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1

Adaptive Response in Animals Exposed to Non-Ionizing Radiofrequency Fields: Some Underlying Mechanisms  

PubMed Central

During the last few years, our research group has been investigating the phenomenon of adaptive response in animals exposed to non-ionizing radiofrequency fields. The results from several separate studies indicated a significant increase in survival, decreases in genetic damage as well as oxidative damage and, alterations in several cellular processes in mice pre-exposed to radiofrequency fields and subsequently subjected to sub-lethal or lethal doses of ?-radiation or injected with bleomycin, a radiomimetic chemical mutagen. These observations indicated the induction of adaptive response providing the animals the ability to resist subsequent damage. Similar studies conducted by independent researchers in mice and rats have supported our observation on increased survival. In this paper, we have presented a brief review of all of our own and other independent investigations on radiofrequency fields-induced adaptive response and some underlying mechanisms discussed. PMID:24758897

Cao, Yi; Tong, Jian

2014-01-01

2

Adaptive response in animals exposed to non-ionizing radiofrequency fields: some underlying mechanisms.  

PubMed

During the last few years, our research group has been investigating the phenomenon of adaptive response in animals exposed to non-ionizing radiofrequency fields. The results from several separate studies indicated a significant increase in survival, decreases in genetic damage as well as oxidative damage and, alterations in several cellular processes in mice pre-exposed to radiofrequency fields and subsequently subjected to sub-lethal or lethal doses of ?-radiation or injected with bleomycin, a radiomimetic chemical mutagen. These observations indicated the induction of adaptive response providing the animals the ability to resist subsequent damage. Similar studies conducted by independent researchers in mice and rats have supported our observation on increased survival. In this paper, we have presented a brief review of all of our own and other independent investigations on radiofrequency fields-induced adaptive response and some underlying mechanisms discussed. PMID:24758897

Cao, Yi; Tong, Jian

2014-04-01

3

Analysis of estimation of electromagnetic dosimetric values from non-ionizing radiofrequency fields in conventional road vehicle environments.  

PubMed

Abstract A high number of wireless technologies can be found operating in vehicular environments with the aim of offering different services. The dosimetric evaluation of this kind of scenarios must be performed in order to assess their compatibility with current exposure limits. In this work, a dosimetric evaluation inside a conventional car is performed, with the aid of an in-house 3D Ray Launching computational code, which has been compared with measurement results of wireless sensor networks located inside the vehicle. These results can aid in an adequate assessment of human exposure to non-ionizing radiofrequency fields, taking into account the impact of the morphology and the topology of the vehicle for current as well as for future exposure limits. PMID:24460417

Aguirre, Erik; Iturri, Peio Lopez; Azpilicueta, Leire; de Miguel-Bilbao, Silvia; Ramos, Victoria; Gárate, Uxue; Falcone, Francisco

2015-03-01

4

Adaptive response in human blood lymphocytes exposed to non-ionizing radiofrequency fields: resistance to ionizing radiation-induced damage  

PubMed Central

The aim of this preliminary investigation was to assess whether human peripheral blood lymphocytes which have been pre-exposed to non-ionizing radiofrequency fields exhibit an adaptive response (AR) by resisting the induction of genetic damage from subsequent exposure to ionizing radiation. Peripheral blood lymphocytes from four healthy donors were stimulated with phytohemagglutinin for 24 h and then exposed for 20 h to 1950 MHz radiofrequency fields (RF, adaptive dose, AD) at an average specific absorption rate of 0.3 W/kg. At 48 h, the cells were subjected to a challenge dose (CD) of 1.0 or 1.5 Gy X-irradiation (XR, challenge dose, CD). After a 72 h total culture period, cells were collected to examine the incidence of micronuclei (MN). There was a significant decrease in the number of MN in lymphocytes exposed to RF + XR (AD + CD) as compared with those subjected to XR alone (CD). These observations thus suggested a RF-induced AR and induction of resistance to subsequent damage from XR. There was variability between the donors in RF-induced AR. The data reported in our earlier investigations also indicated a similar induction of AR in human blood lymphocytes that had been pre-exposed to RF (AD) and subsequently treated with a chemical mutagen, mitomycin C (CD). Since XR and mitomycin-C induce different kinds of lesions in cellular DNA, further studies are required to understand the mechanism(s) involved in the RF-induced adaptive response. PMID:23979077

Sannino, Anna; Zeni, Olga; Romeo, Stefania; Massa, Rita; Gialanella, Giancarlo; Grossi, Gianfranco; Manti, Lorenzo; Vijayalaxmi; Scarfì, Maria Rosaria

2014-01-01

5

Estimation of electromagnetic dosimetric values from non-ionizing radiofrequency fields in an indoor commercial airplane environment.  

PubMed

In this article, the impact of topology as well as morphology of a complex indoor environment such as a commercial aircraft in the estimation of dosimetric assessment is presented. By means of an in-house developed deterministic 3D ray-launching code, estimation of electric field amplitude as a function of position for the complete volume of a commercial passenger airplane is obtained. Estimation of electromagnetic field exposure in this environment is challenging, due to the complexity and size of the scenario, as well as to the large metallic content, giving rise to strong multipath components. By performing the calculation with a deterministic technique, the complete scenario can be considered with an optimized balance between accuracy and computational cost. The proposed method can aid in the assessment of electromagnetic dosimetry in the future deployment of embarked wireless systems in commercial aircraft. PMID:23915231

Aguirre, Erik; Arpón, Javier; Azpilicueta, Leire; López, Peio; de Miguel, Silvia; Ramos, Victoria; Falcone, Francisco

2014-12-01

6

Genetic damage in human cells exposed to non-ionizing radiofrequency fields: a meta-analysis of the data from 88 publications (1990-2011).  

PubMed

Based on the 'limited' evidence suggesting an association between exposure to radiofrequency fields (RF) emitted from mobile phones and two types of brain cancer, glioma and acoustic neuroma, the International Agency for Research on Cancer has classified RF as 'possibly carcinogenic to humans' in group 2B. In view of this classification and the positive correlation between increased genetic damage and carcinogenesis, a meta-analysis was conducted to determine whether a significant increase in genetic damage in human cells exposed to RF provides a potential mechanism for its carcinogenic potential. The extent of genetic damage in human cells, assessed from various end-points, viz., single-/double-strand breaks in the DNA, incidence of chromosomal aberrations, micronuclei and sister chromatid exchanges, reported in a total of 88 peer-reviewed scientific publications during 1990-2011 was considered in the meta-analysis. Among the several variables in the experimental protocols used, the influence of five specific variables related to RF exposure characteristics was investigated: (i) frequency, (ii) specific absorption rate, (iii) exposure as continuous wave, pulsed wave and occupationally exposed/mobile phone users, (iv) duration of exposure, and (v) different cell types. The data indicated the following. (1) The magnitude of difference between RF-exposed and sham-/un-exposed controls was small with some exceptions. (2) In certain RF exposure conditions there was a statistically significant increase in genotoxicity assessed from some end-points: the effect was observed in studies with small sample size and was largely influenced by publication bias. Studies conducted within the generally recommended RF exposure guidelines showed a smaller effect. (3) The multiple regression analyses and heterogeneity goodness of fit data indicated that factors other than the above five variables as well as the quality of publications have contributed to the overall results. (4) More importantly, the mean indices for chromosomal aberrations, micronuclei and sister chromatid exchange end-points in RF-exposed and sham-/un-exposed controls were within the spontaneous levels reported in a large data-base. Thus, the classification of RF as possibly carcinogenic to humans in group 2B was not supported by genotoxicity-based mechanistic evidence. PMID:23022599

Vijayalaxmi; Prihoda, Thomas J

2012-12-12

7

[Saccharomyces cerevisiae as a model organism for studying the carcinogenicity of non-ionizing electromagnetic fields and radiation].  

PubMed

Medical and biological aspects of the effects of non-ionizing electromagnetic (EM) fields and radiation on human health are the important issues that have arisen as a result of anthropogenic impact on the biosphere. Safe use of man-made sources of non-ionizing electromagnetic fields and radiation in a broad range of frequencies--static, radio-frequency and microwave--is a subject of discussions and speculations. The main problem is the lack of understanding of the mechanism(s) of reception of EMFs by living organisms. In this review we have analyzed the existing literature data regarding the effects of the electromagnetic radiation on the model eukaryotic organism--yeast Saccharomyces cerevisiae. An attempt was made to estimate the probability of induction of carcinogenesis in humans under the influence of magnetic fields and electromagnetic radiation of extremely low frequency, radio frequency and microwave ranges. PMID:24800516

Vo?chuk, S I

2014-01-01

8

Non-ionizing radiation generated by nanosecond pulsed electric fields (nsPEFS) induce apoptosis in cancer in vivo  

Microsoft Academic Search

Summary form only given. Over the last several years pulse power technology has developed into a novel and innovative time domain nanotechnology as a new modality to treat cancer. The technology treats cancer in the absence of drugs by generating non-ionizing radiation with nanosecond pulsed electric fields (nsPEFs or nanopulses) that are high in power (gigawatts) and low in energy

S. J. Beebe; Xinhua Chen; J. Kolb; K. H. Schoenbach

2008-01-01

9

Exposure to electromagnetic fields (non-ionizing radiation) and its relationship with childhood leukemia: A systematic review  

Microsoft Academic Search

Childhood exposure to physical contamination, including non-ionizing radiation, has been implicated in numerous diseases, raising concerns about the widespread and increasing sources of exposure to this type of radiation. The primary objective of this review was to analyze the current state of knowledge on the association between environmental exposure to non-ionizing radiation and the risk of childhood leukemia. Scientific publications

I. Calvente; M. F. Fernandez; J. Villalba; N. Olea; M. I. Nuñez

2010-01-01

10

Magnetoreception in birds: the effect of radio-frequency fields.  

PubMed

The avian magnetic compass, probably based on radical pair processes, works only in a narrow functional window around the local field strength, with cryptochrome 1a as most likely receptor molecule. Radio-frequency fields in the MHz range have been shown to disrupt the birds' orientation, yet the nature of this interference is still unclear. In an immuno-histological study, we tested whether the radio-frequency fields interfere with the photoreduction of cryptochrome, but this does not seem to be the case. In behavioural studies, birds were not able to adjust to radio-frequency fields like they are able to adjust to static fields outside the normal functional range: neither a 2-h pre-exposure in a 7.0 MHz field, 480 nT, nor a 7-h pre-exposure in a 1.315 MHz field, 15 nT, allowed the birds to regain their orientation ability. This inability to adjust to radio-frequency fields suggests that these fields interfere directly with the primary processes of magnetoreception and therefore disable the avian compass as long as they are present. They do not have lasting adverse after-effects, however, as birds immediately after exposure to a radio-frequency field were able to orient in the local geomagnetic field. PMID:25540238

Wiltschko, Roswitha; Thalau, Peter; Gehring, Dennis; Nießner, Christine; Ritz, Thorsten; Wiltschko, Wolfgang

2015-02-01

11

International and National Expert Group Evaluations: Biological/Health Effects of Radiofrequency Fields  

PubMed Central

The escalated use of various wireless communication devices, which emit non-ionizing radiofrequency (RF) fields, have raised concerns among the general public regarding the potential adverse effects on human health. During the last six decades, researchers have used different parameters to investigate the effects of in vitro and in vivo exposures of animals and humans or their cells to RF fields. Data reported in peer-reviewed scientific publications were contradictory: some indicated effects while others did not. International organizations have considered all of these data as well as the observations reported in human epidemiological investigations to set-up the guidelines or standards (based on the quality of published studies and the “weight of scientific evidence” approach) for RF exposures in occupationally exposed individuals and the general public. Scientists with relevant expertise in various countries have also considered the published data to provide the required scientific information for policy-makers to develop and disseminate authoritative health information to the general public regarding RF exposures. This paper is a compilation of the conclusions, on the biological effects of RF exposures, from various national and international expert groups, based on their analyses. In general, the expert groups suggested a reduction in exposure levels, precautionary approach, and further research. PMID:25211777

Vijayalaxmi; Scarfi, Maria R.

2014-01-01

12

Effects of Radiofrequency Electromagnetic Fields on the Human Nervous System  

Microsoft Academic Search

The effects of exposure to radiofrequency electromagnetic fields (EMF), specifically related to the use of mobile telephones, on the nervous system in humans have been the subject of a large number of experimental studies in recent years. There is some evidence of an effect of exposure to a Global System for Mobile Telecommunication (GSM)-type signal on the spontaneous electroencephalogram (EEG).

Eric van Rongen; Rodney Croft; Jukka Juutilainen; Isabelle Lagroye; Junji Miyakoshi; Richard Saunders; René de Seze; Thomas Tenforde; Luc Verschaeve; Bernard Veyret; Zhengping Xu

2009-01-01

13

Resonant radiofrequency magnetic field effects on a chemical reaction  

NASA Astrophysics Data System (ADS)

Observations of the effect of a radiofrequency magnetic field on the progress of a chemical reaction are reported. It is shown that the fluorescence of an exciplex formed in the photoreaction of anthracene-d 10 and 1,3-dicyanobenzene (DCB) is attenuated when a 30-40 MHz oscillating field is applied. The effect is interpreted in the framework of the radical pair mechanism, in terms of a change in the extent of singlet?triplet interconversion in the {anthracene cation-DCB anion} radical pair when the oscillating field is in resonance with hyperfine splittings in the DCB anion radical.

Woodward, J. R.; Jackson, R. J.; Timmel, C. R.; Hore, P. J.; McLauchlan, K. A.

1997-07-01

14

A radio-frequency quadrupole accelerator longitudinal field stabilizer  

SciTech Connect

The fields in a 600-MHz model of a radio-frequency quadrupole (RFQ) accelerator have been longitudinally stabilized over 86% of its length. The stabilizing elements consist of four external transverse electromagnetic (TEM) lines. Each line is coupled to the RFQ by two magnetic loops attached to voltage maxima of the TEM line. These resonant lines stabilize the RFQ fields by providing an alternate longitudinal power flow path in the RFQ. Stabilization depends on the TEM line Q and the TEM line RFQ coupling. Each stabilizer coupling-loop location in the RFQ needs to be fully azimuthally stabilized. Substantial coupling between stabilizer elements destroys stabilization. 3 refs., 13 figs., 2 tabs.

Gray, E.R.; Spalek, G.; Shapiro, A.

1988-01-01

15

Radiofrequency electromagnetic field exposure and non-specific symptoms of ill health: a systematic review.  

PubMed

This article is a systematic review of whether everyday exposure to radiofrequency electromagnetic field (RF-EMF) causes symptoms, and whether some individuals are able to detect low-level RF-EMF (below the ICNIRP [International Commission on Non-Ionizing Radiation Protection] guidelines). Peer-reviewed articles published before August 2007 were identified by means of a systematic literature search. Meta-analytic techniques were used to pool the results from studies investigating the ability to discriminate active from sham RF-EMF exposure. RF-EMF discrimination was investigated in seven studies including a total of 182 self-declared electromagnetic hypersensitive (EHS) individuals and 332 non-EHS individuals. The pooled correct field detection rate was 4.2% better than expected by chance (95% CI: -2.1 to 10.5). There was no evidence that EHS individuals could detect presence or absence of RF-EMF better than other persons. There was little evidence that short-term exposure to a mobile phone or base station causes symptoms based on the results of eight randomized trials investigating 194 EHS and 346 non-EHS individuals in a laboratory. Some of the trials provided evidence for the occurrence of nocebo effects. In population based studies an association between symptoms and exposure to RF-EMF in the everyday environment was repeatedly observed. This review showed that the large majority of individuals who claims to be able to detect low level RF-EMF are not able to do so under double-blind conditions. If such individuals exist, they represent a small minority and have not been identified yet. The available observational studies do not allow differentiating between biophysical from EMF and nocebo effects. PMID:18359015

Röösli, Martin

2008-06-01

16

Bray-Liebhafsky oscillatory reaction in the radiofrequency electromagnetic field  

NASA Astrophysics Data System (ADS)

Oscillatory Bray-Liebhafsky (BL) reaction is capacitively coupled with the electromagnetic radiation in the frequency range 60-110 MHz. Because of the specific reaction dynamics characterized by several characteristic parameters (induction period, period between chemical oscillations and their amplitude) it served as a good model system for the investigation of the effects of radiofrequent (RF) radiation. RF power of up to 0.2 W did not produce observable changes of the BL reaction parameters in the limit of the experiment reproductivity. Results indicate that, under the given experimental conditions, both dissipative and reactive properties of the solution are not considerably coupled with the RF electrical field.

Stanisavljev, Dragomir R.; Veliki?, Zoran; Veselinovi?, Dragan S.; Jaci?, Nevena V.; Milenkovi?, Maja C.

2014-09-01

17

Ionization of N2 in radio-frequent electric field  

NASA Astrophysics Data System (ADS)

Rate coefficients for the electron impact ionization of the N2 molecule are calculated in non-equilibrium conditions in the presence of time-dependent electric field. A Monte Carlo simulation has been developed in order to determine non-equilibrium electron energy distribution functions within one period of the radio-frequent (RF) electric field. By using these distribution functions, rate coefficients for ionization of the N2 molecule have been obtained time resolved within one period in the frequency range from 13.56 up to 500 MHz, at effective reduced electric field values up to 700 Td. This work presents an insight into the temporal characteristics of ionizing process and provides the ionization rate coefficients that can be of great use for correct implementation in modeling RF plasma discharges. A behavior of rate coefficients under the influence of magnitude and frequency of the fields was studied separately revealing some interesting features in time dependence.

Popovi?, M. P.; Vojnovi?, M. M.; Aoneas, M. M.; Risti?, M. M.; Vi?i?, M. D.; Popari?, G. B.

2014-06-01

18

Biological effects and exposure criteria for radiofrequency electromagnetic fields  

SciTech Connect

This report, which begins with a discussion of fundamental studies at the molecular level, presents a review of the subject matter covered in NCRP Report No. 67 on mechanisms of interaction of radiofrequency electromagnetic (RFEM) fields with tissue. The discussion continues to progressively larger scales of interaction, beginning with macromolecular and cellular effects, chromosomal and mutagenic effects, and carcinogenic effects. The scope of the subject matter is then expanded to include systemic effects such as those on reproduction, growth, and development, hematopoiesis and immunology, endocrinology and autonomic nervous function, cardiovascular effects and cerebrovascular effects. The interaction of electromagnetic fields with the central nervous system and special senses is also discussed. Also included are epidemiological studies, a discussion of thermoregulation, and a history of therapeutic applications of RFEM fields. The report concludes with human exposure criteria and rationale.

Not Available

1986-01-01

19

Imaging radio-frequency fields using a scanning SQUID microscope  

SciTech Connect

Using a liquid-nitrogen-cooled scanning SQUID magnetic microscope, we have developed a technique for broadband imaging of radio-frequency (rf) and microwave fields with a spatial resolution of about 15 [mu]m. We have produced images of the amplitude of 50 MHz fields with an rms noise of 2.6 nT and a 300 [mu]m/s scan rate. Detection is accomplished by using the nonlinearity of the voltage-flux characteristic of the SQUID to rectify the rf fields. Our present technique is limited by cavity mode resonances in the SrTiO[sub 3] substrate of our SQUID sensor. Using a small excitation probe, we have directly imaged these resonances at frequencies up to about 12.5 GHz.

Black, R.C.; Wellstood, F.C. (Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742-4111 (United States)); Dantsker, E.; Miklich, A.H.; Koelle, D.; Ludwig, F.; Clarke, J. (Department of Physics, University of California and Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States))

1995-03-06

20

Radiofrequency fields associated with the Itron smart meter.  

PubMed

This study examined radiofrequency (RF) emissions from smart electric power meters deployed in two service territories in California for the purpose of evaluating potential human exposure. These meters included transmitters operating in a local area mesh network (RF LAN, ?250 mW); a cell relay, which uses a wireless wide area network (WWAN, ?1 W); and a transmitter serving a home area network (HAN, ?70 mW). In all instances, RF fields were found to comply by a wide margin with the RF exposure limits established by the US Federal Communications Commission. The study included specialised measurement techniques and reported the spatial distribution of the fields near the meters and their duty cycles (typically <1 %) whose value is crucial to assessing time-averaged exposure levels. This study is the first to characterise smart meters as deployed. However, the results are restricted to a single manufacturer's emitters. PMID:22234423

Tell, R A; Sias, G G; Vazquez, A; Sahl, J; Turman, J P; Kavet, R I; Mezei, G

2012-08-01

21

Characterization of radiofrequency field emissions from smart meters.  

PubMed

This study presents measurement data that describe radiofrequency emission levels and patterns from smart meters (rated nominally at 1 W) currently deployed in Pacific Gas and Electric Company's service territory in northern California. The smart meters in our investigation could not be set to operate continuously and required a Field Service Unit to induce short periods of emitted fields. To obtain peak field data under both laboratory and ambient conditions, a spectrum analyzer scanned across the 83 transmitting channels between 902 and 928 MHz used by the smart meter on a random frequency-hopping basis. To obtain data describing temporal emission patterns, the analyzer operated in scope mode. Duty cycle was estimated using transmit data acquired by the system operator from over 88,000 m. Instantaneous peak fields at 0.3 m in front of the meters were no more than 15% of the US Federal Communications Commission (FCC) exposure limit for the general public, and 99.9% of the meters operated with a duty cycle of 1.12% or less during the sampling period. In a sample of measurements in six single-detached residences equipped with individual smart meters, no interior measurement of peak field exceeded 1% of the FCC's general public exposure limit. PMID:23131714

Tell, Richard A; Kavet, Robert; Mezei, Gabor

2013-01-01

22

Recent Advances in Research on Radiofrequency Fields and Health: 2001–2003  

Microsoft Academic Search

The widespread use of wireless telecommunications devices, particularly mobile phones, has resulted in increased human exposure to radiofrequency (RF) fields. Although national and international agencies have established safety guidelines for exposure to RF fields, concerns remain about the potential for adverse health outcomes to occur in relation to RF field exposure. The extensive literature on RF fields and health has

Daniel Krewski; Barry W. Glickman; Riadh W. Y. Habash; Brian Habbick; W. Gregory Lotz; Rosemonde Mandeville; Frank S. Prato; Tarek Salem; Donald F. Weaver

2007-01-01

23

Recent Advances in Research on Radiofrequency Fields and Health: 2004–2007  

Microsoft Academic Search

The widespread use of wireless telecommunications devices, particularly mobile phones and wireless networks, has resulted in increased human exposure to radiofrequency (RF) fields. Although national and international agencies have established safety guidelines for exposure to RF fields, concerns remain about the potential for adverse health outcomes to occur in relation to RF field exposure. The extensive literature on RF fields

Riadh W. Y. Habash; J. Mark Elwood; Daniel Krewski; W. Gregory Lotz; James P. McNamee; Frank S. Prato

2009-01-01

24

Effect of a 2.45-GHz radiofrequency electromagnetic field on neutrophil chemotaxis and phagocytosis in differentiated human HL-60 cells.  

PubMed

The potential public health risks of radiofrequency (RF) fields have been discussed at length, especially with the use of mobile phones spreading extensively throughout the world. In order to investigate the properties of RF fields, we examined the effect of 2.45-GHz RF fields at the specific absorption rate (SAR) of 2 and 10 W/kg for 4 and 24 h on neutrophil chemotaxis and phagocytosis in differentiated human HL-60 cells. Neutrophil chemotaxis was not affected by RF-field exposure, and subsequent phagocytosis was not affected either compared with that under sham exposure conditions. These studies demonstrated an initial immune response in the human body exposed to 2.45-GHz RF fields at the SAR of 2 W/kg, which is the maximum value recommended by the International Commission for Non-Ionizing Radiation Protection (ICNIRP) guidelines. The results of our experiments for RF-field exposure at an SAR under 10 W/kg showed very little or no effects on either chemotaxis or phagocytosis in neutrophil-like human HL-60 cells. PMID:25194051

Koyama, Shin; Narita, Eijiro; Suzuki, Yoshihisa; Taki, Masao; Shinohara, Naoki; Miyakoshi, Junji

2015-01-01

25

Thermal effects of radiofrequency fields in magnetic resonance imaging on implanted medical devices  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is a well established diagnostic technique, one which all patients should be able to benefit from, including those with implanted medical devices. This study focuses on determining the heating effects of the radiofrequency (RF) fields generated in MRI on a typical geometry that is representative of leads associated with implanted medical devices, such as cardiac pacemakers,

Christopher Don Smith

2000-01-01

26

Maximum therapeutic effect of glioma treatment by radio-frequency electric field  

NASA Astrophysics Data System (ADS)

An influence of a radio-frequency electric field on glioma - brain cancer development is considered. A specific task emerging here is whether this new medical technology is effective against invasive cells with a high motility, when switching between migrating and proliferating phenotypes takes place. This therapeutic effect is studied in the framework of a continuous time random walk. It is shown that the migration proliferation dichotomy of cancer cells leads to the weakening of the electric field treatment.

Iomin, Alexander

2015-02-01

27

Exposure to Radiofrequency Electromagnetic Fields and Sleep Quality: A Prospective Cohort Study  

Microsoft Academic Search

BackgroundThere is persistent public concern about sleep disturbances due to radiofrequency electromagnetic field (RF-EMF) exposure. The aim of this prospective cohort study was to investigate whether sleep quality is affected by mobile phone use or by other RF-EMF sources in the everyday environment.MethodsWe conducted a prospective cohort study with 955 study participants aged between 30 and 60 years. Sleep quality

Evelyn Mohler; Patrizia Frei; Jürg Fröhlich; Charlotte Braun-Fahrländer; Martin Röösli

2012-01-01

28

The temperature field simulation of radiofrequency catheter-based renal sympathetic denervation for resistant hypertension.  

PubMed

Renal sympathetic denervation (RSD) by the radiofrequency ablation was used to treat the resistant hypertension in clinic and has achieved curative effect. But the temperature distribution in the artery walls and the blood flow have not been investigated. Finite element method (FEM) based on Comsol Multiphysics 4.3a software was used to simulate the temperature distribution in the renal artery. The results of renal artery temperature distribution as well as blood flow effect on the temperature field were obtained, which demonstrated that the blood velocity is very crucial in the temperature distribution of blood vessel near antenna. When the speed of blood is 0.4 m/s, the highest temperature rise of arterial wall near the antenna is 8.882°C (37°C to 45.882°C) and contralateral artery wall's highest temperature rise is about 5°C (37°C to 42°C). This temperature value can damage renal sympathetic nerves to cure the resistant hypertension. Due to the blood flow, the temperature field stretches to the direction of blood flow. The temperature rise of blood is only in a small range (37°C to 41°C) at both ends of the antenna. The simulation of RSD by the radiofrequency ablation can give doctors a better scheme to avoid the vascular injury in different blood flow rates and radiofrequency voltages. PMID:24211912

Guo, Xuemei; Zhai, Fei; Nan, Qun

2014-01-01

29

MRI safety: Radiofrequency field induced heating of implanted medical devices  

Microsoft Academic Search

The RF field in Magnetic Resonance Imaging (MRI) induces currents in the human body, and the principal bioeffect is tissue heating. The presence of an electrically conducting medical implant will concentrate the RF-induced currents that may cause additional and possibly dangerous tissue heating. For this reason, metallic implants are generally considered to be contraindicated for MR imaging. However, patients with

Sung-Min Park

2006-01-01

30

Electromagnetic field exposure assessment in Europe radiofrequency fields (10?MHz-6?GHz).  

PubMed

Average levels of exposure to radiofrequency (RF) electromagnetic fields (EMFs) of the general public in Europe are difficult to summarize, as exposure levels have been reported differently in those studies in which they have been measured, and a large proportion of reported measurements were very low, sometimes falling below detection limits of the equipment used. The goal of this paper is to present an overview of the scientific literature on RF EMF exposure in Europe and to characterize exposure within the European population. A comparative analysis of the results of spot or long-term RF EMF measurements in the EU indicated that mean electric field strengths were between 0.08?V/m and 1.8?V/m. The overwhelming majority of measured mean electric field strengths were <1?V/m. It is estimated that <1% were above 6?V/m and <0.1% were above 20?V/m. No exposure levels exceeding European Council recommendations were identified in these surveys. Most population exposures from signals of radio and television broadcast towers were observed to be weak because these transmitters are usually far away from exposed individuals and are spatially sparsely distributed. On the other hand, the contribution made to RF exposure from wireless telecommunications technology is continuously increasing and its contribution was above 60% of the total exposure. According to the European exposure assessment studies identified, three population exposure categories (intermittent variable partial body exposure, intermittent variable low-level whole-body (WB) exposure and continuous low-level WB exposure) were recognized by the authors as informative for possible future risk assessment. PMID:23942394

Gajšek, Peter; Ravazzani, Paolo; Wiart, Joe; Grellier, James; Samaras, Theodoros; Thuróczy, György

2015-01-01

31

Intracellular hyperthermia mediated by nanoparticles in radiofrequency fields in the treatment of pancreatic cancer  

NASA Astrophysics Data System (ADS)

Intracellular hyperthermic therapy may prove to be a unique and novel approach to the management of pancreatic cancer. Utilizing the principle of photothermal destruction, selective killing of cancer cells with minimal injury to normal tissues may be possible. This dissertation investigated the role of antibody targeted metal nanoparticles and the cytotoxic effects of nonionizing radiofrequency fields in pancreatic cancer. Cancer cell death was induced by heat release from intracellular metal nanoparticles after radiofrequency field exposure. Fluorescent and gold nanoparticles were delivered with two antibodies, cetuximab and PAM-4, to pancreatic cancer cells in vitro and mouse xenografts in vivo. Selective delivery of these nanoparticles induced cell death in vitro and decreased tumor burden in vivo after whole animal RF field exposure. This occurred through both apoptosis and necrosis. In addition, activated caspase-3 was increased after antibody treatment and RF field exposure. Furthermore, although there was non-specific uptake by the liver and spleen in vivo, there was no evidence of acute or chronic toxicity in the animals. These results are in agreement with the principle that malignant cells are more thermally sensitive than normal cells or tissues. Selective intracellular delivery of metal nanoparticles coupled with whole body RF field exposure may be a beneficial therapy against micrometastases and unresectable pancreatic cancer in the future. Further studies are planned with more specific antibodies, other nanoparticles, and other cancer targets.

Glazer, Evan Scott

32

Human exposure to radiofrequency electromagnetic fields. Final rule.  

PubMed

This document resolves several issues regarding compliance with the Federal Communications Commission's (FCC's) regulations for conducting environmental reviews under the National Environmental Policy Act (NEPA) as they relate to the guidelines for human exposure to RF electromagnetic fields. More specifically, the Commission clarifies evaluation procedures and references to determine compliance with its limits, including specific absorption rate (SAR) as a primary metric for compliance, consideration of the pinna (outer ear) as an extremity, and measurement of medical implant exposure. The Commission also elaborates on mitigation procedures to ensure compliances with its limits, including labeling and other requirements for occupational exposure classification, clarification of compliance responsibility at multiple transmitter sites, and labeling of fixed consumer transmitters. PMID:23734401

2013-06-01

33

Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices  

SciTech Connect

Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling. The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE. To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance. EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ~140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ~140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ~140 MV/m. To address concerns on the effect of natural air drying process on EFE, a comparative study was conducted on Nb and the results showed insignificant difference under the experimental conditions. Nb thin films deposited on Cu present a possible alternative to bulk Nb in superconducting cavities. The EFE performance of a preliminary energetically deposited Nb thin film sample are presented.

Tong Wang

2002-09-18

34

COMAR technical information statement: expert reviews on potential health effects of radiofrequency electromagnetic fields and comments on the bioinitiative report.  

PubMed

The Committee on Man and Radiation (COMAR) is a technical committee of the Engineering in Medicine and Biology Society (EMBS) of the Institute of Electrical and Electronics Engineers (IEEE). Its primary area of interest is biological effects of non-ionizing electromagnetic radiation, including radiofrequency (RF) energy. The public interest in possible health effects attributed to RF energy, such as emitted by mobile phones, wireless telephone base stations, TV and radio broadcasting facilities, Wi-Fi systems and many other sources, has been accompanied by commentary in the media that varies considerably in reliability and usefulness for their audience. The focus of this COMAR Technical Information Statement is to identify quality sources of scientific information on potential health risks from exposure to RF energy. This Statement provides readers with references to expert reports and other reliable sources of information about this topic, most of which are available on the Internet. This report summarizes the conclusions from several major reports and comments on the markedly different conclusions in the BioInitiative Report (abbreviated BIR below). Since appearing on the Internet in August 2007, the BIR has received much media attention but, more recently, has been criticized by several health organizations (see Section titled "Views of health agencies about BIR"). COMAR concludes that the weight of scientific evidence in the RF bioeffects literature does not support the safety limits recommended by the BioInitiative group. For this reason, COMAR recommends that public health officials continue to base their policies on RF safety limits recommended by established and sanctioned international organizations such as the Institute of Electrical and Electronics Engineers International Committee on Electromagnetic Safety and the International Commission on Non-Ionizing Radiation Protection, which is formally related to the World Health Organization. PMID:19741364

2009-10-01

35

Ionization of N{sub 2} in radio-frequent electric field  

SciTech Connect

Rate coefficients for the electron impact ionization of the N{sub 2} molecule are calculated in non-equilibrium conditions in the presence of time-dependent electric field. A Monte Carlo simulation has been developed in order to determine non-equilibrium electron energy distribution functions within one period of the radio-frequent (RF) electric field. By using these distribution functions, rate coefficients for ionization of the N{sub 2} molecule have been obtained time resolved within one period in the frequency range from 13.56 up to 500?MHz, at effective reduced electric field values up to 700 Td. This work presents an insight into the temporal characteristics of ionizing process and provides the ionization rate coefficients that can be of great use for correct implementation in modeling RF plasma discharges. A behavior of rate coefficients under the influence of magnitude and frequency of the fields was studied separately revealing some interesting features in time dependence.

Popovi?, M. P.; Vojnovi?, M. M.; Aoneas, M. M.; Vi?i?, M. D.; Popari?, G. B., E-mail: goran-poparic@ff.bg.ac.rs [Faculty of Physics, University of Belgrade, Studentski trg 12, P.O. Box 44, 11000 Belgrade (Serbia); Risti?, M. M. [Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12, P.O. Box 47, 11158 Belgrade (Serbia)

2014-06-15

36

Radio-frequency sheath-plasma interactions with magnetic field tangency points along the sheath surface  

SciTech Connect

Computer simulations of radio-frequency (RF) waves propagating across a two-dimensional (2D) magnetic field into a conducting boundary are described. The boundary condition for the RF fields at the metal surface leads to the formation of an RF sheath, which has previously been studied in one-dimensional models. In this 2D study, it is found that rapid variation of conditions along the sheath surface promote coupling of the incident RF branch (either fast or slow wave) to a short-scale-length sheath-plasma wave (SPW). The SPW propagates along the sheath surface in a particular direction dictated by the orientation of the magnetic field with respect to the surface, and the wave energy in the SPW accumulates near places where the background magnetic field is tangent to the surface.

Kohno, H. [Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015 (United States)] [Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, Pennsylvania 18015 (United States); Myra, J. R.; D'Ippolito, D. A. [Lodestar Research Corporation, 2400 Central Avenue P-5, Boulder, Colorado 80301 (United States)] [Lodestar Research Corporation, 2400 Central Avenue P-5, Boulder, Colorado 80301 (United States)

2013-08-15

37

Simulation on Temperature Field of Radiofrequency Lesions System Based on Finite Element Method  

NASA Astrophysics Data System (ADS)

This paper mainly describes the way to get the volume model of damaged region according to the simulation on temperature field of radiofrequency ablation lesion system in curing Parkinson's disease based on finite element method. This volume model reflects, to some degree, the shape and size of the damaged tissue during the treatment with all tendencies in different time or core temperature. By using Pennes equation as heat conduction equation of radiofrequency ablation of biological tissue, the author obtains the temperature distribution field of biological tissue in the method of finite element for solving equations. In order to establish damage models at temperature points of 60°C, 65°C, 70°C, 75°C, 80°C, 85°C and 90 °C while the time points are 30s, 60s, 90s and 120s, Parkinson's disease model of nuclei is reduced to uniform, infinite model with RF pin at the origin. Theoretical simulations of these models are displayed, focusing on a variety of conditions about the effective lesion size on horizontal and vertical. The results show the binary complete quadratic non-linear joint temperature-time models of the maximum damage diameter and maximum height. The models can comprehensively reflect the degeneration of target tissue caused by radio frequency temperature and duration. This lay the foundation for accurately monitor of clinical RF treatment of Parkinson's disease in the future.

Xiao, D.; Qian, L.; Qian, Z.; Li, W.

2011-01-01

38

Radiofrequency hydrogen ion source with permanent magnets providing axial magnetic field.  

PubMed

Uniform axial magnetic field of about 70 G is applied to a radiofrequency (rf) hydrogen ion source by arrays of permanent magnets. The plasma density and electron temperature downstream of the source and near the magnetic filter are compared with those in the previously described ion source, where the axial field has been applied by two solenoids. The source is operated at ?350 kHz and above 10 kW rf power with a field-effect-transistor-based invertor power supply in 1.5 Pa hydrogen. The results show that the plasma density of ?10(19) m(-3) near the source exit and ?10(18) m(-3) near the magnetic filter can be obtained, which are higher than those with the solenoids. PMID:24593564

Oikawa, Kohei; Saito, Yuta; Komizunai, Shota; Takahashi, Kazunori; Ando, Akira

2014-02-01

39

Calculation of Radiofrequency Electromagnetic Fields and Their Effects in MRI of Human Subjects  

PubMed Central

Radiofrequency magnetic fields are critical to nuclear excitation and signal reception in Magnetic Resonance Imaging (MRI). The interactions between these fields and human tissues in anatomical geometries results in a variety of effects regarding image integrity and safety of the human subject. In recent decades numerical methods of calculation have been used increasingly to understand the effects of these interactions and aid in engineering better, faster, and safer equipment and methods. As MRI techniques and technology have evolved through the years, so too have the requirements for meaningful interpretation of calculation results. Here we review the basic physics of RF electromagnetics in MRI and discuss a variety of ways RF field calculations are used in MRI in engineering and safety assurance from simple systems and sequences through advanced methods of development for the future. PMID:21381106

Collins, Christopher M.; Wang, Zhangwei

2011-01-01

40

National surveys of radiofrequency field strengths from radio base stations in Africa  

PubMed Central

The authors analysed almost 260 000 measurement points from surveys of radiofrequency (RF) field strengths near radio base stations in seven African countries over two time frames from 2001 to 2003 and 2006 to 2012. The results of the national surveys were compared, chronological trends investigated and potential exposures compared by technology and with frequency modulation (FM) radio. The key findings from thes data are that irrespective of country, the year and mobile technology, RF fields at a ground level were only a small fraction of the international human RF exposure recommendations. Importantly, there has been no significant increase in typical measured levels since the introduction of 3G services. The mean levels in these African countries are similar to the reported levels for countries of Asia, Europe and North America using similar mobile technologies. The median level for the FM services in South Africa was comparable to the individual but generally lower than the combined mobile services. PMID:24044904

Joyner, Ken H.; Van Wyk, Marthinus J.; Rowley, Jack T.

2014-01-01

41

Tunable Atomic Magnetometer for Detection of Radio-Frequency Magnetic Fields  

SciTech Connect

We describe an alkali-metal magnetometer for detection of weak magnetic fields in the radio-frequency (rf) range. High sensitivity is achieved by tuning the Zeeman resonance of alkali atoms to the rf frequency and partially suppressing spin-exchange collisions in the alkali-metal vapor. We demonstrate magnetic field sensitivity of 2 fT/Hz{sup 1/2} at a frequency of 99 kHz with a resonance width of 400 Hz. We also derive a simple analytic expression for the fundamental limit on the sensitivity of the rf magnetometer and show that a sensitivity of about 0.01 fT/Hz{sup 1/2} can be achieved in a practical system with a measurement volume of 200 cm{sup 3}.

Savukov, I.M.; Seltzer, S.J.; Romalis, M.V.; Sauer, K.L. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Department of Physics and Astronomy, George Mason University, Fairfax, Virginia 22030 (United States)

2005-08-05

42

Analytical mean-field scaling theory of radio-frequency heating in a Paul trap  

NASA Astrophysics Data System (ADS)

While the microscopic origins of radio-frequency (rf) heating of simultaneously stored, charged particles in a Paul trap are not yet understood in detail, a universal heating curve [J. D. Tarnas, Y. S. Nam, and R. Blümel, Phys. Rev. A 88, 041401 (2013), 10.1103/PhysRevA.88.041401] was recently discovered that collapses scaled rf heating data onto a single universal curve. Based on a simple analytical mean-field theory, we derive an analytical expression for the universal heating curve, which is in excellent agreement with numerical data. We find that for spherical clouds the universal curve depends only on a single scaling parameter, ? =[q(N-1)]2/3/T, where N is the number of trapped particles, q is the Paul-trap control parameter, and T is the temperature.

Nam, Y. S.; Jones, E. B.; Blümel, R.

2014-07-01

43

The argument for a unified approach to non-ionizing radiation protection  

SciTech Connect

In the next decade military equipment will be required to operate in severe electromagnetic environments. These environments are expected to contain most non-ionizing frequencies (D.C. to GHz), from hostile and/or non-hostile sources, and be severe enough to cause temporary upset or even catastrophic failure of electronic equipment. Over the past thirty years considerable emphasis has been placed on hardening critical systems to one or more of these non-ionizing radiation environments, the most prevalent being the nuclear-induced electromagnetic pulse (EMD). From this technology development there has evolved a hardening philosophy that applies to most of these non-ionizing radiation environments. The philosophy, which stresses the application of zonal shields plus penetration protection, can provide low-cost hardening against such diverse non-ionizing radiation as p-static, lightning, electromagnetic interference (EMI), EMP, high intensity radiated fields (HIRF), electromagnetic radiation (EMR), and high power microwaves (HPM). The objective in this paper is to describe the application of this philosophy to Army helicopters. The authors develop a unified specification complete with threat definitions and test methods which illustrates integration of EMP, lightning, and HIRF at the box qualification level. This paper is a summary of the effort documented in a cited reference.

Perala, R.A.; Rigden, G.J. (Electro Magnetic Applications, Inc., Lakewood, CO (United States)); Pfeffer, R.A. (Army Nuclear and Chemical Agency, Springfield, VA (United States))

1993-12-01

44

Effects of low intensity radiofrequency electromagnetic fields on electrical activity in rat hippocampal slices.  

PubMed

Slices of rat hippocampus were exposed to 700 MHz continuous wave radiofrequency (RF) fields (25.2-71.0 V m(-1), 5-15 min exposure) in a stripline waveguide. At low field intensities, the predominant effect on the electrically evoked field potential in CA1 was a potentiation of the amplitude of the population spike by up to 20%, but higher intensity fields could produce either increases or decreases of up to 120 and 80%, respectively, in the amplitude of the population spike. To eliminate the possibility of RF-induced artefacts due to the metal stimulating electrode, the effect of RF exposure on spontaneous epileptiform activity induced in CA3 by 4-aminopyridine (50-100 microM) was investigated. Exposure to RF fields (50.0 V m(-1)) reduced or abolished epileptiform bursting in 36% of slices tested. The maximum field intensity used in these experiments, 71.0 V m(-1), was calculated to produce a specific absorption rate (SAR) of between 0.0016 and 0.0044 W kg(-1) in the slices. Measurements with a Luxtron fibreoptic probe confirmed that there was no detectable temperature change (+/- 0.1 degrees C) during a 15 min exposure to this field intensity. Furthermore, imposed temperature changes of up to 1 degrees C failed to mimic the effects of RF exposure. These results suggest that low-intensity RF fields can modulate the excitability of hippocampal tissue in vitro in the absence of gross thermal effects. The changes in excitability may be consistent with reported behavioural effects of RF fields. PMID:11516410

Tattersall, J E; Scott, I R; Wood, S J; Nettell, J J; Bevir, M K; Wang, Z; Somasiri, N P; Chen, X

2001-06-15

45

Analytic model of near-field radio-frequency sheaths. I. Tenuous plasma limit  

NASA Astrophysics Data System (ADS)

An analytic model is derived for electromagnetic radio-frequency (rf) wave propagation in a waveguide filled by a tenuous plasma with a slightly tilted equilibrium magnetic field B, i.e., by=By/B?1. The calculation includes the self-consistent coupling between the rf fields and the sheaths at the sheath-plasma interface and can be used to describe antenna sheath formation in the ion cyclotron range of frequencies. The sheaths are treated as thin vacuum regions separating the plasma and metal wall. It is shown that (i) the launched fast wave is coupled parasitically to the slow wave by the magnetic field structure when by?0 and by the sheath boundary condition, (ii) the sheath voltage Vsh is dependent on the wave parity (the "antenna phasing"), and (iii) integrating the vacuum rf fields, Vvac=-?dzE?(vac), gives an overestimate of the sheath voltage. An expression for the self-consistent Vsh including plasma effects and satisfying the Child-Langmuir law is obtained.

D'Ippolito, D. A.; Myra, J. R.

2009-02-01

46

Health problems among operators of plastic welding machines and exposure to radiofrequency electromagnetic fields.  

