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[PMID]:28554139
[Au] Autor:Li C; Le Roux G; Sonke J; van Beek P; Souhaut M; Van der Putten N; De Vleeschouwer F
[Ad] Endereço:EcoLab, Université de Toulouse, CNRS, INPT, UPS, Tolosan, France. Electronic address: chuxian.li@ensat.fr.
[Ti] Título:Recent Pb, Cs and Am accumulation in an ombrotrophic peatland from Amsterdam Island (Southern Indian Ocean).
[So] Source:J Environ Radioact;175-176:164-169, 2017 Sep.
[Is] ISSN:1879-1700
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:Over the past 50 years, Pb, Cs and Am have been abundantly used in reconstructing recent sediment and peat chronologies. The study of global aerosol-climate interaction is also partially depending on our understanding of Rn- Pb cycling, as radionuclides are useful aerosol tracers. However, in comparison with the Northern Hemisphere, few data are available for these radionuclides in the Southern Hemisphere, especially in the South Indian Ocean. A peat core was collected in an ombrotrophic peatland from the remote Amsterdam Island (AMS) and was analyzed for Pb, Cs and Am radionuclides using an underground ultra-low background gamma spectrometer. The Pb Constant Rate of Supply (CRS) model of peat accumulations is validated by peaks of artificial radionuclides ( Cs and Am) that are related to nuclear weapon tests. We compared the AMS Pb data with an updated Pb deposition database. The Pb flux of 98 ± 6 Bq·m ·y derived from the AMS core agrees with data from Madagascar and South Africa. The elevated flux observed at such a remote location may result from the enhanced Rn activity and frequent rainfall in AMS. This enhanced Rn activity itself may be explained by continental air masses passing over southern Africa and/or Madagascar. The Pb flux at AMS is higher than those derived from cores collected in coastal areas in Argentina and Chile, which are areas dominated by marine westerly winds with low Rn activities. We report a Cs inventory at AMS of 144 ± 13 Bq·m (corrected to 1969). Our data thus contribute to the under-represented data coverage in the mid-latitudes of the Southern Hemisphere.
[Mh] Termos MeSH primário: Amerício/análise
Radioisótopos de Césio/análise
Radioisótopos de Chumbo/análise
Monitoramento de Radiação
Poluentes Radioativos da Água/análise
[Mh] Termos MeSH secundário: Oceano Índico
Ilhas
Solo
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Cesium Radioisotopes); 0 (Lead Radioisotopes); 0 (Soil); 0 (Water Pollutants, Radioactive); VW92PHU2UY (Americium)
[Em] Mês de entrada:1706
[Cu] Atualização por classe:171116
[Lr] Data última revisão:
171116
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170530
[St] Status:MEDLINE


  2 / 1105 MEDLINE  
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[PMID]:28441286
[Au] Autor:Poudel D; Guilmette RA; Bertelli L; Klumpp JA; Brey RR
[Ad] Endereço:*Radiation Protection Division, Los Alamos National Laboratory, Los Alamos, NM 87545; †Lovelace Respiratory Research Institute, Albuquerque, NM and Ray Guilmette and Associates, LLC, Perry, ME; ‡Department of NE and Health Physics, Idaho State University, Pocatello, ID 83209.
[Ti] Título:Behavior of Americium in Simulated Wounds in Nonhuman Primates.
[So] Source:Health Phys;112(6):544-549, 2017 Jun.
[Is] ISSN:1538-5159
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:An americium solution injected intramuscularly into several nonhuman primates (NHPs) was found to behave differently than predicted by the wound models described in the NCRP Report 156. This was because the injection was made along with a citrate solution, which is known to be more soluble than chlorides, oxides, or nitrates on which the NCRP Report was based. A multi-exponential wound model specific to the injected americium solution was developed based on the retention in the intramuscular sites. The model was coupled with the americium systemic model to interpret the urinary excretion data and assess the intake, and it was determined that the models were adequate to predict early urinary excretion in most cases but unable to predict late urinary excretion. This was attributed to the differences in the systemic handling of americium between humans and nonhuman primates. Information on the type of wounds, solubility, particle size, mass, chemical form, etc., should always be considered when performing wound dosimetry.
