RESUMEN
Changes in cosmic-ray intensity can significantly influence the search for rare events or processes in nuclear and astroparticle physics through corresponding variations in detector background count rate. In this work, we present an approach to explore cosmic-ray intensity and corresponding cascade production of secondary particles in the detector vicinity using low-energy photon background spectra induced by cosmic rays at the earth's surface. The coincidence system based on a plastic scintillator and an extended range HPGe detector, including a multiparameter device, was used for the acquisition of low-energy photon spectra. This system was also simulated by the GEANT4 toolkit, and the simulated and experimental spectra were compared. Single aperiodic events, as well as possible periodic behavior of low-energy photon emission were searched for.
RESUMEN
It is well known that protection from the external irradiation produced by beta emitters is simpler than the corresponding shielding of radioactive sources that emit gamma radiation. This is caused by the relatively strong absorption (i.e. short range) of electrons in different materials. However, for strong beta sources specific attention should be paid to the bremsstrahlung radiation induced in the source encapsulation (matrix), especially for emitters with relatively high beta-endpoint energy (1 MeV) that are frequently used in nuclear medicine. In the present work, the bremsstrahlung spectra produced in various materials by the following beta emitters, Sr-90 (together with its daughter Y-90), P-32 and Bi-210, were investigated by Monte Carlo simulations using Geant4 software. In these simulations, it is supposed that the point radioactive sources are surrounded by cylindrically shaped capsules made from different materials: Pb, Cu, Al, glass and plastic. For the case of Y-90(Sr-90) in cylindrical lead and aluminum capsules, the dimensions of these capsules have also been varied. The absorbed dose rates from bremsstrahlung radiation were calculated for cases where the encapsulated point source is placed at a distance of 30 mm from the surface of a water cylinder with a mass of 75 kg (approximately representing the human body). The bremsstrahlung dose rate and bremsstrahlung spectrum from the Y-90(Sr-90) point source encapsulated in an Al capsule were also measured experimentally and compared with the corresponding simulation results. In addition, the bremsstrahlung radiation risk for medical staff in therapies using Y-90 was considered in simulations, relating to finger dose as well as whole-body dose during preparation and injection of this radioisotope. The corresponding annual doses were obtained for medical workers for specified numbers of Y-90 applications to patients.
Asunto(s)
Partículas beta , Electrones , Método de Montecarlo , Humanos , Exposición Profesional/efectos adversos , Dosis de Radiación , Radioisótopos de Estroncio , Radioisótopos de ItrioRESUMEN
Terrestrial mosses are a promising medium for investigation and monitoring of airborne radionuclide depositions due to their widespread occurrence, ease of sampling, and the possibility of high-resolution gamma spectrometry measurements without preparatory chemical treatment of samples. The overall objective of the present study was to compare (7)Be, (210)Pb and (137)Cs activity concentrations (in Bq/kg) in moss samples collected at two different climate zones: the south of Thailand (7 °N) and in Serbia (â¼45 °N) in order to examine deposition of airborne radionuclide in these distant areas. Significant difference of the (210)Pb content (almost a factor of 2) in mosses was observed. The mean value of (7)Be activity in samples from Serbia was almost 40% higher than activity of those collected in Thailand. Level of (137)Cs in Thailand mosses was below the detection limit. It was shown that air transport of water droplets in the area of waterfalls and strong turbulence can deposit U and Th daughter nuclei.
Asunto(s)
Briófitas/química , Monitoreo de Radiación/métodos , Radioisótopos/análisis , Serbia , TailandiaRESUMEN
The correlation between activity concentrations of some natural radionuclides ((238)U, (226)Ra, (232)Th, (40)K) measured in soil and in sediment taken from the Danube River and nearby irrigation channels was studied. The soil samples were collected from the northern part of Serbia and the sediment from the Serbian part of the Danube River and from the surrounding irrigation channels. The correlation between (238)U and other natural radionuclides in irrigation channel sediments was not as good as in the Danube. One of the possible explanations for this weak correlation can be the different chemical dynamics of (238)U in the irrigation channel sediment or changes of the (238)U activity concentration in irrigation channel sediment due to some human activities. The evaluation of ratios of activity concentrations of some natural radionuclides could be a more sensitive method for the determination of contaminant, rather than the straightforward analysis of activity concentrations.