PubMed

To study possible medical effects of high radiofrequency radiation (RF), 113 Swedish men and women were studied by means of a structured interview and rating of subjective symptoms. A test session was included in order to examine coordination and muscular function of the hands. A neurological test concerning two-point discrimination (2-PD) was also done. As referents, 23 women, sewing machine operators and assembly workers, were chosen, interviewed and likewise tested. Exposure measurements were taken of the RF fields around the welding machines. The present Swedish ceiling value of 250 W/m2 for the equivalent power density was exceeded in more than 50% of the machines. The highest leakage fields, both for electric and magnetic fields, were found near machines used in factories for ready-made clothing, which gave a high exposure to the hands. Irritative eye symptoms were reported by 23% of the men and 40% of the women. A group of 27 persons was selected for a clinical eye examination and checked by photographs, and nine persons had modest conjunctivitis. A high prevalence of numbness in hands, especially among women, was found. A significantly impaired 2-PD was found in the exposed women as compared to the referent group. The pregnancy outcome for 305 female plastic welders during 1974-1984 did not show any significant differences with the Swedish average concerning malformation or prenatal mortality. PMID:3372031

Kolmodin-Hedman, B; Hansson Mild, K; Hagberg, M; Jönsson, E; Andersson, M C; Eriksson, A

1988-01-01

47

Targeted treatment of cancer with radiofrequency electromagnetic fields amplitude-modulated at tumor-specific frequencies  

PubMed Central

In the past century, there have been many attempts to treat cancer with low levels of electric and magnetic fields. We have developed noninvasive biofeedback examination devices and techniques and discovered that patients with the same tumor type exhibit biofeedback responses to the same, precise frequencies. Intrabuccal administration of 27.12 MHz radiofrequency (RF) electromagnetic fields (EMF), which are amplitude-modulated at tumor-specific frequencies, results in long-term objective responses in patients with cancer and is not associated with any significant adverse effects. Intrabuccal administration allows for therapeutic delivery of very low and safe levels of EMF throughout the body as exemplified by responses observed in the femur, liver, adrenal glands, and lungs. In vitro studies have demonstrated that tumor-specific frequencies identified in patients with various forms of cancer are capable of blocking the growth of tumor cells in a tissue- and tumor-specific fashion. Current experimental evidence suggests that tumor-specific modulation frequencies regulate the expression of genes involved in migration and invasion and disrupt the mitotic spindle. This novel targeted treatment approach is emerging as an appealing therapeutic option for patients with advanced cancer given its excellent tolerability. Dissection of the molecular mechanisms accounting for the anti-cancer effects of tumor-specific modulation frequencies is likely to lead to the discovery of novel pathways in cancer. PMID:24206915

Zimmerman, Jacquelyn W.; Jimenez, Hugo; Pennison, Michael J.; Brezovich, Ivan; Morgan, Desiree; Mudry, Albert; Costa, Frederico P.; Barbault, Alexandre; Pasche, Boris

2013-01-01

48

Noninvasive Radiofrequency Field Destruction of Pancreatic Adenocarcinoma Xenografts Treated with Targeted Gold Nanoparticles  

PubMed Central

Purpose Pancreatic carcinoma is one of the deadliest cancers with few effective treatments. Gold nanoparticles (AuNPs) are potentially therapeutic because of the safety demonstrated thus far and their physio-chemical characteristics. We utilized the astounding heating rates of AuNPs in nonionizing radiofrequency (RF) radiation to investigate human pancreatic xenograft destruction in a murine model. Experimental Design Weekly, Panc-1 and Capan-1 human pancreatic carcinoma xenografts in immunocompromised mice were exposed to an RF field 36 hours after treatment (intraperitoneal) with cetuximab or PAM4 antibody conjugated AuNPs, respectively. Tumor sizes were measured weekly while necrosis and cleaved caspase-3 were investigated with H&E staining and immunofluorescence, respectively. In addition, AuNP internalization and cytotoxicity were investigated in vitro with confocal microscopy and flow cytometry, respectively. Results Panc-1 cells demonstrated increased apoptosis with decreased viability after treatment with cetuximab conjugated AuNPs and RF field exposure (p = 0.00005). Differences in xenograft volumes were observed within 2 weeks of initiating therapy. Cetuximab-conjugated and PAM4-conjugated AuNPs demonstrated RF field-induced destruction of Panc-1 and Capan-1 pancreatic carcinoma xenografts after six weeks of weekly treatment (p = 0.004 and p = 0.035, respectively). There was no evidence of injury to murine organs. Cleaved caspase-3 and necrosis were both increased in treated tumors. Conclusions This study demonstrates a potentially novel cancer therapy by non-invasively inducing intracellular hyperthermia with targeted AuNPs in an RF field. While the therapy is dependent on the specificity of the targeting antibody, normal tissues were without toxicity despite systemic therapy and whole body RF field exposure. PMID:21138869

Glazer, Evan S.; Zhu, Cihui; Massey, Katheryn L.; Thompson, C. Shea; Kaluarachchi, Warna D.; Hamir, Amir N.; Curley, Steven A.

2010-01-01

49

Aspergillus fumigatus Hyphal Damage Caused by Noninvasive Radiofrequency Field-Induced Hyperthermia  

PubMed Central

We studied the effect of noninvasive radiofrequency-induced hyperthermia on the viability of Aspergillus fumigatus hyphae in vitro. Radiofrequency-induced hyperthermia resulted in significant (>70%, P < 0.0001) hyphal damage in a time and thermal dose-dependent fashion as assessed by XTT [(sodium 2,3,-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)-carbonyl] (1)-2H-tetrazolium inner salt)], DiBAC [bis-(1,3-dibutylbarbituric acid) trimethine oxonol] staining, and transmission electron microscopy. For comparison, water bath hyperthermia was used over the range of 45 to 55°C to study hyphal damage. Radiofrequency-induced hyperthermia resulted in severe damage to the outer fibrillar layer of hyphae at a shorter treatment time compared to water bath hyperthermia. Our preliminary data suggest that radiofrequency-induced hyperthermia might be an additional therapeutic approach to use in the management of mold infections. PMID:23836166

Kaluarachchi, Warna D.; Cisneros, Brandon T.; Corr, Stuart J.; Albert, Nathaniel D.; Curley, Steven A.

2013-01-01

50

Operation of an ungated diamond field-emission array cathode in a L-band radiofrequency electron source  

NASA Astrophysics Data System (ADS)

We report on the operation of a field-emitter-array cathode in a conventional L-band radio-frequency electron source. The cathode consisted of an array of ˜106 diamond tips on pyramids. Maximum current on the order of 15 mA was reached and the cathode did not show appreciable signs of fatigue after weeks of operation. The measured Fowler-Nordheim characteristics, transverse beam density, and current stability are discussed.

Piot, P.; Brau, C. A.; Choi, B. K.; Blomberg, B.; Gabella, W. E.; Ivanov, B.; Jarvis, J.; Mendenhall, M. H.; Mihalcea, D.; Panuganti, H.; Prieto, P.; Reid, J.

2014-06-01

51

Operation of an ungated diamond field-emission array cathode in a L-band radiofrequency electron source  

SciTech Connect

We report on the operation of a field-emitter-array cathode in a conventional L-band radio-frequency electron source. The cathode consisted of an array of ?10{sup 6} diamond tips on pyramids. Maximum current on the order of 15?mA was reached and the cathode did not show appreciable signs of fatigue after weeks of operation. The measured Fowler-Nordheim characteristics, transverse beam density, and current stability are discussed.

Piot, P. [Northern Illinois Center for Accelerator and Detector Development and Department of Physics, Northern Illinois University, DeKalb, Illinois 60115 (United States); Accelerator Physics Center, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Brau, C. A.; Gabella, W. E.; Ivanov, B.; Mendenhall, M. H. [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); Choi, B. K. [Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee 37235 (United States); Vanderbilt Institute of Nanoscale Science and Engineering, Vanderbilt University, Nashville, Tennessee 37235 (United States); Blomberg, B.; Mihalcea, D.; Panuganti, H. [Northern Illinois Center for Accelerator and Detector Development and Department of Physics, Northern Illinois University, DeKalb, Illinois 60115 (United States); Jarvis, J. [Advanced Energy Systems, Inc., Medford, New York 11763 (United States); Prieto, P.; Reid, J. [Accelerator Division, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States)

2014-06-30

52

Effects of field orientation during 700-MHz radiofrequency irradiation of rats  

SciTech Connect

Ketamine-anesthetized Sprague-Dawley rats were exposed to far-field 700-MHz continuous-wave radiofrequency radiation (RFR) in both E and H orientations. Irradiation was conducted at whole-body average specific absorption rates (SARs) of 9.2 and 13.0 W/kg (E and H, respectively) that resulted in approximately equivalent colonic specific heating rates (SHRs). Exposures were performed to repeatedly increase colonic temperature by 1 deg C (38.5 to 39.5 deg C). Tympanic, tail, left and right subcutaneous (toward and away from RFR source), and colonic temperatures, arterial blood pressure, and respiratory rate were continuously recorded. In spite of equivalent colonic SHRs and the reduced E-orientation average SAR, the right subcutaneous, tympanic, and tail SARs, SHRs and absolute temperature increases were significantly greater in E than in H orientation. The cooling rate at all monitoring sites was also significantly greater in E than in H orientation. Heart rate and mean arterial blood pressure significantly increased during irradiation; however, changer between orientations were not different. Respiratory rate significantly increased during irradiation in H, but not in E orientation. These results indicate that during resonant frequency irradiation, differences occur in the pattern of heat deposition between E- and H-orientation exposure. When compared with previous investigations performed at supraresonant frequencies, the lower level of cardiovascular change in this study was probably related to the lower periphery-to-core thermal gradient.

Frei, M.R.; Jauchem, J.R.; Padilla, J.M.

1989-01-01

53

Effects of field orientation during 700-MHz radiofrequency irradiation of rats  

SciTech Connect

Ketamine-anesthetized Sprague-Dawley rats were exposed to far-field 700-MHz continuous-wave radiofrequency radiation (RFR) in both E and H orientations. Irradiation was conducted at whole-body average specific absorption rates (SARs) of 9.2 and 13.0 W/kg (E and H, respectively) that resulted in approximately equivalent colonic specific heating rates (SHRs). Exposures were performed to repeatedly increase colonic temperature by 1 degree C (38.5 to 39.5 degrees C). Tympanic, tail, left and right subcutaneous (toward and away from RFR source), and colonic temperatures, arterial blood pressure, and respiratory rate were continuously recorded. In spite of equivalent colonic SHRs and the reduced E-orientation average SAR, the right subcutaneous, tympanic, and tail SARs, SHRs and absolute temperature increases were significantly greater in E than in H orientation. The cooling rate at all monitoring sites was also significantly greater in E than in H orientation. Heart rate and mean arterial blood pressure significantly increased during irradiation; however, changes between orientations were not different. Respiratory rate significantly increased during irradiation in H, but not in E orientation. These results indicate that during resonant frequency irradiation, differences occur in the pattern of heat deposition between E- and H-orientation exposure. When compared with previous investigations performed at supraresonant frequencies, the lower level of cardiovascular change in this study was probably related to the lower periphery-to-core thermal gradient.

Frei, M.R.; Jauchem, J.R.; Padilla, J.M. (School of Aerospace Medicine, Brooks AFB, TX (USA))

1989-01-01

54

Optimization and validation of methods for mapping of the radiofrequency transmit field at 3T.  

PubMed

MRI techniques such as quantitative imaging and parallel transmit require precise knowledge of the radio-frequency transmit field (B(1) (+)). Three published methods were optimized for robust B(1) (+) mapping at 3T in the human brain: three-dimensional (3D) actual flip angle imaging (AFI), 3D echo-planar imaging (EPI), and two-dimensional (2D) stimulated echo acquisition mode (STEAM). We performed a comprehensive comparison of the methods, focusing on artifacts, reproducibility, and accuracy compared to a reference 2D double angle method. For the 3D AFI method, the addition of flow-compensated gradients for diffusion damping reduced the level of physiological artifacts and improved spoiling of transverse coherences. Correction of susceptibility-induced artifacts alleviated image distortions and improved the accuracy of the 3D EPI imaging method. For the 2D STEAM method, averaging over multiple acquisitions reduced the impact of physiological noise and a new calibration method enhanced the accuracy of the B(1) (+) maps. After optimization, all methods yielded low noise B(1) (+) maps (below 2 percentage units), of the nominal flip angle value (p.u.) with a systematic bias less than 5 p.u. units. Full brain coverage was obtained in less than 5 min. The 3D AFI method required minimal postprocessing and showed little sensitivity to off-resonance and physiological effects. The 3D EPI method showed the highest level of reproducibility. The 2D STEAM method was the most time-efficient technique. PMID:20572153

Lutti, Antoine; Hutton, Chloe; Finsterbusch, Jürgen; Helms, Gunther; Weiskopf, Nikolaus

2010-07-01

55

DNA strand breaks are not induced in human cells exposed to 2.1425 GHz band CW and W-CDMA modulated radiofrequency fields allocated to mobile radio base stations.  

PubMed

We conducted a large-scale in vitro study focused on the effects of low level radiofrequency (RF) fields from mobile radio base stations employing the International Mobile Telecommunication 2000 (IMT-2000) cellular system in order to test the hypothesis that modulated RF fields may act as a DNA damaging agent. First, we evaluated the responses of human cells to microwave exposure at a specific absorption rate (SAR) of 80 mW/kg, which corresponds to the limit of the average whole body SAR for general public exposure defined as a basic restriction in the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. Second, we investigated whether continuous wave (CW) and Wideband Code Division Multiple Access (W-CDMA) modulated signal RF fields at 2.1425 GHz induced different levels of DNA damage. Human glioblastoma A172 cells and normal human IMR-90 fibroblasts from fetal lungs were exposed to mobile communication frequency radiation to investigate whether such exposure produced DNA strand breaks in cell culture. A172 cells were exposed to W-CDMA radiation at SARs of 80, 250, and 800 mW/kg and CW radiation at 80 mW/kg for 2 and 24 h, while IMR-90 cells were exposed to both W-CDMA and CW radiations at a SAR of 80 mW/kg for the same time periods. Under the same RF field exposure conditions, no significant differences in the DNA strand breaks were observed between the test groups exposed to W-CDMA or CW radiation and the sham exposed negative controls, as evaluated immediately after the exposure periods by alkaline comet assays. Our results confirm that low level exposures do not act as a genotoxicant up to a SAR of 800 mW/kg. PMID:16283663

Sakuma, N; Komatsubara, Y; Takeda, H; Hirose, H; Sekijima, M; Nojima, T; Miyakoshi, J

2006-01-01

56

A method to measure specific absorption rate of nanoparticles in colloidal suspension using different configurations of radio-frequency fields  

NASA Astrophysics Data System (ADS)

We report a method for characterization of the efficiency of radio-frequency (rf) heating of nanoparticles (NPs) suspended in an aqueous medium. Measurements were carried out for water suspended 5 nm superparamagnetic iron-oxide NPs with 30 nm dextran matrix for three different configurations of rf electric and magnetic fields. A 30 MHz high-Q resonator was designed to measure samples placed inside a parallel plate capacitor and solenoid coil with or without an rf electric field shield. All components of rf losses were analyzed and rf electric and magnetic field induced heating of NPs and the dispersion medium was determined and discussed.

Ketharnath, Dhivya; Pande, Rohit; Xie, Leiming; Srinivasan, Srimeenakshi; Godin, Biana; Wosik, Jarek

2012-08-01

57

Field orientation effects during 5. 6-GHz radiofrequency irradiation of rats  

SciTech Connect

Ketamine-anesthetized Sprague-Dawley rats were exposed in E and H orientations (long axis parallel to electric and magnetic fields, respectively) to far-field 5.6-GHz continuous-wave radio-frequency radiation (RFR). Power densities were used that resulted in equivalent whole-body average specific absorption rates of 14 W/kg in both orientations (90 mW/cm2 for E and 66 mW/cm2 for H). Irradiation was conducted to increase colonic temperature by 1 degree C (from 38.5 to 39.5 degrees C). During experimentation, arterial blood pressure and respiratory rate and colonic, tympanic, left and right subcutaneous (sides toward and away from RFR source), and tail temperatures were continuously recorded. Results showed no significant difference in the times required to cause a 1 degree C increase or to recover to the initial temperature when irradiation was stopped. Significant differences between E- and H-orientation exposure were seen in the patterns of localized heating. The tail and left subcutaneous temperature increases were significantly greater during E-orientation exposure, the tympanic site showed no difference, and the right subcutaneous temperature increase was significantly greater during H-orientation exposure. Under both exposure conditions, heart rate and mean arterial blood pressure significantly increased during irradiation; however, there were no significant differences between E and H orientation responses. These findings at 5.6 GHz are in contrast to the significant cardiovascular response differences between E- and H-orientation exposure noted during a previous study of irradiation at 2.45 GHz.

Frei, M.R.; Jauchem, J.R.; Price, D.L.; Padilla, J.M. (USAF School of Aerospace Medicine, Brooks AFB, TX (USA))

1990-12-01

58

Targeted Radiofrequency Field Mapping using 3D Reduced Field-of-View Catalyzed Double-Angle Method  

PubMed Central

Purpose To develop a targeted volumetric radiofrequency (RF) field (B1+) mapping technique to provide region-of-interest B1+ information. Materials and Methods Targeted B1+ maps were acquired using 3D reduced field-of-view (FOV) inner volume turbo spin echo catalyzed double-angle method (DAM). Targeted B1+ maps were compared with full FOV B1+ maps acquired using 3D catalyzed DAM in a phantom and in the brain of a healthy volunteer. In addition, targeted volumetric abdomeninal B1+ mapping was demonstrated in the abdomen of another healthy volunteer. Results The targeted reduced FOV images demonstrated no aliasing artifacts in all experiments. Close match between targeted B1+ map and reference full FOV B1+ map in the same region was observed, with percentage root-mean-squared error < 0.4% in the phantom and < 0.8% in the healthy volunteer brain. The abdominal B1+ maps showed small B1+ variation in the kidneys and liver from the healthy volunteer. Conclusion The proposed 3D reduced FOV catalyzed DAM provides a rapid, simple, and accurate method for targeted volumetric B1+ mapping, and can be easily implemented for applications related to RF field mapping in small targeted regions. PMID:21705167

Wang, Dingxin; Zuehlsdorff, Sven; Omary, Reed A.; Larson, Andrew C.

2012-01-01

59

Image-Guided Radio-Frequency Gain Calibration for High-Field MRI  

PubMed Central

High-field (? 3T) MRI provides a means to increase the signal-to-noise ratio, due to its higher tissue magnetization compared with 1.5T. However, both the static magnetic field (B0) and the transmit radio-frequency (RF) field (B1+) inhomogeneities are comparatively higher than those at 1.5T. These challenging factors at high-field strengths make it more difficult to accurately calibrate the transmit RF gain using standard RF calibration procedures. An image-based RF calibration procedure was therefore developed, in order to accurately calibrate the transmit RF gain within a specific region-of-interest (ROI). Using a single-shot ultra-fast gradient echo pulse sequence with centric k-space reordering, a series of “saturation-no-recovery” images was acquired by varying the flip angle of the preconditioning pulse. In the resulting images, the signal null occurs in regions where the flip angle of the preconditioning pulse is 90°. For a given ROI, the mean signal can be plotted as a function of the nominal flip angle, and the resulting curve can be used to quantitatively identify the signal null. This image-guided RF calibration procedure was evaluated through phantom and volunteer imaging experiments at 3T and 7T. The image-guided RF calibration results in vitro were consistent with standard B0 and B1+ maps. The standard automated RF calibration procedure produced approximately 20% and 15–30% relative error in the transmit RF gain in the left kidney at 3T and brain at 7T, respectively. For initial application, a T2 mapping pulse sequence was applied at 7T. The T2 measurements in the thalamus at 7T were 60.6 ms and 48.2 ms using the standard and image-guided RF calibration procedures, respectively. This rapid, image-guided RF calibration procedure can be used to optimally calibrate the flip angle for a given ROI and thus minimize measurement errors for quantitative MRI and MR spectroscopy. PMID:20014333

Breton, Elodie; McGorty, KellyAnne; Wiggins, Graham C.; Axel, Leon; Kim, Daniel

2010-01-01

60

Exposure to Radiofrequency Electromagnetic Fields and Sleep Quality: A Prospective Cohort Study  

PubMed Central

Background There is persistent public concern about sleep disturbances due to radiofrequency electromagnetic field (RF-EMF) exposure. The aim of this prospective cohort study was to investigate whether sleep quality is affected by mobile phone use or by other RF-EMF sources in the everyday environment. Methods We conducted a prospective cohort study with 955 study participants aged between 30 and 60 years. Sleep quality and daytime sleepiness was assessed by means of standardized questionnaires in May 2008 (baseline) and May 2009 (follow-up). We also asked about mobile and cordless phone use and asked study participants for consent to obtain their mobile phone connection data from the mobile phone operators. Exposure to environmental RF-EMF was computed for each study participant using a previously developed and validated prediction model. In a nested sample of 119 study participants, RF-EMF exposure was measured in the bedroom and data on sleep behavior was collected by means of actigraphy during two weeks. Data were analyzed using multivariable regression models adjusted for relevant confounders. Results In the longitudinal analyses neither operator-recorded nor self-reported mobile phone use was associated with sleep disturbances or daytime sleepiness. Also, exposure to environmental RF-EMF did not affect self-reported sleep quality. The results from the longitudinal analyses were confirmed in the nested sleep study with objectively recorded exposure and measured sleep behavior data. Conclusions We did not find evidence for adverse effects on sleep quality from RF-EMF exposure in our everyday environment. PMID:22624036

Mohler, Evelyn; Frei, Patrizia; Fröhlich, Jürg; Braun-Fahrländer, Charlotte; Röösli, Martin

2012-01-01

61

2.2.2 Non-Ionizing Radiations  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A 'Fundamentals and Data in Radiobiology, Radiation Biophysics, Dosimetry and Medical Radiological Protection' of Volume 7 'Medical Radiological Physics' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It contains the Subsection '2.2.2 Non-Ionizing Radiations' of the Section '2.2 Kinds of Radiation' of the Chapter '2 Radiation and Biological Effects' with the contents:

Bernhardt, J. H.

62

Effects of radiofrequency field on the blood-brain barrier: A systematic review from 2005 to 2009  

NASA Astrophysics Data System (ADS)

The published results available in 2005 were insufficient to draw firm conclusions concerning the possible non-thermal effects of radiofrequency fields on the blood-brain barrier (BBB). This critical review deals with 16 articles on this topic published since 2005. The methodological quality of these articles was not equivalent. We therefore analysed the underlying methodologies from both their biological and physical aspects. We conclude that recent studies provide no convincing proof of deleterious effects of RF on the integrity of the BBB, for specific absorption rates (SAR) up to 6 W/kg.

Perrin, Anne; Cretallaz, Celine; Collin, Alice; Amourette, Christine; Yardin, Catherine

2010-11-01

63

Plasma stabilization and improvement in the performance of a nonequilibrium disk MHD generator by a radio-frequency electromagnetic field  

SciTech Connect

By applying a radio-frequency (RF) electromagnetic field, the feasibility of improvement in the performance of a nonequilibrium disk-shaped magnetohydrodynamic (MHD) generator suffering from water vapor contamination in the working gas is investigated with r-[theta] two-dimensional numerical simulations. Attention is paid to the relation between the behavior of MHD plasma in the presence of the RF electric field and the generator performance. The water contamination causes the strongly nonuniform and unsteady plasma, and deteriorates its performance. The fluctuations of the electron temperature and of the ionization degree of seed atoms are found to be suppressed by applying the RF electric field. As a result, the enthalpy extraction ratio and the isentropic efficiency of the generator improve. The ratio of the required additional joule heating by the RF electric field to the thermal input to the generator for the stabilization of the plasma and the improvement in the performance is estimated to be about 0.9%.

Murakami, Tomoyuki; Okuno, Yoshihiro; Kabashima, Shigeharu (Tokyo Inst. of Tech., Yokohama (Japan). Dept. of Energy Sciences)

1999-04-01

64

[Exposure of workers to electric and magnetic fields from radiofrequency dielectric heaters to process polyvinyl chloride material].  

PubMed

Exposure of workers to electric and magnetic fields from radiofrequency dielectric heaters (RF heaters) to process polyvinyl chloride material was surveyed. Measurements of electric and magnetic field strengths were made in 10 workers operating 7 RF heaters at 3 plants in Japan. Six of the RF heaters are of the sewing machine type and the other is of the shuttle tray type. In all the RF heaters surveyed the nominal frequency of the radiofrequency generator was 40 MHz, and therefore electric and magnetic field from these are assumed to oscillate at the same frequency. The power output ranged from 0.83 W to 1.8 W for the sewing machine type and was 2.4 W for this shuttle tray type. Measurements were made at about 5 cm from the surface of the hand, eye, chest, waist, knee and foot of each worker. The meter readings were converted to equivalent plane wave power density and corrected for duty cycle (0.073 to 0.27). It was found that all the workers surveyed were exposed to electric and magnetic field strengths greater than the TLV recommended by ACGIH (1 mW/cm2). For the hand, eye, chest, waist, knee and foot of the worker, 95%, 63%, 32%, 47% and 36% and 27% of the measured field strengths exceeded the TLV, respectively. Especially for the sewing machine type RF heaters, electric fields at the hand and eye were extremely strong. Thus, for the hand, 100%, 75% and 38% of the measured electric field strengths exceeded the TLV, ten times the TLV, and one hundred times the TLV, respectively, and for the eye, 88% and 25% exceeded the TLV and ten times the TLV, respectively. No correlation was observed between power output of the RF heaters and measured electric and magnetic field strengths at any anatomical site of the worker. PMID:1770616

Okuno, T; Jonai, H; Kawakami, T

1991-11-01

65

Radio-frequency measurements of UNiX compounds (X= Al, Ga, Ge) in high magnetic fields  

SciTech Connect

We performed radio-frequency (RF) skin-depth measurements of antiferromagnetic UNiX compounds (X=Al, Ga, Ge) in magnetic fields up to 60 T and at temperatures between 1.4 to {approx}60 K. Magnetic fields are applied along different crystallographic directions and RF penetration-depth was measured using a tunnel-diode oscillator (TDO) circuit. The sample is coupled to the inductive element of a TDO resonant tank circuit, and the shift in the resonant frequency {Delta}f of the circuit is measured. The UNiX compounds exhibit field-induced magnetic transitions at low temperatures, and those transitions are accompanied by a drastic change in {Delta}f. The results of our skin-depth measurements were compared with previously published B-T phase diagrams for these three compounds.

Mielke, Charles H [Los Alamos National Laboratory; Mcdonald, David R [Los Alamos National Laboratory; Zapf, Vivien [Los Alamos National Laboratory; Altarawneh, Moaz M [Los Alamos National Laboratory; Lacerda, Alex H [Los Alamos National Laboratory; Adak, Sourav [Los Alamos National Laboratory; Karunakar, Kothapalli [Los Alamos National Laboratory; Nakotte, Heinrich [Los Alamos National Laboratory; Chang, S [NIST; Alsmadi, A M [HASHEMITE UNIV; Alyones, S [HASHEMIT UNIV

2009-01-01

66

ECG changes in factory workers exposed to 27.2 ?MHz radiofrequency radiation.  

PubMed

To research the effect of 27.2?MHz radiofrequency radiation on electrocardiograms (ECG), 225 female workers operating radiofrequency machines at a shoe factory were chosen as the exposure group and 100 female workers without exposure from the same factory were selected as the control group. The 6?min electric field strength that the female workers were exposed to was 64.0?±?25.2?V/m (mean?±?SD), which exceeded 61?V/m, the International Commission on Non-Ionizing Radiation Protection reference root mean square levels for occupational exposure. A statistical difference was observed between the exposed group and the control group in terms of the rate of sinus bradycardia (?(2) ?=?11.48, P?=?0.003). When several known risk factors for cardiovascular disease were considered, including smoking, age, alcohol ingestion habit, and so on, the exposure duration was not an effective factor for ECG changes, sinus arrhythmia, or sinus bradycardia according to ??=?0.05, while P?=?0.052 for sinus arrhythmia was very close to 0.05. We did not find any statistical difference in heart rate, duration of the QRS wave (ventricular depolarization), or corrected QT intervals (between the start of the Q wave and end of the T wave) between the exposed and control groups. Occupational exposure to radiofrequency radiation was not found to be a cause of ECG changes after consideration of the confounding factors. PMID:23280584

Chen, Qingsong; Xu, Guoyong; Lang, Li; Yang, Aichu; Li, Shilin; Yang, Liwen; Li, Chaolin; Huang, Hanlin; Li, Tao

2013-05-01

67

Effect of orthodontic brackets and different wires on radiofrequency heating and magnetic field interactions during 3-T MRI  

PubMed Central

Objectives: To evaluate the heating and magnetic field interactions of fixed orthodontic appliances with different wires and ligaments in a 3-T MRI environment and to estimate the safety of these orthodontic materials. Methods: 40 non-carious extracted human maxillary teeth were embedded in polyvinyl chloride boxes, and orthodontic brackets were bonded. Nickel–titanium and stainless steel arch wires, and elastic and stainless steel ligaments were used to obtain four experimental groups in total. Specimens were evaluated at 3?T for radiofrequency heating and magnetic field interactions. Radiofrequency heating was evaluated by placing specimens in a cylindrical plastic container filled with isotonic solution and measuring changes in temperature after T1 weighted axial sequencing and after completion of all sequences. Translational attraction and torque values of specimens were also evaluated. One-way ANOVA test was used to compare continuous variables of temperature change. Significance was set at p?field interactions changed depending on the material used. Although the brackets presented minor interactions that would not cause movement in situ, nickel–titanium and stainless steel wires presented great interactions that may pose a risk for the patient. Conclusions: The temperature changes of the specimens were considered to be within acceptable ranges. With regard to magnetic field interactions, brackets can be considered “MR safe”; however, it would be safe to replace the wires before MRI. PMID:24257741

Görgülü, S; Ayy?ld?z, S; Gökçe, S; Ozen, T

2014-01-01

68

International workshop on non-ionizing radiation protection in medicine.  

PubMed

An international workshop brought together a range of stakeholders to consider protection from non-ionizing radiation used in medicine, research and cosmetics. Presentations on specific topics were followed by a general discussion on possible improvements in protection. Participants considered that adherence to science-based, harmonized exposure guidelines to limit exposures for clinical staff and other workers was a key prerequisite to safety in all situations. In addition, to engender an awareness of the risks involved to both the patient as well as the operator, equipment should be operated only by suitably qualified persons who have received appropriate training in the safe use of that device. This training should be carried out under the auspices of an accredited safety provider, and preferably offer a recognized qualification. Specific advice included the necessity for correct eye protection with higher power optical radiation sources, and avoiding the use of ultrasound for all exposures without medical benefit. Finally, the possibility of a harmonized approach to safety for both non-ionizing and ionizing radiation was considered worthy of further discussion. PMID:24320477

Sienkiewicz, Zenon

2013-11-01

69

Tunable Atomic Magnetometer for Detection of Radio-Frequency Magnetic Fields I. M. Savukov, S. J. Seltzer, and M. V. Romalis  

E-print Network

Tunable Atomic Magnetometer for Detection of Radio-Frequency Magnetic Fields I. M. Savukov, S. J (Received 25 January 2005; published 3 August 2005) We describe an alkali-metal magnetometer for detection on the sensitivity of the rf magnetometer and show that a sensitivity of about 0:01 fT=Hz1=2 can be achieved

Romalis, Mike

70

Extensive frequency selective measurements of radiofrequency fields in outdoor environments performed with a novel mobile monitoring system.  

PubMed

A novel, car based, measuring system for estimation of general public outdoor exposure to radiofrequency fields (RF) has been developed. The system enables fast, large area, isotropic spectral measurements with a bandwidth covering the frequency range of 30?MHz to 3?GHz. Measurements have shown that complete mapping of a town with 15000 inhabitants and a path length of 115?km is possible to perform within 1 day. The measured areas were chosen to represent typical rural, urban and city areas of Sweden. The data sets consist of more than 70000 measurements. All measurements were performed during the daytime. The median power density was 16?µW/m(2) in rural areas, 270?µW/m(2) in urban areas, and 2400?µW/m(2) in city areas. In urban and city areas, base stations for mobile phones were clearly the dominating sources of exposure. PMID:24375568

Estenberg, Jimmy; Augustsson, Torsten

2014-04-01

71

Genetic, carcinogenic and teratogenic effects of radiofrequency fields 1 This is the second in a series of four papers, the first of which was published in Mutation Res. 387 (1997) pp. 165–171. 1  

Microsoft Academic Search

This paper reviews the literature data on the genetic toxicology of radiofrequency (RF) radiation. Whereas in the past most studies were devoted to microwave ovens and radar equipment, it is now mobile telecommunication that attracts most attention. Therefore we focus on mobile telephone frequencies where possible. According to a great majority of the papers, radiofrequency fields, and mobile telephone frequencies

L. Verschaeve; A. Maes

1998-01-01

72

Radio-frequency dispersive detection of donor atoms in a field-effect transistor  

SciTech Connect

Radio-frequency dispersive read-out can provide a useful probe to nano-scale structures, such as nano-wire devices, especially, when the implementation of charge sensing is not straightforward. Here, we demonstrate dispersive “gate-only” read-out of phosphor donors in a silicon nano-scale transistor. The technique enables access to states that are only tunnel-coupled to one contact, which is not easily achievable by other methods. This allows us to locate individual randomly placed donors in the device channel. Furthermore, the setup is naturally compatible with high bandwidth access to the probed donor states and may aid the implementation of a qubit based on coupled donors.

Verduijn, J., E-mail: a.verduijn@unsw.edu.au; Rogge, S. [Centre for Quantum Computation and Communication Technology, University of New South Wales, Sydney NSW 2052 (Australia)] [Centre for Quantum Computation and Communication Technology, University of New South Wales, Sydney NSW 2052 (Australia); Vinet, M. [CEA/LETI-MINATEC, CEA-Grenoble, 17 rue des martyrs, F-38054 Grenoble (France)] [CEA/LETI-MINATEC, CEA-Grenoble, 17 rue des martyrs, F-38054 Grenoble (France)

2014-03-10

73

Radiofrequency: Thermage.  

PubMed

Nonablative procedures for facial rejuvenation have become increasingly popular. One such method to improve laxity and diminish rhytids is monopolar capacitively coupled radiofrequency (MRF). The authors discuss clinical studies using MRF. The authors also discuss their clinical experiences as well as recommendations for optimal results. MRF using the Thermage CPT system (Solta Medical, Hayward, California) offers minimal downtime with a favorable side-effect profile. Although there are many radiofrequency devices on the market for aesthetic use, MRF has the most clinical trials to date to support its use as an effective, evidence-based modality to improve rhytids and tighten the skin. PMID:21763995

Polder, Kristel D; Bruce, Suzanne

2011-05-01

74

Particle modelling of low-pressure radio-frequency magnetron discharges including the effects of self-induced electromagnetic fields  

NASA Astrophysics Data System (ADS)

Modelling of radio-frequency (RF) magnetron discharges is performed using a particle-in-cell/Monte Carlo technique in the case of low-pressure argon gas at 4 mTorr and high external magnetic field in order to self-maintain the discharge and to generate an energetic quasi-ion beam required for cathode sputtering applications. An emphasis is made, for the first time in the literature in the case of low-pressure RF discharges, on the development of a particle model coupled with the full set of electromagnetic field equations. The aim is to analyse the effect on the RF plasma features of the plasma-induced magnetic field resulting from the coupling of the Maxwell-Ampere equation. We also analysed the effect of the electric field due to the time variation of magnetic field resulting from the coupling of the Maxwell-Faraday equation. For the present asymmetrical plasma reactor, the mean relative difference on, for instance, the ion density with and without the consideration of plasma-induced magnetic and electric fields due to the time variation of the magnetic field can reach about 2.5% in the region of the plasma bulk and about 10% in the lateral sheath. The effects of these two induced electromagnetic fields are in fact higher in the regions where the radial magnetic field generated by the external magnets belonging to the magnetron configuration is low. These non-negligible relative differences clearly show the importance of rigorously taking into account, beyond the usual Poisson's equation for the space charge electric field, the full set of electromagnetic Maxwell equations for a more accurate modelling of these low-pressure discharges, particularly when the total current density reaches a few mA cm-2.

Benyoucef, D.; Yousfi, M.

2014-08-01

75

Animal carcinogenicity studies on radiofrequency fields related to mobile phones and base stations.  

PubMed

Since a report in 1997 on an increased lymphoma incidence in mice chronically exposed to a mobile phone radiofrequency signal, none of the subsequent long-term studies in rodents have confirmed these results. On the other hand, several of the follow-up co- and carcinogenicity studies are still underway or are presently being initiated. Most of the published long-term studies used 1 exposure level only and suffer from a poor dosimetry which does not consider the animal's growth. Additional points of criticism are a limited, in some cases, questionable histopathology and inadequate group sizes. Overall, if dealing with new chemicals or drugs, these studies would not be acceptable for registration with the responsible authorities. The major critical points are taken into consideration within the European co- and carcinogenicity projects (CEMFEC and PERFORM-A), which are in their final stages and in the US long-term studies in mice and rats which are about to be initiated. Nevertheless, the WHO evaluation for health risk assessment of long-term telephone use and base station exposure will start in late 2005. PMID:16039683

Dasenbrock, Clemens

2005-09-01

76

Animal carcinogenicity studies on radiofrequency fields related to mobile phones and base stations  

SciTech Connect

Since a report in 1997 on an increased lymphoma incidence in mice chronically exposed to a mobile phone radiofrequency signal, none of the subsequent long-term studies in rodents have confirmed these results. On the other hand, several of the follow-up co- and carcinogenicity studies are still underway or are presently being initiated. Most of the published long-term studies used 1 exposure level only and suffer from a poor dosimetry which does not consider the animal's growth. Additional points of criticism are a limited, in some cases, questionable histopathology and inadequate group sizes. Overall, if dealing with new chemicals or drugs, these studies would not be acceptable for registration with the responsible authorities. The major critical points are taken into consideration within the European co- and carcinogenicity projects (CEMFEC and PERFORM-A), which are in their final stages and in the US long-term studies in mice and rats which are about to be initiated. Nevertheless, the WHO evaluation for health risk assessment of long-term telephone use and base station exposure will start in late 2005.

Dasenbrock, Clemens [Fraunhofer Institute of Toxicology and Experimental Medicine (ITEM), Nikolai-Fuchs-Str. 1, 30625 Hannover (Germany)]. E-mail: clemens-dasebrock@bc.boehringer-ingelheim.com

2005-09-01

77

Citrate-capped gold nanoparticle electrophoretic heat production in response to a time-varying radiofrequency electric-field  

PubMed Central

The evaluation of heat production from gold nanoparticles (AuNPs) irradiated with radiofrequency (RF) energy has been problematic due to Joule heating of their background ionic buffer suspensions. Insights into the physical heating mechanism of nanomaterials under RF excitations must be obtained if they are to have applications in fields such as nanoparticle-targeted hyperthermia for cancer therapy. By developing a purification protocol which allows for highly-stable and concentrated solutions of citrate-capped AuNPs to be suspended in high-resistivity water, we show herein, for the first time, that heat production is only evident for AuNPs of diameters ? 10 nm, indicating a unique size-dependent heating behavior not previously observed. Heat production has also shown to be linearly dependent on both AuNP concentration and total surface area, and severely attenuated upon AuNP aggregation. These relationships have been further validated using permittivity analysis across a frequency range of 10 MHz to 3 GHz, as well as static conductivity measurements. Theoretical evaluations suggest that the heating mechanism can be modeled by the electrophoretic oscillation of charged AuNPs across finite length scales in response to a time-varying electric field. It is anticipated these results will assist future development of nanoparticle-assisted heat production by RF fields for applications such as targeted cancer hyperthermia. PMID:23795228

Corr, Stuart J.; Raoof, Mustafa; Mackeyev, Yuri; Phounsavath, Sophia; Cheney, Matthew A.; Cisneros, Brandon T.; Shur, Michael; Gozin, Michael; McNally, Patrick J.; Wilson, Lon J.; Curley, Steven A.

2013-01-01

78

Evaluation of safety and patient subjective efficacy of using radiofrequency and pulsed magnetic fields for the treatment of striae (stretch marks).  

PubMed

Stretch marks are common skin disorders that are dermal scars with associated epidermal atrophy. They are of significant concern or psychological concern to many. This manuscript describes the use of multipolar radiofrequency with pulsed magnetic fields that was successfully used to diminish these lesions in 16 subjects undergoing a series of treatments. The improvements noted were statistically significant and no serious adverse events were noted. PMID:25276274

Dover, Jeffrey S; Rothaus, Kenneth; Gold, Michael H

2014-09-01

79

Evaluation of Safety and Patient Subjective Efficacy of Using Radiofrequency and Pulsed Magnetic Fields for the Treatment of Striae (Stretch Marks)  

PubMed Central

Stretch marks are common skin disorders that are dermal scars with associated epidermal atrophy. They are of significant concern or psychological concern to many. This manuscript describes the use of multipolar radiofrequency with pulsed magnetic fields that was successfully used to diminish these lesions in 16 subjects undergoing a series of treatments. The improvements noted were statistically significant and no serious adverse events were noted. PMID:25276274

Dover, Jeffrey S.; Rothaus, Kenneth

2014-01-01

80

Complete description of the interactions of a quadrupolar nucleus with a radiofrequency field. Implications for data fitting.  

PubMed

We present a theory, with experimental tests, that treats exactly the effect of radiofrequency (RF) fields on quadrupolar nuclei, yet retains the symbolic expressions as much as possible. This provides a mathematical model of these interactions that can be easily connected to state-of-the-art optimization methods, so that chemically-important parameters can be extracted from fits to experimental data. Nuclei with spins >1/2 typically experience a Zeeman interaction with the (possibly anisotropic) local static field, a quadrupole interaction and are manipulated with RF fields. Since RF fields are limited by hardware, they seldom dominate the other interactions of these nuclei and so the spectra show unusual dependence on the pulse width used. The theory is tested with (23)Na NMR nutation spectra of a single crystal of sodium nitrate, in which the RF is comparable with the quadrupole coupling and is not necessarily on resonance with any of the transitions. Both the intensity and phase of all three transitions are followed as a function of flip angle. This provides a more rigorous trial than a powder sample where many of the details are averaged out. The formalism is based on a symbolic approach which encompasses all the published results, yet is easily implemented numerically, since no explicit spin operators or their commutators are needed. The classic perturbation results are also easily derived. There are no restrictions or assumptions on the spin of the nucleus or the relative sizes of the interactions, so the results are completely general, going beyond the standard first-order treatments in the literature. PMID:23611427

Spencer, T Leigh; Goward, Gillian R; Bain, Alex D

2013-06-01

81

Young’s Modulus Reconstruction for Radio-frequency Ablation Electrode-induced Displacement Fields: A Feasibility Study  

PubMed Central

Radiofrequency (RF) ablation is a minimally invasive treatment for tumors in various abdominal organs. It is effective if good tumor localization and intra-procedural monitoring can be done. In this paper, we investigate the feasibility of using an ultrasound-based Young’s modulus reconstruction algorithm to image an ablated region whose stiffness is elevated due to tissue coagulation. To obtain controllable tissue deformations for abdominal organs during and/or intermediately after the RF ablation, the proposed modulus imaging method is specifically designed for using tissue deformation fields induced by the RF electrode. We have developed a new scheme under which the reconstruction problem is simplified to a two-dimensional problem. Based on this scheme, an iterative Young’s modulus reconstruction technique with edge-preserving regularization was developed to estimate the Young’s modulus distribution. The method was tested in experiments using a tissue-mimicking phantom and on ex vivo bovine liver tissues. Our preliminary results suggest that high contrast modulus images can be successfully reconstructed. In both experiments, the geometries of the reconstructed modulus images of thermal ablation zones match well with the phantom design and the gross pathology image, respectively. PMID:19258195

Jiang, Jingfeng; Varghese, Tomy; Brace, Chris L.; Madsen, Ernest L.; Hall, Timothy J.; Bharat, Shyam; Hobson, Maritza A.; Zagzebski, James A.; Lee, Fred T.

2009-01-01

82

Near-field radio-frequency thermo-acoustic imaging based on transmission lines for optimized performance  

NASA Astrophysics Data System (ADS)

Near-field Radio-frequency Thermoacoustic Imaging (NRTI) is an imaging modality that was recently introduced to generate thermoacoustic signals using ultra-short high energy impulses. Because it allows for a higher energy coupling within an ultra-short time, it can achieve higher resolutions and higher signal to noise ratio, compared to traditional thermoacoustic tomography based on radiating sources at single frequencies. As for traditional thermoacoustic imaging the contrast comes from the conductivity and the dielectric properties of the tissues, while the resolution depends on the measured acoustic waves. Since NRTI depends on the efficient generation of high energy short impulses, the ability to control their time width and pulse shape is of high importance. We present here a methodology for generating such impulses based on transmission lines. The ability of such generators to generate impulses in the range of tens of nanoseconds enables high resolution images in the range of tens of microns to hundreds of microns without compromising the amount of the energy coupled. Finally the pulser is used to generate high resolution images of small absorbing insertions, of phantoms with different conductivities and of ex-vivo mouse images. From the phantoms it is possible to see both the capabilities of the system to accurately image small insertions as well as the high quality images generated from imaging phantoms, from ex-vivo mouse images it is possible to see several anatomical characteristics, such as the mouse boundary, the spine and some other characteristics in the mouse abdomens.

Omar, Murad; Kellnberger, Stephan; Sergiadis, George; Razansky, Daniel; Ntziachristos, Vasilis

2012-02-01

83

Incidence of micronuclei in human peripheral blood lymphocytes exposed to modulated and unmodulated 2450?MHz radiofrequency fields.  