[Mh] Termos MeSH primário: Amerício/farmacocinética
Ferimentos e Lesões/metabolismo
[Mh] Termos MeSH secundário: Amerício/administração & dosagem
Amerício/urina
Animais
Modelos Animais de Doenças
Feminino
Injeções Intramusculares/veterinária
Injeções Intravenosas/veterinária
Funções Verossimilhança
Macaca
Macaca fascicularis
Masculino
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
VW92PHU2UY (Americium)
[Em] Mês de entrada:1707
[Cu] Atualização por classe:170721
[Lr] Data última revisão:
170721
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170426
[St] Status:MEDLINE
[do] DOI:10.1097/HP.0000000000000658


  3 / 1105 MEDLINE  
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[PMID]:28350701
[Au] Autor:Klumpp J; Bertelli L; Waters T
[Ad] Endereço:*Los Alamos National Laboratory, Los Alamos, NM 87545.
[Ti] Título:Interpretation of Nasal Swab Measurements Following Suspected Releases of Actinide Aerosols.
[So] Source:Health Phys;112(5):465-469, 2017 May.
[Is] ISSN:1538-5159
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:For radionuclides such as plutonium and americium, detection of removable activity in the nose (i.e., nasal swab measurements) are frequently used to determine whether follow-up bioassay measurements are warranted following a potential intake. For this paper, the authors analyzed 429 nasal swab measurements taken following incidents or suspicious circumstances (such as an air monitor alarming) at Los Alamos National Laboratory (LANL) for which the dose was later evaluated using in vitro bioassay. Nasal swab measurements were found to be very poor predictors of dose and should not be used as such in the field. However, nasal swab measurements can be indicative of whether a reliably detectable committed effective dose (CED) occurred. About 14% of nasal swab measurements between 1.25 and 16.7 Bq corresponded to CEDs greater than 1 mSv, so in general, positive nasal swabs always indicate that follow-up bioassay should be performed (positive nasal swabs less than 1.25 Bq are considered separately). This probability increased significantly for nasal swabs greater than 16.7 Bq. Only about 3% of nasal swabs with no detectable activity (NDA) corresponded to reliably detectable CEDs. A nasal swab with NDA is therefore necessary, but not sufficient, to negate the need for a follow-up bioassay if it was collected following other workplace indicators of a potential intake.
[Mh] Termos MeSH primário: Aerossóis/análise
Poluentes Radioativos do Ar/análise
Amerício/análise
Bioensaio/métodos
Mucosa Nasal/química
Plutônio/análise
Monitoramento de Radiação/métodos
[Mh] Termos MeSH secundário: Seres Humanos
Dose de Radiação
Exposição à Radiação/análise
Liberação Nociva de Radioativos
Reprodutibilidade dos Testes
Sensibilidade e Especificidade
[Pt] Tipo de publicação:EVALUATION STUDIES; JOURNAL ARTICLE; VALIDATION STUDIES
[Nm] Nome de substância:
0 (Aerosols); 0 (Air Pollutants, Radioactive); 53023GN24M (Plutonium); VW92PHU2UY (Americium)
[Em] Mês de entrada:1707
[Cu] Atualização por classe:170703
[Lr] Data última revisão:
170703
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170329
[St] Status:MEDLINE
[do] DOI:10.1097/HP.0000000000000648


  4 / 1105 MEDLINE  
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[PMID]:28350699
[Au] Autor:Yoon S; Ha WH; Park S; Lee SS; Jin YW
[Ad] Endereço:*Korea Institute of Radiological and Medical Sciences, Seoul, Korea.
[Ti] Título:Rapid Analysis of 239,238Pu, 241Am, and 90Sr for Nasal Smear Samples in Radiation Emergency and Evaluation of Intake Retention Fraction.
[So] Source:Health Phys;112(5):451-457, 2017 May.