Asunto(s)
Radioisótopos/análisis , Suelo/análisis , Riego Agrícola , Monitoreo del Ambiente , Sedimentos Geológicos/análisis , Ríos/química , SerbiaRESUMEN
Concentrations of (210)Pb, (7)Be and (137)Cs in moss samples were continuously measured, using low-background HPGe spectrometer at Novi Sad, Serbia (45 degrees 14'45''N, 19 degrees 51'35''E). Weekly data collected over 14 month period from January 2007 to March 2008 are presented and discussed. Measured values of (7)Be activity concentrations in dry moss samples are ranged from 201 to 920 Bq/kg showing prominent increase in summer and autumn season. Data for (210)Pb, ranged from 347 to 885 Bq/kg do not show such trend. The average concentration of (137)Cs is 8.9 Bq/kg. It is shown that yield of (7)Be can be estimated using average values of activity concentrations. Precipitation amount and duration of precipitation are measured and their possible influence on activity concentrations measured in moss samples was considered.
Asunto(s)
Briófitas/química , Contaminantes Radiactivos/análisis , Estaciones del Año , Berilio/análisis , Radioisótopos de Cesio/análisis , Radioisótopos de Plomo/análisis , Dosis de Radiación , Monitoreo de Radiación , Radioisótopos/análisis , Espectrometría gammaRESUMEN
The results of indoor radon survey in the South-Pannonian Province Vojvodina (Serbia and Montenegro) are presented. The sampling strategy was oriented towards suburban and urban regions in the Province. For the dwellings typical for such regions the geometric mean annual radon activity concentration of 76.1 Bq m(-3) is measured (1000 measurements). This result leads to the annual dose estimate of 4.3 mSv y(-1), which is above the recommended action limit of ICRP. For urban dwellings in Novi Sad (the Province capital), the annual mean value of 54 Bq m(-3) (220 measurements) is obtained. By comparison of these two results it is concluded that radon surveys based on measurements in urban environment may seriously underestimate the radon-related health risk. The elevated radon levels could not be explained by elevated uranium levels of surface soil.
Asunto(s)
Contaminantes Radiactivos del Aire/análisis , Contaminación del Aire Interior/análisis , Contaminación del Aire Interior/estadística & datos numéricos , Monitoreo de Radiación/métodos , Radón/análisis , Población Rural/estadística & datos numéricos , Dosis de Radiación , Medición de Riesgo/métodos , Factores de Riesgo , YugoslaviaRESUMEN
The Bega canal is one among many heavily polluted canals in Vojvodina (the northern province of Serbia and Montenegro). In the framework of the revitalization of this canal, the radionuclide content of the sediment was investigated in order to support the safe deposition after excavation. It was found that, in comparison with the Danube sediment and Vojvodina soil, the Bega sediment is contaminated with (238)U and (137)Cs. The origin of this contamination is discussed. No traces of contamination by nuclear power plants in the region were found, while the presence of technologically enhanced, natural occurring radioactive materials (TENORM) was proved.
Asunto(s)
Radiación de Fondo , Agua Dulce/análisis , Sedimentos Geológicos/análisis , Monitoreo de Radiación/métodos , Radioisótopos/análisis , Contaminantes Radiactivos del Suelo/análisis , Contaminantes Radiactivos del Agua/análisis , Dosis de Radiación , Protección Radiológica/métodos , Medición de Riesgo/métodos , Factores de Riesgo , YugoslaviaRESUMEN
The widespread public belief that during the bombardment of Vojvodina (Yugoslavia) this region was contaminated by depleted uranium has recently raised public concern with respect to the potential contamination of agricultural products due to soil radioactivity. Based on the gamma-spectrometric analysis of 50 soil samples taken from the region of Vojvodina we concluded that there is no increase of radioactivity that could endanger the food production. Taking into account the transfer factors of 137Cs to plants, the measured activity concentrations of this isotope should not endanger the health safety of the produced food. No traces of depleted uranium have been found. The natural radioactivity levels are compared with the results form other countries.
Asunto(s)
Radioisótopos de Cesio/análisis , Monitoreo del Ambiente/estadística & datos numéricos , Radioisótopos de Potasio/análisis , Radio (Elemento)/análisis , Contaminantes Radiactivos del Suelo/análisis , Torio/análisis , Uranio/análisis , Espectrometría gamma , YugoslaviaRESUMEN
Variation of the photoactivation rate across radiation fields of three different bremsstrahlung beams of two medical accelerators has been measured, making use of the photonuclear reactions in natural indium probes: 115In(y,y')115mIn and 115In(y,n)114mIn. The third nuclear reaction, 115In(n,y)116mIn, was used to detect the presence of neutrons in the photon beam and to estimate the spatial distribution of thermal and fast neutrons in the patient plane as a function of collimator opening.