PubMed

Peripheral blood samples from four healthy volunteers were collected and aliquots were exposed in vitro for 2?h to either (i) modulated (wideband code division multiple access, WCDMA) or unmodulated continuous wave (CW) 2450?MHz radiofrequency (RF) fields at an average specific absorption rate of 10.9?W/kg or (ii) sham-exposed. Aliquots of the same samples that were exposed in vitro to an acute dose of 1.5?Gy ionizing gamma-radiation (GR) were used as positive controls. Half of the aliquots were treated with melatonin (Mel) to investigate if such treatment offers protection to the cells from the genetic damage, if any, induced by RF and GR. The cells in all samples were cultured for 72?h and the lymphocytes were examined to determine the extent of genetic damage assessed from the incidence of micronuclei (MN). The results indicated the following: (i) the incidence of MN was similar in incubator controls, and those exposed to RF/sham and Mel alone; (ii) there were no significant differences between WCDMA and CW RF exposures; (iii) positive control cells exposed to GR alone exhibited significantly increased MN; and (iv) Mel treatment had no effect on cells exposed to RF and sham, while such treatment significantly reduced the frequency of MN in GR-exposed cells. PMID:23720062

Vijayalaxmi; Reddy, Abhishek B; McKenzie, Raymond J; McIntosh, Robert L; Prihoda, Thomas J; Wood, Andrew W

2013-10-01

84

[Cosmetic radiofrequency].  

PubMed

Cosmetic radio frequency uses an electric current of high frequency that generates heat through the subcutaneous tissues enough to break the collagen fibers and allow synthesis of a neo-collagen. It permits cutaneous resurfacing, improving the tone and quality of the skin (wrinkles and enlarged pores), and delicately reshaping facial volumes. The principle of a type Ellman monopolar radiofrequency at a rate of 4 MHz Pellevé, Surgitron Dual RF S 5 is described. Its use inclines more towards anti-aging and natural rejuvenation of the face, neck and neckline. It may be associated with other rejuvenation techniques such as fillers and botulinum toxin within certain time limits. PMID:21284234

Huth, J

2010-01-01

85

Design of an ecological momentary assessment study of exposure to radiofrequency electromagnetic fields and non-specific physical symptoms  

PubMed Central

Introduction Idiopathic Environmental Intolerance (IEI) attributed to electromagnetic fields (EMF) refers to self-reported sensitivity mainly characterised by the attribution of non-specific physical symptoms to low-level EMF exposure emitted from sources such as mobile phones. Scientific studies have not provided evidence for the existence of IEI-EMF, but these studies did not resemble the real-life situation or suffered from poor exposure characterisation and biased recall of health symptoms. To improve existing methods for the study of IEI-EMF, an Ecological Momentary Assessment (EMA) study is designed. Methods and analysis The study is an EMA study in which respondents carry personal exposure metres (exposimeters) that measure radiofrequency (RF) EMF, with frequent assessment of health symptoms and perceived EMF exposure through electronic diary registration during five consecutive days. Participants will be a selection from an epidemiological study who report to be sensitive to RF EMF. The exposimeters measure electric field strength in 12 frequency bands. Diary questions include the occurrence and severity of 10 non-specific physical symptoms, mood states and perceived exposure to (sources of) EMF. The relationship of actual and perceived EMF exposure and mood with non-specific physical symptoms will be analysed using multilevel regression analysis with time-shift models. Discussion The study has several advantages over previous studies, including assessment of personal EMF exposure and non-specific physical symptoms by an ecological method with a minimised chance of recall bias. The within-person design reduces confounding by time-stable factors (eg, personal characteristics). In the conduct of the study and the analysis and interpretation of its outcomes, some methodological issues including a high participant burden, reactivity, compliance to the study protocol and the potential of chance findings due to multiple statistical testing will be accounted for and limited as much as possible. PMID:23988360

Bogers, Rik P; Bolte, John F B; Houtveen, Jan H; Lebret, Erik; van Strien, Rob T; Schipper, C Maarten A; Alkadhimi, Mehdi; Baliatsas, Christos; van Kamp, Irene

2013-01-01

86

Performance of field-emitting resonating carbon nanotubes as radio-frequency demodulators  

NASA Astrophysics Data System (ADS)

We report on a systematic study of the use of resonating nanotubes in a field emission (FE) configuration to demodulate radio frequency signals. We particularly concentrate on how the demodulation depends on the variation of the field amplification factor during resonance. Analytical formulas describing the demodulation are derived as functions of the system parameters. Experiments using AM and FM demodulations in a transmission electron microscope are also presented with a determination of all the pertinent experimental parameters. Finally we discuss the use of CNTs undergoing FE as nanoantennae and the different geometries that could be used for optimization and implementation.

Vincent, P.; Poncharal, P.; Barois, T.; Perisanu, S.; Gouttenoire, V.; Frachon, H.; Lazarus, A.; de Langre, E.; Minoux, E.; Charles, M.; Ziaei, A.; Guillot, D.; Choueib, M.; Ayari, A.; Purcell, S. T.

2011-04-01

87

Anomalous Capacitive Sheath with Deep Radio-Frequency Electric-Field Penetration Igor D. Kaganovich  

E-print Network

cooling of the energetic electrons and an additional heating of the cold electrons. DOI: 10.1103/Phys in a distance of order the debye length, and reaches a value E0=" in the plasma, where " is the plasma dielectric constant. In many practical appli- cations, the value of the external electric field is large

Kaganovich, Igor

88

Study of Oxidative Stress in Human Lens Epithelial Cells Exposed to 1.8 GHz Radiofrequency Fields  

PubMed Central

Objectives The aims of the present study were to determine oxidative stress and to explore possible reasons of reactive oxygen species (ROS) increase in human lens epithelial (HLE) B3 cells exposed to low intensity 1.8 GHz radiofrequency fields (RF). Methods The HLE B3 cells were divided into RF exposure and RF sham-exposure groups. The RF exposure intensity was at specific absorption rate (SAR) of 2, 3, or 4 W/kg. The ROS levels were measured by a fluorescent probe 2?7?-dichlorofluorescin diacetate (DCFH-DA) assay in the HLE B3 cells exposed to 1.8 GHz RF for 0.5, 1, and 1.5 h. Lipid peroxidation and cellular viability were detected by an MDA test and Cell Counting Kit-8 (CCK-8) assays, respectively, in the HLE B3 cells exposed to 1.8 GHz RF for 6, 12, and 24 h, respectively. The mRNA expression of SOD1, SOD2, CAT, and GPx1 genes and the expression of SOD1, SOD2, CAT, and GPx1 proteins was measured by qRT-PCR and Western blot assays in the HLE B3 cells exposed to 1.8 GHz RF for 1 h. Results The ROS and MDA levels significantly increased (P<0.05) in the RF exposure group and that the cellular viability, mRNA expression of four genes, and expression of four proteins significantly decreased (P<0.05) compared with the RF sham-exposure group. Conclusions Oxidative stress is present in HLE B3 cells exposed to 1.8 GHz low-intensity RF and that the increased production of ROS may be related to down-regulation of four antioxidant enzyme genes induced by RF exposure. PMID:23991100

Ni, Shuang; Yu, Yibo; Zhang, Yidong; Wu, Wei; Lai, Kairan; Yao, Ke

2013-01-01

89

Gold-gold sulfide nanoshell as a novel intensifier for anti-tumor effects of radiofrequency fields  

PubMed Central

Objective(s): Several studies have been carried out to investigate the effect of various nanoparticles exposed to radiofrequency (RF) waves on cancerous tissues. In this study, a colon carcinoma tumor model was irradiated by RF in the presence of gold-gold sulfide (GGS) nanoshells. Materials and Methods: Synthesis and characterization of GGS nanoshells were initially performed. CT26 cells were subcutaneously injected into the flank of BALB/c mice to create the colon carcinoma tumor models. Then the tumors were subjected to different treatments. Treatment factors included intratumoral injection of GGS and RF radiation. Different groups were considered as control with no treatment, receiving GGS, RF irradiated and simultaneous administration of GGS and RF. Efficacy of the treatments was evaluated by daily monitoring of tumor volume and recording the relative changes in it, the time needed for a 5-fold increase in the volume of tumor (T5) and utilizing pathologic studies to determine the lost volume of the tumors. Results: In comparison with control group, tumor growth was not markedly inhibited in the groups receiving only GGS or RF, while in the group receiving GGS and RF, tumor growth was effectively inhibited compared with the other groups. In addition, the lost volume of the tumor and T5 was markedly higher in groups receiving GGS and RF compared with other groups. Conclusion: This study showed that RF radiation can markedly reduce the tumor growth in presence of GGS. Hence, it can be predicted that GGS nanoshells convert sub-lethal effects of noninvasive RF fields into lethal damages. PMID:25429343

Sadeghi, Hamid Reza; Bahreyni-Toosi, Mohammad Hossein; Meybodi, Naser Tayebi; Esmaily, Habibollah; Soudmand, Samaneh; Eshghi, Hossein; Soudmand, Samaneh; Sazgarnia, Ameneh

2014-01-01

90

PHYSICAL REVIEW B 83, 155446 (2011) Performance of field-emitting resonating carbon nanotubes as radio-frequency demodulators  

E-print Network

. Experiments using AM and FM demodulations in a transmission electron microscope are also presented, and the demodulator. They performed demodulation of both frequency modulated (FM) and amplitude modulated (AM) signals as radio-frequency demodulators P. Vincent,1,* P. Poncharal,1 T. Barois,1 S. Perisanu,1 V. Gouttenoire,1 H

Boyer, Edmond

91

An Exploration of the Effects of Strong Radio-Frequency Fields on MicroOrganisms in Aqueous Solutions  

Microsoft Academic Search

Radio-frequency power generators have been widely used in many industrial heating operations. Limited applications have been made in the treatment of food, where internally induced heat has been used to inactivate enzymes, as well as to pasteurize or sterilize the material.

G. H. Brown; W. C. Morrison

1956-01-01

92

Searching for the Perfect Wave: The Effect of Radiofrequency Electromagnetic Fields on Cells  

PubMed Central

There is a growing concern in the population about the effects that environmental exposure to any source of “uncontrolled” radiation may have on public health. Anxiety arises from the controversial knowledge about the effect of electromagnetic field (EMF) exposure to cells and organisms but most of all concerning the possible causal relation to human diseases. Here we reviewed those in vitro and in vivo and epidemiological works that gave a new insight about the effect of radio frequency (RF) exposure, relating to intracellular molecular pathways that lead to biological and functional outcomes. It appears that a thorough application of standardized protocols is the key to reliable data acquisition and interpretation that could contribute a clearer picture for scientists and lay public. Moreover, specific tuning of experimental and clinical RF exposure might lead to beneficial health effects. PMID:24681584

Gherardini, Lisa; Ciuti, Gastone; Tognarelli, Selene; Cinti, Caterina

2014-01-01

93

Variable rotation composite pulses for high resolution nuclear magnetic resonance using inhomogeneous magnetic and radiofrequency fields  

NASA Astrophysics Data System (ADS)

An approach toward high-resolution NMR spectroscopy on samples located outside the physical confines of a magnet (ex situ NMR), has recently been described [C.A. Meriles, D. Sakellariou, H. Heise, A.J. Moulé, A. Pines, Science 293 (2001) 82]. Nutation echoes are generated by a train of z-rotation pulses in the presence of spatially matched static and rf field gradients. These pulses were based on a combination of `perfect' ?/2 constant rotation composite pulses and `imperfect' ordinary pulses of variable length. Here we introduce a new class of `self-compensated' z-rotation composite pulses based only on variable rotation inversion pulses that lead to an rf dependent phase shift. Experiments and simulations show that these new pulses perform well at high B0 gradients and require less rf power than previous schemes.

Sakellariou, Dimitris; Meriles, Carlos A.; Moulé, Adam; Pines, Alexander

2002-09-01

94

Broadband magnetization transfer using moderate radio-frequency fields for NMR with very high static fields and spinning speeds  

E-print Network

static fields and spinning speeds Markus Weingarth a , Geoffrey Bodenhausen a,b , Piotr Tekely a at very high magnetic field strengths and spinning speeds. Experimental observations for a wide range of spinning frequencies 30 6 mrot 6 60 kHz and magnetic field strengths (B0 = 9.4, 17.6 and 21.2 T) are backed

95

Effect of high SARs produced by cell phone like radiofrequency fields on mollusk single neuron.  

PubMed

During exposure to the cell phone electromagnetic field (EMF), some neurons in the brain at areas of peak specific absorption rate (SAR) absorb more electromagnetic energy than is permitted by existing guidelines. The goal of the present work was to investigate the influence of cell phone-like EMF signal on excitability and memory processes in single neurons. A Transverse Electromagnetic Cell (TEM Cell) was used to expose single neurons of mollusk to the EMF. Finite-Difference Time-Domain (FDTD) method was used for modeling the TEM Cell and the EMF interactions with living nerve ganglion and neurons. Neuron electrophysiology was investigated using standard microelectrode technique. SAR deposited into the single neuron was calculated to be 8.2 W/kg with a temperature increment of 1.21°C. After acute exposure, the threshold of firing of action potentials (AP) was significantly decreased (p ? 0.001). Time of habituation to stimulation with the intracellular current injection was increased (p ? 0.003). These results indicate that acute exposure to EMF at high SARs impairs the ability of neurons to store information. PMID:23046101

Partsvania, B; Sulaberidze, T; Shoshiashvili, L

2013-03-01

96

New-generation radiofrequency technology.  

PubMed

Radiofrequency (RF) technology has become a standard treatment in aesthetic medicine with many indications due to its versatility, efficacy, and safety. It is used worldwide for cellulite reduction; acne scar revision; and treatment of hypertrophic scars and keloids, rosacea, and inflammatory acne in all skin types. However, the most common indication for RF technology is the nonablative tightening of tissue to improve skin laxity and reduce wrinkles. Radiofrequency devices are classified as unipolar, bipolar, or multipolar depending on the number of electrodes used. Additional modalities include fractional RF; sublative RF; phase-controlled RF; and combination RF therapies that apply light, massage, or pulsed electromagnetic fields (PEMFs). This article reviews studies and case series on these devices. Radiofrequency technology for aesthetic medicine has seen rapid advancements since it was used for skin tightening in 2003. Future developments will continue to keep RF technology at the forefront of the dermatologist's armamentarium for skin tightening and rejuvenation. PMID:23461058

Krueger, Nils; Sadick, Neil S

2013-01-01

97

Radiofrequency Gaseous Detection Device.  

PubMed

A radiofrequency gaseous detection device is proposed for use with instruments employing charged particle beams, such as electron microscopes and ion beam technologies, as well as for detection of ionizing radiations as in proportional counters. An alternating (oscillating) electromagnetic field in the radiofrequency range is applied in a gaseous environment of the instrument. Both the frequency and amplitude of oscillation are adjustable. The electron or ion beam interacts with a specimen and releases free electrons in the gas. Similarly, an ionizing radiation source releases free electrons in the gas. The free electrons are acted upon by the alternating electromagnetic field and undergo an oscillatory motion resulting in multiple collisions with the gas molecules, or atoms. At sufficiently low pressures, the oscillating electrons also collide with surrounding walls. These processes result in an amplified electron signal and an amplified photon signal in a controlled discharge. The amplified signals, which are proportional to the initial number of free electrons, are collected by suitable means for further processing and analysis. PMID:10675439

Danilatos

2000-01-01

98

LSU School of Dentistry Laser Safety : Clinical SAFETY PROCEDURES FOR LASER (NON-IONIZING) RADIATION  

E-print Network

.POLICY The LSU System policy is to limit exposure to personnel from non-ionizing radiation to levels Amplification by Stimulated Emission of Radiation." The effects of laser radiation are essentially the same system is one that is considered to be incapable of producing damaging radiation levels during operation

99

[Patient exposure to electromagnetic fields in magnetic resonance scanners: a review].  

PubMed

The use of non-ionizing electromagnetic fields in the low frequency end of the electromagnetic spectrum and static fields, radiofrequencies (RF), and microwaves is fundamental both in modern communication systems and in diagnostic medical imaging techniques like magnetic resonance imaging (MRI). The proliferation of these applications in recent decades has led to intense activity in developing regulations to guarantee their safety and to the establishment of guidelines and legal recommendations for the public, workers, and patients. In April 2012 it was foreseen that the European Parliament and Council would approve and publish a directive on the minimum health and safety requirements regarding the exposure of workers to the risks arising from electromagnetic fields, which would modify Directive 2004/40/EC. New studies related to the exposure to electromagnetic radiation and its impact on health published in recent years have led to a new postponement, and it is now foreseen that the directive will come into effect in October 2013. One of the most noteworthy aspects of the new version of the directive is the exclusion of the limits of occupational exposure to electromagnetic fields in the clinical use of MRI. In exchange for this exception, physicians and experts in protection against non-ionizing radiation are asked to make additional efforts to train workers exposed to non-ionizing radiation and to establish mechanisms to guarantee the correct application of non-ionizing electromagnetic fields in patients, along similar lines to the principles of justification and optimization established for ionizing radiation. On the basis of the most recently published studies, this article reviews some safety-related aspects to take into account when examining patients with MRI with high magnetic fields. PMID:24246885

Guibelalde del Castillo, E

2013-12-01

100

Summary of measured radiofrequency electric and magnetic fields (10 kHz to 30 GHz) in the general and work environment.  

PubMed

We have plotted data from a number of studies on the range of radiofrequency (RF) field levels associated with a variety of environmental and occupational sources. Field intensity is shown in units of volts/meter (V/m) for electric field strength and amps/meter (A/m) for magnetic field strength. Duty factors, modulation frequencies, and modulation indices are also reported for some sources. This paper is organized into seven sections, each cataloging sources into appropriate RF frequency bands from very-low frequency (VLF) to super-high frequency (SHF), and covers frequencies from 10 kHz to 30 GHz. Sources included in this summary are the following: Coast Guard navigational transmitters, a Navy VLF transmitter, computer visual display terminals (VDTs), induction stoves or range tops, industrial induction and dielectric heaters, radio and television broadcast transmitters, amateur and citizens band (CB) transmitters, medical diathermy and electrosurgical units, mobile and handheld transmitters, cordless and cellular telephones, microwave ovens, microwave terrestrial relay and satellite uplinks, and police, air traffic, and aircraft onboard radars. For the sources included in this summary, the strongest fields are found near industrial induction and dielectric heaters, and close to the radiating elements or transmitter leads of high power antenna systems. Handheld transmitters can produce near fields of about 500 V/m at the antenna. Fields in the general urban environment are principally associated with radio and TV broadcast services and measure about 0.1 V/m root-mean-square (rms). Peak fields from air traffic radars sampled in one urban environment were about 10 V/m, 300 times greater than the rms value of 0.03 V/m when the duty factor associated with antenna rotation and pulsing are factored in. PMID:9383245

Mantiply, E D; Pohl, K R; Poppell, S W; Murphy, J A

1997-01-01

101

2.3.2 Biological Effects of Non-Ionizing Radiations  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A 'Fundamentals and Data in Radiobiology, Radiation Biophysics, Dosimetry and Medical Radiological Protection' of Volume 7 'Medical Radiological Physics' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It contains the Subsection '2.3.2 Biological Effects of Non-Ionizing Radiations' of the Section '2.3 Biological Effects' of the Chapter '2 Radiation and Biological Effects' with the contents:

Bernhardt, J. H.

102

Evaluating the biological effects of intermittent 1.9 GHz pulse-modulated radiofrequency fields in a series of human-derived cell lines.  

PubMed

Several recent studies have suggested that radiofrequency (RF) fields may cause changes in a variety of cellular functions that may eventually lead to potential long-term health effects. In the present study, we have assessed the ability of non-thermal RF-field exposure to affect a variety of biological processes (including apoptosis, cell cycle progression, viability and cytokine production) in a series of human-derived cell lines (TK6, HL60 and Mono-Mac-6). Exponentially growing cells were exposed to intermittent (5 min on, 10 min off) 1.9 GHz pulse-modulated RF fields for 6 h at mean specific absorption rates (SARs) of 0, 1 and 10 W/kg. Concurrent negative (incubator) and positive (heat shock for 1 h at 43 degrees C) controls were included in each experiment. Immediately after the 6-h exposure period and 18 h after exposure, cell pellets were collected and analyzed for cell viability, the incidence of apoptosis, and alterations in cell cycle kinetics. The cell culture supernatants were assessed for the presence of a series of human inflammatory cytokines (TNFA, IL1B, IL6, IL8, IL10, IL12) using a cytometric bead array assay. No detectable changes in cell viability, cell cycle kinetics, incidence of apoptosis, or cytokine expression were observed in any of RF-field-exposed groups in any of the cell lines tested, relative to the sham controls. However, the positive (heat-shock) control samples displayed a significant decrease in cell viability, increase in apoptosis, and alteration in cell cycle kinetics (G(2)/M block). Overall, we found no evidence that non-thermal RF-field exposure could elicit any detectable biological effect in three human-derived cell lines. PMID:17214515

Chauhan, V; Mariampillai, A; Kutzner, B C; Wilkins, R C; Ferrarotto, C; Bellier, P V; Marro, L; Gajda, G B; Lemay, E; Thansandote, A; McNamee, J P

2007-01-01

103

Monopolar radiofrequency skin tightening.  

PubMed

The development of nonablative monopolar capacitive radiofrequency technology (ThermaCool System, Thermage, Inc., Hayward, California) has contributed to the noninvasive trend in facial skin rejuvenation. In contrast to traditional ablative resurfacing techniques, the ThermaCool System protects the skin surface from injury while selectively heating the underlying dermis. Preservation of epidermal integrity minimizes recovery and the risk of complications. Published clinical evidence documents the efficacy of monopolar capacitive radiofrequency skin tightening and supports its use for mild to moderate facial skin laxity and rhytides. Currently, monopolar capacitive radiofrequency represents the gold standard of treatments designed to tighten skin in a noninvasive fashion. PMID:17544932

Abraham, Manoj T; Mashkevich, Grigoriy

2007-05-01

104

Radiofrequency electromagnetic fields emitted from base stations of DECT cordless phones and the risk of glioma and meningioma (Interphone Study Group, Germany).  

PubMed

The objective of this study was to test the hypothesis that exposure to continuous low-level radiofrequency electromagnetic fields (RF EMFs) increases the risk of glioma and meningioma. Participants in a population-based case-control study in Germany on the risk of brain tumors in relation to cellular phone use were 747 incident brain tumor cases between the ages of 30 and 69 years and 1494 matched controls. The exposure measure of this analysis was the location of a base station of a DECT (Digital Enhanced Cordless Telecommunications) cordless phone close to the bed, which was used as a proxy for continuous low-level exposure to RF EMFs during the night. Estimated odds ratios were 0.82 (95% confidence interval: 0.29-2.33) for glioma and 0.83 (0.29-2.36) for meningioma. There was also no increasing risk observed with duration of exposure to DECT cordless phone base stations. Although the study was limited due to the small number of exposed subjects, it is still a first indication that residential low-level exposure to RF EMFs may not pose a higher risk of brain tumors. PMID:16808597

Schüz, Joachim; Böhler, Eva; Schlehofer, Brigitte; Berg, Gabriele; Schlaefer, Klaus; Hettinger, Iris; Kunna-Grass, Katharina; Wahrendorf, Jürgen; Blettner, Maria

2006-07-01

105

Exposure to radio-frequency electromagnetic fields from broadcast transmitters and risk of childhood cancer: a census-based cohort study.  

PubMed

We investigated the association between exposure to radio-frequency electromagnetic fields (RF-EMFs) from broadcast transmitters and childhood cancer. First, we conducted a time-to-event analysis including children under age 16 years living in Switzerland on December 5, 2000. Follow-up lasted until December 31, 2008. Second, all children living in Switzerland for some time between 1985 and 2008 were included in an incidence density cohort. RF-EMF exposure from broadcast transmitters was modeled. Based on 997 cancer cases, adjusted hazard ratios in the time-to-event analysis for the highest exposure category (>0.2 V/m) as compared with the reference category (<0.05 V/m) were 1.03 (95% confidence interval (CI): 0.74, 1.43) for all cancers, 0.55 (95% CI: 0.26, 1.19) for childhood leukemia, and 1.68 (95% CI: 0.98, 2.91) for childhood central nervous system (CNS) tumors. Results of the incidence density analysis, based on 4,246 cancer cases, were similar for all types of cancer and leukemia but did not indicate a CNS tumor risk (incidence rate ratio = 1.03, 95% CI: 0.73, 1.46). This large census-based cohort study did not suggest an association between predicted RF-EMF exposure from broadcasting and childhood leukemia. Results for CNS tumors were less consistent, but the most comprehensive analysis did not suggest an association. PMID:24651167

Hauri, Dimitri D; Spycher, Ben; Huss, Anke; Zimmermann, Frank; Grotzer, Michael; von der Weid, Nicolas; Spoerri, Adrian; Kuehni, Claudia E; Röösli, Martin

2014-04-01

106

Reduction of Averaging Time for Evaluation of Human Exposure to Radiofrequency Electromagnetic Fields from Cellular Base Stations  

NASA Astrophysics Data System (ADS)

In order to determine exposure compliance with the electromagnetic fields from a base station's antenna in the far-field region, we should calculate the spatially averaged field value in a defined space. This value is calculated based on the measured value obtained at several points within the restricted space. According to the ICNIRP guidelines, at each point in the space, the reference levels are averaged over any 6min (from 100kHz to 10GHz) for the general public. Therefore, the more points we use, the longer the measurement time becomes. For practical application, it is very advantageous to spend less time for measurement. In this paper, we analyzed the difference of average values between 6min and lesser periods and compared it with the standard uncertainty for measurement drift. Based on the standard deviation from the 6min averaging value, the proposed minimum averaging time is 1min.

Kim, Byung Chan; Park, Seong-Ook

107

Resonant radiofrequency effects in spin chemistry  

NASA Astrophysics Data System (ADS)

The effect of a magnetic field on the exciplex fluorescence from the photochemical reaction of pyrene with 1,3-dicyanobenzene is influenced by radiation in the low radiofrequency region. It is suggested that resonant effects are observed when the radiation is applied at the frequencies of the hyperfine couplings.

Jackson, R. J.; McLauchlan, K. A.; Woodward, J. R.

1995-04-01

108

Studies of the electric-field distribution in biological bodies - experimental dosimetry at radiofrequencies. Final report, December 1981-September 1985  

SciTech Connect

The objective of the project was to develop and evaluate a computer-controlled system for measurements of the spatial distribution of the specific absorption rate (SAR) in biological bodies and to perform measurements on a model of the human body, with particular emphasis on exposures in the near-field of antennas. Far-Field Exposures. At frequencies above 160 MHz, in spite of large gradieints, local values of the SAR are only about 20 times higher than the whole-body average SAR for homogeneous models of human body. However, an additional increase by a factor of 4-5 can be anticipated at interfaces of high water content tissues with air (gas) pockets and low-water-content tissues. The existence of large gradients and high local SARs, as confirmed by the results, further supports an accepted view that biological effects at relatively low average SARs are due to thermal interactions. For humans, high SARs occur in the neck, and the ratio of the SAR in the neck to the whole-body average increases with frequency. Near-field Exposures. Based on the experimental findings the authors believe that, because of the spatial pattern of energy deposition, the whole-body average SAR is not an adequate dosimetric measure for near-field exposures.

Stuchly, S.S.; Stuchly, M.A.

1985-12-05

109

Radio-frequency electromagnetic field measurements for direct detection of electron Bernstein waves in a torus plasma  

SciTech Connect

To identify the mode-converted electron Bernstein wave (EBW) in a torus plasma directly, we have developed an interferometry system, in which a diagnostic microwave injected outside of the plasma column was directly detected with the probing antenna inserted into the plasma. In this work, plasma production and heating are achieved with 2.45 GHz, 2.5 kW electron cyclotron heating (ECH), whereas diagnostics are carried out with a lower power (10 W) separate frequency (1-2.1 GHz) microwave. Three components, i.e., two electromagnetic (toroidal and poloidal directions) and an electrostatic (if refractive index is sufficiently higher than unity, it corresponds to radial component), of ECRF electric field are simultaneously measured with three probing antennas, which are inserted into plasma. Selectivities of each component signal were checked experimentally. Excitation antennas have quite high selectivity of direction of linear polarization. As probing antennas for detecting electromagnetic components, we employed a monopole antenna with a length of 35 mm, and the separation of the poloidal (O-wave) and toroidal (X-wave) components of ECRF electric field could be available with this antenna. To detect EBW, which is an electrostatic wave, a small tip (1 mm) antenna was used. As the preliminary results, we detected signals that have three characteristics of EBW, i.e., short wavelength, backward propagation, and electrostatic.

Yatsuka, Eiichi; Kinjo, Kiyotake; Morikawa, Junji; Ogawa, Yuichi [Graduate School of Frontier Sciences, University of Tokyo, Chiba 277-8568 (Japan)

2009-02-15

110

[Dynamics of morphological changes in the spinal cord following exposure to non-ionizing microwave radiation].  

PubMed

The structure of different portions (cervical, thoracic, lumbar, sacral and coccygeal) of the spinal cord were studied in the experiments on 50 animals with the use of the Nissl, Zimmermann, Cajal and other methods on days 1, 10, 20 and 30 after exposure to non-ionizing microwave radiation (NMI). Single exposure to NMI (wave length 12.6 cm, intensity 400-500 mW/cm2) for one hour (cats) or four hours (dogs) produces a severe distress of glial neurones and cells, which is marked by the appearance of dystrophic processes along the entire spinal cord. The disease progresses, leading to abnormalities of motor and other physiological functions of the body. PMID:6850099

Belokrinitski?, V S

1983-05-01

111

Superconducting radiofrequency window assembly  

Microsoft Academic Search

The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40)

Harry L. Phillips; Thomas S. Elliott

1997-01-01

112

Superconductive radiofrequency window assembly  

Microsoft Academic Search

The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The SRF window assembly has a superconducting metal-ceramic design. The SRF window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron

H. L. Phillips; T. S. Elliott

1998-01-01

113

Superconducting radiofrequency window assembly  

Microsoft Academic Search

The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly has a superconducting metal-ceramic design. The srf window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron

H. L. Phillips; T. S. Elliott

1997-01-01

114

Superconductive radiofrequency window assembly  

Microsoft Academic Search

The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40)

Harry Lawrence Phillips; Thomas S. Elliott

1998-01-01

115

Self-reporting of symptom development from exposure to radiofrequency fields of wireless smart meters in victoria, australia: a case series.  

PubMed

Context • In 2006, the government in the state of Victoria, Australia, mandated the rollout of smart meters in Victoria, which effectively removed a whole population's ability to avoid exposure to human-made high-frequency nonionizing radiation. This issue appears to constitute an unprecedented public health challenge for Victoria. By August 2013, 142 people had reported adverse health effects from wireless smart meters by submitting information on an Australian public Web site using its health and legal registers. Objective • The study evaluated the information in the registers to determine the types of symptoms that Victorian residents were developing from exposure to wireless smart meters. Design • In this case series, the registers' managers eliminated those cases that did not clearly identify the people providing information by name, surname, postal address, and/or e-mail to make sure that they were genuine registrants. Then they obtained consent from participants to have their deidentified data used to compile the data for the case series. The author later removed any individual from outside of Victoria. Participants • The study included 92 residents of Victoria, Australia. Outcome Measures • The author used her medical experience and judgment to group symptoms into clinically relevant clusters (eg, pain in the head was grouped with headache, tinnitus was grouped with ringing in the ears). The author stayed quite close to the wording used in the original entries. She then calculated total numbers and percentages for each symptom cluster. Percentages were rounded to the nearest whole number.Results • The most frequently reported symptoms from exposure to smart meters were (1) insomnia, (2) headaches, (3) tinnitus, (4) fatigue, (5) cognitive disturbances, (6) dysesthesias (abnormal sensation), and (7) dizziness. The effects of these symptoms on people's lives were significant. Conclusions • Review of some key studies, both recent and old (1971), reveals that the participants' symptoms were the same as those reported by people exposed to radiofrequency fields emitted by devices other than smart meters. Interestingly, the vast majority of Victorian cases did not state that they had been sufferers of electromagnetic hypersensitivity syndrome (EHS) prior to exposure to the wireless meters, which points to the possibility that smart meters may have unique characteristics that lower people's threshold for symptom development. PMID:25478801

Lamech, Federica

2014-11-01

116

Personal radiofrequency electromagnetic field measurements in The Netherlands: exposure level and variability for everyday activities, times of day and types of area.  

PubMed

Knowledge of the exposure to radiofrequency electromagnetic fields is necessary for epidemiological studies on possible health effects. The main goal of this study is to determine the exposure level and spatial and temporal variances during 39 everyday activities in 12 frequency bands used in mobile telecommunication and broadcasting. Therefore, 24 h measurements were gathered from 98 volunteers living in or near Amsterdam and Purmerend, The Netherlands. They carried an activity diary to be kept to the minute, a GPS logger sampling at an interval of 1 s, and an EME Spy exposimeter with a detection limit of 0.0066 mW/m(2) sampling at an interval of 10s in 12 frequency bands. The mean exposure over 24 h, excluding own mobile phone use, was 0.180 mW/m(2). During daytime exposure was about the same, but during night it was about half, and in the evening it was about twice as high. The main contribution to environmental exposure (calling by participant not included) is from calling with mobile phones (37.5%), from cordless DECT phones and their docking stations (31.7%), and from the base stations (12.7%). The exposure to mobile phone base stations increases with the percentage of urban ground use, which is an indication for high people density. In agreement, the highest mean exposure relates to the activities with high people density, such as travelling by public transport, visiting social events, pubs or shopping malls. Exposure at home depends mainly on exposure from people calling in the neighbourhood of the participant and thus on the number of persons in a household. In addition just the possession of DECT docking stations leads to exposure as most models transmit continuously in stand-by. Also wireless internet routers continuously transmit in the WiFi band. Though the highest exposure peaks in the WiFi band, up to 0.265 W/m(2), come from stray radiation of microwave ovens. The mean total exposure largely depends on phone calls of a high exposure level and short duration. These calls lead to potentially high contrasts as well in exposure levels between sessions of the same activity as between persons, thus posing a challenge for personal exposure prediction. PMID:22906414

Bolte, John F B; Eikelboom, Tessa

2012-11-01

117

Radiofrequency plasma antenna generated by femtosecond laser filaments in air  

SciTech Connect

We demonstrate tunable radiofrequency emission from a meter-long linear plasma column produced in air at atmospheric pressure. A short-lived plasma column is initially produced by femtosecond filamentation and subsequently converted into a long-lived discharge column by application of an external high voltage field. Radiofrequency excitation is fed to the plasma by induction and detected remotely as electromagnetic radiation by a classical antenna.

Brelet, Y.; Houard, A.; Point, G.; Prade, B.; Carbonnel, J.; Andre, Y.-B.; Mysyrowicz, A. [Laboratoire d'Optique Appliquee, ENSTA ParisTech, Ecole Polytechnique, CNRS, 91761 Palaiseau (France); Arantchouk, L. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, CNRS, Palaiseau (France); Pellet, M. [Etat-major de la Marine Nationale, Paris (France)

2012-12-24

118

Radiofrequency ablation of solid tumors.  

PubMed

Radiofrequency ablation of solid tumors is produced by frictional heating caused when ions in the tissue attempt to follow the changing directions of a high-frequency alternating current. The radiofrequency probe is typically placed under ultrasound guidance, and the ablation is performed with real-time ultrasound monitoring. Radiofrequency ablation has been demonstrated to be effective in the treatment of unresectable hepatic tumors, and promising results have also been obtained in tumors of the lung, bone, brain, kidney, prostate gland, and pancreas. Most recently, radiofrequency ablation has been tested in the treatment of invasive breast tumors. A preliminary study reported that intraoperative radiofrequency ablation causes invasive breast cancer cell death in patients with locally advanced breast cancer. An ongoing study is investigating the use of radiofrequency ablation for the treatment of breast tumors 2 cm or less in diameter. PMID:11324771

Mirza, A N; Fornage, B D; Sneige, N; Kuerer, H M; Newman, L A; Ames, F C; Singletary, S E

2001-01-01

119

Occupational exposure to ionizing and non-ionizing radiation and risk of non-Hodgkin lymphoma  

Microsoft Academic Search

Objective  To investigate the association between occupational exposure to ionizing, ultraviolet (UV), radiofrequency (RF) and extremely\\u000a low frequency (ELF) radiation and risk of developing non-Hodgkin lymphoma (NHL) in a population-based case-control study.\\u000a \\u000a \\u000a \\u000a Methods  The study population consisted of 694 NHL cases, first diagnosed between 1 January 2000 and 31 August 2001, and 694 controls\\u000a from two regions in Australia, matched by age,

Ken K. Karipidis; Geza Benke; Malcolm R. Sim; Timo Kauppinen; Anne Kricker; Ann Maree Hughes; Andrew E. Grulich; Claire M. Vajdic; John Kaldor; Bruce Armstrong; Lin Fritschi

2007-01-01

120

Radiofrequency Ablation of Lung Tumors  

MedlinePLUS

Radiofrequency Ablation (RFA) of Lung Tumors • Overview View larger with caption Drawing of a 4-prong needle electrode. An electric current has caused heat around ... Radiofrequency ablation is used to treat early-stage lung cancer and tumors that have spread to the ...

121

Radiofrequency in cosmetic dermatology.  

PubMed

The demand for noninvasive methods of facial and body rejuvenation has experienced exponential growth over the last decade. There is a particular interest in safe and effective ways to decrease skin laxity and smooth irregular body contours and texture without downtime. These noninvasive treatments are being sought after because less time for recovery means less time lost from work and social endeavors. Radiofrequency (RF) treatments are traditionally titrated to be nonablative and are optimal for those wishing to avoid recovery time. Not only is there minimal recovery but also a high level of safety with aesthetic RF treatments. PMID:24267424

Beasley, Karen L; Weiss, Robert A

2014-01-01

122

Minimizing the effects of radio-frequency heating in multidimensional NMR experiments.  

PubMed

Application of radio-frequency power in multidimensional NMR experiments can significantly increase the sample temperature compared to that of the surrounding gas flow. Radio-frequency heating effects become more severe at higher magnetic field strengths and ionic strengths. The effects are particularly noticeable for experiments that utilize 1H and/or 13C isotropic mixing and broadband decoupling. If radio-frequency power is applied during the systematically increasing evolution period t1, the sample temperature can change with t1 and thereby cause line-shape distortions. Such distortions are easily avoided by ensuring that the average radio-frequency power remains constant during the entire experiment. PMID:8111234

Wang, A C; Bax, A

1993-11-01

123

Longevity of radiofrequency identification device microchips in citrus trees  

Technology Transfer Automated Retrieval System (TEKTRAN)

Long-term identification of individual plants in the field is an important part of many types of botanical and horticultural research. In a previous report, we described methods for using implanted radiofrequency (RFID) microchips to tag citrus trees for field research. This report provides an upd...

124

Superconductive radiofrequency window assembly  

DOEpatents

The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The SRF window assembly has a superconducting metal-ceramic design. The SRF window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron beam welded to frame. A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the SRF window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator. 11 figs.

Phillips, H.L.; Elliott, T.S.

1998-05-19

125

Radiofrequency attenuator and method  

DOEpatents

Radiofrequency attenuator and method. The attenuator includes a pair of transparent windows. A chamber between the windows is filled with molten salt. Preferred molten salts include quarternary ammonium cations and fluorine-containing anions such as tetrafluoroborate (BF.sub.4.sup.-), hexafluorophosphate (PF.sub.6.sup.-), hexafluoroarsenate (AsF.sub.6.sup.-), trifluoromethylsulfonate (CF.sub.3SO.sub.3.sup.-), bis(trifluoromethylsulfonyl)imide ((CF.sub.3SO.sub.2).sub.2N.sup.-), bis(perfluoroethylsulfonyl)imide ((CF.sub.3CF.sub.2SO.sub.2).sub.2N.sup.-) and tris(trifluoromethylsulfonyl)methide ((CF.sub.3SO.sub.2).sub.3 C.sup.-). Radicals or radical cations may be added to or electrochemically generated in the molten salt to enhance the RF attenuation.

Warner, Benjamin P. (Los Alamos, NM); McCleskey, T. Mark (Los Alamos, NM); Burrell, Anthony K. (Los Alamos, NM); Agrawal, Anoop (Tucson, AZ); Hall, Simon B. (Palmerston North, NZ)

2009-11-10

126

Radiofrequency attenuator and method  

DOEpatents

Radiofrequency attenuator and method. The attenuator includes a pair of transparent windows. A chamber between the windows is filled with molten salt. Preferred molten salts include quarternary ammonium cations and fluorine-containing anions such as tetrafluoroborate (BF.sub.4.sup.-), hexafluorophosphate (PF.sub.6.sup.-), hexafluoroarsenate (AsF.sub.6.sup.-), trifluoromethylsulfonate (CF.sub.3SO.sub.3.sup.-), bis(trifluoromethylsulfonyl)imide ((CF.sub.3SO.sub.2).sub.2N.sup.-), bis(perfluoroethylsulfonyl)imide ((CF.sub.3CF.sub.2SO.sub.2).sub.2N.sup.-) and tris(trifluoromethylsulfonyl)methide ((CF.sub.3SO.sub.2).sub.3C.sup.-). Radicals or radical cations may be added to or electrochemically generated in the molten salt to enhance the RF attenuation.

Warner, Benjamin P. (Los Alamos, NM); McCleskey, T. Mark (Los Alamos, NM); Burrell, Anthony K. (Los Alamos, NM); Agrawal, Anoop (Tucson, AZ); Hall, Simon B. (Palmerston North, NZ)

2009-01-20

127

47 CFR 2.1093 - Radiofrequency radiation exposure evaluation: portable devices.  

...Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz...Criteria for Radiofrequency Electromagnetic Fields,” NCRP Report...safety program in a work environment. (ii) Visual advisories...population/uncontrolled environments as defined above....

2014-10-01

128

Use of Semiflexible Applicators for Radiofrequency Ablation of Liver Tumors  

Microsoft Academic Search

Purpose  To evaluate the feasibility and potential advantages of the radiofrequency ablation of liver tumors using new MRI-compatible\\u000a semiflexible applicators in a closed-bore high-field MRI scanner.\\u000a \\u000a \\u000a \\u000a Methods  We treated 8 patients with 12 malignant liver tumors of different origin (5 colorectal carcinoma, 2 cholangiocellular carcinoma,\\u000a 1 breast cancer) under MRI guidance. Radiofrequency ablation (RFA) was performed using 5 cm Rita Starburst Semi-Flex

G. Gaffke; B. Gebauer; F. D. Knollmann; T. Helmberger; J. Ricke; H. Oettle; R. Felix; C. Stroszczynski

2006-01-01

129

Validation of self-reported start year of mobile phone use in a Swedish case-control study on radiofrequency fields and acoustic neuroma risk.  

PubMed

The possible effect of radiofrequency exposure from mobile phones on tumor risk has been studied since the late 1990s. Yet, empirical information about recall of the start of mobile phone use among adult cases and controls has never been reported. Limited knowledge about recall errors hampers interpretations of the epidemiological evidence. We used network operator data to validate the self-reported start year of mobile phone use in a case-control study of mobile phone use and acoustic neuroma risk. The answers of 96 (29%) cases and 111 (22%) controls could be included in the validation. The larger proportion of cases reflects a more complete and detailed reporting of subscription history. Misclassification was substantial, with large random errors, small systematic errors, and no significant differences between cases and controls. The average difference between self-reported and operator start year was -0.62 (95% confidence interval: -1.42, 0.17) years for cases and -0.71 (-1.50, 0.07) years for controls, standard deviations were 3.92 and 4.17 years, respectively. Agreement between self-reported and operator-recorded data categorized into short, intermediate and long-term use was moderate (kappa statistic: 0.42). Should an association exist, dilution of risk estimates and distortion of exposure-response patterns for time since first mobile phone use could result from the large random errors in self-reported start year. Retrospective collection of operator data likely leads to a selection of "good reporters", with a higher proportion of cases. Thus, differential recall cannot be entirely excluded. PMID:25352163

Pettersson, David; Bottai, Matteo; Mathiesen, Tiit; Prochazka, Michaela; Feychting, Maria

2015-01-01

130

Statistical Analysis of Real Radiofrequencies Exposure in a Realistic Environment  

E-print Network

of the distribution of FM, TV, and GSM signals in a realistic electromagnetic environment in Indoor distinguishing of emissions. Usually, electromagnetic-field measurements are performed in a real environment with a spectrumStatistical Analysis of Real Radiofrequencies Exposure in a Realistic Environment Zaher MAHFOUZ

Paris-Sud XI, Université de

131

Principles and practice of radiofrequency neurolysis  

Microsoft Academic Search

The history, theory, and methods of modern radiofrequency lesioning are reviewed.Various considerations are advanced including\\u000a suggestion of inclusion and exclusion criteria for treatment, methods of ensuring accuracy of radiofrequency lesioning, and\\u000a potential side effects of radiofrequency lesioning.The authors also review the reasons why lesioning may be ineffective for\\u000a some patients. Chronic pain syndromes that may benefit from treatment with radiofrequency

Michael Hammer; William Meneese

1998-01-01

132

Dosimetry associated with exposure to non-ionizing radiation: very low frequency to microwaves.  