[Is] ISSN:1538-5159
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:The efficiency of the nasal smear method was reviewed to perform a method of sample collection, analysis and initial dose estimation. The screening method of alpha-emitting radionuclides using chemical separation and alpha spectrometry was also studied. To rapidly conduct the appropriate response to victims, special monitoring for Pu, Am, and Sr using sequential analysis was established, and the method was successfully validated through participation in an international inter-comparison program. The duration of the analysis method was evaluated with regard to application in emergency situations because of its relatively rapid treatment and counting time. The intake retention fraction was calculated and evaluated to review the characteristics of each radionuclide in the anterior nasal passage of the extra-thoracic region. No large difference was observed among the four radionuclides. However, the values of the intake retention fraction were affected by age groups because of the different respiratory rates. The effects of the Y ingrowth and particle size were also discussed.
[Mh] Termos MeSH primário: Poluentes Radioativos do Ar/análise
Amerício/análise
Bioensaio/métodos
Mucosa Nasal/química
Plutônio/análise
Radioisótopos de Estrôncio/análise
[Mh] Termos MeSH secundário: Absorção de Radiação/fisiologia
Seres Humanos
Exposição à Radiação/análise
Monitoramento de Radiação/métodos
Liberação Nociva de Radioativos
Reprodutibilidade dos Testes
Sensibilidade e Especificidade
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Air Pollutants, Radioactive); 0 (Strontium Radioisotopes); 53023GN24M (Plutonium); VW92PHU2UY (Americium)
[Em] Mês de entrada:1707
[Cu] Atualização por classe:170703
[Lr] Data última revisão:
170703
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170329
[St] Status:MEDLINE
[do] DOI:10.1097/HP.0000000000000635


  5 / 1105 MEDLINE  
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[PMID]:28350695
[Au] Autor:Alomairy NA; Brey RR; Guilmette RA
[Ad] Endereço:*Department of Nuclear Engineering & Health Physics, Idaho State University, Pocatello, ID; †Lovelace Respiratory Research Institute, Albuqerque, NM; ‡and Ray Guilmette and Associates LLC, Perry, ME.
[Ti] Título:ICRP 67 Biokinetic Models for AM-241 Applied to Nonhuman Primates.
[So] Source:Health Phys;112(5):423-429, 2017 May.
[Is] ISSN:1538-5159
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Between 1960 and 1985, Patricia Durbin and colleagues performed studies on the distribution of intravenously and intramuscularly injected Am citrate with dosages ranging from 16 to 32 kBq kg in 30 male and female non-human primates (NHP). Dr. Durbin died unexpectedly in March of 2009, leaving much of the extensive serial blood, bioassay, and autopsy data from these NHP studies unanalyzed. As part of the experimental design, serial blood samples were taken, and urine and feces samples were collected separately for the duration of the study. The measurements of urine, fecal excretion, blood samples, and organ burden data obtained from the animals were used to evaluate the transfer rates of the ICRP 67 biokinetic model for Am. Seven cases, in which the primates were administered Am citrate by intravenous injection, were evaluated using the ICRP 67 systemic model. There were differences ranging from 51.4% underestimated to 102.7% overestimated activity between the predicted intake, which was calculated using IMBA Professional Plus software and based upon the urine bioassay data and the actual activity. The difference between the predicted activity at the time of death in the liver and skeleton using IMBA professional software and the value of the measured activity at the time of death were also compared. Generally, the ratios of predicted activity in the liver and skeleton at the time of death to the measured activity were consistently more than 1. However, the ratios were less than 1 in the skeleton for animals that were sacrificed 2,199 and 973 d post injection. The posterior probability distributions for model parameters derived using WeLMoS method were inconsistent with the ICRP 67 default parameters. The prediction made based on the posterior probability distributions for model parameters derived using WeLMoS gave the best fit to these data; however, the modified parameters overestimated the activity in almost all cases. The difference between the predicted Am activity and the value of the measured activity may be due to the physiological age-related characteristics relative to the age of the animal at the time of the injection and early and long scarified time.