Asunto(s)
Radioisótopos de Indio , Neutrones , Fotones , Radioterapia de Alta Energía , Calibración , Neutrones Rápidos , Rayos gamma , Humanos , Aceleradores de PartículasRESUMEN
A modified method for the evaluation of bremsstrahlung spectra on the basis of transmission measurements is presented. The method is tested for two 4 MeV therapy accelerators. The calculated spectra are compared with other experimental results and Monte Carlo simulation.
Asunto(s)
Modelos Estructurales , Aceleradores de Partículas , Fantasmas de Imagen , Dosificación Radioterapéutica , Radioterapia/métodos , Humanos , Matemática , Método de Montecarlo , FotonesRESUMEN
Sonographic and clinical features of 26 fetal cephaloceles were reviewed retrospectively. The most frequent reason for referral was elevated maternal serum alpha-fetoprotein levels. The smallest lesion identified was 0.4 x 0.5 cm (frontal, at 20 weeks); the largest was 9.0 x 10.0 cm (frontal, at 27 weeks). Twenty-four of 26 cephaloceles were detected on prenatal ultrasound examination; in 13 of these, more than 50% of the intracranial contents were exteriorized. Fifteen of 24 cephaloceles detected prenatally had a sulcal pattern (identified between 16 and 36 weeks' gestation); five were solid without a sulcal pattern (identified between 13 and 21 weeks' gestation), three were cystic, and one underwent a change in appearance from solid at 21 weeks to cystic at 26 weeks. Other cranial features were evaluated and included visible skull defect, seen in 23/24 (96%), ventriculomegaly, in 6/26 (23%); microcephaly, in 12/24 (50%); beaked tectal plate, in 6/16 (38%); and flattened basiocciput, in 9/24 (38%). Of the 26 cases, 14 had normal amniotic fluid volume, five had oligohydramnios and seven had polyhydramnios. Fetuses with oligohydramnios had the highest incidence of concurrent fetal abnormalities; four of five fetuses (80%) with oligohydramnios had additional structural abnormalities. In the overall population, a very high incidence of other abnormalities was found; 17/26 (65%) cases showed additional abnormalities, some of which were not detected by ultrasound. Five fetuses had Meckel-Gruber syndrome and three had amniotic band syndrome. Only one of the 18 karyotypes obtained was abnormal (trisomy 18). Survival was very poor; only two of the eight who survived until birth are currently living.
Asunto(s)
Encefalocele/diagnóstico por imagen , Enfermedades Fetales/diagnóstico por imagen , Ultrasonografía Prenatal , Anomalías Múltiples/diagnóstico por imagen , Síndrome de Bandas Amnióticas/patología , Líquido Amniótico/diagnóstico por imagen , Encefalopatías/diagnóstico por imagen , Ventrículos Cerebrales/diagnóstico por imagen , Cromosomas Humanos Par 18 , Encefalocele/patología , Femenino , Enfermedades Fetales/patología , Humanos , Recién Nacido , Microcefalia/diagnóstico por imagen , Hueso Occipital/anomalías , Hueso Occipital/diagnóstico por imagen , Oligohidramnios/diagnóstico por imagen , Polihidramnios/diagnóstico por imagen , Embarazo , Estudios Retrospectivos , Cráneo/anomalías , Cráneo/diagnóstico por imagen , Tasa de Supervivencia , Síndrome , Techo del Mesencéfalo/anomalías , Techo del Mesencéfalo/diagnóstico por imagen , TrisomíaRESUMEN
The purpose of this 3-week, double-blind study was to determine the effect of a stannous fluoride-containing mouthrinse on existing and developing dental plaque. A total of 55 subjects (mean age = 31.42 yrs.) received a professional prophylaxis in randomly assigned contralateral quadrants and were then stratified into two balanced groups based on screening plaque scores: one group (27 subjects) used the placebo rinse, the second group (28 subjects) used the test mouthrinse (0.63% diluted to 0.1% stannous fluoride). Plaque index (PI) and stain index (SI) were scored at baseline, week 1 and week 3. Gingival inflammation (GI) was monitored as a measure of product irritancy potential. The PI for the stannous fluoride rinse was significantly lower than the placebo, (p < 0.0001), for both prophied and unprophied sites with an average reduction of 29% at week 1 and 28% at week 3. There was no statistically significant difference between the presence or absence of prophylaxis. Plaque indexes for both stannous fluoride and placebo showed significant reduction (p < 0.0001) compared to baseline in all sites. Differences in staining potential between stannous fluoride and placebo were not significant (p > 0.05) at any time during the study. The stain index for both stannous fluoride and placebo showed a non-significant increase from baseline in the prophied and unprophied sites. No irritancy was noted, although a trend towards lower GI scores was observed at 3 weeks for the stannous fluoride group.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Placa Dental/tratamiento farmacológico , Antisépticos Bucales/uso terapéutico , Fluoruros de Estaño/uso terapéutico , Adolescente , Adulto , Anciano , Análisis de Varianza , Índice de Placa Dental , Método Doble Ciego , Humanos , Persona de Mediana Edad , Decoloración de Dientes/tratamiento farmacológicoRESUMEN
Oral cholecystography (OCG) has traditionally been delayed until several weeks after hospitalization for pancreatitis because of the putative frequent poor visualization during the acute episode. Recently, OCG with iopanoic acid was reported successful in most patients with acute pancreatitis soon after resumption of a solid diet. We evaluated OCG with sodium tyropanoate, a pharmacokinetically different contrast material, in 30 hospitalized patients with pancreatitis before resumption of solid food. It accurately evaluated the gallbladder in 24 cases (80%). Abnormal liver function tests, including mild hyperbilirubinemia, did not interfere with the examination. Consequently, 1) tyropanoate OCG adequately opacifies the gallbladder in most patients with acute pancreatitis who are fasting or taking liquids only; 2) allows gallbladder evaluation earlier than with iopanoic acid OCG; 3) is less affected by hepatic dysfunction; and 4) provides an alternative to ultrasonography.