PubMed

The interpretation of the effects in biological systems exposed to electromagnetic (EM) fields requires knowledge of the internal fields and absorbed energy. The quantification of the specific absorption rate (SAR) is called dosimetry. The SAR given in units of watts per kilogram is a complex function of the source configuration, shape and size of the exposed subjects, orientation of the subject with respect to the source, and the frequency. The average and maximum SAR in the exposed subject may vary over many orders of magnitude for a given exposure level. In order to relate observed biological effects in exposed laboratory animals to safe exposure levels for man, both the fields within the environment and SAR within the exposed tissues must be determined. The environmental fields and the SAR can often be determined from EM theory, but in most cases one must rely on instrumentation such as field survey meters for quantifying the exposure fields and electric field probes, thermocouples, thermistors, fiber optic probes, thermography, and calorimetry for quantifying the SAR in the tissues or equivalent models. A combination of techniques, each valid for a particular model over a particular frequency range, have been used to determine average and peak SARs in humans and animals exposed to plane wave radiation. Though it has been considerably more difficult to quantify these quantities for near field and partial-body exposure conditions, progress is continually being made in this area. PMID:3679822

Guy, A W

1987-12-01

133

Radiofrequency thermal ablationof hepatic metastases  

Microsoft Academic Search

Percutaneous radiofrequency (RF) ablation is a promising therapeutic option for liver metastases, which may result in prolonged survival and chance for cure. Recent technological advancements provide larger coagulation volumes, allowing treatment of medium- and large-size metastases. Candidates are patients with metachronous liver metastases from colorectal or other primary cancers, in whom surgery is contraindicated and with one to four nodules

Luigi Solbiati; Tiziana Ierace; Massimo Tonolini; Valeria Osti; Luca Cova

2001-01-01

134

BIOLOGICAL EFFECTS OF RADIOFREQUENCY RADIATION  

EPA Science Inventory

The document presents a critical review of the available literature on the biological effects of radiofrequency (RF) radiation. The objective was to summarize and evaluate the existing database for use in developing RF-radiation exposure guidance for the general public. The frequ...

135

Bipolar radiofrequency for facial rejuvenation.  

PubMed

Combined approaches using light and radiofrequency represent an innovative approach to whole body rejuvenation. Synergistic results using combined modalities are a major advantage of this technology. In addition, by using lower levels of light energy, darker skin phenotypes can be treated with a lower risk for pigment dyschromia and scarring. PMID:17544931

Sadick, Neil

2007-05-01

136

Radiofrequency ablation of renal tumors  

Microsoft Academic Search

Percutaneous thermal ablation is increasingly applied in the therapy of renal tumors. Various techniques are available, allowing a safe and accurate therapy of renal tumors either using hyperthermia such as radiofrequency ablation (RFA), laser-induced thermotherapy (LITT) and microwave ablation (MW) or by hypothermia (cryoablation). As thermal ablation is a minimally invasive and nephron-sparing procedure, it is ideally suited for patients

Andreas H. Mahnken; Rolf W. Günther; Josef Tacke

2004-01-01

137

[Safety of use assessment in a radio-frequency medical device].  

PubMed

The authors assessed the operating safety physical parameters of a bipolar radiofrequency device for aesthetic purposes. According to both Italian and EU guidelines, the authors considered: magnetic field environmental emission levels, electricity induced in the opertator's limbs, operator's exposure and radiofrequency specific absorbance rate (SAR) in treated tissues. Measurements were carried out with isotropic sensors and an inductive current indicator. Results pointed out excellent safety levels regarding environment, operators and patients as well, although such radiofrequency equipment cannot be used on patients with pacemakers, neurostimulators and other vital function controlling devices. PMID:25369715

Nicoletti, Giovanni; Coppola, Antonio; Di Liberto, Riccardo; Faga, Angela; Scevola, Silvia

2014-01-01

138

Teratogenic effects of 27. 12 MHz radiofrequency radiation in rats  

Microsoft Academic Search

High-intensity 27.12 MHz radiofrequency (RF) radiation was determined to be teratogenic in rats during most of the gestation period. Eight groups of pregnant rats were exposed to a magnetic field strength of 55 amps\\/meter and an electric field strength of 300 volts\\/meter on gestation days 1, 3, 5, 7, 9, 11, 13, or 15. Exposures ceased once the dam's colonic

Joseph M. Lary; David L. Conover; Edward D. Foley; Peggy L. Hanser

1982-01-01

139

Non-Ionizing Radiation: Evaluation of General Public's Exposures in Greece and Albania  

NASA Astrophysics Data System (ADS)

With the growth of electric power generation and transmission, the development of new telecommunication systems and advances in medical and industrial applications, humans are increasingly exposed to electromagnetic fields (EMF). The need to understand the potentially harmful effects of EMF on human health has been met by several decades of research, but the development of exposure standards is more recent and a variety of national standards now exist. A number of organizations have formulated guidelines establishing limits for occupational and residential EMF exposure. The exposure limits for EMF developed by the ICNIRP were based in large reviews of scientific literature, including thermal and non-thermal effects.

Ylli, Fatos; Karabetsos, Efthymios; Dollani, Kostandin; Koutounidis, Dimitris

2010-01-01

140

Red eyes of PC users due to the effects of non-ionized electromagnetic radiation  

NASA Astrophysics Data System (ADS)

This work presents an experimental study of the appearance of redness on the surface of the eye on PC users due to the exposition to low frequency electromagnetic fields LF, VLF and ELF that VDTs with TRC monitors radiate, based on the measurement of the level of pigmentation and temperature. The total of the samples was analyzed using digital processing of images extracting the component of red color of the sclera. We demonstrated that under the same ergonomics and operating conditions, TRC monitors cause a higher heating and greater pigmentation in the users eyes as compared to LCD screens, due to the higher low frequency radiation.

Soto-Bernal, J. J.; Huizar-Gonzalez, A. A.; Rosales-Candelas, I.; Cardoza-Rodriguez, A. R.

2007-03-01

141

Superconducting Radio-Frequency Cavities  

NASA Astrophysics Data System (ADS)

Superconducting cavities have been operating routinely in a variety of accelerators with a range of demanding applications. With the success of completed projects, niobium cavities have become an enabling technology, offering upgrade paths for existing facilities and pushing frontier accelerators for nuclear physics, high-energy physics, materials science, and the life sciences. With continued progress in basic understanding of radio-frequency superconductivity, the performance of cavities has steadily improved to approach theoretical capabilities.

Padamsee, Hasan S.

2014-10-01

142

21 CFR 882.4400 - Radiofrequency lesion generator.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Radiofrequency lesion generator. 882.4400 Section 882.4400... § 882.4400 Radiofrequency lesion generator. (a) Identification. A radiofrequency lesion generator is a device used to produce...

2011-04-01

143

21 CFR 882.4400 - Radiofrequency lesion generator.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 false Radiofrequency lesion generator. 882.4400 Section 882.4400... § 882.4400 Radiofrequency lesion generator. (a) Identification. A radiofrequency lesion generator is a device used to produce...

2012-04-01

144

21 CFR 882.4400 - Radiofrequency lesion generator.  

...2014-04-01 false Radiofrequency lesion generator. 882.4400 Section 882.4400... § 882.4400 Radiofrequency lesion generator. (a) Identification. A radiofrequency lesion generator is a device used to produce...

2014-04-01

145

21 CFR 882.4400 - Radiofrequency lesion generator.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Radiofrequency lesion generator. 882.4400 Section 882.4400... § 882.4400 Radiofrequency lesion generator. (a) Identification. A radiofrequency lesion generator is a device used to produce...

2010-04-01

146

21 CFR 882.4400 - Radiofrequency lesion generator.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Radiofrequency lesion generator. 882.4400 Section 882.4400... § 882.4400 Radiofrequency lesion generator. (a) Identification. A radiofrequency lesion generator is a device used to produce...

2013-04-01

147

47 CFR 2.801 - Radiofrequency device defined.  

Code of Federal Regulations, 2013 CFR

...is capable of emitting radiofrequency energy by radiation, conduction, or other means. Radiofrequency devices include, but are...thereof which in use emits radiofrequency energy by radiation, conduction, or other means. [35 FR 7898, May 22, 1970, as...

2013-10-01

148

47 CFR 2.801 - Radiofrequency device defined.  

Code of Federal Regulations, 2011 CFR

...is capable of emitting radiofrequency energy by radiation, conduction, or other means. Radiofrequency devices include, but are...thereof which in use emits radiofrequency energy by radiation, conduction, or other means. [35 FR 7898, May 22, 1970, as...

2011-10-01

149

47 CFR 2.801 - Radiofrequency device defined.  

Code of Federal Regulations, 2010 CFR

...is capable of emitting radiofrequency energy by radiation, conduction, or other means. Radiofrequency devices include, but are...thereof which in use emits radiofrequency energy by radiation, conduction, or other means. [35 FR 7898, May 22, 1970, as...

2010-10-01

150

47 CFR 2.801 - Radiofrequency device defined.  

...is capable of emitting radiofrequency energy by radiation, conduction, or other means. Radiofrequency devices include, but are...thereof which in use emits radiofrequency energy by radiation, conduction, or other means. [35 FR 7898, May 22, 1970, as...

2014-10-01

151

47 CFR 2.801 - Radiofrequency device defined.  

Code of Federal Regulations, 2012 CFR

...is capable of emitting radiofrequency energy by radiation, conduction, or other means. Radiofrequency devices include, but are...thereof which in use emits radiofrequency energy by radiation, conduction, or other means. [35 FR 7898, May 22, 1970, as...

2012-10-01

152

Pulsed radiofrequency neurotomy: advances in pain medicine  

Microsoft Academic Search

In the past three decades, radiofrequency neurotomy (RFN) has been established as a safe and effective treatment for facet\\u000a and sacroiliac arthropathy. However, early reports of deafferentation pain syndromes and motor deficit with the application\\u000a of radiofrequency lesions to other neural structures effectively halted further development of this technology for other applications\\u000a until recent years. Pulsed radiofrequency neurotomy (PRFN) represents

Farshad M. Ahadian

2004-01-01

153

Radio-frequency quadrupole linear accelerator  

SciTech Connect

The radio-frequency quadrupole (RFQ) is a new linear accelerator concept in which rf electric fields are used to focus, bunch, and accelerate the beam. Because the RFQ can provide strong focusing at low velocities, it can capture a high-current dc ion beam from a low-voltage source and accelerate it to an energy of 1 MeV/nucleon within a distance of a few meters. A recent experimental test at the Los Alamos Scientific Laboratory (LASL) has confirmed the expected performance of this structure and has stimulated interest in a wide variety of applications. The general properties of the RFQ are reviewed and examples of applications of this new accelerator are presented.

Wangler, T.P.; Stokes, R.H.

1980-01-01

154

Four-Sector Cylindrical Radio-Frequency Ion Trap  

NASA Technical Reports Server (NTRS)

Proposed linear radio-frequency ion trap consists of closed metal cylinder partitioned into four equal cylindrical-sector electrodes and two circular end electrodes. Features include relatively large ion-storage capacity and shielding against external fields. Used in frequency-standard laboratories to confine 199Hg+ ions electrodynamically in isolation from external environment. Similar to device described in "Linear Ion Trap for Atomic Clock" (NPO-17758).

Melbourne, Ruthann K.; Prestage, John D.; Maleki, Lutfollah

1992-01-01

155

Design and Evaluation of a Hybrid Radiofrequency Applicator for Magnetic Resonance Imaging and RF Induced Hyperthermia: Electromagnetic Field Simulations up to 14.0 Tesla and Proof-of-Concept at 7.0 Tesla  

PubMed Central

This work demonstrates the feasibility of a hybrid radiofrequency (RF) applicator that supports magnetic resonance (MR) imaging and MR controlled targeted RF heating at ultrahigh magnetic fields (B0?7.0T). For this purpose a virtual and an experimental configuration of an 8-channel transmit/receive (TX/RX) hybrid RF applicator was designed. For TX/RX bow tie antenna electric dipoles were employed. Electromagnetic field simulations (EMF) were performed to study RF heating versus RF wavelength (frequency range: 64 MHz (1.5T) to 600 MHz (14.0T)). The experimental version of the applicator was implemented at B0?=?7.0T. The applicators feasibility for targeted RF heating was evaluated in EMF simulations and in phantom studies. Temperature co-simulations were conducted in phantoms and in a human voxel model. Our results demonstrate that higher frequencies afford a reduction in the size of specific absorption rate (SAR) hotspots. At 7T (298 MHz) the hybrid applicator yielded a 50% iso-contour SAR (iso-SAR-50%) hotspot with a diameter of 43 mm. At 600 MHz an iso-SAR-50% hotspot of 26 mm in diameter was observed. RF power deposition per RF input power was found to increase with B0 which makes targeted RF heating more efficient at higher frequencies. The applicator was capable of generating deep-seated temperature hotspots in phantoms. The feasibility of 2D steering of a SAR/temperature hotspot to a target location was demonstrated by the induction of a focal temperature increase (?T?=?8.1 K) in an off-center region of the phantom. Temperature simulations in the human brain performed at 298 MHz showed a maximum temperature increase to 48.6C for a deep-seated hotspot in the brain with a size of (19×23×32)mm3 iso-temperature-90%. The hybrid applicator provided imaging capabilities that facilitate high spatial resolution brain MRI. To conclude, this study outlines the technical underpinnings and demonstrates the basic feasibility of an 8-channel hybrid TX/RX applicator that supports MR imaging, MR thermometry and targeted RF heating in one device. PMID:23613896

Winter, Lukas; Özerdem, Celal; Hoffmann, Werner; Santoro, Davide; Müller, Alexander; Waiczies, Helmar; Seemann, Reiner; Graessl, Andreas; Wust, Peter; Niendorf, Thoralf

2013-01-01

156

Design and evaluation of a hybrid radiofrequency applicator for magnetic resonance imaging and RF induced hyperthermia: electromagnetic field simulations up to 14.0 Tesla and proof-of-concept at 7.0 Tesla.  

PubMed

This work demonstrates the feasibility of a hybrid radiofrequency (RF) applicator that supports magnetic resonance (MR) imaging and MR controlled targeted RF heating at ultrahigh magnetic fields (B0?7.0T). For this purpose a virtual and an experimental configuration of an 8-channel transmit/receive (TX/RX) hybrid RF applicator was designed. For TX/RX bow tie antenna electric dipoles were employed. Electromagnetic field simulations (EMF) were performed to study RF heating versus RF wavelength (frequency range: 64 MHz (1.5T) to 600 MHz (14.0T)). The experimental version of the applicator was implemented at B0?=?7.0T. The applicators feasibility for targeted RF heating was evaluated in EMF simulations and in phantom studies. Temperature co-simulations were conducted in phantoms and in a human voxel model. Our results demonstrate that higher frequencies afford a reduction in the size of specific absorption rate (SAR) hotspots. At 7T (298 MHz) the hybrid applicator yielded a 50% iso-contour SAR (iso-SAR-50%) hotspot with a diameter of 43 mm. At 600 MHz an iso-SAR-50% hotspot of 26 mm in diameter was observed. RF power deposition per RF input power was found to increase with B0 which makes targeted RF heating more efficient at higher frequencies. The applicator was capable of generating deep-seated temperature hotspots in phantoms. The feasibility of 2D steering of a SAR/temperature hotspot to a target location was demonstrated by the induction of a focal temperature increase (?T?=?8.1 K) in an off-center region of the phantom. Temperature simulations in the human brain performed at 298 MHz showed a maximum temperature increase to 48.6C for a deep-seated hotspot in the brain with a size of (19×23×32)mm(3) iso-temperature-90%. The hybrid applicator provided imaging capabilities that facilitate high spatial resolution brain MRI. To conclude, this study outlines the technical underpinnings and demonstrates the basic feasibility of an 8-channel hybrid TX/RX applicator that supports MR imaging, MR thermometry and targeted RF heating in one device. PMID:23613896

Winter, Lukas; Özerdem, Celal; Hoffmann, Werner; Santoro, Davide; Müller, Alexander; Waiczies, Helmar; Seemann, Reiner; Graessl, Andreas; Wust, Peter; Niendorf, Thoralf

2013-01-01

157

Predicting nurses' acceptance of radiofrequency identification technology.  

PubMed

The technology of radiofrequency identification allows for the scanning of radiofrequency identification-tagged objects and individuals without line-of-sight requirements. Healthcare organizations use radiofrequency identification to ensure the health and safety of patients and medical personnel and to uncover inefficiencies. Although the successful implementation of a system incorporating radiofrequency identification technologies requires acceptance and use of the technology, some nurses using radiofrequency identification in hospitals feel like "Big Brother" is watching them. This predictive study used a theoretical model assessing the effect of five independent variables: privacy concerns, attitudes, subjective norms, controllability, and self-efficacy, on a dependent variable, nurses' behavioral intention to use radiofrequency identification. A Web-based questionnaire containing previously validated questions was answered by 106 US RNs. Multiple linear regression showed that all constructs together accounted for 60% of the variance in nurses' intention to use radiofrequency identification. Of the predictors in the model, attitudes provided the largest unique contribution when the other predictors in the model were held constant; subjective norms also provided a unique contribution. Privacy concerns, controllability, and self-efficacy did not provide a significant contribution to nurses' behavioral intention to use radiofrequency identification. PMID:22805120

Norten, Adam

2012-10-01

158

Thermal and nonthermal mechanisms of interaction of radio-frequency energy with biological systems  

Microsoft Academic Search

This paper reviews thermal and nonthermal mechanisms of interaction between radiofrequency (RF) fields and biological systems, focusing on pulsed fields with high peak power but low duty cycle. Models with simplified geometry are used to illustrate the coupling between external electromagnetic fields and the body, and with cellular and subcellular structures. Mechanisms of interaction may be linear or nonlinear with

Kenneth R. Foster

2000-01-01

159

Laser Navigation for Radiofrequency Ablation  

SciTech Connect

A 45-year-old male with renal cell carcinoma secondary to von-Hippel Lindau (VHL) disease presented for radiofrequency ablation (RFA) of kidney tumors. Due to his prior history of several partial nephrectomies and limited renal reserve, RFA was chosen because of its relatively nephron-sparing nature. A laser guidance device was used to help guide probe placement in an attempt to reduce procedure time and improve targeting accuracy. The device was successful at guiding needle placement, as both tumors were located with a single pass. Follow-up CT scan confirmed accurate needle placement, showing an area of coagulation necrosis covering the previously seen tumor.

Varro, Zoltan; Locklin, Julia K., E-mail: bwood@nih.gov; Wood, Bradford J. [National Institutes of Health, Warren G. Magnuson Clinical Center, Diagnostic Radiology Department (United States)

2004-09-15

160

Radiofrequency heating pathways for gold nanoparticles  

NASA Astrophysics Data System (ADS)

This feature article reviews the thermal dissipation of nanoscopic gold under radiofrequency (RF) irradiation. It also presents previously unpublished data addressing obscure aspects of this phenomenon. While applications in biology motivated initial investigation of RF heating of gold nanoparticles, recent controversy concerning whether thermal effects can be attributed to nanoscopic gold highlight the need to understand the involved mechanism or mechanisms of heating. Both the nature of the particle and the nature of the RF field influence heating. Aspects of nanoparticle chemistry which may affect thermal dissipation include the hydrodynamic diameter of the particle, the oxidation state and related magnetism of the core, and the chemical nature of the ligand shell. Aspects of RF which may affect thermal dissipation include power, frequency and antenna designs that emphasize relative strength of magnetic or electric fields. These nanoparticle and RF properties are analysed in the context of three heating mechanisms proposed to explain gold nanoparticle heating in an RF field. This article also makes a critical analysis of the existing literature in the context of the nanoparticle preparations, RF structure, and suggested mechanisms in previously reported experiments.

Collins, C. B.; McCoy, R. S.; Ackerson, B. J.; Collins, G. J.; Ackerson, C. J.

2014-07-01

161

Non-invasive radiofrequency ablation of malignancies mediated by quantum dots, gold nanoparticles and carbon nanotubes  

PubMed Central

Various types of nanoparticles efficiently heat in radiofrequency fields, which can potentially be used to produce cancer cell cytotoxicity within minutes. Multifunctional and targeted nanoparticles have demonstrated effective cancer control in vivo without significant toxicity associated with radiofrequency field exposure. Importantly, animals treated systemically with targeted nanoparticles smaller than 50 nm demonstrate tumor necrosis after radiofrequency field exposure without acute or chronic toxicity to normal tissues. Likewise, the future holds great promise for multifunctional imaging as well as multimodality therapy with chemotherapeutic molecules and ionizing radiation sensitizing agents attached to nanoparticle constructs. However, the appropriate balance of safety and efficacy for diagnosis, therapy, and therapeutic monitoring with these nanoparticles remains to be fully elucidated. PMID:22826886

Glazer, Evan S; Curley, Steven A

2013-01-01

162

47 CFR 2.1091 - Radiofrequency radiation exposure evaluation: mobile devices.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 false Radiofrequency radiation exposure evaluation: mobile devices...Authorization Procedures Radiofrequency Radiation Exposure § 2.1091 Radiofrequency radiation exposure evaluation: mobile...

2013-10-01

163

47 CFR 2.1091 - Radiofrequency radiation exposure evaluation: mobile devices.  

... 2014-10-01 false Radiofrequency radiation exposure evaluation: mobile devices...Authorization Procedures Radiofrequency Radiation Exposure § 2.1091 Radiofrequency radiation exposure evaluation: mobile...

2014-10-01

164

Radiofrequency Ablation Effective Against Barrett Esophagus  

Cancer.gov

In a randomized phase II trial, radiofrequency ablation led to high rates of eradication of the cell abnormalities associated with Barrett esophagus, according to the May 28, 2009, New England Journal of Medicine.

165

Nonablative cutaneous remodeling using radiofrequency devices.  

PubMed

In recent years, several new radiofrequency devices have been introduced for treatment of a variety of skin conditions, particularly, skin wrinkling and laxity. These nonsurgical systems induce tissue tightening and contour changes through dermal collagen remodeling without disruption of the overlying epidermis, obviating a significant recovery period or risk of serious adverse sequelae. As such, radiofrequency-based systems have been used successfully for nonablative skin rejuvenation, atrophic scar revision, and treatment of unwanted hair, vascular lesions, and inflammatory acne. PMID:17870527

Alster, Tina S; Lupton, Jason R

2007-01-01

166

Radiofrequency radiation leakage from microwave ovens.  

PubMed

This work presents data on the amount of radiation leakage from 117 microwave ovens in domestic and restaurant use in the West Bank, Palestine. The study of leakage is based on the measurements of radiation emissions from the oven in real-life conditions by using a frequency selective field strength measuring system. The power density from individual ovens was measured at a distance of 1 m and at the height of centre of door screen. The tested ovens were of different types, models with operating powers between 1000 and 1600 W and ages ranging from 1 month to >20 y, including 16 ovens with unknown ages. The amount of radiation leakage at a distance of 1 m was found to vary from 0.43 to 16.4 ?W cm(-2) with an average value equalling 3.64 ?W cm(-2). Leakages from all tested microwave ovens except for seven ovens (?6 % of the total) were below 10 ?W cm(-2). The highest radiation leakage from any tested oven was ?16.4 ?W cm(-2), and found in two cases only. In no case did the leakage exceed the limit of 1 mW cm(-2) recommended by the ICNIRP for 2.45-GHz radiofrequency. This study confirms a linear correlation between the amount of leakage and both oven age and operating power, with a stronger dependence of leakage on age. PMID:23861537

Lahham, Adnan; Sharabati, Afifeh

2013-12-01

167

Epidemiology of Health Effects of Radiofrequency Exposure  

PubMed Central

We have undertaken a comprehensive review of epidemiologic studies about the effects of radiofrequency fields (RFs) on human health in order to summarize the current state of knowledge, explain the methodologic issues that are involved, and aid in the planning of future studies. There have been a large number of occupational studies over several decades, particularly on cancer, cardiovascular disease, adverse reproductive outcome, and cataract, in relation to RF exposure. More recently, there have been studies of residential exposure, mainly from radio and television transmitters, and especially focusing on leukemia. There have also been studies of mobile telephone users, particularly on brain tumors and less often on other cancers and on symptoms. Results of these studies to date give no consistent or convincing evidence of a causal relation between RF exposure and any adverse health effect. On the other hand, the studies have too many deficiencies to rule out an association. A key concern across all studies is the quality of assessment of RF exposure. Despite the ubiquity of new technologies using RFs, little is known about population exposure from RF sources and even less about the relative importance of different sources. Other cautions are that mobile phone studies to date have been able to address only relatively short lag periods, that almost no data are available on the consequences of childhood exposure, and that published data largely concentrate on a small number of outcomes, especially brain tumor and leukemia. PMID:15579422

Ahlbom, Anders; Green, Adele; Kheifets, Leeka; Savitz, David; Swerdlow, Anthony

2004-01-01

168

Comparison of Renal Ablation with Cryotherapy, Dry Radiofrequency, and Saline Augmented Radiofrequency in a Porcine Model  

Microsoft Academic Search

BACKGROUND: Needle ablative therapy has recently generated a lot of interest in the urologic community. We compare renal lesions produced in a porcine model using three forms of needle ablative energy: cryoablation (CR), dry radiofrequency (RF), and saline augmented radiofrequency (SARF). STUDY DESIGN: In 10 farm pigs, under ultrasonographic guidance, 40 laparoscopic renal lesions were produced: 825-mm CR lesions were

William C Collyer; Jaime Landman; Ephrem O Olweny; Cassio Andreoni; Kurt Kerbl; David G Bostwick; Ralph V Clayman

169

Characterization of superconducting radiofrequency breakdown by two-mode excitation  

SciTech Connect

We show that thermal and magnetic contributions to the breakdown of superconductivity in radiofrequency (RF) fields can be separated by applying two RF modes simultaneously to a superconducting surface. We develop a simple model that illustrates how mode-mixing RF data can be related to properties of the superconductor. Within our model the data can be described by a single parameter, which can be derived either from RF or thermometry data. Our RF and thermometry data are in good agreement with the model. We propose to use mode-mixing technique to decouple thermal and magnetic effects on RF breakdown of superconductors.

Eremeev, Grigory V. [JLAB, Newport News, VA (United States); Palczewski, Ari D. [JLAB, Newport News, VA (United States)

2014-01-01

170

Risk assessment and management of radiofrequency radiation exposure  

NASA Astrophysics Data System (ADS)

Radiofrequency radiation (RFR) industry managers, occupational physicians, security department, and other practitioners must be advised on the basic of biophysics and the health effects of RF electromagnetic fields so as to guide the management of exposure. Information on biophysics of RFR and biological/heath effects is derived from standard texts, literature and clinical experiences. Emergency treatment and ongoing care is outlined, with clinical approach integrating the circumstances of exposure and the patient's symptoms. Experimental risk assessment model in RFR chronic exposure is proposed. Planning for assessment and monitoring exposure, ongoing care, safety measures and work protection are outlining the proper management.

Dabala, Dana; Surducan, Emanoil; Surducan, Vasile; Neamtu, Camelia

2013-11-01

171

Risk assessment and management of radiofrequency radiation exposure  

SciTech Connect

Radiofrequency radiation (RFR) industry managers, occupational physicians, security department, and other practitioners must be advised on the basic of biophysics and the health effects of RF electromagnetic fields so as to guide the management of exposure. Information on biophysics of RFR and biological/heath effects is derived from standard texts, literature and clinical experiences. Emergency treatment and ongoing care is outlined, with clinical approach integrating the circumstances of exposure and the patient's symptoms. Experimental risk assessment model in RFR chronic exposure is proposed. Planning for assessment and monitoring exposure, ongoing care, safety measures and work protection are outlining the proper management.

Dabala, Dana [Railways Medical Clinic Cluj-Napoca, Occupational Medicine Department, 16-20 Bilascu Gheorghe St., 400015 Cluj-Napoca (Romania)] [Railways Medical Clinic Cluj-Napoca, Occupational Medicine Department, 16-20 Bilascu Gheorghe St., 400015 Cluj-Napoca (Romania); Surducan, Emanoil; Surducan, Vasile; Neamtu, Camelia [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath St., 400293 Cluj-Napoca (Romania)] [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath St., 400293 Cluj-Napoca (Romania)

2013-11-13

172

A Comparative PCET Study of a Donor-Acceptor Pair Linked by Ionized and Non-ionized Asymmetric Hydrogen-Bonded Interfaces  

PubMed Central

A Zn(II) porphyrin-amidinium is the excited state electron donor (D) to a naphthalene diimide acceptor (A) appended with either a carboxylate or sulfonate functionality. The two-point hydrogen bond (---[H+]---) formed between the amidinium and carboxylate or sulfonate establishes a proton-coupled electron transfer (PCET) pathway for charge transfer. The two D---[H+]---A assemblies differ only by the proton configuration within the hydrogen bonding interface. Specifically, the amidinium transfers a proton to the carboxylate to form a non-ionized amidine-carboxylic acid two-point hydrogen network whereas the amidinium maintains both protons when bound to the sulfonate functionality forming an ionized amidinium-sulfonate two-point hydrogen network. These two interface configurations within the dyads thus allow for a direct comparison of PCET kinetics for the same donor and acceptor juxtaposed by an ionized and non-ionized hydrogen-bonded interface. Analysis of PCET kinetics ascertained from transient absorption and transient emission spectroscopy reveal that the ionized interface is more strongly impacted by the local solvent environment, thus establishing that the initial static configuration of the proton interface is a critical determinant to the kinetics of PCET. PMID:19489645

Young, Elizabeth R.; Rosenthal, Joel; Hodgkiss, Justin M.

2012-01-01

173

Effect of Large Quadrupole Interactions on Nuclear Radiofrequency Spectra at Twice Larmor Frequency  

Microsoft Academic Search

The work of B. T. Feld and W. E. Lamb [Phys. Rev. 67, 15 (1945)] on the effect of a nuclear electrical quadrupole moment on the radiofrequency absorption spectrum of a heteronuclear diatomic molecule in a magnetic field is extended to a special case not considered by them. This is a case in which the electrical quadrupole interaction energy is

Norman F. Ramsey

1948-01-01

174

Intracellular gold nanoparticles enhance non-invasive radiofrequency thermal destruction of human gastrointestinal cancer cells  

Microsoft Academic Search

BACKGROUND: Novel approaches to treat human cancer that are effective with minimal toxicity profiles are needed. We evaluated gold nanoparticles (GNPs) in human hepatocellular and pancreatic cancer cells to determine: 1) absence of intrinsic cytotoxicity of the GNPs and 2) external radiofrequency (RF) field-induced heating of intracellular GNPs to produce thermal destruction of malignant cells. GNPs (5 nm diameter) were

Christopher J Gannon; Chitta Ranjan Patra; Resham Bhattacharya; Priyabrata Mukherjee; Steven A Curley

2008-01-01

175

Radiofrequency ablation technique eradicating palpebral margin neoplasm  

PubMed Central

AIM To report the study on radiofrequency ablation technique for eradication of palpebral margin neoplasm and its clinical effects. METHODS One hundred and six cases with the palpebral margin neoplasm were performed surgical removal with radiofrequency ablation technique. The 1-2 months postoperative follow-up was investigated and the lost cases were excluded from statistics. The continuing follow-up lasted about 6-16months. RESULTS One hundred cases underwent one treatment and 6 cases underwent two treatments. Six cases were missed. All the cases followed up healed well without pigmentation or scar left, nor eyelash loss or palpebral margin deformation. No case was recurrent. CONCLUSION Radiofrequency ablation has significant efficiency in eradicating the palpebral margin neoplasm. PMID:22553639

Jiang, Tian-Yu; Wang, Xing-Lin; Suo, Wei; He, Qing-Hua; Xiao, Hong-Yu

2011-01-01

176

Histopomorphic Evaluation of Radiofrequency Mediated Débridement Chondroplasty  

PubMed Central

The use of radiofrequency devices has become widespread for surgical ablation procedures. When ablation devices have been deployed in treatment settings requiring tissue preservation like débridement chondroplasty, adoption has been limited due to the collateral damage caused by these devices in healthy tissue surrounding the treatment site. Ex vivo radiofrequency mediated débridement chondroplasty was performed on osteochondral specimens demonstrating surface fibrillation obtained from patients undergoing knee total joint replacement. Three radiofrequency systems designed to perform débridement chondroplasty were tested each demonstrating different energy delivery methods: monopolar ablation, bipolar ablation, and non-ablation energy. Treatment outcomes were compared with control specimens as to clinical endpoint and histopomorphic characteristics. Fibrillated cartilage was removed in all specimens; however, the residual tissue remaining at the treatment site displayed significantly different characteristics attributable to radiofrequency energy delivery method. Systems that delivered ablation-based energies caused tissue necrosis and collateral damage at the treatment site including corruption of cartilage Superficial and Transitional Zones; whereas, the non-ablation system created a smooth articular surface with Superficial Zone maintenance and without chondrocyte death or tissue necrosis. The mechanism of radiofrequency energy deposition upon tissues is particularly important in treatment settings requiring tissue preservation. Ablation-based device systems can cause a worsened state of articular cartilage from that of pre-treatment. Non-ablation energy can be successful in modifying/preconditioning tissue during débridement chondroplasty without causing collateral damage. Utilizing a non-ablation radiofrequency system provides the ability to perform successful débridement chondroplasty without causing additional articular cartilage tissue damage and may allow for other cartilage intervention success. PMID:20721322

Ganguly, Kumkum; McRury, Ian D; Goodwin, Peter M; Morgan, Roy E; Augé II, Wayne K

2010-01-01

177

Model of Inductive Plasma Production Assisted by Radio-Frequency Wave in Tokamaks  

Microsoft Academic Search

For initial plasma production, an induction electric field generated by applying voltage to a poloidal field (PF) coil system is used to produce a Townsend avalanche breakdown. When the avalanche margins are small, as for the International Thermonuclear Experimental Reactor (ITER) in which the induction electric field is about 0.3 V\\/m, the assistance of radio-frequency waves (RF) is provided to

Makoto Hasegawa; Kazuaki Hanada; Kohnosuke Sato; Kazuo Nakamura; Hideki Zushi; Mizuki Sakamoto; Hiroshi Idei; Shoji Kawasaki; Hisatoshi Nakashima; Aki Higashijima

2007-01-01

178

Thermage: the nonablative radiofrequency for rejuvenation.  

PubMed

Thermage is a noninvasive nonablative device that uses monopolar radiofrequency energy to bulk heat underlying skin while protecting the epidermis to produce skin tightening. It is used for the treatment of rhytids on the face including the periorbital region and lower face, and more recently, for off-face applications. Studies have shown that it can impart mild tightening of periorbital mid, and lower facial laxity. Other radiofrequency devices have also shown objective improvements in cellulite of the buttocks and thigh regions. Thermage is an efficacious and safe nonsurgical alternative for treating mild skin laxity. PMID:18940540

Sukal, Sean A; Geronemus, Roy G

2008-01-01

179

A practical method to evaluate radiofrequency exposure of mast workers.  

PubMed

Assessment of occupational exposure to radiofrequency (RF) fields in telecommunication transmitter masts is a challenging task. For conventional field strength measurements using manually operated instruments, it is difficult to document the locations of measurements while climbing up a mast. Logging RF dosemeters worn by the workers, on the other hand, do not give any information about the location of the exposure. In this study, a practical method was developed and applied to assess mast workers' exposure to RF fields and the corresponding location. This method uses a logging dosemeter for personal RF exposure evaluation and two logging barometers to determine the corresponding height of the worker's position on the mast. The procedure is not intended to be used for compliance assessments, but to indicate locations where stricter assessments are needed. The applicability of the method is demonstrated by making measurements in a TV and radio transmitting mast. PMID:19054796

Alanko, Tommi; Hietanen, Maila

2008-01-01

180

Effects of damage caused by non-ionizing energy loss in Si Mini-Pad sensors for the PHENIX MPC-EX  

NASA Astrophysics Data System (ADS)

The PHENIX MPC-EX is an W/Si pre-shower detector operating at small angles with respect to the beam in the Relativistic Heavy Ion Collider (RHIC). The Si Mini-Pad sensors are the active element of the detector. The expected hadron flux to the Si Mini-Pad sensors will generate significant non-ionizing energy loss in the sensors, which may damage the crystalline structure of the sensor's bulk material. We investigated the nature of the hadron flux to the Si Mini-Pad sensors through a full simulation and determined its effect on the sensor's characteristics based on a beam test. The investigation showed key issues in designing a preshower detector using silicon sensors and operating under a large neutron fluence and offered valuable information on the operation of the MPC-EX detector.

Chai, J.-S.; Ghergherehchi, M.; Hahn, K. I.; Han, S. Y.; Jeong, I. W.; Joo, K. S.; Kim, E. J.; Kim, S. G.; Kim, Y. K.; Kistenev, E.; Kwon, Y.; Lajoie, J. G.; Li, Z.; Lee, J. H.; Lim, K. S.; Lim, S. H.; Park, J. M.; Park, K. S.; Park, S. Y.; Song, H. S.; Sue, D. G.; Sukhanov, A.

2014-12-01

181

Radiofrequency ablation for chronic pain control  

Microsoft Academic Search

With an increased knowledge of neural anatomy and technologic improvement, radiofrequency ablation (RFA) became an often-used\\u000a technique for the pain control over an extended time period. Today, RFA is used safely for spinal pains of facet or discogenic\\u000a origin, sympathetically maintained pain, and other pains of neural origin.

Leonardo Kapural; Nagy Mekhail

2001-01-01

182

Radiofrequency sacroiliac joint denervation for sacroiliac syndrome  

Microsoft Academic Search

Background and Objectives: Radiofrequency (RF) denervation of the sacroiliac (SI) joint has been advocated for the treatment of sacroiliac syndrome, yet no clinical studies or case series support its use. Methods: We report the results of a consecutive series of 50 SI joint RF denervations performed in 33 patients with sacroiliac syndrome. All patients underwent diagnostic SI joint injections with

F. Michael Ferrante; Lawrence F. King; Elizabeth A. Roche; Philip S. Kim; Margaret Aranda; Leslie R. DeLaney; Issam A. Mardini; Andrew J. Mannes

2001-01-01

183

Complications of radiofrequency ablation in hepatocellular carcinoma  

Microsoft Academic Search

Radiofrequency thermal ablation has been accepted as a promising technique to treat unresectable liver tumors. However, any interventional procedure should be performed only if the procedure is safe, with minimal morbidity and mortality rates. Recently, three separate multicenter surveys have reported acceptable morbidity and mortality rates for a minimally invasive technique. The mortality rate ranged from 0.1% to 0.5%, the

H. Rhim

2005-01-01

184

Studies Of Apnea Monitor Radiofrequency Electromagnetic Interference  

Microsoft Academic Search

Reports that radiofrequency (RF) electromagnetic interference (EMI) was responsible for infant apnea (breath cessation) monitor disfunction have prompted an in-depth engineering investigation by the Center for Devices and Radiological Health (CDRH). Two studies were undertaken using several apnea monitors currently in use in the U.S. A laboratory study was done under controlled, repeatable conditions using a transverse electromagnetic (\\

P. S. Ruggera; Eugene R O'Bryan

1991-01-01

185

EFFECT OF RADIOFREQUENCY RADIATION ON THERMOREGULATION  

EPA Science Inventory

In the past 30 years there have been numerous studies on the patho-physiological effects of exposure to radiofrequency (RF) radiation. t is clear that the majority of these effects can be attributed to the thermogenic action of RF radiation. uring exposure to RF radiation the the...

186

Radiofrequency thermal ablation of hepatocellular carcinoma  

Microsoft Academic Search

Radiofrequency (RF) ablation resulted in a higher complete necrosis than percutaneous ethanol injection (PEI), above all in infiltrating lesions, and requires fewer treatment sessions in the treatment of small size tumors. We achieved 90% of complete necrosis in hepatocellular carcinoma (HCC)

Tito Livraghi; Sergio Lazzaroni; Franca Meloni

2001-01-01

187

Cytogenetic investigation of subjects professionally exposed to radiofrequency radiation.  

PubMed

Nowadays, virtually everybody is exposed to radiofrequency radiation (RFR) from mobile phone base station antennas or other sources. At least according to some scientists, this exposure can have detrimental health effects. We investigated cytogenetic effects in peripheral blood lymphocytes from subjects who were professionally exposed to mobile phone electromagnetic fields in an attempt to demonstrate possible RFR-induced genetic effects. These subjects can be considered well suited for this purpose as their RFR exposure is 'normal' though rather high, and definitely higher than that of the 'general population'. The alkaline comet assay, sister chromatid exchange (SCE) and chromosome aberration tests revealed no evidence of RFR-induced genetic effects. Blood cells were also exposed to the well known chemical mutagen mitomycin C in order to investigate possible combined effects of RFR and the chemical. No cooperative action was found between the electromagnetic field exposure and the mutagen using either the comet assay or SCE test. PMID:16481348

Maes, Annemarie; Van Gorp, Urbain; Verschaeve, Luc

2006-03-01

188

MR imaging-guided radiofrequency thermal ablation in the porcine brain at 0.2 T  

Microsoft Academic Search

The aim of this study was to test the hypotheses that (a) MR imaging-guided radiofrequency (RF) thermal ablation is safe\\u000a and feasible in porcine brain using an open C-arm-shaped low-field MR system, and that (b) induced thermal lesion size can\\u000a be predicted using low-field MR imaging. Magnetic resonance-guided RF ablation was performed in the cerebral frontal lobes\\u000a of six pigs.

Elmar M. Merkle; Jason R. Shonk; L. Zheng; Jeffrey L. Duerk; Jonathan S. Lewin

2001-01-01

189

Skin tightening with fractional lasers, radiofrequency, Smartlipo.  

PubMed

Skin tightening occurs with the use of fractional lasers, radiofrequency, and Smartlipo. The fractional lasers Fraxel (1550 nm; Solta Medical, Inc., Hayward, CA) and Affirm (1440 nm, 1320 nm) (Cynosure, Westford, MA) when used in combination tighten skin and lessen solar keratoses, and improve acne scars. With radiofrequency, further tightening occurs. Smartlipo (Cynosure, Westford, MA) (1064 nm or the newer MPX with combined 1064 nm and 1320 nm) results in skin tightening and has been very helpful in improving skin tightness and smoothness on the neck either singularly or in combination with the above procedures; and with the addition of the Affirm fractional CO2 laser (Cynosure, Westford, MA), further skin improvement and tightening occurs. PMID:20354432

Collawn, Sherry S

2010-05-01

190

Fraxelated radiofrequency device for acne scars  

NASA Astrophysics Data System (ADS)

Acne scars can be improved with various treatments such as topical creams, chemical peels, dermal fillers, microdermabrasion, laser, and radiofrequency devices. Some of these treatments especially lasers and deep chemical peels can have significant side effects such as post inflammatory hyperpigmentation in darker skin types. Fraxelated RF Laser devices have been reported to have lower incidence of side effects in all skin phototypes. Nine patients between ages 18 and 35 of various skin phototypes were selected from a private practice and treated with a RF fraxelated device (E-matrix) for acne scars. Outcomes were measured by physician observation, subjective feedback received by patients, and comparison of before and after photographs. In this small group of patients with various skin phototypes, fraxelated radiofrequency device improved acne scars with minimal side effects and downtime.

Rao, Babar K.; Khokher, Sairah

2012-09-01

191

Radiofrequency thermal ablation of liver tumors  

Microsoft Academic Search

Radiofrequency ablation (RFA) of liver tumors was first proposed in 1990. New technologies enable us to produce liver thermal lesions of approximately 3–3.5 cm in diameter; RFA has consequently become an emerging percutaneous therapeutic option both for small hepatocellular carcinoma (HCC) and for non-resectable liver metastases, mainly from colorectal cancer. New devices (for example, triplet of cooled needles, wet needles) and

Elisabetta Buscarini; Agostino Savoia; Gianfranco Brambilla; Fernanda Menozzi; Luigi Reduzzi; Deike Strobel; Johannes Hänsler; Luigi Buscarini; Luigi Gaiti; Alessandro Zambelli

2005-01-01

192

The Importance of Radiofrequency Safety into Occupational Safety Coursework  

NSDL National Science Digital Library

Typical safety programs, both undergraduate and graduate, do not explore issues related with RF hazards and safety. Without federal regulations and enforcement, the topic is usually disregarded and thus creating future safety professionals without any knowledge of the possibilities of RF hazards at the future employment. This paper will discuss what is radiofrequency, how radiofrequency is used, regulatory agencies and compliance issues in regards to radiofrequency and finally research of Safety, Health and Environmental programs across the United States.

2010-07-29

193

Plasma-beam traps and radiofrequency quadrupole beam coolers  

SciTech Connect

Two linear trap devices for particle beam manipulation (including emittance reduction, cooling, control of instabilities, dust dynamics, and non-neutral plasmas) are here presented, namely, a radiofrequency quadrupole (RFQ) beam cooler and a compact Penning trap with a dust injector. Both beam dynamics studies by means of dedicated codes including the interaction of the ions with a buffer gas (up to 3 Pa pressure), and the electromagnetic design of the RFQ beam cooler are reported. The compact multipurpose Penning trap is aimed to the study of multispecies charged particle samples, primarily electron beams interacting with a background gas and/or a micrometric dust contaminant. Using a 0.9 T solenoid and an electrode stack where both static and RF electric fields can be applied, both beam transport and confinement operations will be available. The design of the apparatus is presented.