[Mh] Termos MeSH primário: Envelhecimento/metabolismo
Amerício/farmacocinética
Bioensaio/métodos
Modelos Biológicos
Contagem Corporal Total/métodos
[Mh] Termos MeSH secundário: Absorção de Radiação/fisiologia
Animais
Simulação por Computador
Feminino
Seres Humanos
Cinética
Macaca
Masculino
Taxa de Depuração Metabólica
Modelos Estatísticos
Especificidade de Órgãos/fisiologia
Dose de Radiação
Reprodutibilidade dos Testes
Sensibilidade e Especificidade
Análise de Sobrevida
Distribuição Tecidual
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
VW92PHU2UY (Americium)
[Em] Mês de entrada:1707
[Cu] Atualização por classe:170703
[Lr] Data última revisão:
170703
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170329
[St] Status:MEDLINE
[do] DOI:10.1097/HP.0000000000000634


  6 / 1105 MEDLINE  
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[PMID]:27234047
[Au] Autor:Tazrart A; Bolzinger MA; Moureau A; Molina T; Coudert S; Angulo JF; Briancon S; Griffiths NM
[Ad] Endereço:Laboratoire de RadioToxicologie, CEA/DRF/iRCM, Bruyères le Châtel, Arpajon, France; Université de Lyon, F-69008, Lyon, France; Laboratoire de Dermopharmacie et Cosmétologie, Laboratoire d'Automatique et de Génie des Procédés (LAGEP), UMR CNRS 5007, 8, Avenue Rockefeller, 69373 Lyon Cedex 08, France.
[Ti] Título:Penetration and decontamination of americium-241 ex vivo using fresh and frozen pig skin.
[So] Source:Chem Biol Interact;267:40-47, 2017 Apr 01.
[Is] ISSN:1872-7786
[Cp] País de publicação:Ireland
[La] Idioma:eng
[Ab] Resumo:Skin contamination is one of the most probable risks following major nuclear or radiological incidents. However, accidents involving skin contamination with radionuclides may occur in the nuclear industry, in research laboratories and in nuclear medicine departments. This work aims to measure the penetration of the radiological contaminant Americium ( Am) in fresh and frozen skin and to evaluate the distribution of the contamination in the skin. Decontamination tests were performed using water, Fuller's earth and diethylene triamine pentaacetic acid (DTPA), which is the recommended treatment in case of skin contamination with actinides such as plutonium or americium. To assess these parameters, we used the Franz cell diffusion system with full-thickness skin obtained from pigs' ears, representative of human skin. Solutions of Am were deposited on the skin samples. The radioactivity content in each compartment and skin layers was measured after 24 h by liquid scintillation counting and alpha spectrophotometry. The Am cutaneous penetration to the receiver compartment is almost negligible in fresh and frozen skin. Multiple washings with water and DTPA recovered about 90% of the initial activity. The rest remains fixed mainly in the stratum corneum. Traces of activity were detected within the epidermis and dermis which is fixed and not accessible to the decontamination.
[Mh] Termos MeSH primário: Amerício/toxicidade
Pele/efeitos dos fármacos
[Mh] Termos MeSH secundário: Compostos de Alumínio/química
Amerício/química
Animais
Autorradiografia
Descontaminação
Congelamento
Compostos de Magnésio/química
Ácido Pentético/química
Silicatos/química
Pele/metabolismo
Pele/patologia
Suínos
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Aluminum Compounds); 0 (Magnesium Compounds); 0 (Silicates); 7A314HQM0I (Pentetic Acid); 8031-18-3 (Fuller's Earth); VW92PHU2UY (Americium)
[Em] Mês de entrada:1703
[Cu] Atualização por classe:170328
[Lr] Data última revisão:
170328
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160529
[St] Status:MEDLINE


  7 / 1105 MEDLINE  
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[PMID]:27038878
[Au] Autor:An DD; Kullgren B; Jarvis EE; Abergel RJ
[Ad] Endereço:Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
[Ti] Título:From early prophylaxis to delayed treatment: Establishing the plutonium decorporation activity window of hydroxypyridinonate chelating agents.