Asunto(s)
Colecistografía/métodos , Yodobencenos , Pancreatitis/diagnóstico , Tiropanoato , Enfermedad Aguda , Adulto , Anciano , Medios de Contraste , Evaluación de Medicamentos , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
In addition to the standard views of the shoulder (external rotation, internal rotation, and axillary), a 40-degree posterior oblique and a 60-degree anterior oblique projection were used to evaluate 105 consecutive shoulder examinations. Of the 32 abnormal shoulders evaluated, the diagnosis was established 97% of the time with a single 40-degree posterior oblique view, as opposed to a 78% rate with the three standard views. The 40-degree posterior oblique view of the shoulder is especially useful in evaluating the glenohumeral joint.
Asunto(s)
Articulación del Hombro/diagnóstico por imagen , Humanos , Artropatías/diagnóstico por imagen , Radiografía , Lesiones del Hombro , Tendinopatía/diagnóstico por imagenRESUMEN
Earlier studies suggest that adverse reactions to injected radiographic contrast media are idiosyncratic. In an attempt to gain a better understanding of pathophysiologic events underlying these reactions, rabbit models injected with lethal dose ranges of a cholangiographic contrast material were studied. These animals showed activation of both the complement and coagulation systems. Externally applied heat potentiated complement consumption and increased mortality. Depleting complement components C3-C9 by cobra venom factor did not prevent activation of coagulation or diminish mortality. However, depleting fibrinogen diminished complement activation and markedly diminished mortality. Heparin, administered at several hourly intervals after contrast challenge, also diminished mortality. These studies suggest that the adverse effects of contrast media in this model system are mediated chiefly by the coagulation system, and that complement, if it participates deleteriously, must involve components up to, but not including, C3. A logical role for the inhibitor of C1 esterase in adverse contrast reactions is considered.
Asunto(s)
Coagulación Sanguínea/efectos de los fármacos , Activación de Complemento/efectos de los fármacos , Yodipamida/análogos & derivados , Ancrod/farmacología , Animales , Pruebas de Coagulación Sanguínea , Proteínas Inactivadoras del Complemento 1/fisiología , Heparina/farmacología , Calor , Yodipamida/efectos adversos , Masculino , Meglumina/efectos adversos , Meglumina/análogos & derivados , Modelos Biológicos , ConejosRESUMEN
Routine cerebral dynamic scanning in two patients revealed unilateral focal areas of decreased radionuclide activity between the anterior and middle cerebral arteries; the subsequent brain scans were normal. Both patients were shown to have porencephaly by isotope cisternography and computed tomography (CT) scans. When a focal avascular area is noted on cerebral dynamic scanning in the presence of normal static images, the possibility of a porencephalic cyst should be considered.
Asunto(s)
Encefalopatías/diagnóstico por imagen , Quistes/diagnóstico por imagen , Adulto , Femenino , Humanos , Masculino , Persona de Mediana Edad , Cintigrafía , Tomografía Computarizada por Rayos XRESUMEN
This report describes 2 patients in whom focal areas of decreased 99mTc sulfur colloid marrow activity were associated with callus formation and healing rib fractures in one case and rib fractures with bony bridging in the second. Since bone marrow scans are occasionally used to select appropriate sites for marrow biopsy in patients with suspected metastatic disease, radiographic correlation of "cold" lesions on marrow scans is recommended prior to biopsy to exclude fracture with callus formation as a benign cause of the abnormality.