Maggiore, M., E-mail: mario.maggiore@lnl.infn.it; Cavenago, M.; Comunian, M.; Chirulotto, F.; Galatà, A.; De Lazzari, M.; Porcellato, A. M.; Roncolato, C.; Stark, S. [INFN-LNL, viale dell’Università 2, 35020 Legnaro (Italy)] [INFN-LNL, viale dell’Università 2, 35020 Legnaro (Italy); Caruso, A.; Longhitano, A. [INFN-LNS, via S. Sofia 54, 95123 Catania (Italy)] [INFN-LNS, via S. Sofia 54, 95123 Catania (Italy); Cavaliere, F.; Maero, G.; Paroli, B.; Pozzoli, R.; Romé, M. [INFN Sezione di Milano and Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy)] [INFN Sezione di Milano and Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy)

2014-02-15

194

Plasma-beam traps and radiofrequency quadrupole beam coolers  

NASA Astrophysics Data System (ADS)

Two linear trap devices for particle beam manipulation (including emittance reduction, cooling, control of instabilities, dust dynamics, and non-neutral plasmas) are here presented, namely, a radiofrequency quadrupole (RFQ) beam cooler and a compact Penning trap with a dust injector. Both beam dynamics studies by means of dedicated codes including the interaction of the ions with a buffer gas (up to 3 Pa pressure), and the electromagnetic design of the RFQ beam cooler are reported. The compact multipurpose Penning trap is aimed to the study of multispecies charged particle samples, primarily electron beams interacting with a background gas and/or a micrometric dust contaminant. Using a 0.9 T solenoid and an electrode stack where both static and RF electric fields can be applied, both beam transport and confinement operations will be available. The design of the apparatus is presented.

Maggiore, M.; Cavenago, M.; Comunian, M.; Chirulotto, F.; Galatà, A.; De Lazzari, M.; Porcellato, A. M.; Roncolato, C.; Stark, S.; Caruso, A.; Longhitano, A.; Cavaliere, F.; Maero, G.; Paroli, B.; Pozzoli, R.; Romé, M.

2014-02-01

195

Plasma-beam traps and radiofrequency quadrupole beam coolers.  

PubMed

Two linear trap devices for particle beam manipulation (including emittance reduction, cooling, control of instabilities, dust dynamics, and non-neutral plasmas) are here presented, namely, a radiofrequency quadrupole (RFQ) beam cooler and a compact Penning trap with a dust injector. Both beam dynamics studies by means of dedicated codes including the interaction of the ions with a buffer gas (up to 3 Pa pressure), and the electromagnetic design of the RFQ beam cooler are reported. The compact multipurpose Penning trap is aimed to the study of multispecies charged particle samples, primarily electron beams interacting with a background gas and/or a micrometric dust contaminant. Using a 0.9 T solenoid and an electrode stack where both static and RF electric fields can be applied, both beam transport and confinement operations will be available. The design of the apparatus is presented. PMID:24593614

Maggiore, M; Cavenago, M; Comunian, M; Chirulotto, F; Galatà, A; De Lazzari, M; Porcellato, A M; Roncolato, C; Stark, S; Caruso, A; Longhitano, A; Cavaliere, F; Maero, G; Paroli, B; Pozzoli, R; Romé, M

2014-02-01

196

Radiofrequency energy exposure from the Trilliant smart meter.  

PubMed

This paper reviews radiofrequency (RF) field levels produced by electric utility meters equipped with RF transceivers (so-called Smart Meters), focusing on meters from one manufacturer (Trilliant, Redwood City, CA, USA, and Granby, QC, Canada). The RF transmission levels are summarized based on publicly available data submitted to the U.S. Federal Communications Commission supplemented by limited independent measurements. As with other Smart Meters, this meter incorporates a low powered radiofrequency transceiver used for a neighborhood mesh network, in the present case using ZigBee-compliant physical and medium access layers, operating in the 2.45 GHz unlicensed band but with a proprietary network architecture. Simple calculations based on a free space propagation model indicate that peak RF field intensities are in the range of 10 mW m or less at a distance of more than 1-2 m from the meters. However, the duty cycle of transmission from the meters is very low (< 1%). Limited measurements identified pulses from the meter that were consistent with data reported by the vendor to the U.S. Federal Communications Commission. Limited measurements conducted in two houses with the meters were unable to clearly distinguish emissions from the meters from the considerable electromagnetic clutter in the same frequency range from other sources, including Wi-Fi routers and, when it was activated, a microwave oven. These preliminary measurements disclosed the difficulties that would be encountered in characterizing the RF exposures from these meters in homes in the face of background signals from other household devices in the same frequency range. An appendix provides an introduction to Smart Meter technology. The RF transmitters in wireless-equipped Smart Meters operate at similar power levels and in similar frequency ranges as many other digital communications devices in common use, and their exposure levels are very far below U.S. and international exposure limits. PMID:23799502

Foster, Kenneth R; Tell, Richard A

2013-08-01

197

Use of Semiflexible Applicators for Radiofrequency Ablation of Liver Tumors  

SciTech Connect

Purpose. To evaluate the feasibility and potential advantages of the radiofrequency ablation of liver tumors using new MRI-compatible semiflexible applicators in a closed-bore high-field MRI scanner. Methods. We treated 8 patients with 12 malignant liver tumors of different origin (5 colorectal carcinoma, 2 cholangiocellular carcinoma, 1 breast cancer) under MRI guidance. Radiofrequency ablation (RFA) was performed using 5 cm Rita Starburst Semi-Flex applicators (Rita Medical Systems, Milwaukee, WI, USA) which are suitable for MR- and CT-guided interventions and a 150 W RF generator. All interventions were performed in a closed-bore 1.5 T high-field MRI scanner for MRI-guided RFA using fast T1-weighted gradient echo sequences and T2-weighted ultra-turbo spin echo sequences. Control and follow-up MRI examinations were performed on the next day, at 6 weeks, and every 3 months after RFA. Control MRI were performed as double-contrast MRI examinations (enhancement with iron oxide and gadopentetate dimeglumine). All interventions were performed with the patient under local anesthesia and analgo-sedation. Results. The mean diameter of the treated hepatic tumors was 2.4 cm ({+-}0.6 cm, range 1.0-3.2 cm). The mean diameter of induced necrosis was 3.1 cm ({+-}0.4 cm). We achieved complete ablation in all patients. Follow-up examinations over a duration of 7 months ({+-}1.3 months, range 4-9 month) showed a local control rate of 100% in this group of patients. All interventions were performed without major complications; only 2 subcapsular hematomas were documented. Conclusion. RFA of liver tumors using semiflexible applicators in closed-bore 1.5 T scanner systems is feasible. These applicators might simplify the RFA of liver tumors under MRI control. The stiff distal part of the applicator facilitates its repositioning.

Gaffke, G., E-mail: gunnar.gaffke@charite.de; Gebauer, B.; Knollmann, F.D. [Universitaetsmedizin Berlin, Klinik fuer Strahlenheilkunde und Poliklinik, Charite (Germany); Helmberger, T. [Universitaet Muenchen, Institut fuer klinische Radiologie Grosshadern (Germany); Ricke, J. [Universitaetsmedizin Berlin, Klinik fuer Strahlenheilkunde und Poliklinik, Charite (Germany); Oettle, H. [Universitaetsmedizin Berlin, Campus-Virchow-Klinikum, Medizinische Klinik mit Schwerpunkt Haematologie und Onkologie der Charite (Germany); Felix, R.; Stroszczynski, C. [Universitaetsmedizin Berlin, Klinik fuer Strahlenheilkunde und Poliklinik, Charite (Germany)

2006-04-15

198

Superconducting Radio-Frequency Systems for High-ß Particle Accelerators  

NASA Astrophysics Data System (ADS)

This article addresses the physics and engineering of the superconducting radio-frequency systems for high-ß particle accelerators. I consider different geometries for cavities, discuss criteria for optimization, and options for higher-order mode damping. In reviewing recent progress in the field, SRF systems are classified according to the functions they perform. These systems are fundamental RF accelerating systems, deflecting/crab cavities, harmonic RF systems, and SRF photoemission electron guns.

Belomestnykh, Sergey

2012-01-01

199

Genetic effects of radio-frequency, atmospheric-pressure glow discharges with helium  

Microsoft Academic Search

Due to low gas temperatures and high densities of active species, atmospheric-pressure glow discharges (APGDs) would have potential applications in the fields of plasma-based sterilization, gene mutation, etc. In this letter, the genetic effects of helium radio-frequency APGD plasmas with the plasmid DNA and oligonucleotide as the treated biomaterials are presented. The experimental results show that it is the chemically

Guo Li; He-Ping Li; Li-Yan Wang; Sen Wang; Hong-Xin Zhao; Wen-Ting Sun; Xin-Hui Xing; Cheng-Yu Bao

2008-01-01

200

Electrical Features of Radio-frequency, Atmospheric-pressure, Bare-metallic-electrode Glow Discharges  

Microsoft Academic Search

Radio-frequency (RF), atmospheric-pressure glow discharge (APGD) plasmas with bare metallic electrodes have promising prospects\\u000a in the fields of plasma-aided etching, deposition, disinfection and sterilization, etc. In this paper, an induced gas discharge\\u000a approach is proposed for obtaining the RF, atmospheric-pressure, ?-mode, glow discharges with pure nitrogen or air as the\\u000a primary plasma-working gas using bare metallic electrodes. The discharge characteristics,

He-Ping Li; Wen-Ting Sun; Hua-Bo Wang; Guo Li; Cheng-Yu Bao

2007-01-01

201

Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD)  

E-print Network

Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD) Kurt Alexander Polzin;Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD) Prepared by: Kurt Alexander Polzin Dr. Michael R. LaPointe Dissertation Reader #12;c Copyright by Kurt Alexander Polzin, 2006. All

Choueiri, Edgar

202

Quadrupolar ion excitation for radiofrequency-only mass filter operation.  

PubMed

Trajectory calculations are used to model a mass filter based on the radiofrequency (rf)-only operation of a linear quadrupole with resonant quadrupole excitation of ions (resonant excitation applied with the same spatial electric field as the main quadrupole rf field). Ions are not trapped, but pass continuously through the quadrupole. Excited ions gain axial kinetic energy in the fringe field at the quadrupole exit, overcome a stopping potential and are transmitted to an external detector. No quadrupole direct current is required, unlike conventional operation at the tip of the first stability diagram. Quadrupole excitation can be applied with amplitude or frequency modulation of the main rf voltage, or with an auxiliary excitation voltage. All three methods give the same mass resolution. The mass resolution, R, is given by R ? 0.5q(d?/dq)n where q is a Mathieu parameter, ?(q), determines the frequency of ion oscillation and n is the number of cycles of the rf field experienced by an ion, determined by the flight time through the quadrupole. A disadvantage of this mode of operation is that the flight times of the ions and the excitation amplitudes or modulation depths need to be synchronized. PMID:24892291

Douglas, Don J; Polyakov, A; Konenkov, Nikolai V

2014-01-01

203

Cooled Radiofrequency Ablation for Bilateral Greater Occipital Neuralgia  

PubMed Central

This report describes a case of bilateral greater occipital neuralgia treated with cooled radiofrequency ablation. The case is considered in relation to a review of greater occipital neuralgia, continuous thermal and pulsed radiofrequency ablation, and current medical literature on cooled radiofrequency ablation. In this case, a 35-year-old female with a 2.5-year history of chronic suboccipital bilateral headaches, described as constant, burning, and pulsating pain that started at the suboccipital region and radiated into her vertex. She was diagnosed with bilateral greater occipital neuralgia. She underwent cooled radiofrequency ablation of bilateral greater occipital nerves with minimal side effects and 75% pain reduction. Cooled radiofrequency ablation of the greater occipital nerve in challenging cases is an alternative to pulsed and continuous RFA to alleviate pain with less side effects and potential for long-term efficacy. PMID:24716017

Chhatre, Akhil

2014-01-01

204

Skin rejuvenation by radiofrequency therapy: methods, effects and risks.  

PubMed

Treatment of sun-damaged skin and wrinkles is attracting increasing interest as the possible approaches expand. Recently mono- und bipolar radiofrequency devices have been introduced as new treatment options for skin rejuvenation. Initial studies have demonstrated changes in collagen content of the skin as the molecular basis of skin texture improvement. However, there are many possible risks and side effects. We describe a patient referred to us with severe facial scarring as a result of a bipolar radiofrequency treatment performed by non-medical personnel. Due to the risk of permanent tissue damage, the indications for radiofrequency interventions should be made carefully. Potential contraindications should be considered and written informed consent about all possible side effects and risk factors should be obtained. According to current knowledge, the experience of the physician using radiofrequency devices is most important in determining the outcome of this procedure. Therefore the use of radiofrequency therapy requires extensive training. PMID:18564210

Paasch, Uwe; Bodendorf, Marc Oliver; Grunewald, Sonja; Simon, Jan Christoph

2009-03-01

205

Absorbed energy distribution from radiofrequency electromagnetic radiation in a mammalian cell model: Effect of membrane-bound water  

Microsoft Academic Search

The spatial distributions of induced 27 or 2,450 MHz radiofrequency (RF) electric fields (E-fields) and specific absorption rates (SARS) in a three-component spherical cell model were determined by Mie scattering theory. The results were compared to results for the same cell model but with 0.5 nm thick of bound water on the inner and outer membrane surfaces. Induced E-fields and

Li-Ming Liu; Stephen F. Cleary

1995-01-01

206

Risk of burn trauma during circumcision with radiofrequency scalpel: case report and review of literature  

PubMed Central

Male circumcision, one of the oldest and most frequent operations performed all over the world, removes 33–50% of the penile skin. Like each surgical procedure, circumcision can leads to complications ranging from the insignificant to the tragic. Circumcision methods can be done with different ways. The radiofrequency (RF) scalpel, an innovative instrument, can be used in circumcision. Here, we present three boys who sustained sever burn injuries during circumcision with RF method. In sum, interesting characteristics made RF procedures so popular in different fields of surgery. Although having low incidence, the important complications of this technology such as burns should raise our attentions. Performing radiofrequency circumcision by an experienced operator, selection of proper size of ground pads, and elimination of any interface between the skin and ground pad are the factors that can prevent such tragedies. PMID:23875124

Mohammadi, Ali Akbar; Seyed Jafari, Seyed Morteza; Abdollahi, Ahmad

2013-01-01

207

Levels of electric field strength within the immediate vicinity of FM radio stations in Accra, Ghana.  

PubMed

Heightened awareness of the ever-expanding use of radiofrequency (RF) techniques and technology has led to mounting concerns from the general public and the scientific community regarding the possible health effects that may arise as a consequence of exposure to RF radiations and has drawn the attention of many researchers the world over. A survey of the RF electromagnetic radiation at public access points in the vicinity of 20 frequency-modulated (FM) radio stations has been made in Accra, Ghana. The fundamental object was to determine the levels of RF fields from FM broadcast antennae within 10-200 m radius about the foot of the FM base station and at a height of 1.5 m above the ground at selected locations. A spectrum analyser and a bi-conical antenna element sensitive and effective within the frequency band of 30-300 MHz were used. Results obtained indicated that the levels of electric field strength ranged from 5.4E-04 V m(-1) at FM station 'O' to 7.4E-08 V m(-1) at FM station 'D'. At a transmission frequency range of 88-108 MHz, the variation of power densities is from 2.5E-10 to 1.5E-17 Wm(-2). These values are very low and are far below the reference level set by the International Commission on Non-Ionizing Radiation Protection and therefore do not pose any known hazard to the inhabitants of Accra, Ghana. The electric field levels presented in this work are comparable with those reported from epidemiological studies conducted elsewhere. PMID:23567196

Azah, C K; Amoako, J K; Fletcher, J J

2013-10-01

208

Looking at the other side of the coin: the search for possible biopositive cognitive effects of the exposure to 900 MHz GSM mobile phone radiofrequency radiation.  

PubMed

Although exposure to electromagnetic radiation in radiofrequency range has caused a great deal of concern globally, radiofrequency radiation has many critical applications in both telecommunication and non-communication fields. The induction of adaptive response phenomena by exposure to radiofrequency radiation as either increased resistance to a subsequent dose of ionizing radiation or resistance to a bacterial infection has been reported recently. Interestingly, the potential beneficial effects of mobile phone radiofrequency radiation are not only limited to the induction of adaptive phenomena. It has previously been indicated that the visual reaction time of university students significantly decreased after a 10 min exposure to radiofrequency radiation emitted by a mobile phone. Furthermore, it has been revealed that occupational exposures to radar radiations decreased the reaction time in radar workers. Based on these findings, it can be hypothesized that in special circumstances, these exposures might lead to a better response of humans to different hazards. Other investigators have also provided evidence that confirms the induction of RF-induced cognitive benefits. Furthermore, some recent reports have indicated that RF radiation may play a role in protecting against cognitive impairment in Alzheimer's disease. In this light, a challenging issue will arise if there are other RF-induced stimulating effects. It is also challenging to explore the potential applications of these effects. Further research may shed light on dark areas of the health effects of short and long-term human exposure to radiofrequency radiation. PMID:24843789

Mortazavi, Seyed Ali Reza; Tavakkoli-Golpayegani, Ali; Haghani, Masoud; Mortazavi, Seyed Mohammad Javad

2014-01-01

209

Looking at the other side of the coin: the search for possible biopositive cognitive effects of the exposure to 900 MHz GSM mobile phone radiofrequency radiation  

PubMed Central

Although exposure to electromagnetic radiation in radiofrequency range has caused a great deal of concern globally, radiofrequency radiation has many critical applications in both telecommunication and non-communication fields. The induction of adaptive response phenomena by exposure to radiofrequency radiation as either increased resistance to a subsequent dose of ionizing radiation or resistance to a bacterial infection has been reported recently. Interestingly, the potential beneficial effects of mobile phone radiofrequency radiation are not only limited to the induction of adaptive phenomena. It has previously been indicated that the visual reaction time of university students significantly decreased after a 10 min exposure to radiofrequency radiation emitted by a mobile phone. Furthermore, it has been revealed that occupational exposures to radar radiations decreased the reaction time in radar workers. Based on these findings, it can be hypothesized that in special circumstances, these exposures might lead to a better response of humans to different hazards. Other investigators have also provided evidence that confirms the induction of RF-induced cognitive benefits. Furthermore, some recent reports have indicated that RF radiation may play a role in protecting against cognitive impairment in Alzheimer’s disease. In this light, a challenging issue will arise if there are other RF-induced stimulating effects. It is also challenging to explore the potential applications of these effects. Further research may shed light on dark areas of the health effects of short and long-term human exposure to radiofrequency radiation. PMID:24843789

2014-01-01

210

Investigation of radiofrequency plasma sources for space travel  

NASA Astrophysics Data System (ADS)

Optimization of radiofrequency (RF) plasma sources for the development of space thrusters differs from other applications such as plasma processing of materials since power efficiency, propellant usage, particle acceleration or heating become driving parameters. The development of two RF (13.56 MHz) plasma sources, the high-pressure (˜1 Torr) capacitively coupled ‘pocket rocket’ plasma micro-thruster and the low-pressure (˜1 mTorr) inductively coupled helicon double layer thruster (HDLT), is discussed within the context of mature and emerging electric propulsion devices. The density gradient in low-pressure expanding RF plasmas creates an electric field that accelerates positive ions out of the plasma. Generally, the total potential drop is similar to that of a wall sheath allowing the plasma electrons to neutralize the ion beam. A high-pressure expansion with no applied magnetic field can result in large dissociation rates and/or a collimated beam of ions of small area and a flowing heated neutral beam (‘pocket rocket’). A low-pressure expansion dominated by a magnetic field can result in the formation of electric double layers which produce a very directed neutralized beam of ions of large area (HDLT).

Charles, C.; Boswell, R. W.; Takahashi, K.

2012-12-01

211

A survey of the urban radiofrequency (RF) environment.  

PubMed

In 1980, Tell and Mantiply published a study of radiofrequency (RF) fields measured across 15 major metropolitan areas in the USA. They required a van fully equipped with instrumentation and computing capability for their measurements. This study aimed to assess whether and how hand-held instrumentation available today would facilitate and enhance the efficiency of large-scale surveys of ambient RF fields. In addition, the data would provide a suggestion as to how the profile of ambient RF fields has changed with respect to frequency content and magnitude. Not unexpectedly, the relative power densities were orders of magnitude lower than the Federal Communications Commission's (FCC) maximum permissible exposure (MPE) for the general public, with a maximum time-averaged value across the VHF-FM-UHF-cellular bands of 0.12 % of the MPE (AM's contribution was negligible). In both the 1980 and the present study, the power density in the FM band was a major contributor to overall power density, but over time, power densities in the VHF and UHF band decreased and increased, respectively. From the perspective of absolute power density, the wideband values in the 1980 study, this study and any number of assessments conducted in European nations are not generally different from one another. PMID:24567499

Tell, Richard A; Kavet, Robert

2014-12-01

212

Impact of monopolar radiofrequency energy on subchondral bone viability.  

PubMed

The purpose of this study was to analyze the impact of monopolar radiofrequency energy treatment on subchondral bone viability. The femoral grooves of six chinchilla bastard rabbits were exposed bilaterally to monopolar radiofrequency energy for 2, 4 and 8 s, creating a total of 36 defects. An intravital fluorescence bone-labeling technique characterized the process of subchondral bone mineralization within the 3 months following exposure to radiofrequency energy and was analyzed by widefield epifluorescence optical sectioning microscopy using an ApoTome. After 2 s of radiofrequency energy exposure, regular fluorescence staining of the subchondral bone was evident in all samples when compared to untreated areas. The depth of osteonecrosis after 4 and 8 s of radiofrequency energy treatment averaged 126 and 942 microm at 22 days (P < .05; P < .01). The 4 s treatment group showed no osteonecrosis after 44 days whereas the depth of osteonecrosis extended from 519 microm at 44 days (P < .01), to 281 microm at 66 days (P < .01) and to 133 microm at 88 days (P < .05) after 8 s of radiofrequency energy application. Though radiofrequency energy may induce transient osteonecrosis in the superficial zone of the subchondral bone, the results of this study suggest that post-arthroscopic osteonecrosis appears to be of only modest risk given the current clinical application in humans. PMID:19838673

Balcarek, Peter; Kuhn, Anke; Weigel, Arwed; Walde, Tim A; Ferlemann, Keno G; Stürmer, Klaus M; Frosch, Karl-Heinz

2010-05-01

213

Radiofrequency Coblation of Congenital Nasopharyngeal Teratoma: A Novel Technique  

PubMed Central

Introduction. Congenital nasopharyngeal teratomas are rare tumours that pose difficulties in diagnosis and surgical management. We report the first use of radiofrequency coblation in the management of such tumours. Case Report. A premature baby with a perinatal diagnosis of a large, obstructing nasooropharyngeal mass was referred to the ENT service for further investigations and management. The initial biopsy was suggestive of a neuroblastoma, but the tumour demonstrated rapid growth despite appropriate chemotherapy. In a novel use of radiofrequency coblation, the nasooropharyngeal mass was completely excised, with the final histopathology revealing a congenital nasopharyngeal teratoma. Conclusion. We report the first use of radiofrequency coblation to excise a congenital nasopharyngeal teratoma and discuss its advantages.

Hwang, Sang Yun; Jefferson, Niall; Mohorikar, Alok; Jacobson, Ian

2015-01-01

214

Clinical applications of radiofrequency: nonsurgical skin tightening (thermage).  

PubMed

Thermage is a nonsurgical treatment for sagging skin in the jowl, neck, and eyelids. Abdominal striae, loose upper arm skin and buttock sagging, and improvement of the appearance of cellulite have become amenable to the radiofrequency treatment. Radiofrequency passed through cooled epidermis allows for radiofrequency-induced thermal damage to the dermis and deep dermal collagen (fibrous septae). The remodeling of the collagen leads to clinically discernible improvement in the sagging skin and skin quality; the remodeling of deep dermal collagen (fibrous septae) allows modeling of contours and improvement of the cellulite appearance. PMID:19309652

Hodgkinson, Darryl J

2009-04-01

215

The influence of radiofrequency/microwave energy absorption on physiological regulation.  

PubMed Central

Physiological regulation represented by thermoregulation, neuro endocrine function, neurochemical activity, and immune responses is a composite of exquisitely "tuned" interrelated systems that constitute sensitive indicators of body responses to environmental stimuli or absorbed physical energies. Exposure to microwave/radiofrequency fields may affect such physiological regulation. Study of the integration and correlation of many body functions relative to the altered homoeostatic status of the microwave/radiofrequency-exposed subject is thus indicated. Microwave-induced physiological changes cannot be dissociated from increases in tissue temperature. Such responses are considered to be essential in defence against environmental changes as a febrile response is essential for host immune defence. These responses can also be considered to reflect the utilization of physiological function to maintain regulations or adjustments. These are not necessarily adverse reactions to environmental stimuli. These responses can be transient or persistent, beneficial or detrimental. Assessment of the integration and correlation of these functions relative to the thermal inputs and homoeokinetic reactions of the individual subjected to microwave/radiofrequency energy should permit differentiation between potential hazards which might compromise the individual's ability to maintain normal physiological function and effects which are compensated by physiological redundancy. PMID:6950745

Michaelson, S. M.

1982-01-01

216

Genetic effects of radio-frequency, atmospheric-pressure glow discharges with helium  

NASA Astrophysics Data System (ADS)

Due to low gas temperatures and high densities of active species, atmospheric-pressure glow discharges (APGDs) would have potential applications in the fields of plasma-based sterilization, gene mutation, etc. In this letter, the genetic effects of helium radio-frequency APGD plasmas with the plasmid DNA and oligonucleotide as the treated biomaterials are presented. The experimental results show that it is the chemically active species, instead of heat, ultraviolet radiation, intense electric field, and/or charged particles, that break the double chains of the plasmid DNA. The genetic effects depend on the plasma operating parameters, e.g., power input, helium flow rate, processing distance, time, etc.

Li, Guo; Li, He-Ping; Wang, Li-Yan; Wang, Sen; Zhao, Hong-Xin; Sun, Wen-Ting; Xing, Xin-Hui; Bao, Cheng-Yu

2008-06-01

217

Genetic effects of radio-frequency, atmospheric-pressure glow discharges with helium  

SciTech Connect

Due to low gas temperatures and high densities of active species, atmospheric-pressure glow discharges (APGDs) would have potential applications in the fields of plasma-based sterilization, gene mutation, etc. In this letter, the genetic effects of helium radio-frequency APGD plasmas with the plasmid DNA and oligonucleotide as the treated biomaterials are presented. The experimental results show that it is the chemically active species, instead of heat, ultraviolet radiation, intense electric field, and/or charged particles, that break the double chains of the plasmid DNA. The genetic effects depend on the plasma operating parameters, e.g., power input, helium flow rate, processing distance, time, etc.

Li Guo; Li Heping; Wang Sen; Sun Wenting; Bao Chengyu [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Wang Liyan; Zhao Hongxin; Xing Xinhui [Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China)

2008-06-02

218

Axial force imparted by a conical radiofrequency magneto-plasma thruster  

SciTech Connect

Direct thrust measurements of a low pressure ({approx}0.133 Pa) conical radiofrequency (rf at 13.56 MHz) argon plasma source show a total axial force of about 5 mN for an effective rf power of 650 W and a maximum magnetic field of 0.018 T, of which a measured value of 2.5 mN is imparted by the magnetic nozzle. A simplified model of thrust including contributions from the electron pressure and from the magnetic field pressure is developed. The magnetic nozzle is modelled as a ''physical'' nozzle of increasing cross-sectional area.

Charles, C.; Takahashi, K.; Boswell, R. W. [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, Australian National University, ACT 0200 (Australia)

2012-03-12

219

Radiofrequency contact currents: sensory responses and dosimetry.  

PubMed

The process of setting science-based exposure standards (or guidelines) for radiofrequency (RF) contact current exposure has been disadvantaged by a lack of relevant data. The authors first review the essential features and results of the available studies and illustrate the apparent discrepancies among them. Then, they examine the manner in which current was administered in these studies and suggest as to how the physical relationship of a contacting finger to the current electrode may play a role in affecting sensory thresholds specific to those configurations. A major factor in this analysis relates to whether current density is uniformly distributed across the contact area or whether an electrode's 'edge effects' enhance currents with a net effect of decreasing apparent thresholds, when expressed as the bulk current entering a subject. For an exposure with a clear hazard potential, thresholds of human sensory response to RF currents require further investigation. PMID:24324252

Kavet, Robert; Tell, R A; Olsen, R G

2014-12-01

220

Radio-frequency low-coherence interferometry.  

PubMed

A method for retrieving low-coherence interferograms, based on the use of a microwave photonics filter, is proposed and demonstrated. The method is equivalent to the double-interferometer technique, with the scanning interferometer replaced by an analog fiber-optics link and the visibility recorded as the amplitude of its radio-frequency (RF) response. As a low-coherence interferometry system, it shows a decrease of resolution induced by the fiber's third-order dispersion (?3). As a displacement sensor, it provides highly linear and slope-scalable readouts of the interferometer's optical path difference in terms of RF, even in the presence of third-order dispersion. In a proof-of-concept experiment, we demonstrate 20-?m displacement readouts using C-band EDFA sources and standard single-mode fiber. PMID:24978555

Fernández-Pousa, Carlos R; Mora, José; Maestre, Haroldo; Corral, Pablo

2014-06-15

221

Radiofrequency Ablation Therapy for Solid Tumors  

SciTech Connect

Surgical resection, systemic chemotherapy, and local radiation have been the conventional treatments for localized solid cancer. Because certain patients are not candidates for tumor resection and because many tumors are poorly responsive to chemotherapy and radiation, there has been an impetus to develop alternative therapies. Radiofrequency ablation (RFA) is a minimally invasive therapy for localized solid cancers that has gained considerable attention in the last 12 years. Advantages of minimally invasive therapies over surgery include less recovery time, lower morbidity and mortality, eligibility of more patients, and lower cost. RFA has been applied most extensively to inoperable hepatic tumors. It is investigational for tumors in the kidney, lung, bone, breast, and adrenal gland. This colloquium will review the mechanism, techniques, limitations, and clinical applications of RFA. The ultimate role that RFA will play in cancer therapy will depend on the results of long-term follow-up and prospective randomized trials.

Kam, Anthony (NIH) [NIH

2002-12-04

222

Palliative Radiofrequency Ablation for Recurrent Prostate Cancer  

SciTech Connect

Percutaneous radiofrequency ablation (RFA) is a minimally invasive local therapy for cancer. Its efficacy is now becoming well documented in many different organs, including liver, kidney, and lung. The goal of RFA is typically complete eradication of a tumor in lieu of an invasive surgical procedure. However, RFA can also play an important role in the palliative care of cancer patients. Tumors which are surgically unresectable and incompatible for complete ablation present the opportunity for RFA to be used in a new paradigm. Cancer pain runs the gamut from minor discomfort relieved with mild pain medication to unrelenting suffering for the patient, poorly controlled by conventional means. RFA is a tool which can potentially palliate intractable cancer pain. We present here a case in which RFA provided pain relief in a patient with metastatic prostate cancer with pain uncontrolled by conventional methods.

Jindal, Gaurav; Friedman, Marc; Locklin, Julia, E-mail: JHvizda@cc.nih.gov; Wood, Bradford J. [National Institutes of Health, Diagnostic Radiology Department (United States)

2006-06-15

223

Electromagnetic limits to radiofrequency (RF) neuronal telemetry  

PubMed Central

The viability of a radiofrequency (RF) telemetry channel for reporting individual neuron activity wirelessly from an embedded antenna to an external receiver is determined. Comparing the power at the transmitting antenna required for the desired Channel Capacity, to the maximum power that this antenna can dissipate in the body without altering or damaging surrounding tissue reveals the severe penalty incurred by miniaturization of the antenna. Using both Specific Absorption Rate (SAR) and thermal damage limits as constraints, and 300?Kbps as the required capacity for telemetry streams 100?ms in duration, the model shows that conventional antennas smaller than 0.1?mm could not support human neuronal telemetry to a remote receiver (1?m away.) Reducing the antenna to 10 microns in size to enable the monitoring of single human neuron signals to a receiver at the surface of the head would require operating with a channel capacity of only 0.3?bps. PMID:24346503

Diaz, R. E.; Sebastian, T.

2013-01-01

224

Genetic effects of radiofrequency radiation (RFR)  

SciTech Connect

The possible effects of radiofrequency (RF) exposure on the genetic material of cells are considered very important since damage to the DNA of somatic cells can be linked to cancer development or cell death whereas damage to germ cells can lead to genetic damage in next and subsequent generations. This is why the scientific literature reports many investigations on the subject. According to a number of review papers, the conclusion so far is that there is little evidence that RFR is directly mutagenic and that adverse effects that were reported in some of the papers are predominantly the result of hyperthermia. Yet, some subtle indirect effects on DNA replication and/or transcription of genes under relatively restricted exposure conditions cannot be ruled out. Furthermore, the possibility of combined effects of RFR with environmental carcinogens/mutagens merits further attention. The present paper takes into account more recent investigations but the conclusion remains the same. A majority of studies report no increased (cyto)genetic damage but yet, a considerable number of investigations do. However, many studies were not sufficiently characterized, are therefore difficult to replicate and cannot be compared to others. Experimental protocols were very different from one study to another and investigations from a single laboratory were very often limited in the sample size or number of cells investigated, preventing a robust statistical analysis. Subtle, but significant differences between RFR-exposed and sham-exposed cells cannot be found in such conditions. For the above reasons, it was concluded at a workshop in Loewenstein (November 2002) that further investigations by individual laboratories most probably will not add much to the discussion of radiofrequency radiation (RFR) genotoxicity. Large, well coordinated, international collaborative studies involving participation of several experienced scientists are considered an alternative of uttermost importance. One such study is now being planned.

Verschaeve, L. [Vito, Environmental Toxicology, Mol (Belgium)]. E-mail: luc.verschaeve@vito.be

2005-09-01

225

Auditory response to pulsed radiofrequency energy.  

PubMed

The human auditory response to pulses of radiofrequency (RF) energy, commonly called RF hearing, is a well established phenomenon. RF induced sounds can be characterized as low intensity sounds because, in general, a quiet environment is required for the auditory response. The sound is similar to other common sounds such as a click, buzz, hiss, knock, or chirp. Effective radiofrequencies range from 2.4 to 10000 MHz, but an individual's ability to hear RF induced sounds is dependent upon high frequency acoustic hearing in the kHz range above about 5 kHz. The site of conversion of RF energy to acoustic energy is within or peripheral to the cochlea, and once the cochlea is stimulated, the detection of RF induced sounds in humans and RF induced auditory responses in animals is similar to acoustic sound detection. The fundamental frequency of RF induced sounds is independent of the frequency of the radiowaves but dependent upon head dimensions. The auditory response has been shown to be dependent upon the energy in a single pulse and not on average power density. The weight of evidence of the results of human, animal, and modeling studies supports the thermoelastic expansion theory as the explanation for the RF hearing phenomenon. RF induced sounds involve the perception via bone conduction of thermally generated sound transients, that is, audible sounds are produced by rapid thermal expansion resulting from a calculated temperature rise of only 5 x 10(-6) degrees C in tissue at the threshold level due to absorption of the energy in the RF pulse. The hearing of RF induced sounds at exposure levels many orders of magnitude greater than the hearing threshold is considered to be a biological effect without an accompanying health effect. This conclusion is supported by a comparison of pressure induced in the body by RF pulses to pressure associated with hazardous acoustic energy and clinical ultrasound procedures. PMID:14628312

Elder, J A; Chou, C K

2003-01-01

226

Numerical modelling of a radio-frequency micro ion thruster  

E-print Network

A simple performance model is developed for an inductively-coupled radio-frequency micro ion thruster. Methods of particle and energy balance are utilized for modeling the chamber plasma discharge. A transformer model is ...

Tsay, Michael Meng-Tsuan

2006-01-01

227

Radio-frequency spectroscopy of ultracold atomic Fermi gases  

E-print Network

This thesis presents experiments investigating the phase diagram of ultracold atomic Fermi gases using radio-frequency spectroscopy. The tunability of many experimental parameters including the temperature, the interparticle ...

Schirotzek, Andre

2010-01-01

228

77 FR 43535 - Grantee Codes for Certified Radiofrequency Equipment  

Federal Register 2010, 2011, 2012, 2013

...Commission operates an equipment authorization program for radiofrequency (RF) devices under part...with the rules. RF devices that are...procedure of the equipment authorization program...certification of RF equipment. The...

2012-07-25

229

Process for selected gas oxide removal by radiofrequency catalysts  

DOEpatents

This process to remove gas oxides from flue gas utilizes adsorption on a char bed subsequently followed by radiofrequency catalysis enhancing such removal through selected reactions. Common gas oxides include SO.sub.2 and NO.sub.x.

Cha, Chang Y. (3807 Reynolds St., Laramie, WY 82070)

1993-01-01

230

Radiofrequency detector coil performance maps for parallel MRI applications  

E-print Network

Parallel MRI techniques allow acceleration of MR imaging beyond traditional speed limits. In parallel MRI, arrays of radiofrequency (RF) detector coil arrays are used to perform some degree of spatial encoding which ...

Lattanzi, Riccardo

2006-01-01

231

Radiofrequency power disinfects and disinfests food, soils and wastewater  

E-print Network

Method with Pulsed Radiofrequency Power Systems. US Patentusing continu- ous and pulsed RF power applied with highpulsed, RF-induced electric effects at the expense of thermal effects. Finally, applications of continuous RF power

Lagunas-Solar, Manuel C.; Zeng, Nolan X.; Essert, Timothy K.; Truong, Tin D.; Pina U., Cecilia

2006-01-01

232

Arthroscopic Triangular Fibrocartilage Complex Debridement Using Radiofrequency Probes  

Microsoft Academic Search

The initial results of using radiofrequency probes for debridement of a torn triangular fibrocartilage complex were studied in 20 patients with a mean age of 44 (range 27–56) years presenting with ulnar-sided wrist pain. On arthroscopic examination, 18 central and two radial triangular fibrocartilage complex tears were identified and debrided to a stable rim using radiofrequency probes. The mean follow-up

N. A. DARLIS; R. W. WEISER; D. G. SOTEREANOS

2005-01-01

233

Treatment of acne vulgaris with fractional radiofrequency microneedling.  

PubMed

Fractional radiofrequency microneedling is a novel radiofrequency technique that uses insulated microneedles to deliver energy to the deep dermis at the point of penetration without destruction of the epidermis. It has been used for the treatment of various dermatological conditions including wrinkles, atrophic scars and hypertrophic scars. There have been few studies evaluating the efficacy of fractional radiofrequency microneedling in the treatment of acne, and none measuring objective parameters like the number of inflammatory and non-inflammatory acne lesions or sebum excretion levels. The safety and efficacy of fractional radiofrequency microneedling in the treatment of acne vulgaris was investigated. In a prospective clinical trial, 25 patients with moderate to severe acne were treated with fractional radiofrequency microneedling. The procedure was carried out three times at 1-month intervals. Acne lesion count, subjective satisfaction score, sebum excretion level and adverse effects were assessed at baseline and at 4, 8 and 12 weeks after the first treatment as well as 4, 8 and 12 weeks after the last treatment. Number of acne lesions (inflammatory and non-inflammatory) decreased. Sebum excretion and subjective satisfaction were more favorable at every time point compared with the baseline values (P < 0.05). Inflammatory lesions responded better than non-inflammatory lesions (P < 0.05). Adverse effects such as pinpoint bleeding, pain and erythema were noted, but were transient and not severe enough to stop treatment. Fractional radiofrequency microneedling is a safe and effective treatment for acne vulgaris. PMID:24807263

Kim, Sang Tae; Lee, Kang Hoon; Sim, Hyung Jun; Suh, Kee Suck; Jang, Min Soo

2014-07-01

234

Successful treatment of refractory pudendal neuralgia with pulsed radiofrequency.  

PubMed

Pudendal neuralgia (PN) involves severe, sharp pain along the course of the pudendal nerve, often aggravated with sitting. Current therapies include medication management, nerve blocks, decompression surgery, and neuromodulation. The ideal management for PN has not been determined. We present a case of a female with 1.5 years of sharp, burning pain of the left gluteal and perineal regions. She could not sit for longer than 10 to 15 minutes. Sacroiliac joint, epidural, and piriformis injections did not improve her pain. She had tried physical therapy, occupational therapy, massage, and acupuncture but the pain persisted. Medication treatment with oxycodone-acetaminophen, extended release morphine sulfate, amitriptyline, and gabapentin provided only minor relief and she had failed other multianalgesic therapy. She had been unable to work at her desk job for over a year. She had a positive response to 2 diagnostic pudendal nerve blocks with lidocaine that provided pain relief for several hours. This patient elected to undergo pulsed radiofrequency (PRF) of the left pudendal nerve in hopes of achieving a longer duration and improved pain relief. PRF was carried out at a frequency of 2 Hz and a pulse width of 20 milliseconds for a duration of 120 seconds at 42 degrees Celsius. After the procedure she reported tolerating sitting for 4 to 5 hours. Her multianalgesic therapy was successfully weaned. At 5 months follow-up she felt motivated to return to work. One and a half years after the procedure the patient is only taking oxycodone-acetaminophen for pain relief and still has good sitting tolerance. There were no procedure-related complications. To our knowledge PRF for the treatment of PN has not been reported elsewhere in the literature. PRF is a relatively new procedure and is felt to be safer than continuous radiofrequency. Current literature suggests that PRF delivers an electromagnetic field, which modifies neuro-cellular function with minimal cellular destruction. We conclude that PRF of the pudendal nerve offers promise as a potential treatment of PN that is refractory to conservative therapy. PMID:19461829

Rhame, Ellen E; Levey, Kenneth A; Gharibo, Christopher G

2009-01-01

235

Radiofrequency transmission line for bioluminescent Vibrio sp. irradiation  

NASA Astrophysics Data System (ADS)

We present the study and the analyses of a transmission line for radiofrequency (RF) irradiation of bacteria belonging to Vibrio harveyi-related strain PS1, a bioluminescent bacterium living in symbiosis with many marine organisms. The bioluminescence represents a new biologic indicator which is useful for studying the behaviour of living samples in the presence of RF waves due to the modern communication systems. A suitable transmission line, used as an irradiating cell and tested up to the maximum frequency used by the global system for mobile communications and universal mobile telecommunications system transmissions, was characterized. In this experiment, the RF voltage applied to the transmission line was 1 V. Due to short dimensions of the line and the applied high frequencies, standing waves were produced in addition to progressing waves and the electric field strength varies particularly along the longitudinal direction. The magnetic field map was not strongly linked to the electric one due to the presence of standing waves and of the outgoing irradiation. RF fields were measured by two homemade suitable probes able to diagnostic fields of high frequency. The field measurements were performed without any specimens inside the line. Being our sample made of living matter, the real field was modified and its value was estimated by a simulation code. The bioluminescence experiments were performed only at 900 MHz for two different measured electric fields, 53 and 140 V/m. The light emission was measured right from the beginning and after 7 and 25 h. Under RF irradiation, we found that the bioluminescence activity decreased. Compared with the control sample, the diminution was 6.8% and 44% after 7 and 25 h of irradiation, respectively, both with the low or high field. No changes of the survival factor for all the samples were observed. Besides, to understand the emission processes, we operated the deconvolution of the spectra by two Gaussian curves. The Gaussian peaks were approximately centered at 460 nm and 490 nm. The 490 nm peak was higher than the control one. Under RF, the 490 nm peak decreased compared to the 460 nm one. The decreasing was stronger for the sample in the higher field. The ratio of the emission area of the 490 nm to 460 nm was 5 for the control sample. It decreased up to 1.6 for the samples under RF. The bioluminescence improves the DNA repair by photoreactivation, and there is evidence that photolyase is preferentially activated by blue/violet light. Our finding suggests that RF exposure may stimulate DNA repair by shifting the emission spectra from blue/green (490 nm) to blue/violet (460 nm).

Nassisi, V.; Alifano, P.; Talà, A.; Velardi, L.