[So] Source:Chem Biol Interact;267:80-88, 2017 Apr 01.
[Is] ISSN:1872-7786
[Cp] País de publicação:Ireland
[La] Idioma:eng
[Ab] Resumo:The potential consequences of a major radiological event are not only large-scale external radiation exposure of the population, but also uncontrolled dissemination of, and internal contamination with, radionuclides. When planning an emergency response to radiological and nuclear incidents, one must consider the need for not only post-exposure treatment for contaminated individuals, but also prophylactic measures to protect the workforce facing contaminated areas and patients in the aftermath of such events. In addition to meeting the desired criteria for post-exposure treatments such as safety, ease of administration, and broad-spectrum efficacy against multiple radionuclides and levels of challenge, ideal prophylactic countermeasures must include rapid onset; induce minimal to no performance-decrementing side effects; be compatible with current military Chemical, Biological, Radiological, Nuclear, and Explosive countermeasures; and require minimal logistical burdens. Hydroxypyridinone-based actinide decorporation agents have shown the most promise as decorporation strategies for various radionuclides of concern, including the actinides plutonium and americium. The studies presented here probe the extent of plutonium decorporation efficacy for two chelating agents, 3,4,3-LI(1,2-HOPO) and 5-LIO(Me-3,2-HOPO), from early pre-exposure time points to a delay of up to 7 days in parenteral or oral treatment administration, i.e., well beyond the initial hours of emergency response. Despite delayed treatment after a contamination event, both ligands clearly enhanced plutonium elimination through the investigated 7-day post-treatment period. In addition, a remarkable prophylactic efficacy was revealed for 3,4,3-LI(1,2-HOPO) with treatment as early as 48 h before the plutonium challenge. This work provides new perspectives in the indication and use of experimental actinide decorporation treatments.
[Mh] Termos MeSH primário: Quelantes/química
Descontaminação/métodos
Plutônio/química
Piridonas/química
[Mh] Termos MeSH secundário: Amerício/análise
Amerício/química
Animais
Fezes/química
Compostos Heterocíclicos com 1 Anel/química
Camundongos
Plutônio/análise
Plutônio/urina
Fatores de Tempo
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (1,5,10,14-tetra(1-hydroxy-2-pyridon-6-oyl)-1,5,10,14-tetraazatetradecane); 0 (4-carbamoyl-3-hydroxy-1-methyl-2(1H)-pyridinone); 0 (Chelating Agents); 0 (Heterocyclic Compounds, 1-Ring); 0 (Pyridones); 53023GN24M (Plutonium); VW92PHU2UY (Americium)
[Em] Mês de entrada:1703
[Cu] Atualização por classe:170410
[Lr] Data última revisão:
170410
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160404
[St] Status:MEDLINE


  8 / 1105 MEDLINE  
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[PMID]:27588898
[Au] Autor:Maloubier M; Shuh DK; Minasian SG; Pacold JI; Solari PL; Michel H; Oberhaensli FR; Bottein Y; Monfort M; Moulin C; Den Auwer C
[Ad] Endereço:Institut de Chimie de Nice, Université Côte d'Azur and Centre National de la Recherche Scientifique , 06108 Nice, France.
[Ti] Título:How Do Radionuclides Accumulate in Marine Organisms? A Case Study of Europium with Aplysina cavernicola.
[So] Source:Environ Sci Technol;50(19):10730-10738, 2016 Oct 04.
