal time for reading the dosimeters during calibration. Four OSLDs per group were calibrated over a clinical dose range of 0-150 cGy. RESULTS: OSLD measurement uncertainties were lowered to within ±2%-3% of the expected dose by minimizing the effect of transient fading that occurs with neutron irradiation and maintaining individual calibration factors for each dosimeter. Dose dependent luminescence fading extended beyond the manufacturer's recommended 10 min period for irradiation with photon or electron beams. To minimize OSL variances caused by inconsistent fading among dosimeters, the observed optimal time for reading the OSLDs postirradiation was between 30 and 90 min. No field size, wedge factor, or gantry angle dependencies were observed in the OSLDs irradiated by the studied fast neutron beam. CONCLUSIONS: Measurements demonstrated that uncertainties less than ±3% were attainable in OSLDs irradiated with fast neutrons under clinical conditions. Accuracy and precision comparable to clinical OSL measurements observed with photons can be achieved by maintaining individual OSLD calibration factors and minimizing transient fading effects.
Tipo de publicação: JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T


  9 / 1945 MEDLINE  
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PMID:26606065
Autor:Nafee SS; Saeed A; Shaheen SA; El Assouli SM; El Assouli MZ; Raouf GA
Endereço:*Physics Department, Faculty of Science, King Abdulaziz University, Jeddah 20589, KSA; †Physics Department, Faculty of Science, Alexandria University, Alexandria 21121, Egypt; ‡Physics Department, Thamar University, Thamar, Yemen; §King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, KSA; **Biology Department, Faculty of Science, King Abdulaziz University, Jeddah 20589, KSA; ††Biochemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 20589, KSA; ‡‡Spectroscopy Department, Physics Division, National Research Center, Cairo 12311, Egypt.
Título:Effect of Very Low Dose Fast Neutrons on the DNA of Rats' Peripheral Blood Mononuclear Cells and Leukocytes.
Fonte:Health Phys; 110(1):50-8, 2016 Jan.
ISSN:1538-5159
País de publicação:United States
Idioma:eng
Resumo:The effect of very low dose fast neutrons on the chromatin and DNA of rats' peripheral blood mononuclear cells (PBMC) and leukocytes has been studied in the present work using Fourier transform infrared (FTIR) and single-cell gel electrophoresis (comet assay). Fourteen female Wistar rats were used; seven were irradiated with neutrons of 0.9 cGy (Am-Be, 0.02 cGy h(-1)), and seven others were used as control. Second derivative and curve fitting were used to analyze the FTIR spectra. In addition, hierarchical cluster analysis (HCA) was used to classify the group spectra. Meanwhile, the tail moment and percentage of DNA in the tail were used as indicators to sense the breaking and the level of damage in DNA. The analysis of FTIR spectra of the PBMC of the irradiated group revealed a marked increase in the area of phosphodiesters of nucleic acids and the area ratios of RNA/DNA and phosphodiesters/carbohydrates. A sharp significant increase and decrease in the areas of RNA and DNA ribose were recorded, respectively. In the irradiated group, leukocytes with different tail lengths were observed. The distributions of tail moments and the percentage of DNA in the tail of irradiated groups were heterogeneous. The mean value of the percentages of DNA in the tail at 0.5 h post-irradiation represented low-level damage in the DNA. Therefore, one can conclude that very low dose fast neutrons might cause changes in the DNA of PBMC at the submolecular level. It could cause low-level damage, double-strand break, and chromatin fragmentation of DNA of leukocytes.
Tipo de publicação: JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
Nome de substância:9007-49-2 (DNA)


  10 / 1945 MEDLINE  
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PMID:26474209
Autor:Adib M; Habib N; Bashter II; El-Mesiry MS; Mansy MS
Endereço:Reactor Physics Department, NRC, Atomic Energy Authority, Cairo, Egypt.
Título:Simulation study of accelerator based quasi-mono-energetic epithermal neutron beams for BNCT.
Fonte:Appl Radiat Isot; 107:98-102, 2016 Jan.
ISSN:1872-9800
País de publicação:England
Idioma:eng
Resumo:Filtered neutron techniques were applied to produce quasi-mono-energetic neutron beams in the energy range of 1.5-7.5 keV at the accelerator port using the generated neutron spectrum from a Li (p, n) Be reaction. A simulation study was performed to characterize the filter components and transmitted beam lines. The feature of the filtered beams is detailed in terms of optimal thickness of the primary and additive components. A computer code named "QMNB-AS" was developed to carry out the required calculations. The filtered neutron beams had high purity and intensity with low contamination from the accompanying thermal, fast neutrons and γ-rays.
Tipo de publicação: JOURNAL ARTICLE



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