2012-07-01

236

Endovascular Radiofrequency Ablation for Varicose Veins  

PubMed Central

Executive Summary Objective The objective of the MAS evidence review was to conduct a systematic review of the available evidence on the safety, effectiveness, durability and cost–effectiveness of endovascular radiofrequency ablation (RFA) for the treatment of primary symptomatic varicose veins. Background The Ontario Health Technology Advisory Committee (OHTAC) met on August 26th, 2010 to review the safety, effectiveness, durability, and cost-effectiveness of RFA for the treatment of primary symptomatic varicose veins based on an evidence-based review by the Medical Advisory Secretariat (MAS). Clinical Condition Varicose veins (VV) are tortuous, twisted, or elongated veins. This can be due to existing (inherited) valve dysfunction or decreased vein elasticity (primary venous reflux) or valve damage from prior thrombotic events (secondary venous reflux). The end result is pooling of blood in the veins, increased venous pressure and subsequent vein enlargement. As a result of high venous pressure, branch vessels balloon out leading to varicosities (varicose veins). Symptoms typically affect the lower extremities and include (but are not limited to): aching, swelling, throbbing, night cramps, restless legs, leg fatigue, itching and burning. Left untreated, venous reflux tends to be progressive, often leading to chronic venous insufficiency (CVI). A number of complications are associated with untreated venous reflux: including superficial thrombophlebitis as well as variceal rupture and haemorrhage. CVI often results in chronic skin changes referred to as stasis dermatitis. Stasis dermatitis is comprised of a spectrum of cutaneous abnormalities including edema, hyperpigmentation, eczema, lipodermatosclerosis and stasis ulceration. Ulceration represents the disease end point for severe CVI. CVI is associated with a reduced quality of life particularly in relation to pain, physical function and mobility. In severe cases, VV with ulcers, QOL has been rated to be as bad or worse as other chronic diseases such as back pain and arthritis. Lower limb VV is a very common disease affecting adults – estimated to be the 7th most common reason for physician referral in the US. There is a very strong familial predisposition to VV. The risk in offspring is 90% if both parents affected, 20% when neither affected and 45% (25% boys, 62% girls) if one parent affected. The prevalence of VV worldwide ranges from 5% to 15% among men and 3% to 29% among women varying by the age, gender and ethnicity of the study population, survey methods and disease definition and measurement. The annual incidence of VV estimated from the Framingham Study was reported to be 2.6% among women and 1.9% among men and did not vary within the age range (40-89 years) studied. Approximately 1% of the adult population has a stasis ulcer of venous origin at any one time with 4% at risk. The majority of leg ulcer patients are elderly with simple superficial vein reflux. Stasis ulcers are often lengthy medical problems and can last for several years and, despite effective compression therapy and multilayer bandaging are associated with high recurrence rates. Recent trials involving surgical treatment of superficial vein reflux have resulted in healing and significantly reduced recurrence rates. Endovascular Radiofrequency Ablation for Varicose Veins RFA is an image-guided minimally invasive treatment alternative to surgical stripping of superficial venous reflux. RFA does not require an operating room or general anaesthesia and has been performed in an outpatient setting by a variety of medical specialties including surgeons and interventional radiologists. Rather than surgically removing the vein, RFA works by destroying or ablating the refluxing vein segment using thermal energy delivered through a radiofrequency catheter. Prior to performing RFA, color-flow Doppler ultrasonography is used to confirm and map all areas of venous reflux to devise a safe and effective treatment plan. The RFA procedure involves the introduction of a guide wire into the target v

2011-01-01

237

Novel Technology in the Treatment of Acne Scars: The Matrix-tunable Radiofrequency Technology  

PubMed Central

Background: Despite the many advances, scarring, particularly acne or pimple scarring, does not have a satisfactory treatment. A new armamentarium in this field is this recently devised matrix-tunable radiofrequency technology, which utilizes radiofrequency emission in the treatment of acne scars. Aims: To evaluate the efficiency of the new matrix-tunable radiofrequency technology in patients with acne scars of varying sizes. Settings and Design: A prospective study of 30 randomly selected patients with acne scars was carried out. Material and Methods: Thirty healthy patients with different types of acne scars – ice pick, box and rolling type – were randomly selected. The scars were either shallow or deep, varied in size from 2 to 20 mm and ranged in number from 10 to 50. These patients were first treated with broad-spectrum antibiotics and local exfoliating agents (topical tretinoin 0.025%) and then subjected to matrix-tunable radiofrequency technology. Each scar was treated at intervals of 1 month. A maximum of four such sittings were carried out. Patients were followed-up every 15 days. Results were noted at the end of 2 months and 6 months. Improvement was assessed by using the visual analog scale (VAS) at 2 months and 6 months, and results were noted in terms of percentage improvement of the whole face by calculating an average of percentage improvement on the basis of interviews of the patient and his/her accompanying relatives. The visual analog scaling was performed by means of high-resolution digital photographs taken at the baseline and at each subsequent visit. Results: The VAS improvement in scars ranged from 10 to 50% at the end of 2 months to 20 to 70% at the end of 6 months. Of the 30 patients of acne scars, the cosmetic result was excellent (>60% improvement) in four, good (35–60% improvement) in 18 and moderate to poor (<35% improvement) in eight. A few patients reported burning sensation and a mild sunburn-like sensation for about 1 h after treatment. The patients reported a pinkish tone for 2–3 days. Importantly, with the help of some slight make up, all the 30 patients could return to work the following day. Conclusion: Matrix-tunable radiofrequency technology is a safe and economically viable option for the dermatologists for the treatment of acne scars, because of the effective results coupled with a low downtime. PMID:21031069

Ramesh, M; Gopal, MG; Kumar, Sharath; Talwar, Ankur

2010-01-01

238

Radio-Frequency Plasma Cleaning of a Penning Malmberg Trap  

NASA Technical Reports Server (NTRS)

Radio-frequency-generated plasma has been demonstrated to be a promising means of cleaning the interior surfaces of a Penning-Malmberg trap that is used in experiments on the confinement of antimatter. {Such a trap was reported in Modified Penning-Malmberg Trap for Storing Antiprotons (MFS-31780), NASA Tech Briefs, Vol. 29, No. 3 (March 2005), page 66.} Cleaning of the interior surfaces is necessary to minimize numbers of contaminant atoms and molecules, which reduce confinement times by engaging in matter/antimatter-annihilation reactions with confined antimatter particles. A modified Penning-Malmberg trap like the one described in the cited prior article includes several collinear ring electrodes (some of which are segmented) inside a tubular vacuum chamber, as illustrated in Figure 1. During operation of the trap, a small cloud of charged antiparticles (e.g., antiprotons or positrons) is confined to a spheroidal central region by means of a magnetic field in combination with DC and radiofrequency (RF) electric fields applied via the electrodes. In the present developmental method of cleaning by use of RF-generated plasma, one evacuates the vacuum chamber, backfills the chamber with hydrogen at a suitable low pressure, and uses an RF-signal generator and baluns to apply RF voltages to the ring electrodes. Each ring is excited in the polarity opposite that of the adjacent ring. The electric field generated by the RF signal creates a discharge in the low-pressure gas. The RF power and gas pressure are adjusted so that the plasma generated in the discharge (see Figure 2) physically and chemically attacks any solid, liquid, and gaseous contaminant layers on the electrode surfaces. The products of the physical and chemical cleaning reactions are gaseous and are removed by the vacuum pumps.

Sims, William Herbert, III; Martin, James; Pearson, J. Boise; Lewis, Raymond

2005-01-01

239

Is Cryoballoon Ablation Preferable to Radiofrequency Ablation for Treatment of Atrial Fibrillation by Pulmonary Vein Isolation? A Meta-Analysis  

PubMed Central

Objective Currently radiofrequency and cryoballoon ablations are the two standard ablation systems used for catheter ablation of atrial fibrillation; however, there is no universal consensus on which ablation is the optimal choice. We therefore sought to undertake a meta-analysis with special emphases on comparing the efficacy and safety between cryoballoon and radiofrequency ablations by synthesizing published clinical trials. Methods and Results Articles were identified by searching the MEDLINE and EMBASE databases before September 2013, by reviewing the bibliographies of eligible reports, and by consulting with experts in this field. Data were extracted independently and in duplicate. There were respectively 469 and 635 patients referred for cryoballoon and radiofrequency ablations from 14 qualified clinical trials. Overall analyses indicated that cryoballoon ablation significantly reduced fluoroscopic time and total procedure time by a weighted mean of 14.13 (95% confidence interval [95% CI]: 2.82 to 25.45; P?=?0.014) minutes and 29.65 (95% CI: 8.54 to 50.77; P?=?0.006) minutes compared with radiofrequency ablation, respectively, whereas ablation time in cryoballoon ablation was nonsignificantly elongated by a weighted mean of 11.66 (95% CI: ?10.71 to 34.04; P?=?0.307) minutes. Patients referred for cryoballoon ablation had a high yet nonsignificant success rate of catheter ablation compared with cryoballoon ablation (odds ratio; 95% CI; P: 1.34; 0.53 to 3.36; 0.538), and cryoballoon ablation was also found to be associated with the relatively low risk of having recurrent atrial fibrillation (0.75; 0.3 to 1.88; 0.538) and major complications (0.46; 0.11 to 1.83; 0.269). There was strong evidence of heterogeneity and low probability of publication bias. Conclusion Our findings demonstrate greater improvement in fluoroscopic time and total procedure duration for atrial fibrillation patients referred for cryoballoon ablation than those for radiofrequency ablation. PMID:24587324

Xu, Junxia; Huang, Yingqun; Cai, Hongbin; Qi, Yue; Jia, Nan; Shen, Weifeng; Lin, Jinxiu; Peng, Feng; Niu, Wenquan

2014-01-01

240

Boltzmann expansion in a radiofrequency conical helicon thruster operating in xenon and argon  

SciTech Connect

A low pressure ({approx}0.5 mTorr in xenon and {approx}1 mTorr in argon) Boltzmann expansion is experimentally observed on axis within a magnetized (60 to 180 G) radiofrequency (13.56 MHz) conical helicon thruster for input powers up to 900 W using plasma parameters measured with a Langmuir probe. The axial forces, respectively, resulting from the electron and magnetic field pressures are directly measured using a thrust balance for constant maximum plasma pressure and show a higher fuel efficiency for argon compared to xenon.

Charles, C.; Boswell, R. [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia)] [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Takahashi, K. [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia) [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Department of Electrical Engineering, Tohoku University, Sendai 980-9579 (Japan)

2013-06-03

241

Percutaneous Radiofrequency Ablation of a Small Renal Mass Complicated by Appendiceal Perforation  

SciTech Connect

Percutaneous radiofrequency ablation (RFA) has gained wide acceptance as nephron-sparing therapy for small renal masses in select patients. Generally, it is a safe procedure with minor morbidity and acceptable short-term oncologic outcome. However, as a result of the close proximity of vital structures, such as the bowel, ureter, and large vessels, to the ablative field, complications regarding these structures may occur. This is the first article describing appendiceal perforation as a complication of computed tomography-guided RFA despite hydrodissection. When performing this innovative and promising procedure one should be aware of the possibility of particular minor and even major complications.

Boone, Judith, E-mail: j.boone@amc.uva.nl [Antoni van Leeuwenhoek Hospital, Department of Radiology, Netherlands Cancer Institute (Netherlands); Bex, Axel, E-mail: a.bex@nki.nl [Antoni van Leeuwenhoek Hospital, Department of Urology, Netherlands Cancer Institute (Netherlands); Prevoo, Warner, E-mail: w.prevoo@nki.nl [Antoni van Leeuwenhoek Hospital, Department of Radiology, Netherlands Cancer Institute (Netherlands)

2012-06-15

242

Effects of acute exposure to ultrahigh radiofrequency radiation on three antenna engineers.  

PubMed Central

Three men were accidentally exposed to high levels of ultrahigh frequency radiofrequency radiation (785 MHz mean frequency) while working on a television mast. They experienced an immediate sensation of intense heating of the parts of the body in the electromagnetic field followed by a variety of symptoms and signs which included pain, headache, numbness, and parasthesiae, malaise, diarrhoea, and skin erythema. The most notable problem was that of acute then chronic headache involving the part of the head which was most exposed. PMID:9166136

Schilling, C J

1997-01-01

243

Nonlinear frequency coupling in dual radio-frequency driven atmospheric pressure plasmas  

SciTech Connect

Plasma ionization, and associated mode transitions, in dual radio-frequency driven atmospheric pressure plasmas are governed through nonlinear frequency coupling in the dynamics of the plasma boundary sheath. Ionization in low-power mode is determined by the nonlinear coupling of electron heating and the momentary local plasma density. Ionization in high-power mode is driven by electron avalanches during phases of transient high electric fields within the boundary sheath. The transition between these distinctly different modes is controlled by the total voltage of both frequency components.

Waskoenig, J.; Gans, T. [Centre for Plasma Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom)

2010-05-03

244

[Radiofrequency of the liver - an update].  

PubMed

The impact of radiofrequency ablation (RFA) as a local ablative tumor therapy is increasing. Randomized trials justify RFA for small hepatocellular carcinoma (HCC) (single tumor ? 5 cm or three or less tumors ? 3 cm). Surgical resection still remains the gold standard for resectable colorectal liver metastases (CRLM). Several single center trials demonstrate improved patient survival by RFA and justify RFA for non-resectable CRLM. Local recurrence increases significantly with tumor diameters > 3 cm. There is insufficient evidence at this time to resolve the issue of optimal approach for treatment of CRLM. Technical development of the electrode design, improved ablation algorithms, and simplification of the exact electrode placement by new real-time fusion techniques of pre-interventional CT or MRT images with intra-interventional ultrasound have the potential to reduce the variable and sometimes high rate of local tumor recurrence. The clinical impact of immunological aspects following RFA with regard to patient survival and local tumor recurrence remains unclear. PMID:21318934

Bangard, C

2011-08-01

245

Directional Radio-Frequency Identification Tag Reader  

NASA Technical Reports Server (NTRS)

A directional radio-frequency identification (RFID) tag reader has been designed to facilitate finding a specific object among many objects in a crowded room. The device could be an adjunct to an electronic inventory system that tracks RFID-tagged objects as they move through reader-equipped doorways. Whereas commercial RFID-tag readers do not measure directions to tagged objects, the device is equipped with a phased-array antenna and a received signal-strength indicator (RSSI) circuit for measuring direction. At the beginning of operation, it is set to address only the RFID tag of interest. It then continuously transmits a signal to interrogate that tag while varying the radiation pattern of the antenna. It identifies the direction to the tag as the radiation pattern direction of peak strength of the signal returned by the tag. An approximate distance to the tag is calculated from the peak signal strength. The direction and distance can be displayed on a screen. A prototype containing a Yagi antenna was found to be capable of detecting a 915.5-MHz tag at a distance of approximately equal to 15 ft (approximately equal to 4.6 m).

Medelius, Pedro J.; Taylor, John D.; Henderson, John J.

2004-01-01

246

Radiofrequency plasma polymerized perfluoroionomer membrane materials  

SciTech Connect

Ion exchange membranes have received considerable attention in recent years. Applications of ion exchange membranes have included such electrochemical systems as water and organic electrolyzers, redox-flow batteries, and sensors. This work is a study of radiofrequency plasma polymerization of perfluorinated acid-containing monomers and a perfluorinated {open_quotes}backbone{close_quotes} comonomer as a method for synthesizing novel polyionomer film coatings for use as membranes on electrodes and biomedical sensors. The results indicate that, by altering the deposition conditions, some control can be exercised over the retention of acid functional groups by plasma polymers. Using AC impedance measurements, the ionic conductivity of these films was found to be two to four orders of magnitude higher than their aqueous environments. In addition, several of the acid-containing plasma polymerized films were hydrophilic, having an advancing water contact angle of less than fifteen degrees. The initial results of this study have demonstrated the feasibility of using acid-containing plasma polymers as crosslinked membrane materials suitable for use with electrochemical sensors and biosensors.

Danilich, M.J.; Gervasio, D.F.; Marchant, R.E. [Case Western Reserve Univ., Cleveland, OH (United States)

1993-12-31

247

Radiofrequency Ablation of Intrahepatic Cholangiocarcinoma: Preliminary Experience  

SciTech Connect

The purpose of this study was to evaluate the safety and efficacy of percutaneous ultrasound (US)-guided radiofrequency ablation (RFA) in patients with intrahepatic cholangiocarcinoma (ICCA) in a small, nonrandomized series. From February 2004 to July 2008, six patients (four men and two women; mean age 69.8 years [range 48 to 83]) with ICCA underwent percutaneous US-guided RFA. Preintervetional transarterial embolization was performed in two cases to decrease heat dispersion during RFA in order to increase the area of ablation. The efficacy of RFA was evaluated using contrast-enhanced dynamic computed tomography (CT) 1 month after treatment and then every 3 months thereafter. Nine RFA sessions were performed for six solid hepatic tumors in six patients. The duration of follow-up ranged from 13 to 21 months (mean 17.5). Posttreatment CT showed total necrosis in four of six tumors after one or two RFA sessions. Residual tumor was observed in two patients with larger tumors (5 and 5.8 cm in diameter). All patients tolerated the procedure, and there with no major complications. Only 1 patient developed post-RFA syndrome (pain, fever, malaise, and leukocytosis), which resolved with oral administration of acetaminophen. Percutaneous RFA is a safe and effective treatment for patients with hepatic tumors: It is ideally suited for those who are not eligible for surgery. Long-term follow-up data regarding local and systemic recurrence and survival are still needed.

Carrafiello, Gianpaolo, E-mail: gcarraf@tin.it; Lagana, Domenico; Cotta, Elisa; Mangini, Monica; Fontana, Federico; Bandiera, Francesca; Fugazzola, Carlo [University of Insubria c/o Ospedale di Circolo, Department of Radiology (Italy)

2010-08-15

248

CUTANEOUS REMODELING AND PHOTOREJUVENATION USING RADIOFREQUENCY DEVICES  

PubMed Central

Radio frequency (RF) is electromagnetic radiation in the frequency range of 3-300GHz. The primary effects of RF energy on living tissue are considered to be thermal. The goal of the new devices based on these frequency ranges is to heat specific layers of the skin. The directed use of RF can induce dermal heating and cause collagen degeneration. Wound healing mechanisms promote the remodeling of collagen and wound contraction, which ultimately clinically enhances the appearance of mild to moderate skin laxity. Preliminary studies have reported efficacy in the treatment of laxity that involves the periorbital area and jowls. Because RF energy is not dependent on specific chromophore interaction, epidermal melanin is not at risk of destruction and treatment of all skin types is possible. As such, radiofrequency-based systems have been used successfully for nonablative skin rejuvenation, atrophic scar revision and treatment of unwanted hair, vascular lesions and inflammatory acne. The use of RF is becoming more popular, although a misunderstanding exists regarding the mechanisms and limitations of its actions. This concise review serves as an introduction and guide to many aspects of RF in the non ablative rejuvenation of skin. PMID:20161847

Elsaie, Mohamed Lotfy

2009-01-01

249

Cutaneous remodeling and photorejuvenation using radiofrequency devices.  

PubMed

Radio frequency (RF) is electromagnetic radiation in the frequency range of 3-300GHz. The primary effects of RF energy on living tissue are considered to be thermal. The goal of the new devices based on these frequency ranges is to heat specific layers of the skin. The directed use of RF can induce dermal heating and cause collagen degeneration. Wound healing mechanisms promote the remodeling of collagen and wound contraction, which ultimately clinically enhances the appearance of mild to moderate skin laxity. Preliminary studies have reported efficacy in the treatment of laxity that involves the periorbital area and jowls. Because RF energy is not dependent on specific chromophore interaction, epidermal melanin is not at risk of destruction and treatment of all skin types is possible. As such, radiofrequency-based systems have been used successfully for nonablative skin rejuvenation, atrophic scar revision and treatment of unwanted hair, vascular lesions and inflammatory acne. The use of RF is becoming more popular, although a misunderstanding exists regarding the mechanisms and limitations of its actions. This concise review serves as an introduction and guide to many aspects of RF in the non ablative rejuvenation of skin. PMID:20161847

Elsaie, Mohamed Lotfy

2009-07-01

250

Radio-frequency compressed electron pulse-width characterization by cross-correlation between electron bunches and laser-induced plasma  

NASA Astrophysics Data System (ADS)

A method is proposed to determine the temporal width of high-brightness radio-frequency compressed electron pulses based on cross-correlation technique involving electron bunches and laser-induced plasma. The temporal evolution of 2-dimensional transverse profile of ultrafast electron bunches repelled by the formed transient electric field of laser-induced plasma on a silver needle is investigated, and the pulse-width can be obtained by analyzing these time-dependent images. This approach can characterize radio-frequency compressed ultrafast electron bunches with picosecond or sub-picosecond timescale and up to 105 electron numbers.

Li, Jing; Pei, Min-Jie; Qi, Da-Long; Qi, Ying-Peng; Yang, Yan; Sun, Zhen-Rong

2014-12-01

251

77 FR 74668 - Compliance Policy Guide; Radiofrequency Identification Feasibility Studies and Pilot Programs for...  

Federal Register 2010, 2011, 2012, 2013

...entitled ``Radiofrequency Identification (RFID) Feasibility Studies and Pilot Programs...entitled ``Radiofrequency Identification (RFID) Feasibility Studies and Pilot Programs...December 23, 2010). FDA has identified RFID as a promising technology to be used...

2012-12-17

252

75 FR 80827 - Compliance Policy Guide; Radiofrequency Identification Feasibility Studies and Pilot Programs for...  

Federal Register 2010, 2011, 2012, 2013

...entitled ``Radiofrequency Identification (RFID) Feasibility Studies and Pilot Programs...entitled ``Radiofrequency Identification (RFID) Feasibility Studies and Pilot Programs...December 22, 2008). FDA has identified RFID as a promising technology to be used...

2010-12-23

253

Towards realistic radiofrequency ablation of hepatic tumors 3D simulation and planning  

E-print Network

in medical imaging. Among them, percutaneous thermal ablation has been studied in different formsTowards realistic radiofrequency ablation of hepatic tumors 3D simulation and planning Caroline Strasbourg, France ABSTRACT Radiofrequency ablation (RFA) has become an increasingly used technique

Essert-Villard, Caroline

254

PHYSICAL REVIEW B VOLUME 48, NUMBER 13 1 OCTOBER 1993-1 Determination of the absolute sign of nuclear quadrupole interactions by laser radio-frequency  

E-print Network

PHYSICAL REVIEW B VOLUME 48, NUMBER 13 1 OCTOBER 1993-1 Determination of the absolute sign of nuclear quadrupole interactions by laser radio-frequency double-resonance experiments Tilo Blasberg the quadrupole moment of nuclear spins I > + with the electric-field-gradient (EFG) tensor leads to a splitting

Suter, Dieter

255

78 FR 33633 - Human Exposure to Radiofrequency Electromagnetic Fields  

Federal Register 2010, 2011, 2012, 2013

...discontinue the Office of Engineering and Technology (OET...induced in the external tissues of the head, e...over any 10 grams of tissue (defined as a tissue volume in the shape...found in the Office of Engineering and Technology...

2013-06-04

256

Radio-frequency induced ground state degeneracy in a Chromium Bose-Einstein condensate  

E-print Network

We study the effect of strong radio-frequency (rf) fields on a chromium Bose-Einstein condensate (BEC), in a regime where the rf frequency is much larger than the Larmor frequency. We use the modification of the Land\\'{e} factor by the rf field to bring all Zeeman states to degeneracy, despite the presence of a static magnetic field of up to 100 mG. This is demonstrated by analyzing the trajectories of the atoms under the influence of dressed magnetic potentials in the strong field regime. We investigate the problem of adiabaticity of the rf dressing process, and relate it to how close the dressed states are to degeneracy. Finally, we measure the lifetime of the rf dressed BECs, and identify a new rf-assisted two-body loss process induced by dipole-dipole interactions.

Q. Beaufils; T. Zanon; R. Chicireanu; B. Laburthe-Tolra; E. Marechal; L. Vernac; J. -C. Keller; O. Gorceix

2008-09-29

257

Faraday accelerator with radio-frequency assisted discharge (FARAD)  

NASA Astrophysics Data System (ADS)

A new electrodeless accelerator concept, called Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD), that relies on an RF-assisted discharge to produce a plasma, an applied magnetic field to guide the plasma into the acceleration region, and an induced current sheet to accelerate the plasma, is presented. The presence of a preionized plasma allows for current sheet formation at lower discharge voltages and energies than those found in other pulsed inductive accelerator concepts. A proof-of-concept experiment, supported by optical and probe diagnostics, was constructed and used to demonstrate the main features of the FARAD and to gain physical insight into the low-voltage, low-energy current sheet formation and acceleration processes. Magnetic field data indicate that the peak sheet velocity in this unoptimized configuration operating at a pulse energy of 78.5 J is 12 km/s. It is found that changes in the background gas pressure and applied field affect the initial preionized plasma distribution which, in turn, affects the sheet's initial location, relative magnetic impermeability and subsequent velocity history. The results of the experimental investigation motivated further theoretical and numerical investigations of pulsed inductive plasma acceleration. A model consisting of a set of coupled circuit equations and a one-dimensional momentum equation was nondimensionalized leading to the identification of several scaling parameters. Numerical analysis revealed the benefits of underdamped current waveforms and led to an efficiency maximization criterion that requires matching the external circuit's natural period to the acceleration timescale. Predictions of the model were compared to experimental measurements and were found to be in good qualitative agreement and reasonable quantitative agreement for most quantities. A set of design rules aimed at producing a high-performance FARAD thruster are derived using the modeling results and physical insights. The rules concern the optimization of each of the major processes in FARAD: plasma acceleration, current sheet formation, applied field generation, and mass injection and preionization, and are cast as specific prescriptions for the dynamic impedance, inductance change, circuit damping, plasma collisionality (or magnetization), magnetic field strength and topology, and intra-pulse sequencing.

Polzin, Kurt Alexander

258

Photoacoustic characterization of radiofrequency ablation lesions  

NASA Astrophysics Data System (ADS)

Radiofrequency ablation (RFA) procedures are used to destroy abnormal electrical pathways in the heart that can cause cardiac arrhythmias. Current methods relying on fluoroscopy, echocardiography and electrical conduction mapping are unable to accurately assess ablation lesion size. In an effort to better visualize RFA lesions, photoacoustic (PA) and ultrasonic (US) imaging were utilized to obtain co-registered images of ablated porcine cardiac tissue. The left ventricular free wall of fresh (i.e., never frozen) porcine hearts was harvested within 24 hours of the animals' sacrifice. A THERMOCOOLR Ablation System (Biosense Webster, Inc.) operating at 40 W for 30-60 s was used to induce lesions through the endocardial and epicardial walls of the cardiac samples. Following lesion creation, the ablated tissue samples were placed in 25 °C saline to allow for multi-wavelength PA imaging. Samples were imaged with a VevoR 2100 ultrasound system (VisualSonics, Inc.) using a modified 20-MHz array that could provide laser irradiation to the sample from a pulsed tunable laser (Newport Corp.) to allow for co-registered photoacoustic-ultrasound (PAUS) imaging. PA imaging was conducted from 750-1064 nm, with a surface fluence of approximately 15 mJ/cm2 maintained during imaging. In this preliminary study with PA imaging, the ablated region could be well visualized on the surface of the sample, with contrasts of 6-10 dB achieved at 750 nm. Although imaging penetration depth is a concern, PA imaging shows promise in being able to reliably visualize RF ablation lesions.

Bouchard, Richard; Dana, Nicholas; Di Biase, Luigi; Natale, Andrea; Emelianov, Stanislav

2012-02-01

259

Laparoscopic radiofrequency ablation of primary and metastaticliver tumors  

Microsoft Academic Search

Background: Radiofrequency thermal ablation is a new technology for the local destruction of liver tumors. Since we first described laparoscopic\\u000a radiofrequency ablation (LRFA) for the treatment of liver tumors, much has been learned about patient selection, laparoscopic\\u000a ultrasound (LU) guided placement of the ablation catheter, monitoring of the ablation process, and patient follow-up.\\u000a \\u000a \\u000a \\u000a \\u000a Methods: Since January 1996 we have performed

A. Siperstein; A. Garland; K. Engle; S. Rogers; E. Berber; A. String; A. Foroutani; T. Ryan

2000-01-01

260

Pulsed Radiofrequency Neuromodulation for the Treatment of Saphenous Neuralgia  

PubMed Central

A 65-year-old male presented with pain in his right medial calf. An imaging study revealed no acute lesions, and a diagnosis of saphenous neuralgia was made by a nerve conduction study. He received temporary pain relief with saphenous nerve blocks twice in a one-week interval. Pulsed radiofrequency neuromodulation reduced pain to 10% of the maximal pain intensity. At 6 months after the procedure, the pain intensity was not aggravated even without medication. Pulsed radiofrequency neuromodulation of the saphenous nerve may offer an effective and minimally invasive treatment for patients with saphenous neuralgia who are refractory to conservative management. PMID:24175030

Han, Bo Ram; Kim, Min Ki; Cho, Yong-Jun

2013-01-01

261

Bipolar radiofrequency ablation of tibialchondroblastomas: A report of three cases  

PubMed Central

Chondroblastoma is a rare benign cartilaginous neoplasm of bone. The recurrence rate is high and complications are frequent following open curettage with bone grafting which is the standard treatment forchondroblastomas. We performed radiofrequency ablation in three cases of tibialchondroblastoma using the bipolar system. One patient experienced residual pain for which repeat ablation was performed. No other complications were observed during follow-up. Radiofrequency ablation may offer an effective alternative for the treatment of selected cases of chondroblastoma. The lesion characteristics which are likely to influence treatment outcome and the advantages offered by the bipolar system are discussed. PMID:22900136

Rajalakshmi, Prathiba; Srivastava, Deep N; Rastogi, Shishir; Julka, Pramod Kumar; Bhatnagar, Sushma; Gamanagatti, Shivanand

2012-01-01

262

Thermal Protection with 5% Dextrose Solution Blanket During Radiofrequency Ablation  

SciTech Connect

A serious complication for any thermal radiofrequency ablation is thermal injury to adjacent structures, particularly the bowel, which can result in additional major surgery or death. Several methods using air, gas, fluid, or thermometry to protect adjacent structures from thermal injury have been reported. In the cases presented in this report, 5% dextrose water (D5W) was instilled to prevent injury to the bowel and diaphragm during radiofrequency ablation. Creating an Insulating envelope or moving organs with D5W might reduce risk for complications such as bowel perforation.

Chen, Enn Alexandria, E-mail: echen@cc.nih.gov; Neeman, Ziv; Lee, Fred T.; Kam, Anthony; Wood, Brad [National Institutes of Health, Radiology Department, Warren G. Magmison Clinical Center (United States)

2006-12-15

263

An unshielded radio-frequency atomic magnetometer with sub-femtoTesla sensitivity  

NASA Astrophysics Data System (ADS)

We demonstrate a radio-frequency potassium-vapor magnetometer operating with sensitivities of 0.3 fT/ ?{ Hz } at 0.5 MHz and 0.9 fT/ ?{ Hz } at 1.31 MHz in the absence of radio-frequency and mu-metal or magnetic shielding. The use of spatially separated magnetometers, two voxels within the same cell, permits for the subtraction of common mode noise and the retention of a gradient signal, as from a local source. At 0.5 MHz the common mode noise was white and measured to be 3.4 fT/ ?{ Hz } ; upon subtraction the noise returned to the values observed when the magnetometer was shielded. At 1.31 MHz, the common mode noise was from a nearby radio station and was reduced by a factor of 33 upon subtraction, limited only by the radio signal picked up by receiver electronics. Potential applications include in-the-field low-field magnetic resonance, such as the use of nuclear quadrupole resonance for the detection of explosives.

Keder, David A.; Prescott, David W.; Conovaloff, Adam W.; Sauer, Karen L.

2014-12-01

264

[Endocavitary ablation for arrhythmias. New modalities of radiofrequency applications. New energy types].  

PubMed

Radiofrequency remains the reference energy type for catheter ablation of rhythm disorders. In the classic indications, which are atrial flutter or tachycardia, nodal re-entry and Wolff-Parkinson-White syndrome, this energy source has the best cost-efficiency-safety ratio, subject to strict conditions of use. Some new modalities of application have further improved performance, especially active irrigation of the electrode which allows induction of deeper lesions which is very useful for the ablation of difficult atrial flutters, epicardial fascicles of Kent and ischaemic ventricular tachycardias. The only emerging alternative energy type, in the framework of classical ablation, is cold, for which the principal advantages are the homogenous and slightly thrombogenic character for the lesion involved, and the possibility of reversible applications tests which are especially useful in the ablation of structures at risk. The situation is more open-ended concerning research on ablation for atrial fibrillation or the so-called new energy types, such as ultrasound and laser, whilst recognising a renewal in interest, especially for circumferential ablation of the pulmonary veins to isolate the ectopic venous foci. Mechanical energy such as luminous energy is emitted across a catheter balloon deployed at the orifice of the vein, perpendicular to its axis, aiming to reach a continuous circumferential lesion with a minimum of applications. Equally radiofrequency has been undergoing significant evolution for this application, such as by the development of porous catheter balloons with a liquid electrode, as well as by the development of deployable circumferential catheters. Ablation is use for atrial fibrillation, by endocavity atrial segmentation remains a field of research in which radiofrequency retains an important place. It is delivered via multi-electrode catheters according to the new application modalities, either pulsed or by phase interval, which secure better efficacy by better continuity of the line of block. Research is equally underway on the use of microwaves and cold in this application. PMID:12055754

Cauchemez, B; Lavergne, Th; Extramiana, F; Siliste, C; Leenhardt, A; Coumel, Ph

2002-04-01

265

Radiofrequency hydrogen ion source with permanent magnets providing axial magnetic fielda)  

NASA Astrophysics Data System (ADS)

Uniform axial magnetic field of about 70 G is applied to a radiofrequency (rf) hydrogen ion source by arrays of permanent magnets. The plasma density and electron temperature downstream of the source and near the magnetic filter are compared with those in the previously described ion source, where the axial field has been applied by two solenoids. The source is operated at ˜350 kHz and above 10 kW rf power with a field-effect-transistor-based invertor power supply in 1.5 Pa hydrogen. The results show that the plasma density of ˜1019 m-3 near the source exit and ˜1018 m-3 near the magnetic filter can be obtained, which are higher than those with the solenoids.

Oikawa, Kohei; Saito, Yuta; Komizunai, Shota; Takahashi, Kazunori; Ando, Akira

2014-02-01

266

Density-dependent response of an ultracold plasma to few-cycle radio-frequency pulses  

NASA Astrophysics Data System (ADS)

Ultracold neutral plasmas exhibit a density-dependent resonant response to applied radio-frequency (rf) fields in the frequency range of several to hundreds of megahertz for achievable densities. We have conducted measurements where short bursts of an rf fieldwere applied to these plasmas, with pulse durations as short as two cycles. We still observed a density-dependent resonant response to these short pulses, but the time scale of the response is too short to be consistent with local heating of electrons in the plasma from collisions under a range of experimental parameters. Instead, our results are consistent with rapid energy transfer to individual electrons from electric fields resulting from an overall displacement of the electron cloud from the ions during the collective motion of the electrons. This collective motion was also observed by applying two sharp electric field pulses separated in time to the plasma. These measurements demonstrate the importance of collective motion in the energy transport in these systems.

Wilson, Truman M.; Chen, Wei-Ting; Roberts, Jacob L.

2013-01-01

267

Analytical model for the radio-frequency sheath.  

PubMed

A simple analytical model for the planar radio-frequency (rf) sheath in capacitive discharges is developed that is based on the assumptions of a step profile for the electron front, charge exchange collisions with constant cross sections, negligible ionization within the sheath, and negligible ion dynamics. The continuity, momentum conservation, and Poisson equations are combined in a single integro-differential equation for the square of the ion drift velocity, the so called sheath equation. Starting from the kinetic Boltzmann equation, special attention is paid to the derivation and the validity of the approximate fluid equation for momentum balance. The integrals in the sheath equation appear in the screening function which considers the relative contribution of the temporal mean of the electron density to the space charge in the sheath. It is shown that the screening function is quite insensitive to variations of the effective sheath parameters. The two parameters defining the solution are the ratios of the maximum sheath extension to the ion mean free path and the Debye length, respectively. A simple general analytic expression for the screening function is introduced. By means of this expression approximate analytical solutions are obtained for the collisionless as well as the highly collisional case that compare well with the exact numerical solution. A simple transition formula allows application to all degrees of collisionality. In addition, the solutions are used to calculate all static and dynamic quantities of the sheath, e.g., the ion density, fields, and currents. Further, the rf Child-Langmuir laws for the collisionless as well as the collisional case are derived. An essential part of the model is the a priori knowledge of the wave form of the sheath voltage. This wave form is derived on the basis of a cubic charge-voltage relation for individual sheaths, considering both sheaths and the self-consistent self-bias in a discharge with arbitrary symmetry. The externally applied rf voltage is assumed to be sinusoidal, although the model can be extended to arbitrary wave forms, e.g., for dual-frequency discharges. The model calculates explicitly the cubic correction parameter in the charge-voltage relation for the case of highly asymmetric discharges. It is shown that the cubic correction is generally moderate but more pronounced in the collisionless case. The analytical results are compared to experimental data from the literature obtained by laser electric field measurements of the mean and dynamic fields in the capacitive sheath for various gases and pressures. Very good agreement is found throughout. PMID:24483571

Czarnetzki, Uwe

2013-12-01

268

Modeling of small scale radio-frequency inductive discharges for electric propulsion applications  

NASA Astrophysics Data System (ADS)

This work is motivated by the increasing interest in small-scale radio-frequency ion thrusters for micro- and nanosatellite applications, in particular for stationkeeping. This specific type of thruster relies on an inductive discharge to produce positive ions that are accelerated by an external electric field in order to produce thrust. Analyzing the particle dynamics within the discharge vessel is critical for determining the performance of these thrusters, particularly as scaling down the size and thrust level of ion thrusters remains a major challenge. Until now the application of this type of propulsion system has been limited to large satellites and space platforms. The approach taken in this work was, first, to perform a simple analysis of the inductive discharge using a transformer model. However, the dimensions of the thruster and the pressure ranges at which it operates called for a different approach than those used in larger thrusters and reactors as the collisional domain and non-locality effects differ significantly. After estimating the non-locality effects by calculating the non-locality parameter, a kinetic description of the discharge was developed. From the input power, mass flow rate, and the properties of the gas used in the discharge, the density numbers, temperatures of the particles, and thrust are calculated. Simulation values are compared with experimental values obtained with the Miniature Radio-frequency Ion Thruster being developed at The Pennsylvania State University. The approach employed to model this small scale inductive discharge can be summarized as follows. First, conditions of operation and the various plasma parameters of the discharge were derived. Then, a one-dimensional kinetic model of an inductive discharge, using a Maxwellian electron distribution, was built. Results from this model were validated on data available in the literature. Finally, from the beam current derived from the 1-D model, using a two-grid ion optics configuration, thrust was calculated. In addition, an existing model of transition between capacitive and inductive modes was applied to the Miniature Radio-frequency Ion Thruster geometry and its electrical properties. A description of the different types of capacitively coupled radio-frequency initiation mechanisms is also given.

Mistoco, Valerie F. M.

269

Carbon Nanotube Radio-Frequency Single-Electron Transistor  

Microsoft Academic Search

We discuss the theory of the radio-frequency single-electron transistor and the measurements that use multiwalled carbon nanotubes as active elements. Our devices made of plasma-enhanced chemical-vapor-deposition nanotubes yield charge sensitivities of 10-20 ?e\\/\\u000a

Leif Roschier; Mika Sillanpää; Wang Taihong; Markus Ahlskog; Sumio Iijima; Pertti Hakonen

2004-01-01

270

Arthroscopic gluteal muscle contracture release with radiofrequency energy.  

PubMed

Gluteal muscle contracture is common after repeated intramuscular injections and sometimes is sufficiently debilitating to require open surgery. We asked whether arthroscopic release of gluteal muscle contracture using radiofrequency energy would decrease complications with clinically acceptable results. We retrospectively reviewed 108 patients with bilateral gluteal muscle contractures (57 males, 51 females; mean age, 23.7 years). We used inferior, anterosuperior, and posterosuperior portals. With the patient lying laterally, we developed and enlarged a potential space between the gluteal muscle group and the subcutaneous fat using blunt dissection. Under arthroscopic guidance through the inferior portal, we débrided and removed fatty tissue overlying the contractile band of the gluteal muscle group using a motorized shaver introduced through the superior portal. Radiofrequency then was introduced through the superior portal to gradually excise the contracted bands from superior to inferior. Finally, hemostasis was ensured using radiofrequency. Patients were followed a minimum of 7 months (mean, 17.4 months; range, 7-42 months). At last followup, the adduction and flexion ranges of the hip were 45.3 degrees +/- 8.7 degrees and 110.2 degrees +/- 11.9 degrees, compared with 10.4 degrees +/- 7.2 degrees and 44.8 degrees +/- 14.1 degrees before surgery. No hip abductor contracture recurred and no patient had residual hip pain or gluteal muscle wasting. We found gluteal muscle contracture could be released effectively with radiofrequency energy. PMID:18975040

Liu, Yu-Jie; Wang, Yan; Xue, Jing; Lui, Pauline Po-Yee; Chan, Kai-Ming

2009-03-01

271

A technique for periorbital syringomas: intralesional radiofrequency ablation  

PubMed Central

AIM To evaluate the efficacy of intralesional radiofrequency ablation in the treatment of periorbital syringomas. METHODS We tried the intralesional radiofrequency ablation for 64 patients with periorbital syringomas from 2007 to 2011. The operation was performed under 2.5 loupe magnifications. The handpiece was assembled with a needle electrode and connected to the radiofrequency ablation apparatus. The electrode was then inserted into the target lesions in dermis and delivering injury to the base of these tumors. Results were assessed clinically by comparing pre- and post-treatment photographs and patient satisfaction rates. RESULTS Clinical improvement increased with each subsequent treatment session. The percent of patients whose clinic improvement grade were?3 after each session was respectively 71.9%(Session1), 83.3%(Session2), and 100%(Session3). The statistical results indicated the concordance of the clinical assessment and the satisfaction level of patients (kappa=0.78 of the session1; kappa=0.82 of the session2). The majority of patients had good or excellent cosmetic results. Postoperatively, there were no permanent side effects or recurrences. CONCLUSION As a new technique of minimally invasion, the intralesional radiofrequency ablation was found to be an effective, inexpensive, highly precise and safe way of treating periorbital syringomas. PMID:22762046

Huang, Li-Ping; Zhang, Leng; Wang, Xing-Lin; Liu, Xiao-Cui; Jiang, Tian-Yu; Lin, Bi-Weng

2012-01-01

272

Osteoid osteoma of the cuboid managed by percutaneous radiofrequency ablation.  

PubMed

We present details of a case of osteoid osteoma of the tarsal cuboid bone. Osteoid osteoma arising in the foot is not very common, and localization in the cuboid is rare. To our knowledge, this is the first case of osteoid osteoma of the cuboid bone treated successfully by percutaneous radiofrequency ablation. PMID:24556489

Chakraverty, Julian; Al-Mokhtar, Namir; James, Steven L

2014-01-01

273

Radiofrequency ablation in the treatment of liver tumors in children  

Microsoft Academic Search

Hepatoblastoma and liver metastasis of Wilms tumors are rare hepatic tumors in children. Treatment of both tumors consists of a combination of chemotherapy and liver surgery. Radiofrequency ablation is frequently used for the treatment of adult liver tumors, but is rarely mentioned as a treatment option in pediatric liver tumors. We present a patient with hepatoblastoma and one with liver

Stijn van Laarhoven; Robertine van Baren; Rienk Yde Johan Tamminga; Koert Pieter de Jong

274

Towards ultrasound cardiac image segmentation based on the radiofrequency signal  

Microsoft Academic Search

In echocardiography, the radio-frequency (RF) image is a rich source of information about the investigated tissues. Nevertheless, very few works are dedicated to boundary detection based on the RF image, as opposed to envelope image. In this paper, we investigate the feasibility and limitations of boundary detection in echocardiographic images based on the RF signal. We introduce two types of

Igor Dydenko; Denis Friboulet; Jean-Marie Gorce; Jan D’hooge; Bart Bijnens; Isabelle E. Magnin

2003-01-01

275

Cardiovascular risk in operators under radiofrequency electromagnetic radiation.  

PubMed

The aim of the study was to assess the long-term effects of radiofrequency electromagnetic radiation (EMR) on the cardiovascular system. Two groups of exposed operators (49 broadcasting (BC) station and 61 TV station operators) and a control group of 110 radiorelay station operators, matched by sex and age, with similar job characteristics except for the radiofrequency EMR were studied. The EMR exposure was assessed and the time-weighted average (TWA) was calculated. The cardiovascular risk factors arterial pressure, lipid profile, body mass index, waist/hip ratio, smoking, and family history of cardiovascular disease were followed. The systolic and diastolic blood pressure (SBP and DBP), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) were significantly higher in the two exposed groups. It was found that the radiofrequency EMR exposure was associated with greater chance of becoming hypertensive and dyslipidemic. The stepwise multiple regression equations showed that the SBP and TWA predicted the high TC and high LDL-C, while the TC, age and abdominal obesity were predictors for high SBP and DBP. In conclusion, our data show that the radiofrequency EMR contributes to adverse effects on the cardiovascular system. PMID:16503299

Vangelova, Katia; Deyanov, Christo; Israel, Mishel

2006-03-01

276

The imprint of radiofrequency in the management of hepatocellular carcinoma  

PubMed Central

Background. This article reviews the current results of radiofrequency application in the management of hepatocellular carcinoma (HCC) with reference to the comparison between the different surgical modalities. Method. An electronic search was performed for studies on the treatment of HCC. Results. Thermoablation by means of radiofrequency (RFA), microwave coagulation therapy (MCT) and laser-induced thermotherapy (LITT) provides tumor necrosis with a low complication rate. These methods are still not predictable and it is difficult to monitor the extent of necrosis in a real-time manner. Combined transarterial embolization and RF ablation is a promising strategy for large HCCs. Radiofrequency-assisted liver resection is unique and has become very popular recently because it permits parenchymal transection with minimal blood loss. Conclusion. Many alternative techniques have been applied recently for the management of HCC but their exact roles need to be defined by randomized studies. Advances in technology and refinements in technique may provide an effective and predictable way to ablate liver tumors using radiofrequency devices. PMID:18333136

Bramis, Ioannis; Triantopoulou, Charikleia; Madariaga, Juan; Dervenis, Christos

2006-01-01

277

Optimizing Needle Placement in Treatment Planning of Radiofrequency Ablation  

E-print Network

. INTRODUCTION Radiofrequency ablation (RFA) has become an increasingly used thermal ablative modality models of ablation have proven integral in understanding the roles that thermal and electrical properties into the planning process. Computational models of thermal ablation processes usually employ Pennes bioheat equation

Miga, Michael I.