[Is] ISSN:1520-5851
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:In the ocean, complex interactions between natural and anthropogenic radionuclides, seawater, and diverse marine biota provide a unique window through which to examine ecosystem and trophic transfer mechanisms in cases of accidental dissemination. The nature of interaction between radionuclides, the marine environment, and marine species is therefore essential for better understanding transfer mechanisms from the hydrosphere to the biosphere. Although data pertaining to the rate of global transfer are often available, little is known regarding the mechanism of environmental transport and uptake of heavy radionuclides by marine species. Among marine species, sponges are immobile active filter feeders and have been identified as hyperaccumulators of several heavy metals. We have selected the Mediterranean sponge Aplysina cavernicola as a model species for this study. Actinide elements are not the only source of radioactive release in cases of civilian nuclear events; however, their physicochemical transfer mechanisms to marine species remain largely unknown. We have targeted europium(III) as a representative of the trivalent actinides such as americium or curium. To unravel biological uptake mechanisms of europium in A. cavernicola, we have combined radiometric (γ) measurements with spectroscopic (time-resolved laser-induced fluorescence spectroscopy, TRLIFS, and X-ray absorption near-edge structure, XANES) and imaging (transmission electron microscopy, TEM, and scanning transmission X-ray microscopy, STXM) techniques. We have observed that the colloids of NaEu(CO ) ·nH O formed in seawater are taken up by A. cavernicola with no evidence that lethal dose has been reached in our working conditions. Spectroscopic results suggest that there is no change of speciation during uptake. Finally, TEM and STXM images recorded at different locations across a sponge cross section, together with differential cell separation, indicate the presence of europium particles (around 200 nm) mainly located in the skeleton and toward the outer surface of the sponge.
[Mh] Termos MeSH primário: Organismos Aquáticos
Európio
[Mh] Termos MeSH secundário: Amerício
Cúrio
Radioisótopos
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Radioisotopes); 444W947O8O (Europium); M5LL84MZ2W (Curium); VW92PHU2UY (Americium)
[Em] Mês de entrada:1706
[Cu] Atualização por classe:170608
[Lr] Data última revisão:
170608
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160903
[St] Status:MEDLINE


  9 / 1105 MEDLINE  
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[PMID]:27532439
[Au] Autor:Rump A; Stricklin D; Lamkowski A; Eder S; Abend M; Port M
[Ad] Endereço:Bundeswehr Institute of Radiobiology, Munich, Germany.
[Ti] Título:The Impact of Time on Decorporation Efficacy After a "Dirty Bomb" Attack Studied by Simulation.
[So] Source:Drug Res (Stuttg);66(11):607-613, 2016 Nov.
[Is] ISSN:2194-9387
[Cp] País de publicação:Germany
[La] Idioma:eng
[Ab] Resumo:In the case of a nuclear or radiological incident, there is a risk of external and internal contamination with radionuclides in addition to external irradiation. There is no consensus whether decorporation treatment should be initiated right away on spec or pending the results of internal dosimetry to determine the indication. Based on biokinetic models for plutonium-239, americium-241 and cesium-137, the efficacy of a decorporation treatment using DTPA or Prussian blue was simulated depending on the initiation time and the duration of treatment for different invasion pathways and physicochemical properties of the inhaled compounds. For the same level of radioactivity incorporated, the committed effective dose increases with the speed of the invasion process. The impact of the initiation time of a decorporation treatment is particularly important when the absorption of the radionuclide is fast. Even if started early after incorporation, the therapeutic efficacy is less for americium-241 or cesium-137 compared to plutonium-239. Therapeutic efficacy increases with treatment duration up to about 90 days for plutonium-239 and cesium-137, whereas a prolongation of the treatment over this limit may further enhance efficacy in the case of americium-241. In the case of a nuclear incident, several fractions with different but a priori unknown physicochemical properties may be inhaled. Thus, decorporation therapy should be started as soon as possible after the incorporation of the radionuclide(s), as a loss of efficacy caused by a delay of treatment initiation possibly cannot be compensated later on. Treatment should be pursued for several months.