278

Nonablative facelift in Indian skin with superpulsed radiofrequency  

PubMed Central

Aims: To evaluate the effect of nonablative superpulsed radiofrequency used for skin tightening and improvement of skin folds in Indian patients. Settings and Design: One hundred patients in the age group of 35-65 years with laxity of skin over face and neck were taken up for study using superpulse radiofrequency. Methods and Materials: Superpulsed radiofrequency is a biterminal, monopolar device which delivers current at the frequency of 1.75 MHz. In this study, current was delivered to the tissue with a capacitive electrode with a diameter of 25 mm. Power of 100-120 W, frequency of 18 Hz and pulse width of 50 ms was used. Statistical Analysis Used: Chi-square test, nonparametric Friedman test. Results: Evaluation was done by two independent observers on the basis of comparative photographs taken before treatment and then monthly after treatment for up to 6 months. A quartile grading scale was used. Patient satisfaction scores matched the clinical improvements observed. Ninety four patients completed a 6 month follow up. The age groups taken were 31-40 years, 41-50 years, 51-60 years, and >60 years and various areas were studied. The difference in improvement in all areas except glabellar folds across all age groups was found to be statistically significant. Conclusions: Nonablative face lift with a superpulsed radiofrequency machine is a safe, convenient and quick office procedure with excellent cosmetic results. It is noninvasive and there is no downtime. It can be used in all skin types and is safe on Indian skin. Longterm studies of effect of nonablative radiofrequency treatment on Indian skin is required. PMID:23130205

Sharad, Jaishree

2011-01-01

279

Multisource, Phase-controlled Radiofrequency for Treatment of Skin Laxity  

PubMed Central

Objective: The objective of this study was to analyze the correlation between degrees of clinical improvement and microscopic changes detected using confocal microscopy at the temperature gradients reached in patients treated for skin laxity with a phase-controlled, multisource radiofrequency system. Design and setting: Patients with skin laxity in the abdominal area were treated in six sessions with radiofrequency (the first 4 sessions were held at 2-week intervals and the 2 remaining sessions at 3-week intervals). Patients attended monitoring at 6, 9, and 12 months. Participants: 33 patients (all women). Measurements: The authors recorded the following: variations in weight, measurements of the contour of the treated area and control area, evaluation of clinical improvement by the clinician and by the patient, images taken using an infrared camera, temperature (before, immediately after, and 20 minutes after the procedure), and confocal microscopy images (before treatment and at 6, 9, and 12 months). The degree of clinical improvement was contrasted by two external observers (clinicians). The procedure was performed using a new phase-controlled, multipolar radiofrequency system. Results: The results reveal a greater degree of clinical improvement in patients with surface temperature increases greater than 11.5ºC at the end of the procedure and remaining greater than 4.5ºC 20 minutes later. These changes induced by radiofrequency were contrasted with the structural improvements observed at the dermal-epidermal junction using confocal microscopy. Changes are more intense and are statistically correlated with patients who show a greater degree of improvement and have higher temperature gradients at the end of the procedure and 20 minutes later. Conclusion: Monitoring and the use of parameters to evaluate end-point values in skin quality treatment by multisource, phased-controlled radiofrequency can help optimize aesthetic outcome. PMID:21278896

Moreno-Moraga, Javier; Muñoz, Estefania; Cornejo Navarro, Paloma

2011-01-01

280

Theoretical modeling for radiofrequency ablation: state-of-the-art and challenges for the future  

PubMed Central

Radiofrequency ablation is an interventional technique that in recent years has come to be employed in very different medical fields, such as the elimination of cardiac arrhythmias or the destruction of tumors in different locations. In order to investigate and develop new techniques, and also to improve those currently employed, theoretical models and computer simulations are a powerful tool since they provide vital information on the electrical and thermal behavior of ablation rapidly and at low cost. In the future they could even help to plan individual treatment for each patient. This review analyzes the state-of-the-art in theoretical modeling as applied to the study of radiofrequency ablation techniques. Firstly, it describes the most important issues involved in this methodology, including the experimental validation. Secondly, it points out the present limitations, especially those related to the lack of an accurate characterization of the biological tissues. After analyzing the current and future benefits of this technique it finally suggests future lines and trends in the research of this area. PMID:16620380

Berjano, Enrique J

2006-01-01

281

Nursing and quality of life in patients with atrial fibrillation before and after radiofrequency ablation.  

PubMed

The importance of nursing and patient quality of life is a top concern for medical professionals. Therefore, participation by medical professionals in raising awareness and continuously supporting improvements in nursing care is an essential part of improving patient quality of life. Modern medical techniques and procedures are changing rapidly, particularly in the field of cardiology. This has resulted in changing roles and increased responsibility for nurses and confirms the necessity for changing the perception of nurses relative to their role in the medical environment and to patient care. This paper presents the results from the first phase of a research project and focuses on quality of life and problematic areas associated with the needs of patients with atrial fibrillation before and after radiofrequency catheter ablation. Atrial fibrillation is one of the most common supraventricular arrhythmias. Its incidence in the general population has risen significantly over the last twenty years. The objective of this research was to assess those areas, which are considered by patients to be problematic before therapeutic intervention. The research was realized through a quantitative survey using a modified questionnaire. Results showed that AF reduced the quality of life both physically and psychologically (i.e. increased levels of anxiety and depression). Results also showed that radiofrequency catheter ablation was able to alleviate symptoms associated with AF and was also able to increase patient quality of life. PMID:25433354

Pavelková, Zde?ka; Bulava, Alan

2014-11-30

282

Nonsurgical nonablative treatment of aging skin: radiofrequency technologies between aggressive marketing and evidence-based efficacy.  

PubMed

The gold standard treatment for the many aesthetic aspects of aging has for many years been surgery in its many forms. However, with increasing patient demand for cosmetic rejuvenation and with the strong desire and drive by patients to attain aesthetic enhancement with minimal risk and rapid recovery, there has been a strong surge inspiring the field of nonsurgical skin rejuvenation. Traditionally, most of the nonsurgical methods have centered around those that destroy the epidermis and cause a dermal wound, with resultant dermal collagen remodeling and secondary skin tightening and rhytid improvement. Currently, there is growing interest in a wide range of nonablative interventions that, predictably, are claimed to rejuvenate skin and subcutaneous tissue "safely and effectively." Although several nonablative systems have been cleared by the U.S. Food and Drug Administration (FDA) for the purpose of skin rejuvenation and despite significant reported improvement in the appearance of signs and symptoms of photoaging by relatively noninvasive means, the clinical results have been generally less than impressive, with most subjects showing only mild improvement. The current review aims at summarizing the various nonablative methods currently in use for skin rejuvenation and to evaluate the evidence-based efficacy of a particular nonablative radiofrequency (NARF) method: monopolar radiofrequency. PMID:19437070

Atiyeh, Bishara S; Dibo, Saad A

2009-05-01

283

Various complications of percutaneous radiofrequency ablation for hepatic tumors: radiologic findings and technical tips.  

PubMed

Radiofrequency ablation is a safe and effective treatment for primary and secondary liver malignancies and has a low complication rate; however, there are various radiofrequency ablation-related complications which can occur from the thorax to the pelvis. Although most of these complications are usually minor and self-limited, they may become fatal if diagnosis and treatment are delayed. It is important for radiologists performing radiofrequency ablation to have a perspective regarding the possible radiofrequency ablation-related complications and their risk factors as well as the radiologic findings for their timely detection and increase of the treatment efficacy, and thereby encouraging the use of the radiofrequency ablation technique. This article illustrates the various imaging features of common and rare radiofrequency ablation-related complications as well as offers technical tips in order to avoid these complications. PMID:24277883

Kwon, Heon-Ju; Kim, Pyo Nyun; Byun, Jae Ho; Kim, Kyoung Won; Won, Hyung Jin; Shin, Yong Moon; Lee, Moon-Gyu

2014-11-01

284

Radio-frequency identification of surgical sponges in the abdominal cavity of pigs  

PubMed Central

Background Counting the sponges is an important step in surgical procedures. A miscount may impact the patient's health, and it also has legal implications for the surgeon. This is an experimental study evaluating radio-frequency technology used in the perioperative period to identify surgical sponges left in the peritoneal cavity of swine. Methods Radio-frequency labeled-disc identification tags were sewn into 40 surgical towels. Twenty labels had the ability to emit radio-frequency waves, and 20 labels were inert to radio-frequency identification. Twenty adult pigs that underwent laparotomy and randomly received two surgical sponges were scanned by a radio-frequency identification antenna. Results This method presented a positive predictive value of 100% and 100% specificity and sensitivity, as all of the tagged surgical sponges were detected. Conclusion Radio-frequency identification has been proved to be a useful method for the identification of surgical sponges within the abdominal cavities of swine. PMID:25568782

Wiederkehr, Julio Cesar; Gama, Ricardo R.; Wiederkehr, Henrique A.; Stelmasuk, Kleber; Carvalho, Caroline A.; Wiederkehr, Barbara A.

2014-01-01

285

Treatment of bone tumours by radiofrequency thermal ablation  

Microsoft Academic Search

Radiofrequency thermal ablation (RFTA) is considered the treatment of choice for osteoid osteomas, in which it has long been\\u000a safely used. Other benign conditions (chondroblastoma, osteoblastoma, giant cell tumour, etc.) can also be treated by this\\u000a technique, which is less invasive than traditional surgical procedures. RFTA ablation is also an option for the palliation\\u000a of localized, painful osteolytic metastatic and

Fernando Ruiz Santiago; María del Mar Castellano García; Jose Luis Martínez Montes; Manuel Ruiz García; Juan Miguel Tristán Fernández

2009-01-01

286

Diaphragmatic Hernia After Radiofrequency Ablation for Hepatocellular Carcinoma  

SciTech Connect

We describe a 71-year-old woman with a hepatocellular carcinoma who underwent percutaneous radiofrequency ablation (RF) with a single internally cooled electrode under computed tomography (CT) fluoroscopic guidance. Nine months after the procedure, CT images showed herniation of the large intestine into the right pleural cavity. To our knowledge this complication of RF performed with a single internally cooled electrode under CT guidance has not been previously reported.

Yamagami, Takuji, E-mail: yamagami@koto.kpu-m.ac.jp; Yoshimatsu, Rika; Matsushima, Shigenori; Tanaka, Osamu; Miura, Hiroshi; Nishimura, Tsunehiko [Kyoto Prefectural University of Medicine, Department of Radiology, Graduate School of Medical Science (Japan)

2011-02-15

287

Pressure micro-sensor based on Radio-Frequency transducer  

Microsoft Academic Search

A new type of pressure micro-sensors is reported in this communication. It is based on the use of a Radio-Frequency transducer. The pressure to be measured is applied on a silicon membrane located in the close vicinity of a coplanar millimeter-wave resonator: when varying the applied pressure, the distance between the membrane and the planar resonator is modified and consequently,

Mohamed Mehdi Jatlaoui; Patrick Pons; Herve Aubert

2008-01-01

288

Percutaneous radiofrequency upper thoracic sympathectomy: a new technique.  

PubMed

The author describes a new technique for performing unilateral or bilateral upper thoracic sympathectomy safely, effectively, and more easily than by any of the surgical methods now in use. The technique described is one of percutaneous radiofrequency sympathectomy, which is usually done on a day surgery or outpatient surgery basis. The technique has been effective and well tolerated in a small group of patients. PMID:6514152

Wilkinson, H A

1984-12-01

289

Recurrent hepatocellular carcinoma successfully treated with radiofrequency thermal ablation  

Microsoft Academic Search

:   We report a patient with hepatocellular carcinoma (HCC) who was successfully treated with radiofrequency thermal ablation\\u000a (RFA). A 71-year-old man was admitted to our hospital in August 1996 with recurrence of HCC. Partial hepatic resection had\\u000a been performed in January 1993 for HCC that had measured 1.3 cm in segment VIII, and subsequently he had received six sessions\\u000a of

Osamu Kainuma; Takehide Asano; Hiromichi Aoyama; Yasushi Shinohara

1999-01-01

290

Local Recurrence After Laparoscopic Radiofrequency Thermal Ablation of Hepatic Tumors  

Microsoft Academic Search

Background: Since we first described laparoscopic radiofrequency ablation (LRFA) of liver tumors, several reports have documented technical and safety aspects of this procedure. Little is known, however, about the long-term follow-up of such patients.Methods: From January 1996 to February 1999, we performed LRFA on 250 liver tumors in 66 patients. Triphasic spiral computed tomographic scanning was obtained preoperatively and at

Allan Siperstein; Adella Garland; Kristen Engle; Stanley Rogers; Eren Berber; Arash Foroutani; Andreas String; Tamara Ryan; Philip Ituarte

2000-01-01

291

Stopping electrons with radio-frequency pulses in the quantum Hall regime  

NASA Astrophysics Data System (ADS)

Most of the functionality of modern electronic circuits relies on the possibility to modify the path followed by the electrons using, e.g., field effect transistors. Here we discuss the interplay between the modification of this path and the quantum dynamics of the electronic flow. Specifically, we study the propagation of charge pulses through the edge states of a two-dimensional electron gas in the quantum Hall regime. By sending radio-frequency (rf) excitations on a top gate capacitively coupled to the electron gas, we manipulate these edge states dynamically. We find that a fast rf change of the gate voltage can stop the propagation of the charge pulse inside the sample. This effect is intimately linked to the vanishing velocity of bulk states in the quantum Hall regime and the peculiar connection between momentum and transverse confinement of Landau levels. Our findings suggest possibilities for stopping, releasing, and switching the trajectory of charge pulses in quantum Hall systems.

Gaury, Benoit; Weston, Joseph; Waintal, Xavier

2014-10-01

292

Modeling and Simulation of the sheath in radio-frequency driven plasmas at atmospheric pressure  

NASA Astrophysics Data System (ADS)

Microplasmas at atmospheric pressure recently gained increasing attention. Due to their extraordinary characteristics new fields of applications are explored. Various aspects of the discharge mechanisms have to be considered to model and simulate microplasmas. Since microplasmas are dominated by their spatial boundaries, this particularly holds for the sheaths. In this paper we focus on the sheath of radio-frequency driven microplasmas at atmospheric pressure. To account for the chemistry of characteristic applications we set up a multi-species model of the sheath. Based on a scale analysis in time and space we discuss resulting assumptions for the fluid equations for electrons and ions. We solve for these equations self-consistently coupled to Poisson's equation for the electrostatic potential. Finally, we present the density profiles of the electrons and ions depending on various discharge parameters.

Hemke, Torben; Mussenbrock, Thomas; Brinkmann, Ralf Peter

2011-11-01

293

Elimination of Radio-Frequency Noise by Identifying and Diverting Large RF Ground Currents  

SciTech Connect

The problem of electromagnetic interference in scientific instruments is compounded for high-power plasma experiments by the large currents and voltages as well as by the broad bandwidths of the instruments. Ground loops are known to allow stray magnetic fields to drive large ground currents that can induce spurious signals and damage electronics. Furthermore, even when a ground loop is broken, capacitive coupling can still permit the flow of radio-frequency current, resulting in high-frequency spurious signals that can overwhelm the desired signal. We present the effects of RF ground loops on the output of vacuum photodiodes used in the Caltech Solar Loop Experiment and demonstrate the elimination of the spurious signals by diverting the ground currents away from the most vulnerable point of the signal line. Techniques for identifying the RF ground loops are also discussed. These techniques should be valuable in many high-power systems where interference from spurious coupling is an issue.

Perkins, R. J.; Bellan, P. M. [Applied Physics, California Institute of Technology (United States)

2011-12-23

294

Radio-Frequency Sustainment of Laser Initiated, High-Pressure Air Constituent Plasmas  

NASA Astrophysics Data System (ADS)

In this paper we investigate the feasibility of creating a high-density ˜ 1012-1014 cm-3, large volume seed plasma in air constituents by laser (300 mJ, 20(±2) ns) preionization of an organic gas seeded in high-pressure gas mixtures and then sustained by efficient absorption of rf power (1-25 kW pulsed) through inductive coupling of the wave fields. A multi-turn helical antenna is used to couple radio-frequency power through a capacitive matching network. A 105 GHz interferometer is employed to obtain the plasma density in the presence of high collisionality utilizing phase shift and amplitude attenuation data. TMAE Plasma decay mechanisms with and without the background gas are examined.

Akhtar, Kamran; Scharer, John E.; Tysk, Shane M.; Denning, Mark

2003-12-01

295

Ultra-sensitive high-density Rb-87 radio-frequency magnetometer  

SciTech Connect

Radio-frequency (RF) atomic magnetometers (AMs) can be used in many applications, such as magnetic resonance imaging and nuclear quadrupole resonance. High-density AMs provide both superior sensitivity and large bandwidth. Previously, high-density potassium AMs were demonstrated, but these magnetometers have various disadvantages, such as high-temperature of operation and bulky design. We demonstrate a rubidium-87 RF AM with 5 fT/Hz{sup 1/2} sensitivity (3 fT Hz{sup 1/2} probe noise), which is comparable to that of the best potassium magnetometers. Our magnetometer also features a simple fiber-optic design, providing maximum flexibility for magnetic-field measurements.

Savukov, I.; Boshier, M. G. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Karaulanov, T. [CNLS - Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2014-01-13

296

Spatial distribution of the plasma parameters in a radio-frequency driven negative ion source.  

PubMed

Results from initial stage of modeling of the SPIDER source of negative hydrogen/deuterium ions currently under development in Consorzio RFX (Padova) regarding ITER are presented. A 2D model developed within the fluid plasma theory for low-pressure discharges (free-fall regime maintenance) is applied to the gas-discharge conditions planned and required for the SPIDER source: gas pressure of 0.3 Pa and radio-frequency (rf) power of 100 kW absorbed in a single driver. The results are for the spatial distribution of the plasma characteristics (charged particle densities, electron temperature and electron energy flux, plasma potential, and dc electric field) with conclusions for the role of the electron energy flux in the formation of the discharge structure. PMID:24593544

Todorov, D; Tarnev, Kh; Paunska, Ts; Lishev, St; Shivarova, A

2014-02-01

297

Application of radiofrequency superconductivity to accelerators for high-current ion beams  

SciTech Connect

A development program is underway to apply rf superconductivity to the design of continuous-wave (cw) linear accelerators for high-current, high-brightness ion beam. During the last few years, considerable progress has been made both experimentally and theoretically toward this application. Recent tests of niobium resonators for ion acceleration have yielded average accelerating gradients as high as 18 MV/m. In an experiment with a radio-frequency quadrupole geometry, niobium was found to sustain cw peak surface electric fields as high as 128 MV/m over large (10 cm) surface areas. Theoretical studies of beam halo, cumulative beam breakup and alternating-phase focusing have also yielded important results. This paper su-summarizes the recent progress and identifies current and future work in the areas of superconducting accelerator technology for high-current ion beams.

Delayen, J.R.; Bohn, C.L.; Kennedy, W.L.; Roche, C.T.; Sagalovsky, L.

1992-12-31

298

Application of radiofrequency superconductivity to accelerators for high-current ion beams  

SciTech Connect

A development program is underway to apply rf superconductivity to the design of continuous-wave (cw) linear accelerators for high-current, high-brightness ion beam. During the last few years, considerable progress has been made both experimentally and theoretically toward this application. Recent tests of niobium resonators for ion acceleration have yielded average accelerating gradients as high as 18 MV/m. In an experiment with a radio-frequency quadrupole geometry, niobium was found to sustain cw peak surface electric fields as high as 128 MV/m over large (10 cm) surface areas. Theoretical studies of beam halo, cumulative beam breakup and alternating-phase focusing have also yielded important results. This paper su-summarizes the recent progress and identifies current and future work in the areas of superconducting accelerator technology for high-current ion beams.

Delayen, J.R.; Bohn, C.L.; Kennedy, W.L.; Roche, C.T.; Sagalovsky, L.

1992-01-01

299

Surface Impedance Measurements of Single Crystal MgB2 Films for Radiofrequency Superconductivity Applications  

SciTech Connect

We report microstructure analyses and superconducting radiofrequency (SRF) measurements of large scale epitaxial MgB{sub 2} films. MgB{sub 2} films on 5 cm dia. sapphire disks were fabricated by a Hybrid Physical Chemical Vapor Deposition (HPCVD) technique. The electron-beam backscattering diffraction (EBSD) results suggest that the film is a single crystal complying with a MgB{sub 2}(0001) {parallel} Al{sub 2}O{sub 3}(0001) epitaxial relationship. The SRF properties of different film thicknesses (200 nm and 350 nm) were evaluated under different temperatures and applied fields at 7.4 GHz. A surface resistance of 9 {+-} 2 {mu}{Omega} has been observed at 2.2 K.

Binping Xiao, Xin Zhao, Joshua Spradlin, Charles Reece, Michael Kelley, Teng Tan, Xi Xiaoxing

2012-07-01

300

21 CFR 870.2910 - Radiofrequency physiological signal transmitter and receiver.  

...FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2910 Radiofrequency physiological signal transmitter and receiver....

2014-04-01

301

21 CFR 870.2910 - Radiofrequency physiological signal transmitter and receiver.  

Code of Federal Regulations, 2013 CFR

...FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2910 Radiofrequency physiological signal transmitter and receiver....

2013-04-01

302

Effects of the shielding cylinder and substrate on the characteristics of an argon radio-frequency atmospheric glow discharge plasma jet  

Microsoft Academic Search

With unique features of low breakdown voltages, large and uniform discharge areas and high concentrations of chemically reactive species, radio-frequency, atmospheric-pressure glow discharge (rf APGD) plasma sources produced with bare-metallic electrodes have shown promising prospects in the field of materials processing. In this paper, the spatial distributions (i.e., the directly measured integrated axial distribution and the radial distribution by using

Guo Li; Pei-Si Le; He-Ping Li; Cheng-Yu Bao

2010-01-01

303

The back-diffusion effect of air on the discharge characteristics of atmospheric-pressure radio-frequency glow discharges using bare metal electrodes  

Microsoft Academic Search

Radio-frequency (RF), atmospheric-pressure glow discharge (APGD) plasmas using bare metal electrodes have promising prospects in the fields of plasma-aided etching, deposition, surface treatment, disinfection, sterilization, etc. In this paper, the discharge characteristics, including the breakdown voltage and the discharge voltage for sustaining a stable and uniform alpha mode discharge of the RF APGD plasmas are presented. The experiments are conducted

Wen-Ting Sun; Tian-Ran Liang; Hua-Bo Wang; He-Ping Li; Cheng-Yu Bao

2007-01-01

304

Dust transport in a magnetized radio-frequency discharge under microgravity conditions.  

PubMed

Dust is found in plasmas used in industrial applications, such as microelectronics and solar cell manufacturing, in fusion plasmas, where it is usually the result of plasma-wall interactions, and in plasmas in space, such as planetary atmospheres, cometary tails, planetary rings, interstellar molecular clouds, and star and planet formation regions. In plasma applications, magnetic fields are occasionally used, mainly to confine the plasma. In space, however, magnetic fields are very often present and they may strongly influence the behavior of dusty plasma, for instance in the formation of stars and planets. We extended a fully self-consistent two-dimensional fluid model for radio-frequency discharges by adding a homogeneous axial magnetic field and the effect it has on the transport of plasma species in a low-temperature dusty discharge. We show that the magnetic field has an important effect on the (ambipolar) diffusion of ions and electrons in the bulk of the discharge. This causes an important change in the force balance of the dust particles and in the time scales of the formation of a dust-free void. Finally, we compare the parameters of the modeled discharge with the parameters of a planet formation region around a young stellar object (YSO). We conclude that a magnetic field in both low-temperature rf discharges under micro-gravity conditions and dusty plasmas around YSO's has an important effect on the transport of dust and must be important for the formation of planets and stars. PMID:16383541

Land, V; Goedheer, W J; Akdim, M R

2005-10-01

305

Radiofrequency magnetoelastic resonators for magnetoelectric applications  

NASA Astrophysics Data System (ADS)

Magnetoelastic resonance measurements are carried out in short ribbons (down to 1 cm length) of Fe59Co16Si15B10 metallic glasses, both as-quenched and after annealing at 400 °C for 10 min. The resonant frequency exceeds 200 kHz with good Q factors for the shortest elements in the as-quenched state. Sandwich-type laminated magnetoelectric (ME) composites are prepared by gluing these ribbons to a PVDF piezoelectric polymer layer, showing good ME response. This effect is discussed as a function of the as-quenched or annealed state, and the length of the magnetoelastic ribbon, and is of interest for near field communication applications.

Lasheras, A.; Gutiérrez, J.; Balza, A.; Barandiarán, J. M.; Rodríguez Pierna, A.

2014-08-01

306

Synthesis of Spinel Ferrites in Radiofrequency Thermal Plasma Reactor J. Szpvlgyi1,2  

E-print Network

Synthesis of Spinel Ferrites in Radiofrequency Thermal Plasma Reactor J. Szépvölgyi1,2 , L. Gál1 conditions on properties of products were studied in details. Keywords: radiofrequency thermal plasma, spinel, ferrite 1. Introduction The spinel ferrites of MeFe2O4 stoichiometry (where Me = Zn2+ , Fe2+ , Ni2+ , Co2

Gubicza, Jenõ

307

Radiofrequency catheter ablation of atrial flutter: Procedural success and long-term outcome  

Microsoft Academic Search

The objective of this study was to describe the procedural success and clinical recurrences after radiofrequency catheter ablation of atrial flutter. A deflectable catheter with a 4 or 5 mm tip was positioned in the posterior right atrium. Radiofrequency energy was delivered sequentially from the tricuspid annulus to the inferior vena cava. Catheter ablation during 18 sessions for 16 patients

Jonathan S. Steinberg; Sanjay Prasher; Steven Zelenkofske; Frederick A. Ehlert

1995-01-01

308

Radiofrequency and Cryoablation of Atrial Fibrillation in Patients Undergoing Valvular Operations  

Microsoft Academic Search

Background. Previous studies have shown that the maze operation can restore sinus rhythm and atrial transport function in patients with chronic atrial fibrillation. The purpose of this study was to test the feasibility of the application of radiofrequency and cryoablation as an alternative to the classic maze operation.Methods. Twelve patients undergoing mitral valve procedures were included in this study. Radiofrequency

Mien-Cheng Chen; G. Bih-Fang Guo; Jen-Ping Chang; Kuo-Ho Yeh; Morgan Fu

1998-01-01

309

Numerical studies of current generation by radio-frequency traveling waves  

E-print Network

Numerical studies of current generation by radio-frequency traveling waves Charles F. F. Karney January 1979; final manuscript received 7 May 1979) By injecting radio-frequency traveling waves of the fusion power output. Recently,' the damping of high-phase-velocity radio- frequency traveling waves has

Karney, Charles

310

RADIO-CONTROLLED CYBORG BEETLES: A RADIO-FREQUENCY SYSTEM FOR  

E-print Network

RADIO-CONTROLLED CYBORG BEETLES: A RADIO-FREQUENCY SYSTEM FOR INSECT NEURAL FLIGHT CONTROL H. Sato1 beetle in free-flight. The microsystem (Figs. 1, 2) consisted of a radio-frequency receiver assembly, a micro battery and a live giant flower beetle platform (Mecynorhina polyphemus or Mecynorhina torquata

Maharbiz, Michel

311

Radiofrequency Ablation Treatment in Proximity to the Gallbladder Without Subsequent Acute Cholecystitis  

PubMed Central

Initial reports have suggested that proximity of liver tumors to the gallbladder may increase the risk for cholecystitis after radiofrequency ablation. A colon adenocarcinoma metastasis to the liver in contact with the gallbladder was successfully treated with radiofrequency ablation without subsequent cholecystitis. PMID:14667129

Patti, Jay W.; Neeman, Ziv; Wood, Bradford J.

2008-01-01

312

A simple way to treat chronic atrial fibrillation during mitral valve surgery: the epicardial radiofrequency approachq  

Microsoft Academic Search

Objective: We describe an original radiofrequency ablation technique to treat chronic atrial fibrillation in patients undergoing mitral valve surgery. Most of the procedure is carried out epicardially, in order to avoid an undue increase of surgical time and trauma. Methods: The ablations are performed using a temperature-controlled multipolar radiofrequency catheter. Two encircling lesions around the ostia of the right and

Stefano Benussi; Carlo Pappone; Simona Nascimbene; Giuseppe Oreto; Alessandro Caldarola; Pier Luigi Stefano; Valter Casati; Ottavio Alfieri

313

Detection of NMR signals with a radio-frequency atomic magnetometer I.M. Savukov 1  

E-print Network

Detection of NMR signals with a radio-frequency atomic magnetometer I.M. Savukov 1 , S.J. Seltzer of proton NMR signals with a radio-frequency (rf) atomic magnetometer tuned to the NMR frequency of 62 kHz. High-frequency operation of the atomic magnetometer makes it relatively insensitive to ambient magnetic

Romalis, Mike

314

Subfemtotesla radio-frequency atomic magnetometer for detection of nuclear quadrupole resonance  

E-print Network

Subfemtotesla radio-frequency atomic magnetometer for detection of nuclear quadrupole resonance S 20 November 2006 A radio-frequency tunable atomic magnetometer is developed for detection of nuclearHz 14 N NQR frequency of ammonium nitrate. A potential application of the magnetometer is detection

Romalis, Mike

315

Room temperature femtotesla radio-frequency atomic magnetometer W. Chalupczak,1  

E-print Network

Room temperature femtotesla radio-frequency atomic magnetometer W. Chalupczak,1 R. M. Godun,1 S online 12 June 2012) A radio-frequency tunable atomic magnetometer with a sensitivity of about 1 fT/Hz1/2 in a range of 10­500 kHz is demonstrated. The magnetometer is operated in the orientation configuration

316

Characterization of tracked radiofrequency ablation in phantom Chun-Cheng R. Chen,a  

E-print Network

developed that attempt to solve partial differential equations describing thermal ablations.11,12 ThoughCharacterization of tracked radiofrequency ablation in phantom Chun-Cheng R. Chen,a Michael I. Miga 2007; published 26 September 2007 In radiofrequency ablation RFA , successful therapy requires accurate

Miga, Michael I.

317

Real-time Semi-automatic Segmentation of Hepatic Radiofrequency Ablated Lesions in an In Vivo  

E-print Network

of Rochester Rochester, NY, USA Abstract-- Radiofrequency ablation (RFA) is a minimally invasive thermal the potential to be used as a complementary technique to conventional ultrasound for thermal ablation monitoring. INTRODUCTION Thermal ablation techniques such as radiofrequency ablation (RFA) and high intensity focused

Parker, Kevin J.

318

Radiofrequency ablation of hepatic tumors: simulation, planning, and contribution of virtual reality and haptics  

E-print Network

to recent advancements in medical imaging. Among them, percutaneous thermal ablation has been studiedRadiofrequency ablation of hepatic tumors: simulation, planning, and contribution of virtual, place de l'H^opital F67091 Strasbourg France Abstract For radiofrequency ablation (RFA) of liver tumors

Essert-Villard, Caroline

319

Experimental and clinical studies with radiofrequency-induced thermal endometrial ablation for functional menorrhagia  

Microsoft Academic Search

A method of ablating the endometrium has been introduced into clinical practice that uses radiofrequency electromagnetic energy to heat the endometrium, using a probe inserted through the cervix. Preliminary studies suggest that over 80% of patients treated will develop either amenorrhea or a significant reduction in flow. The advantages of radiofrequency endometrial ablation over laser ablation or resection are the

Jeffrey H. Phipps; B. V. Lewis; Michael V. Prior; Terry Roberts

1990-01-01

320

Virtual Radiofrequency Ablation of Liver Caroline Villard, Luc Soler, Nicolas Papier, Vincent Agnus, Sylvain Thery,  

E-print Network

-resectable. Among them, percutaneous thermal ablation has been studied in different forms, such as microwave, laserVirtual Radiofrequency Ablation of Liver Tumors Caroline Villard, Luc Soler, Nicolas Papier://www.ircad.org/ Abstract. In the last few years, radiofrequency ablation has become one of the most promising techniques

Essert-Villard, Caroline

321

Electromagnetic Radiofrequency Radiation Emitted from GSM Mobile Phones Decreases the Accuracy of Home Blood Glucose Monitors.  

PubMed

Mobile phones are two-way radios that emit electromagnetic radiation in microwave range. As the number of mobile phone users has reached 6 billion, the bioeffects of exposure to mobile phone radiation and mobile phone electromagnetic interference with electronic equipment have received more attention, globally. As self-monitoring of blood glucose can be a beneficial part of diabetes control, home blood glucose testing kits are very popular. The main goal of this study was to investigate if radiofrequency radiation emitted from a common GSM mobile phone can alter the accuracy of home blood glucose monitors. Forty five female nondiabetic students aged 17-20 years old participated in this study. For Control-EMF group (30 students), blood glucose concentration for each individual was measured in presence and absence of radiofrequency radiation emitted by a common GSM mobile phone (HTC touch, Diamond 2) while the phone was ringing. For Control- Repeat group (15 students), two repeated measurements were performed for each participant in the absence of electromagnetic fields. The magnitude of the changes between glucose levels in two repeated measurements (|?C|) in Control-Repeat group was 1.07 ± 0.88 mg/dl while this magnitude for Control-EMF group was 7.53 ± 4.76 mg/dl (P < 0.001, two-tailed test). To the best of our knowledge, this is the first study to assess the electromagnetic interference in home blood glucose monitors. It can be concluded that electromagnetic interference from mobile phones has an adverse effect on the accuracy of home blood glucose monitors. We suggest that mobile phones should be used at least 50 cm away from home blood glucose monitors. PMID:25505778

Mortazavi, Smj; Gholampour, M; Haghani, M; Mortazavi, G; Mortazavi, Ar

2014-09-01

322

Electromagnetic Radiofrequency Radiation Emitted from GSM Mobile Phones Decreases the Accuracy of Home Blood Glucose Monitors  

PubMed Central

Mobile phones are two-way radios that emit electromagnetic radiation in microwave range. As the number of mobile phone users has reached 6 billion, the bioeffects of exposure to mobile phone radiation and mobile phone electromagnetic interference with electronic equipment have received more attention, globally. As self-monitoring of blood glucose can be a beneficial part of diabetes control, home blood glucose testing kits are very popular. The main goal of this study was to investigate if radiofrequency radiation emitted from a common GSM mobile phone can alter the accuracy of home blood glucose monitors. Forty five female nondiabetic students aged 17-20 years old participated in this study. For Control-EMF group (30 students), blood glucose concentration for each individual was measured in presence and absence of radiofrequency radiation emitted by a common GSM mobile phone (HTC touch, Diamond 2) while the phone was ringing. For Control- Repeat group (15 students), two repeated measurements were performed for each participant in the absence of electromagnetic fields. The magnitude of the changes between glucose levels in two repeated measurements (|?C|) in Control-Repeat group was 1.07 ± 0.88 mg/dl while this magnitude for Control-EMF group was 7.53 ± 4.76 mg/dl (P < 0.001, two-tailed test). To the best of our knowledge, this is the first study to assess the electromagnetic interference in home blood glucose monitors. It can be concluded that electromagnetic interference from mobile phones has an adverse effect on the accuracy of home blood glucose monitors. We suggest that mobile phones should be used at least 50 cm away from home blood glucose monitors. PMID:25505778

Mortazavi, SMJ; Gholampour, M; Haghani, M; Mortazavi, G; Mortazavi, AR

2014-01-01

323

Hepatic radiofrequency ablation at low frequencies preferentially heats tumour tissue  

PubMed Central

Purpose Radiofrequency ablation is a clinically accepted treatment modality for liver cancer. There are significant differences in dielectric properties between normal and cancer tissue in the liver, which are particularly pronounced at frequencies below 100 kHz. This study performed computer simulations to determine whether radiofrequency (RF) ablation at lower frequencies than currently employed (450-500 kHz) can take advantage of this differenceto preferentially deposit energy within the tumour. Materials and methods Finite Element Method computer models were created for a cooled needle electrode and a multi-tine RF electrode inserted into a 2 cm diameter tumour. RF ablation was simulated and current density as well as tissue temperature distribution determined. In vivo data were used on electrical conductivity of normal and cancer tissue in the models to simulate RF ablation in liver at the currently used frequency of 500 kHz and at 10 kHz. Results At 500 kHz there was little difference in RF current density and final tissue temperature between normal and cancer tissue. Due to the more pronounced differences in electrical conductivity at 10 kHz, cancer tissue was heated preferentially at this frequency. Depending on power control algorithm, this resulted in either higher intra-tumour temperatures or lower temperatures outside the tumour at 10 kHz compared to 500 kHz. Conclusion Radiofrequency ablation at lower frequencies than currently used may preferentially heat the tumour and preserve normal tissue. A targeted device for selective tumour destruction may be designed to make use of this principle. PMID:17079214

HAEMMERICH, DIETER; WOOD, BRADFORD J.

2008-01-01

324

The radio-frequency impedance of individual intrinsic Josephson junctions  

SciTech Connect

We have measured the response of an array of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} intrinsic Josephson junctions to irradiation at 3 GHz. By measuring the dependence of the switching current upon the radio-frequency current for five of the junctions in the array we show quantitatively that the junctions have identical impedances at 3 GHz, this impedance being given by the inverse of the slope of the current-voltage characteristics.

Leiner, Johannes; Saleem, Sajid; Fenton, J. C.; Warburton, P. A. [London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH (United Kingdom); Yamamoto, Takashi; Kadowaki, Kazuo [Institute of Materials Science, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan)

2009-12-21

325

Measuring Radiofrequency and Microwave Radiation from Varying Signal Strengths  

NASA Technical Reports Server (NTRS)

This viewgraph presentation discusses the process of measuring radiofrequency and microwave radiation from various signal strengths. The topics include: 1) Limits and Guidelines; 2) Typical Variable Standard (IEEE) Frequency Dependent; 3) FCC Standard 47 CFR 1.1310; 4) Compliance Follows Unity Rule; 5) Multiple Sources Contribute; 6) Types of RF Signals; 7) Interfering Radiations; 8) Different Frequencies Different Powers; 9) Power Summing - Peak Power; 10) Contribution from Various Single Sources; 11) Total Power from Multiple Sources; 12) Are You Out of Compliance?; and 13) In Compliance.

Davis, Bette; Gaul, W. C.

2007-01-01

326

Multiplexing of Radio-Frequency Single Electron Transistors  

NASA Technical Reports Server (NTRS)

We present results on wavelength division multiplexing of radio-frequency single electron transistors. We use a network of resonant impedance matching circuits to direct applied rf carrier waves to different transistors depending on carrier frequency. A two-channel demonstration of this concept using discrete components successfully reconstructed input signals with small levels of cross coupling. A lithographic version of the rf circuits had measured parameters in agreement with electromagnetic modeling, with reduced cross capacitance and inductance, and should allow 20 to 50 channels to be multiplexed.

Stevenson, Thomas R.; Pellerano, F. A.; Stahle, C. M.; Aidala, K.; Schoelkopf, R. J.; Krebs, Carolyn (Technical Monitor)

2001-01-01

327

Diffuse ?-mode atmospheric pressure radio-frequency discharge in neon  

NASA Astrophysics Data System (ADS)

In this work, a radio-frequency (RF) atmospheric pressure glow discharge burning in neon between planar metal electrodes is achieved for the first time. The RF discharge can operate in two stable modes: in a diffuse ?-mode with uniformly covered electrode surfaces and in a constricted ?-mode. Similarities are revealed when the discharge is compared against the RF atmospheric pressure glow discharge in helium, namely both discharges show a discontinuity and a hysteresis in the current-voltage characteristic at the mode transition; the spatio-temporal profiles of the light emission in the ?-mode from neon, helium and atomic oxygen are also similar.

Navrátil, Z.; Dosoudilová, L.; Josepson, R.; Dvo?ák, P.; Trunec, D.

2014-08-01

328

Pulmonary Artery Pseudoaneurysm Related to Radiofrequency Ablation of Lung Tumor  

SciTech Connect

We describe a case of pulmonary artery (PA) pseudoaneurysm related to radiofrequency ablation (RFA) of lung tumor. We performed RFA for a pulmonary epithelioid hemangioendothelioma directly adjacent to a branch of the PA. Seventeen days later, the patient complained of hemoptysis. A chest CT image revealed PA pseudoaneurysm. Transcatheter coil embolization was performed 59 days after RFA. Although PA pseudoaneurysm is rare, with an incidence of 0.2% (1/538 sessions) at our institution, it should be recognized as a risk when treating lung tumors adjacent to a branch of the PA.

Sakurai, Jun, E-mail: sakurai@cc.okayama-u.ac.jp; Mimura, Hidefumi; Gobara, Hideo; Hiraki, Takao; Kanazawa, Susumu [Okayama University Medical School, Department of Radiology (Japan)

2010-04-15

329

Treatment of recurrent hepatocellular carcinoma by radiofrequency thermal ablation  

Microsoft Academic Search

.\\u000a Abstract.  \\u000a \\u000a \\u000a Background and aims:   The treatment of choice for hepatocellular carcinoma is surgical resection. Recurrence occurs in most patients. Aggressive\\u000a treatment of liver recurrence increases patients' survival, but most frequently, these patients are not suitable for surgery.\\u000a The aim of this study was to analyze the indications for and results of radiofrequency thermal ablation (RFTA) in the treatment\\u000a of

Nicola Nicoli; Andrea Casaril; Luigi Marchiori; Gerardo Mangiante; Alì Reza Hasheminia

2001-01-01

330

Comparison of renal ablation with cryotherapy, dry radiofrequency, and saline augmented radiofrequency in a porcine model 1 1 No competing interests declared  

Microsoft Academic Search

BACKGROUND:Needle ablative therapy has recently generated a lot of interest in the urologic community. We compare renal lesions produced in a porcine model using three forms of needle ablative energy: cryoablation (CR), dry radiofrequency (RF), and saline augmented radiofrequency (SARF).STUDY DESIGN:In 10 farm pigs, under ultrasonographic guidance, 40 laparoscopic renal lesions were produced: 825-mm CR lesions were produced with 2.4-mm

William C. Collyer; Jaime Landman; Ephrem O. Olweny; Cassio Andreoni; Kurt Kerbl; David G. Bostwick; Ralph V. Clayman

2001-01-01

331

Black phosphorus radio-frequency transistors.  

PubMed

Few-layer and thin film forms of layered black phosphorus (BP) have recently emerged as a promising material for applications in high performance nanoelectronics and infrared optoelectronics. Layered BP thin films offer a moderate bandgap of around 0.3 eV and high carrier mobility, which lead to transistors with decent on-off ratios and high on-state current densities. Here, we demonstrate the gigahertz frequency operation of BP field-effect transistors for the first time. The BP transistors demonstrated here show respectable current saturation with an on-off ratio that exceeds 2 × 10(3). We achieved a current density in excess of 270 mA/mm and DC transconductance above 180 mS/mm for hole conduction. Using standard high frequency characterization techniques, we measured a short-circuit current-gain cutoff frequency fT of 12 GHz and a maximum oscillation frequency fmax of 20 GHz in 300 nm channel length devices. BP devices may offer advantages over graphene transistors for high frequency electronics in terms of voltage and power gain due to the good current saturation properties arising from their finite bandgap, thus can be considered as a promising candidate for the future high performance thin film electronics technology for operation in the multi-GHz frequency range and beyond. PMID:25347787

Wang, Han; Wang, Xiaomu; Xia, Fengnian; Wang, Luhao; Jiang, Hao; Xia, Qiangfei; Chin, Matthew L; Dubey, Madan; Han, Shu-jen

2014-11-12

332

Evaluation of the co-genotoxic effects of 1800 MHz GSM radiofrequency exposure and a chemical mutagen in cultured human cells  

NASA Astrophysics Data System (ADS)

We investigated the effect of a 1800 MHz radiofrequency GSM signal combined with a known chemical mutagen (4-nitroquinoline-N-oxide: 4NQO) on human THP1 cells. Comet and ?-H2AX assays were used to assess DNA damage. No heating of the cell cultures was noted during exposure (2 h). The exposure of cells to electromagnetic fields with SARs of 2 to 16 W/kg did not increase the DNA damage induced by 4NQO, whereas the number of DNA strand breaks increased with a temperature increase of at least 4 °C. In conclusion, no co-genotoxic effect of radiofrequency was found at levels of exposure that did not induce heating.

Perrin, Anne; Freire, Maëlle; Bachelet, Christine; Collin, Alice; Levêque, Philippe; Pla, Simon; Debouzy, Jean-Claude

2010-11-01

333

Ionizing and Non-Ionizing Radiation  

MedlinePLUS

... remove tightly bound electrons from atoms, thus creating ions. This is the type of radiation that people ... in the formation of two charged particles or ions: the molecule with a net positive charge and ...

334

Estimation of urinary flow velocity in models of obstructed and unobstructed urethras by decorrelation of ultrasound radiofrequency signals.  

PubMed

The feasibility of estimating urinary flow velocity from the decorrelation of radiofrequency (RF) signals was investigated in soft tissue-mimicking models of obstructed and unobstructed urethras. The decorrelation was studied in the near field, focal zone and far field of the ultrasound beam. Furthermore, the effect of beam width was investigated. The results of this study suggest that it is feasible to estimate flow velocity in models of the urethra by quantifying the decorrelation of RF ultrasound signals. The decorrelation slope increased more rapidly and more linearly with increasing velocity in the focal zone than in the near and far field. A preliminary example of an in vivo measurement in a healthy volunteer illustrated that this method has potential for clinical use in the future. PMID:24412180

Arif, Muhammad; Idzenga, Tim; van Mastrigt, Ron; de Korte, Chris L

2014-05-01

335

Radio-frequency identification: its potential in healthcare.  