[Mh] Termos MeSH primário: Descontaminação/métodos
Ferrocianetos/química
Ácido Pentético/química
Radioisótopos/química
[Mh] Termos MeSH secundário: Amerício/química
Césio/química
Simulação por Computador
Exposição por Inalação
Modelos Biológicos
Armas Nucleares
Plutônio/química
Radiometria/métodos
Fatores de Tempo
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Ferrocyanides); 0 (Radioisotopes); 1KSV9V4Y4I (Cesium); 53023GN24M (Plutonium); 7A314HQM0I (Pentetic Acid); TLE294X33A (ferric ferrocyanide); VW92PHU2UY (Americium)
[Em] Mês de entrada:1703
[Cu] Atualização por classe:170330
[Lr] Data última revisão:
170330
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160818
[St] Status:MEDLINE


  10 / 1105 MEDLINE  
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[PMID]:27370130
[Au] Autor:Shen H; Culberson WS; Ross CK
[Ad] Endereço:Ionizing Radiation Standards, National Research Council, Ottawa, Ontario K1A 0R6, Canada.
[Ti] Título:Technical Note: An investigation of polarity effects for wide-angle free-air chambers.
[So] Source:Med Phys;43(7):4106, 2016 Jul.
[Is] ISSN:2473-4209
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:PURPOSE: Wide-angle free-air chambers (WAFACs) are used as primary standard measurement devices for establishing the air-kerma strength of low-energy, low-dose rate brachytherapy seeds. The National Research Council of Canada (NRC) is commissioning a primary standard wide-angle free-air chamber (NRC WAFAC) to serve the calibration needs of Canadian clients. The University of Wisconsin has developed a similar variable-aperture free-air chamber (UW VAFAC) to be used as a research tool. As part of the NRC commissioning, measurements were carried out for both polarities of the applied bias voltage and the resulting effects were observed to be very large. Similar effects were identified with the UW VAFAC. The authors describe the measurements carried out to determine the underlying causes of the polarity effect and the approach used to eliminate it. METHODS: The NRC WAFAC is based on the WAFAC design developed at the National Institute of Standards and Technology in the USA. Charge measurements for (125)I and (241)Am sources were carried out for both negative and positive polarities on the NRC WAFAC and UW VAFAC. Two aperture sizes were also investigated with the UW VAFAC. In addition, measurements on the NRC WAFAC were carried out with a small bias between the collecting electrode and the shield foil at the downstream end of the chamber. To mitigate all of the polarity effects, the downstream surface of the collecting electrode was covered with a thin layer of graphite on both the NRC and UW chambers. RESULTS: Both chamber designs showed a difference of more than 30 % between the charge collected with positive and negative bias voltages for the smallest electrode separation. It was shown for the NRC WAFAC that charge could be collected in the small gap downstream of the collecting volume by applying a voltage between the shield foil and the collecting electrode, even though an insulating foil (Mylar or polyimide film) separated the conducting surface from the small gap region. The unwanted additional current was shown to be proportional to the size of the aperture for the UW VAFAC. The extra ionization produced in the small gap region was eliminated for both chambers by covering the insulating side of the collecting electrode with a grounded conducting layer. CONCLUSIONS: The small gap region downstream of the collecting electrode in the NRC WAFAC and UW VAFAC can serve as an unwanted source of ion current. It is concluded that a residual electric field in the small gap region may lead to ion transport and to charge being trapped on the surface of the foil. The foil then acts as a capacitor with an equal charge, but of opposite sign, being attracted to the conducting surface. Covering the back of the collecting electrode surface with a grounded conducting layer eliminated the polarity effect.
[Mh] Termos MeSH primário: Braquiterapia/instrumentação
[Mh] Termos MeSH secundário: Algoritmos
Amerício/uso terapêutico
Calibragem
Simulação por Computador
Eletrodos
Desenho de Equipamento
Grafite
Radioisótopos do Iodo/uso terapêutico
Método de Monte Carlo
[Pt] Tipo de publicação:COMPARATIVE STUDY; JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Iodine Radioisotopes); 7782-42-5 (Graphite); VW92PHU2UY (Americium)
[Em] Mês de entrada:1703
[Cu] Atualização por classe:170308
[Lr] Data última revisão:
170308
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:160703
[St] Status:MEDLINE
[do] DOI:10.1118/1.4951727



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