PubMed

Radio-frequency identification (RFID) technology is just starting to make inroads into healthcare. RFID uses radio-frequency tags attached to people or objects to provide identification, tracking, security, and other functions that fall under the general heading of automatic identification and data capture (AIDC). In the retail supply chain, RFID is already well established as a way to reduce theft and track objects from manufacture through shipment to delivery. In healthcare, basic RFID is already being used to track patients for anti-elopement and anti-abduction programs. As more sophisticated systems move into hospitals, RFID is also beginning to see use to provide more extensive patient identification than traditional bar coding can, and to track and locate capital equipment within the hospital. In years to come, RFID could be used for a variety of applications, including tracking and matching blood for transfusions, tracking pharmaceuticals, and combating the counterfeiting of medical products. RFID may ultimately be used for many of the functions currently carried out using bar coding--but not until the cost of RFID comes down. For the foreseeable future, the two technologies are likely to be used in tandem in many hospitals. In this article, we describe the components and operation of RFID systems and detail the different ways in which these systems are being used, and could be used, in hospitals. PMID:16048121

2005-05-01

336

Mathematical Modeling of Radiofrequency Ablation for Varicose Veins  

PubMed Central

We present a three-dimensional mathematical model for the study of radiofrequency ablation (RFA) with blood flow for varicose vein. The model designed to analyze temperature distribution heated by radiofrequency energy and cooled by blood flow includes a cylindrically symmetric blood vessel with a homogeneous vein wall. The simulated blood velocity conditions are U = 0, 1, 2.5, 5, 10, 20, and 40?mm/s. The lower the blood velocity, the higher the temperature in the vein wall and the greater the tissue damage. The region that is influenced by temperature in the case of the stagnant flow occupies approximately 28.5% of the whole geometry, while the region that is influenced by temperature in the case of continuously moving electrode against the flow direction is about 50%. The generated RF energy induces a temperature rise of the blood in the lumen and leads to an occlusion of the blood vessel. The result of the study demonstrated that higher blood velocity led to smaller thermal region and lower ablation efficiency. Since the peak temperature along the venous wall depends on the blood velocity and pullback velocity, the temperature distribution in the model influences ablation efficiency. The vein wall absorbs more energy in the low pullback velocity than in the high one. PMID:25587351

Choi, Sun Young; Kwak, Byung Kook

2014-01-01

337

[Electromagnetic fields in hospitals: wireless-LAN as a risk factor?].  

PubMed

The actual level of exposure to non-ionizing radiation in Swiss hospitals is not well known. Therefore, the electromagnetic field of wireless LAN (WLAN) and other non-ionizing radiation sources in the publicly funded Hospital Thun (Switzerland), where WLAN supports bedside access to the computerized patient record for more than three years, has been measured. The results are compared to the international and national exposure limits for the general public. Nurse workplaces as well as patient rooms show exposure levels well below the legal (national and international) exposure limits. In the investigated patients' room the electromagnetic field of GSM and broadband cellular phone networks are dominant, whereas at the nurse workplace WLAN exposure is the most important source of exposure. The results of a questionnaire survey emphasize, that the hospital staff does not worry much about electromagnetic fields of new ICT technologies. PMID:16783890

Oertle, M; Lehmann, H; Fritschi, P; Müller, M; Berz, R

2006-06-01

338

Experimental simulation of beam propagation over long path lengths using radio-frequency and magnetic traps  

NASA Astrophysics Data System (ADS)

An overview is given of the novel beam-dynamics experiments based on compact non-neutral plasma traps at Hiroshima University. We have designed and constructed two different classes of trap systems, one of which uses a radio-frequency electric field (Paul trap) and the other uses an axial magnetic field (Penning trap) for transverse plasma confinement. These systems are called "S-POD" (Simulator for Particle Orbit Dynamics). The S-POD systems can approximately reproduce the collective motion of a charged-particle beam propagating through long alternating-gradient (AG) quadrupole focusing channels using the Paul trap and long continuous focusing channels using the Penning trap. This allows us to study various beam-dynamics issues in compact and inexpensive experiments without relying on large-scale accelerators. So far, the linear Paul traps have been applied for the study of resonance-related issues including coherent-resonance-induced stop bands and their dependence on AG lattice structures, resonance crossing in fixed-field AG accelerators, ultralow-emittance beam stability, etc. The Penning trap with multi-ring electrodes has been employed primarily for the study of beam halo formation driven by initial distribution perturbations. In this paper, we briefly overview the S-POD systems, and then summarize recent experimental results on resonance effects and halo formation.

Okamoto, H.; Endo, M.; Fukushima, K.; Higaki, H.; Ito, K.; Moriya, K.; Yamaguchi, S.; Lund, S. M.

2014-01-01

339

The Biological Effects of Quadripolar Radiofrequency Sequential Application: A Human Experimental Study  

PubMed Central

Abstract Objective: An experimental study was conducted to assess the effectiveness and safety of an innovative quadripolar variable electrode configuration radiofrequency device with objective measurements in an ex vivo and in vivo human experimental model. Background data: Nonablative radiofrequency applications are well-established anti-ageing procedures for cosmetic skin tightening. Methods: The study was performed in two steps: ex vivo and in vivo assessments. In the ex vivo assessments the radiofrequency applications were performed on human full-thickness skin and subcutaneous tissue specimens harvested during surgery for body contouring. In the in vivo assessments the applications were performed on two volunteer patients scheduled for body contouring surgery at the end of the study. The assessment methods were: clinical examination and medical photography, temperature measurement with thermal imaging scan, and light microscopy histological examination. Results: The ex vivo assessments allowed for identification of the effective safety range for human application. The in vivo assessments allowed for demonstration of the biological effects of sequential radiofrequency applications. After a course of radiofrequency applications, the collagen fibers underwent an immediate heat-induced rearrangement and were partially denaturated and progressively metabolized by the macrophages. An overall thickening and spatial rearrangement was appreciated both in the collagen and elastic fibers, the latter displaying a juvenile reticular pattern. A late onset in the macrophage activation after sequential radiofrequency applications was appreciated. Conclusions: Our data confirm the effectiveness of sequential radiofrequency applications in obtaining attenuation of the skin wrinkles by an overall skin tightening. PMID:25244081

Cornaglia, Antonia Icaro; Faga, Angela; Scevola, Silvia

2014-01-01

340

Examining the feasibility of radiofrequency treatment for chronic knee pain after total knee arthroplasty.  

PubMed

Recently, investigators began using radiofrequency to manage knee osteoarthritis pain in patients at high risk who cannot undergo surgical intervention. To our knowledge, no study has investigated the use of radiofrequency ablation of the genicular nerves to alleviate chronic knee pain after total knee replacement. A single case is presented here in which genicular nerve ablation successfully improved pain and restored function. We believe that these preliminary results could be used in the development of future prospective cohort studies and randomized controlled trials that focus on the use of radiofrequency ablation to treat persistent knee pain after total knee replacement. PMID:24373908

Protzman, Nicole M; Gyi, Jennifer; Malhotra, Amit D; Kooch, Jason E

2014-04-01

341

Health implications of exposure to radiofrequency/microwave energies  

PubMed Central

ABSTRACT The rapid development of and the increase in the number and variety of devices that emit microwave/radiofrequency (MW/RF) energies has resulted in a growing interest regarding the potential effects on health of these energies. The frequency ranges considered in this review are: 300 kHz to 300 MHz (radiofrequency) and 300 MHz to 300 GHz (microwaves). Investigations have shown that exposure to certain power densities for several minutes or hours can result in pathophysiological manifestations in laboratory animals. Such effects may or may not be characterised by a measurable rise in temperature, which is a function of thermal regulatory processes and active adaptation by the animal. The end result is either a reversible or irreversible change, depending on the irradiation conditions and the physiological state of the animal. At lower power densities, evidence of pathological changes or physiological alteration is non-existent or equivocal. Much discussion, nevertheless, has taken place on the relative importance of thermal or non-thermal effects of radiofrequency and microwave radiation. Several retrospective studies have been done on human populations exposed or believed to have been exposed to MW/RF energies. Those performed in the US have not shown any relationship of altered morbidity or mortality to MW/RF exposure. Reactions referrable to the central nervous system and cardiovascular effects from exposure of man to microwave energy have been reported mostly in Eastern European publications. Individuals suffering from various ailments or psychological factors may exhibit the same dysfunctions of the central nervous and cardiovascular systems as those reported to result from exposure to MW/RF; thus it is extremely difficult, if not impossible, to rule out other factors in attempting to relate MW/RF exposure to clinical conditions. There is a need to set limits on the amount of exposure to MW/RF energies that individuals can accept with safety. Operative protection standards have apparently provided adequate safety to workers and the general population to permit the use of MW/RF energies without harm or detriment. PMID:7039662

Michaelson, S M

1982-01-01

342

[Role of power and temperature monitoring in radiofrequency ablation].  

PubMed

Variations of temperature, impedance and power and the relationship between these three factors were studied in 20 patients during 351 applications of radiofrequency energy delivered by a generator with a regulated output power. The applications were divided into 3 groups according to the maximal temperature attained: group I (< 50 degrees C; n = 112), group II (50-60 degrees C; n = 100), and group III (60-70 degrees C; n = 139). Analysis of the total duration of time of applications (average +/- standard deviation) showed: the duration (seconds) was 23.9 +/- 11.9 seconds for group I, 36.1 +/- 18.7 seconds for group II and 45 +/- 23.6 seconds for group III. The time to attain maximal temperature was 6.8 +/- 9.6 seconds in group I, 11.7 +/- 12.7 in group II and 10 +/- 10.4 seconds in group III. The impedance remained under 200 omega in all applications, the target temperature being set at 70 degrees C. Analysis of the first three seconds of application: correlations coefficients between temperature and impedance were -0.08 (p < 0.001) in group I and -0.23 (p < 0.0001) in groups II and III. These coefficients were recalculated with respect to the average power delivered during the applications: < 40 watts (n = 79), r = -0.33; < 30 watts (n = 55), r = -0.41; < 20 watts (n = 33), r = 0.49 and < 10 watts (n = 15), r = -0.7 (p < 0.0001). The authors conclude that radiofrequency generators with thermal regulation allow early interruption of ineffective applications of radiofrequency and avoid increases in impedance. The poor correlations observed between increase in temperature (measured at the tip of the catheter) and the fall in impedance (related to tissue heating) for the first 3 groups, show that temperature alone is not a good indicator of contact. The improvement of the correlations for decreasing output power applications indicates better thermal transfer between the electrode and endocardium. Therefore a low power delivered in the first seconds at > 50 degrees C is to be interpreted as a marker of the quality of contact and a predictive factor of efficacy. PMID:8678756

Halimi, F; Frank, R; Tonet, J; Fontaine, G

1996-02-01

343

Radio-frequency sheaths physics: Experimental characterization on Tore Supra and related self-consistent modeling  

SciTech Connect

During the 2011 experimental campaign, one of the three ion cyclotron resonance heating (ICRH) antennas in the Tore Supra tokamak was equipped with a new type of Faraday screen (FS). The new design aimed at minimizing the integrated parallel electric field over long field lines as well as increasing the heat exhaust capability of the actively cooled screen. It proved to be inefficient for attenuating the radio-frequency (RF)-sheaths on the screen itself on the contrary to the heat exhaust concept that allowed operation despite higher heat fluxes on the antenna. In parallel, a new approach has been proposed to model self-consistently RF sheaths: the SSWICH (Self-consistent Sheaths and Waves for IC Heating) code. Simulations results from SSWICH coupled with the TOPICA antenna code were able to reproduce the difference between the two FS designs and part of the spatial pattern of heat loads and Langmuir probe floating potential. The poloidal pattern is a reliable result that mainly depends on the electrical design of the antenna while the radial pattern is on the contrary highly sensitive to loosely constrained parameters such as perpendicular conductivity that generates a DC current circulation from the private region inside the antenna limiters to the free scrape off layer outside these limiters. Moreover, the cantilevered bars seem to be the element in the screen design that enhanced the plasma potential.

Jacquot, Jonathan; Colas, Laurent, E-mail: laurent.colas@cea.fr; Corre, Yann; Goniche, Marc; Gunn, Jamie; Kubi?, Martin [CEA, IRFM, F-13108 saint-Paul-Lez-Durance (France); Milanesio, Daniele [Department of Electronics Politecnico di Torino, Torino (Italy); Heuraux, Stéphane [IJL UMR 7198, U. de Lorraine P2M, Fac. Des Sciences, BP 70239, F-54506 Vandoeuvre Cedex (France)

2014-06-15

344

Study of Characteristics of the Radio-Frequency Sheath over a Substrate with a Circular Trench  

NASA Astrophysics Data System (ADS)

Since processed substrates usually exhibit nonplanar surface structures in micro-electro-mechanical-systems (MEMS) etching, a two-dimensional (2D) fluid model is developed to simulate the characteristics of the sheath near a conductive substrate with a circular trench, which is placed in an argon discharge powered by a radio-frequency (RF) current source. The model consists of 2D time-dependent fluid equations, the Poisson equation, and a current balance equation that can self-consistently determine the instantaneous voltage on the substrate placed on a powered electrode. The effects of both the aspect ratio (depth/width) and the structure of the trench on the characteristics of the sheath are simulated. The time-averaged potential and electric field in the sheath are calculated and compared for different discharge parameters. The results show that the radial sheath profile is not uniform and always tends to adapt to the contour of the substrate, which is believed to be the moulding effect. Affected by the structure of the substrate surface, the potential and electric field near the inner and outer sidewalls of the trench exhibit obvious non-uniformity, which will inevitably lead to non-uniformity in etching, such as notching. Furthermore, with a fixed amplitude of the RF current source, the potential drops and the sheath thickness decrease with an increase in aspect ratio.

Dai, Zhongling; Hao, Meilan; Wang, Younian

2011-02-01

345

First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities  

NASA Astrophysics Data System (ADS)

Niobium hydride is suspected to be a major contributor to degradation of the quality factor of niobium superconducting radio-frequency (SRF) cavities. In this study, we connect the fundamental properties of hydrogen in niobium to SRF cavity performance and processing. We modeled several of the niobium hydride phases relevant to SRF cavities and present their thermodynamic, electronic, and geometric properties determined from calculations based on density functional theory. We find that the absorption of hydrogen from the gas phase into niobium is exothermic and hydrogen becomes somewhat anionic. The absorption of hydrogen by niobium lattice vacancies is strongly preferred over absorption into interstitial sites. A single vacancy can accommodate six hydrogen atoms in the symmetrically equivalent lowest energy sites and additional hydrogen in the nearby interstitial sites affected by the strain field: this indicates that a vacancy can serve as a nucleation center for hydride phase formation. Small hydride precipitates may then occur near lattice vacancies upon cooling. Vacancy clusters and extended defects should also be enriched in hydrogen, potentially resulting in extended hydride phase regions upon cooling. We also assess the phase changes in the niobium-hydrogen system based on charge transfer between niobium and hydrogen, the strain field associated with interstitial hydrogen, and the geometry of the hydride phases. The results of this study stress the importance of not only the hydrogen content in niobium, but also the recovery state of niobium for the performance of SRF cavities.

Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

2013-09-01

346

Survey of ambient electromagnetic and radio-frequency interference levels in nuclear power plants  

SciTech Connect

This document reports the results of a survey of ambient electromagnetic conditions in representative nuclear power plants. The U.S. Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research engaged the Oak Ridge National Laboratory (ORNL) to perform these measurements to characterize the electromagnetic interference (EMI) and radio-frequency interference (RFI) levels that can be expected in nuclear power plant environments. This survey is the first of its kind, being based on long-term unattended observations. The data presented in this report were measured at eight different nuclear units and required 14 months to collect. A representative sampling of power plant conditions (reactor type, operating mode, site location) monitored over extended observation periods (up to 5 weeks) were selected to more completely determine the characteristic electromagnetic environment for nuclear power plants. Radiated electric fields were measured over the frequency range of 5 MHz to 8 GHz. Radiated magnetic fields and conducted EMI events were measured over the frequency range of 305 Hz to 5 MHz. Highest strength observations of the electromagnetic ambient environment across all measurement conditions at each site provide frequency-dependent profiles for EMI/RFI levels in nuclear power plants.

Kercel, S.W.; Moore, M.R.; Blakeman, E.D.; Ewing, P.D.; Wood, R.T.

1996-11-01

347

Modeling of EEG electrode artifacts and thermal ripples in human radiofrequency exposure studies.  

PubMed

The effects of radiofrequency (RF) exposure on wake and sleep electroencephalogram (EEG) have been in focus since mobile phone usage became pervasive. It has been hypothesized that effects may be explained by (1) enhanced induced fields due to RF coupling with the electrode assembly, (2) the subsequent temperature increase around the electrodes, or (3) RF induced thermal pulsing caused by localized exposure in the head. We evaluated these three hypotheses by means of both numerical and experimental assessments made with appropriate phantoms and anatomical human models. Typical and worst-case electrode placements were examined at 900 and 2140?MHz. Our results indicate that hypothesis 1 can be rejected, as the induced fields cause <20% increase in the 10?g-averaged specific absorption rate (SAR). Simulations with an anatomical model indicate that hypothesis 2 is also not supported, as the realistic worst-case electrode placement results in a maximum skin temperature increase of 0.31?°C while brain temperature elevations remained <0.1?°C. These local short-term temperature elevations are unlikely to change brain physiology during the time period from minutes to several hours after exposure. The maximum observed temperature ripple due to RF pulses is <0.001?°C for GSM-like signals and <0.004?°C for 20-fold higher pulse energy, and offers no support for hypothesis 3. Thus, the mechanism of interaction between RF and changes in the EEG power spectrum remains unknown. PMID:24523224

Murbach, Manuel; Neufeld, Esra; Christopoulou, Maria; Achermann, Peter; Kuster, Niels

2014-05-01

348

Radio-frequency sheaths physics: Experimental characterization on Tore Supra and related self-consistent modeling  

NASA Astrophysics Data System (ADS)

During the 2011 experimental campaign, one of the three ion cyclotron resonance heating (ICRH) antennas in the Tore Supra tokamak was equipped with a new type of Faraday screen (FS). The new design aimed at minimizing the integrated parallel electric field over long field lines as well as increasing the heat exhaust capability of the actively cooled screen. It proved to be inefficient for attenuating the radio-frequency (RF)-sheaths on the screen itself on the contrary to the heat exhaust concept that allowed operation despite higher heat fluxes on the antenna. In parallel, a new approach has been proposed to model self-consistently RF sheaths: the SSWICH (Self-consistent Sheaths and Waves for IC Heating) code. Simulations results from SSWICH coupled with the TOPICA antenna code were able to reproduce the difference between the two FS designs and part of the spatial pattern of heat loads and Langmuir probe floating potential. The poloidal pattern is a reliable result that mainly depends on the electrical design of the antenna while the radial pattern is on the contrary highly sensitive to loosely constrained parameters such as perpendicular conductivity that generates a DC current circulation from the private region inside the antenna limiters to the free scrape off layer outside these limiters. Moreover, the cantilevered bars seem to be the element in the screen design that enhanced the plasma potential.

Jacquot, Jonathan; Milanesio, Daniele; Colas, Laurent; Corre, Yann; Goniche, Marc; Gunn, Jamie; Heuraux, Stéphane; Kubi?, Martin

2014-06-01

349

Thermal mechanisms of interaction of radiofrequency energy with biological systems with relevance to exposure guidelines.  

PubMed

This article reviews thermal mechanisms of interaction between radiofrequency (RF) fields and biological systems, focusing on theoretical frameworks that are of potential use in setting guidelines for human exposure to RF energy. Several classes of thermal mechanisms are reviewed that depend on the temperature increase or rate of temperature increase and the relevant dosimetric considerations associated with these mechanisms. In addition, attention is drawn to possible molecular and physiological reactions that could be induced by temperature elevations below 0.1 degrees, which are normal physiological responses to heat, and to the so-called microwave auditory effect, which is a physiologically trivial effect resulting from thermally-induced acoustic stimuli. It is suggested that some reported "nonthermal" effects of RF energy may be thermal in nature; also that subtle thermal effects from RF energy exist but have no consequence to health or safety. It is proposed that future revisions of exposure guidelines make more explicit use of thermal models and empirical data on thermal effects in quantifying potential hazards of RF fields. PMID:17495663

Foster, Kenneth R; Glaser, Roland

2007-06-01

350

Energetic electron avalanches and mode transitions in planar inductively coupled radio-frequency driven plasmas operated in oxygen  

SciTech Connect

Space and phase resolved optical emission spectroscopic measurements reveal that in certain parameter regimes, inductively coupled radio-frequency driven plasmas exhibit three distinct operation modes. At low powers, the plasma operates as an alpha-mode capacitively coupled plasma driven through the dynamics of the plasma boundary sheath potential in front of the antenna. At high powers, the plasma operates in inductive mode sustained through induced electric fields due to the time varying currents and associated magnetic fields from the antenna. At intermediate powers, close to the often observed capacitive to inductive (E-H) transition regime, energetic electron avalanches are identified to play a significant role in plasma sustainment, similar to gamma-mode capacitively coupled plasmas. These energetic electrons traverse the whole plasma gap, potentially influencing plasma surface interactions as exploited in technological applications.

Zaka-ul-Islam, M.; Niemi, K. [Centre for Plasma Physics, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN, Northern Ireland (United Kingdom); Gans, T.; O'Connell, D. [Centre for Plasma Physics, School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN, Northern Ireland (United Kingdom); York Plasma Institute, Department of Physics, University of York, Innovation Way, Heslington York YO10 5DQ (United Kingdom)

2011-07-25

351

A review of selected biological effects and dosimetric data useful for development of radiofrequency safety standards for human exposure.  

PubMed

This report examines the bases for developing radiofrequency exposure standards which can be related to the thermogenic properties of electromagnetic fields. A review of selected biological effects, including dosimetric data and simulation of human thermodyanmic characteristics that are pertinent to standards development, is presented. Based on the analogy of thermal-stress standards that have been developed for hot industrial environments, limits on increases of body temperature are proposed as criteria for limiting exposure to radiofrequency fields, i.e., occupational exposures involving deep heating of the whole body should not increase core temperature in excess of 1 degree C. Since energy deposition from exposure to some RF fields is likely to be non-uniform and may be high in tissues that are not adapted to high rates of absorption or dissipation of thermalizing energy, means are needed to adjust focal thermal loading against the whole-body averages. A limit on core temperature is inadequate when focal elevations of temperature are close to the limits for protein denaturation, as may well occur even though the core temperature may rise less than 1 degree C. Safety limits for the general population are also discussed and here the permissible thermal load should be low enough to cause no more than an insignificant increase in core temperature. Areas needing further research to reduce the uncertainties in developing safe exposure limits for man are delineated. Even in highly adverse environmental conditions the gross thermal load and consequential heat stress from exposure to radiofrequency fields at the 10 mW/cm2 level will be small compared with that generated by any physical effort. On the basis of available data, it is concluded that the safe value for continuous exposure to 10 mW/cm2, widely used in Western countries, appears to provide an adequate margin of safety for both occupational and environmental exposure for frequencies above about 1 GHz. This limit may well be too high (perhaps by an order of magnitude) for some frequencies below 1 GHz where body resonances cause a significant increase in energy deposition and where local temperature rises occur. At the same time the present averaging period of 0.1 h seems unjustifiably short. PMID:397349

Tell, R A; Harlen, F

1979-12-01

352

Novel Treatment of Neck Wrinkles with an Intradermal Radiofrequency Device  

PubMed Central

Neck wrinkles commonly develop owing to the aging process. However, recently, the number of patients with neck wrinkles has been increasing. Also, an increasing number of young patients have presented with this condition, possibly because of the effect of the head-down posture that they adopt when using their computer or smartphone. We report two cases of young adults with a prominent neck wrinkle. In case 1, a 29-year-old woman with a neck wrinkle was treated with six intradermal radiofrequency (RF) procedures. Her neck wrinkle was significantly improved with the RF treatment. In case 2, a 32-year-old woman with a wrinkle and generalized light brownish tiny papules on the neck was treated with three intradermal RF procedures simultaneously with 30% glycolic acid peeling. Her wrinkle and skin tone were improved dramatically. We conclude that intradermal RF has a considerable efficacy for reducing neck wrinkles. PMID:25673937

Hyun, Moo Yeol; Li, Kapsok; Kim, Myeung Nam; Hong, Chang Kwun; Kim, Hyuk; Koh, Hyun-Ju; Park, Won-Seok

2015-01-01

353

Radiofrequency ablation for incidentally identified primary intrahepatic cholangiocarcinoma  

PubMed Central

Cholangiocarcinoma is the second most common primary hepato-biliary malignancy. The majority of patients with primary hepatic tumors are not suitable candidates for resection, due to advanced stage of the disease at presentation, anatomic limitations and medical co-morbidities. At present, radiofrequency ablation (RFA) may offer an alternative, feasible and safe therapy for selected patients with hepatic tumors, who are not otherwise candidates for hepatic resection. Herein, we present the case of successful RFA in a patient with a solitary, primary intrahepatic cholangiocarcinoma. The patient remained free of disease 24 mo after the procedure, and is still followed up. This is the first report of RFA application in the treatment of primary intrahepatic cholangiocarcinoma. PMID:16127762

Zgodzinski, Witold; Espat, N. Joseph

2005-01-01

354

Effects of radiofrequency hyperthermia on the healthy canine cornea  

SciTech Connect

Radiofrequency hyperthermia was used to induce axial corneal lesions in the eyes of 10 dogs. Clinical observations were continued for up to 6 months, using biomicroscopy and indirect ophthalmoscopy. Eyes were harvested at intervals for light and electron microscopic evaluation. Clinical alterations included immediate corneal opacification and epithelial disruption at the site of electrode contact. Ulcerative keratitis persisted for 4 to 6 days, accompanied by anterior uveitis. Additional corneal changes included stromal thinning, edema, and vascularization. Final evaluation revealed negligible alterations in corneal contour or clarity 6 months after treatment. Microscopically, epithelial and superficial stromal necrosis preceded epithelial loss. Stromal alterations included edema (associated with focal endothelial detachments), vascularization, and inflammatory cell infiltration. Recovery was characterized by keratocytic hyperplasia and hypertrophy, epithelial proliferation, and stromal condensation.

Glaze, M.B.; Turk, M.A.

1986-04-01

355

Phosphatidylcholine and bipolar radiofrequency for treatment of localized fat deposits.  

PubMed

Bipolar radiofrequency (RF) is capable of delivering higher energy fluencies direct to the dermis through a needle electrode. This produces heat when the tissue electrical resistance converts the electric current to thermal energy in the tissue. A 38-year-old man visited our clinic for reduction of submental fat deposit, but otherwise in overall good health. After deciding to perform phosphatidylcholine (PPC) injections subcutaneously, we concerned about edema and swelling of injection site lasted several weeks. We wanted to shorten the period of edema and swelling, and we decided to add bipolar RF treatment. After 1 week of PPC injection combined with RF treatment, overall volume of jowl was decreased and edema and swelling on the PPC injected site markedly subsided. This reduction of fat deposit lasts longer than 1 year. Follow-up for 1 year demonstrated that the cosmetic results were well maintained. PMID:23621400

Kim, In Su; Hyun, Moo Yeol; Park, Kui Young; Kim, Chan Woong; Kim, Beom Joon; Kim, Myeung Nam

2014-08-01

356

Bronchopleural Fistula After Radiofrequency Ablation of Lung Tumours  

SciTech Connect

The present article describes two cases of bronchopleural fistula (BPF) occurring after radiofrequency ablation of lung tumors. Both procedures were carried out using expandable multitined electrodes, with no coagulation of the needle track. After both ablations, ground-glass opacities encompassed the nodules and abutted the visceral pleura. The first patient had a delayed pneumothorax, and the second had a recurrent pneumothorax. Both cases of BPF were diagnosed on follow-up computed tomography chest scans (i.e., visibility of a distinct channel between the lung or a peripheral bronchus and the pleura) and were successfully treated with chest tubes alone. Our goal is to highlight the fact that BPF can occur without needle-track coagulation and to suggest that minimally invasive treatment is sufficient to cure BPFs of this specific origin.

Cannella, Mathieu; Cornelis, Francois; Descat, Edouard; Ferron, Stephane; Carteret, Thibault; Castagnede, Hugues; Palussiere, Jean, E-mail: palussiere@bergonie.org [Regional Cancer Center, Department of Interventional Radiology, Institut Bergonie (France)

2011-02-15

357

Characteristics of Radio-Frequency Circuits Utilizing Ferroelectric Capacitors  

NASA Technical Reports Server (NTRS)

Ferroelectric capacitors, most commonly used in memory circuits and variable components, were studied in simple analog radio-frequency circuits such as the RLC resonator and Colpitts oscillator. The goal was to characterize the RF circuits in terms of frequency of oscillation, gain, etc, using ferroelectric capacitors. Frequencies of oscillation of both circuits were measured and studied a more accurate resonant frequency can be obtained using the ferroelectric capacitors. Many experiments were conducted and data collected. A model to simulate the experimental results will be developed. Discrepancies in gain and frequency in these RF circuits when conventional capacitors are replaced with ferroelectric ones were studied. These results will enable circuit designers to anticipate the effects of using ferroelectric components in their radio- frequency applications.

Eskridge, Michael; Gui, Xiao; MacLeod, Todd; Ho, Fat D.

2011-01-01

358

Small hepatocellular carcinomas: ultrasonography guided percutaneous radiofrequency ablation.  

PubMed

Current guidelines advocate percutaneous radiofrequency (RF) ablation as a standard treatment of early stage hepatocellular carcinoma (HCC) for up to three tumors ?3 cm in diameter. The local efficacy evaluated with short-term radiological examination may be overrated, whereas that assessed by histopathological measure might be underestimated. Long-term clinical follow-up studies guarantee the effectiveness of RF ablation for small HCC, which is now almost comparable in benefits to surgical resection. US is the most common guiding modality for percutaneous RF ablation for small HCC. However, the technical feasibility is often limited due to poor conspicuity of the index tumor on US. Implementation of artificial ascites, contrast-enhanced harmonic US, and fusion imaging of US with CT/MR can be helpful to enhance the technical feasibility of US-guided RF ablation of small HCC. PMID:22467060

Kim, Young Jun; Lee, Min Woo; Park, Hee Sun

2013-02-01

359

Ethical implications of implantable radiofrequency identification (RFID) tags in humans.  

PubMed

This article reviews the use of implantable radiofrequency identification (RFID) tags in humans, focusing on the VeriChip (VeriChip Corporation, Delray Beach, FL) and the associated VeriMed patient identification system. In addition, various nonmedical applications for implanted RFID tags in humans have been proposed. The technology offers important health and nonhealth benefits, but raises ethical concerns, including privacy and the potential for coercive implantation of RFID tags in individuals. A national discussion is needed to identify the limits of acceptable use of implantable RFID tags in humans before their use becomes widespread and it becomes too late to prevent misuse of this useful but ethically problematic technology. PMID:18802863

Foster, Kenneth R; Jaeger, Jan

2008-08-01

360

The genotoxic effect of radiofrequency waves on mouse brain.  

PubMed

Concerns about the health effects of radiofrequency (RF) waves have been raised because of the gradual increase in usage of cell phones, and there are scientific questions and debates about the safety of those instruments in daily life. The aim of this study is to evaluate the genotoxic effects of RF waves in an experimental brain cell culture model. Brain cell cultures of the mice were exposed to 10.715 GHz with specific absorbtion rate (SAR) 0.725 W/kG signals for 6 h in 3 days at 25°C to check for the changes in the micronucleus (MNi) assay and in the expression of 11 proapoptotic and antiapoptotic genes. It was found that MNi rate increased 11-fold and STAT3 expression decreased 7-fold in the cell cultures which were exposed to RF. Cell phones which spread RF may damage DNA and change gene expression in brain cells. PMID:21732071

Karaca, Emin; Durmaz, Burak; Aktug, Huseyin; Altug, Huseyin; Yildiz, Teoman; Guducu, Candan; Irgi, Melis; Koksal, Mehtap Gulcihan Cinar; Ozkinay, Ferda; Gunduz, Cumhur; Cogulu, Ozgur

2012-01-01

361

Laparoscopic Ultrasound-Guided Radiofrequency Ablation of Uterine Fibroids  

SciTech Connect

Four patients with symptomatic uterine fibroids measuring less than 6 cm underwent laparoscopic ultrasound-guided radiofrequency ablation (RFA) using multiprobe-array electrodes. Follow-up of the treated fibroids was performed with gadolinium-enhanced magnetic resonance imaging (MRI) and patients' symptoms were assessed by telephone interviews. The procedure was initially technically successful in 3 of the 4 patients and MRI studies at 1 month demonstrated complete fibroid ablation. Symptom improvement, including a decrease in menstrual bleeding and pain, was achieved in 2 patients at 3 months. At 7 months, 1 of these 2 patients experienced symptom worsening which correlated with recurrent fibroid on MRI. The third, initially technically successfully treated patient did not experience any symptom relief after the procedure and was ultimately diagnosed with adenomyosis. Our preliminary results suggest that RFA is a technically feasible treatment for symptomatic uterine fibroids in appropriately selected patients.

Milic, Andrea [University of Toronto, Department of Medical Imaging (Canada); Asch, Murray R. [Lakeridge Health Corporation, Department of Diagnostic Radiology (Canada)], E-mail: masch@lakeridgehealth.on.ca; Hawrylyshyn, Peter A.; Allen, Lisa M. [Mount Sinai Hospital, Department of Obstetrics and Gynecology (Canada); Colgan, Terence J. [Mount Sinai Hospital, Department of Pathology (Canada); Kachura, John R. [Toronto General Hospital, Department of Diagnostic Imaging (Canada); Hayeems, Eran B. [Mount Sinai Hospital, Department of Diagnostic Imaging (Canada)

2006-08-15

362

Superconducting radio-frequency modules test faciilty operating experience  

SciTech Connect

Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R&D). Four major SRF test areas are being constructed to enable vertical and horizontal cavity testing, as well as cryomodule testing. The existing Fermilab cryogenic infrastructure has been modified to service Fermilab SRF R&D needs. The first stage of the project has been successfully completed, which allows for distribution of cryogens for a single cavity cryomodule using the existing Cryogenic Test Facility (CTF) that houses three Tevatron satellite refrigerators. The cooling capacity available for cryomodule testing at MDB results from the liquefaction capacity of the CTF cryogenic system. The cryogenic system for a single 9-cell cryomodule is currently operational. The paper describes the status, challenges and operational experience of the initial phase of the project.

Soyars, W.; Bossert, R.; Darve, C.; Degraff, B.; Klebaner, A.; Martinez, A.; Pei, L.; Theilacker, J.; /Fermilab

2007-07-01

363

Radiofrequency (GFX) ablation for the reduction of glabellar frowning.  

PubMed

A new minimally invasive procedure is described for the reduction of glabellar frowning. Glabellar furrow relaxation or GFX (TM) utilizes bipolar radiofrequency energy targeted at peripheral motor nerve fibers to the depressor muscles of the forehead. This procedure is a useful adjunct in forehead rejuvenation when performed concomitantly with blepharoplasty or forehead lifting in a surgical setting. With proper training the procedure can be performed under local anesthesia in the office setting to produce very natural results. The relevant anatomy and technique is described here in detail because this represents new knowledge in facial plastic surgery. A cohort of patients has been studied for over 12 months demonstrating the efficacy of the relaxation that can be achieved with the procedure. The GFX procedure offers the patients and surgeons an alternative treatment to botulinum toxin A when longer lasting relaxation of the forehead depressor muscles is desired. PMID:20524175

Newman, James

2010-08-01

364

Electromagnetic and mechanical design of gridded radio-frequency cavity windows  

SciTech Connect

Electromagnetic, thermal and structural analyses of radio-frequency (RF) cavities were performed as part of a developmental RF cavity program for muon cooling. RF cavities are necessary to provide longitudinal focusing of the muons and to compensate for their energy loss. Closing the cavity ends by electrically conducting windows reduces the power requirement and increases the on-axis electric field for a given maximum surface electric field. Many factors must be considered in the design of RF cavity windows. RF heating can cause the windows to deform in the axial direction of the cavity. The resulting thermal stresses in the window must be maintained below the yield stress of the window material. The out-of-plane deflection must be small enough so that the consequent frequency shift is tolerable. For example, for an 805 MHz cavity, the out-of-plane deflection must be kept below 25 microns to prevent the frequency of the cavity from shifting more than 10 kHz. In addition, the window design should yield smooth electric and magnetic fields, terminate field leakage beyond the window, and minimize beam scattering. In the present thesis, gridded-tube window designs were considered because of their high structural integrity. As a starting point in the analysis, a cylindrical pillbox cavity was considered as a benchmark problem. Analytical and finite element solutions were obtained for the electric and magnetic fields, power loss density, and temperature profile. Excellent agreement was obtained between the analytical and finite element results. The finite element method was then used to study a variety of gridded-tube windows. It was found that cooling of the gridded-tube windows by passing helium gas inside the tubes significantly reduces the out-of-plane deflection and the thermal stresses. Certain tube geometries and grid patterns were found to satisfy all of the design requirements.

Alsharoa, Mohammad M.; /IIT, Chicago /Fermilab; ,

2004-12-01

365

Successful Treatment of Erythematotelangiectatic Rosacea with Pulsed Light and Radiofrequency  

PubMed Central

Introduction: Many laser and light devices have reported to be successful in the treatment of the flushing, background erythema, and telangiectasias that characterize erythematotelangiectatic rosacea including pulsed dye laser, potassium titanyl phosphate, intense pulsed light, and dual-wavelength lasers. A technology called ELOS (electro-optical synergy) combines pulsed light or laser with bipolar radiofrequency. This combination, developed in 2000, was based on the premise that these two forms of energy could be synergistic. One such device (Aurora SRA—skin-rejuvenation advanced handpiece, Syneron Medical Ltd., Yokneam, Israel) has a light spectrum of 470 to 980nm, energy up to 45J/cm2, and a range of radiofrequency energy of 5 to 25J/cm3 and is indicated for the treatment of vascular and pigmented lesions. Methods: We attempted to quantify the improvement of moderate-to-severe type-1 rosacea after three and five full-face treatments with this modality. Twenty-one patients with moderate-to-severe rosacea underwent five monthly full-face treatments with this device. The patients were evaluated with high-resolution photographs (Canfield Visia CR, Canfield, Fairfield, New Jersey) and self-evaluated via the National Rosacea Society's official “Scorecard.” Results: Erythema and telangiectasia (physician assessed) as well as flushing and global status (patient assessed) achieved improvement that was statistically significant. Five treatments were no more effective than three, although the photographs reveal subtle improvements. There were no significant adverse events. Conclusion: The results of this study suggest that the combination of optical and RF energies is effective for the treatment of rosacea. ELOS, as well as other vascular-focused lasers and light sources, provides an important treatment option for patients who fail medical therapy, reach a plateau in their response to medical therapy, or wish to avoid chronic oral therapy. PMID:21103309

DeVita, Erin C.

2008-01-01

366

Design and characterization of a radio-frequency dc/dc power converter  

E-print Network

The use of radio-frequency (RF) amplifier topologies in dc/dc power converters allows the operating frequency to be increased by more than two orders of magnitude over the frequency of conventional converters. This enables ...

Jackson, David A. (David Alexander)

2005-01-01

367

21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.  

Code of Federal Regulations, 2013 CFR

...AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) IRRADIATION IN THE PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency...

2013-04-01

368

21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.  

Code of Federal Regulations, 2012 CFR

...AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) IRRADIATION IN THE PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency...

2012-04-01

369

21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.  

...Section 179.30 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) IRRADIATION IN THE PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency...

2014-04-01

370

21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.  

Code of Federal Regulations, 2011 CFR

... Radiofrequency radiation for the heating...DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED...HANDLING OF FOOD Radiation and Radiation Sources...is necessary and effective in the...

2011-04-01

371

21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.  

Code of Federal Regulations, 2010 CFR

... Radiofrequency radiation for the heating...DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED...HANDLING OF FOOD Radiation and Radiation Sources...is necessary and effective in the...

2010-04-01

372

Computer simulation of a novel technique for Radio-Frequency Ablation of ventricular arrhythmias  

E-print Network

Ventricular Tachycardia (VT) is a rapid arrhythmia, most commonly due to reentrant electrical activity in the heart. A common treatment for VT is Radio-Frequency Ablation (RFA), which is minimally invasive, but requires ...

Rosbury, Tamara S

2006-01-01

373

Base-level management of radio-frequency radiation-protection program. Final report  

SciTech Connect

AFOEHL developed this report to assist the base-level aerospace medical team manage their radio-frequency radiation-protection program. This report supersedes USAFOEHL Report 80-42, 'A Practical R-F Guide for BEES.'

Rademacher, S.E.; Montgomery, N.D.

1989-04-01

374

Base-level management of radio-frequency radiation-protection program. Final report  

SciTech Connect

AFOEHL developed this report to assist the base-level aerospace medical team manage their radio-frequency radiation protection program. This report supersedes USAFOEHL Report 80-42, 'A practical R-F Guide for BEES.'

Rademacher, S.E.; Montgomery, N.D.

1989-04-01

375

APPLICATION OF A FINITE-DIFFERENCE TECHNIQUE TO THE HUMAN RADIOFREQUENCY DOSIMETRY PROBLEM  

EPA Science Inventory

A powerful finite difference numerical technique has been applied to the human radiofrequency dosimetry problem. The method possesses inherent advantages over the method of moments approach in that its implementation requires much less computer memory. Consequently, it has the ca...

376

Ultrabroad-bandwidth arbitrary radiofrequency waveform generation with a silicon photonic chip-based spectral shaper  

Microsoft Academic Search

Ultrabroad-bandwidth radiofrequency pulses offer significant applications potential, such as increased data transmission rate and multipath tolerance in wireless communications. Such ultrabroad-bandwidth pulses are inherently difficult to generate with chip-based electronics due to limits in digital-to-analog converter technology and high timing jitter. Photonic means of radiofrequency waveform generation, for example, by spectral shaping and frequency-time mapping, can overcome the bandwidth limit

Maroof H. Khan; Hao Shen; Yi Xuan; Lin Zhao; Shijun Xiao; Daniel E. Leaird; Andrew M. Weiner; Minghao Qi

2010-01-01

377

Radiofrequency ablation of benign thyroid nodules and recurrent thyroid cancers: consensus statement and recommendations.  

PubMed

Thermal ablation using radiofrequency is a new, minimally invasive modality employed as an alternative to surgery in patients with benign thyroid nodules and recurrent thyroid cancers. The Task Force Committee of the Korean Society of Thyroid Radiology has developed recommendations for the optimal use of radiofrequency ablation for thyroid nodules. These recommendations are based on a comprehensive analysis of the current literature, the results of multicenter studies, and expert consensus. PMID:22438678

Na, Dong Gyu; Lee, Jeong Hyun; Jung, So Lyung; Kim, Ji-Hoon; Sung, Jin Yong; Shin, Jung Hee; Kim, Eun-Kyung; Lee, Joon Hyung; Kim, Dong Wook; Park, Jeong Seon; Kim, Kyu Sun; Baek, Seon Mi; Lee, Younghen; Chong, Semin; Sim, Jung Suk; Huh, Jung Yin; Bae, Jae-Ik; Kim, Kyung Tae; Han, Song Yee; Bae, Min Young; Kim, Yoon Suk; Baek, Jung Hwan

2012-01-01

378

Radiofrequency Ablation of Benign Thyroid Nodules and Recurrent Thyroid Cancers: Consensus Statement and Recommendations  

PubMed Central

Thermal ablation using radiofrequency is a new, minimally invasive modality employed as an alternative to surgery in patients with benign thyroid nodules and recurrent thyroid cancers. The Task Force Committee of the Korean Society of Thyroid Radiology has developed recommendations for the optimal use of radiofrequency ablation for thyroid nodules. These recommendations are based on a comprehensive analysis of the current literature, the results of multicenter studies, and expert consensus. PMID:22438678

Na, Dong Gyu; Lee, Jeong Hyun; Jung, So Lyung; Kim, Ji-hoon; Sung, Jin Yong; Shin, Jung Hee; Kim, Eun-Kyung; Lee, Joon Hyung; Kim, Dong Wook; Park, Jeong Seon; Kim, Kyu Sun; Baek, Seon Mi; Lee, Younghen; Chong, Semin; Sim, Jung Suk; Huh, Jung Yin; Bae, Jae-Ik; Kim, Kyung Tae; Han, Song Yee; Bae, Min Young; Kim, Yoon Suk

2012-01-01

379

An evaluation of safety guidelines to restrict exposure to stray radiofrequency radiation from short-wave diathermy units  

NASA Astrophysics Data System (ADS)

Short-wave diathermy (SWD), a form of radiofrequency radiation used therapeutically by physiotherapists, may be applied in continuous (CSWD) or pulsed (PSWD) mode using either capacitive or inductive methods. Stray radiation emitted by these units may exceed exposure guidelines close to the equipment. Discrepant guidelines exist on a safe distance from an operating unit for operators and other personnel. Stray electric (E-field) and magnetic (H-field) field strengths from 10 SWD units in six departments were examined using a PMM 8053 meter and two isotropic probes (EP-330, HP-032). A 5 l saline phantom completed the patient circuit. Measurements were recorded in eight directions between 0.5 m and 2 m at hip and eye levels while the units operated at maximum output and data compared to current guidelines. Results found stray fields from capacitive CSWD fell below operator limits at 2 m (E-field 4.8-39.8 V/m; H-field 0.015-0.072 A/m) and at 1 m for inductive CSWD (E-field 0-36 V/m; H-field 0.01-0.065 A/m). Capacitive PSWD fields fell below the limits at 1.5 m (E-field 1.2-19.9 V/m; H-field 0.002-0.045 A/m) and at 1m for inductive PSWD (E-field 0.7-4.0 V/m; H-field 0.009-0.03 A/m). An extra 0.5 m was required before fields fell below the guidelines for other personnel. These results demonstrate, under a worst case scenario, emissions from SWD exceed the guidelines for operators at distances currently recommended as safe. Future guidelines should include recommendations for personnel other than physiotherapists.

Shields, Nora; O'Hare, Neil; Gormley, John

2004-07-01

380

On-body calibration and processing for a combination of two radio-frequency personal exposimeters.  

PubMed

Two radio-frequency personal exposimeters (PEMs) worn on both hips are calibrated on a subject in an anechoic chamber. The PEMs' response and crosstalk are determined for realistically polarised incident electric fields using this calibration. The 50 % confidence interval of the PEMs' response is reduced (2.6 dB on average) when averaged over both PEMs. A significant crosstalk (up to a ratio of 1.2) is measured, indicating that PEM measurements can be obfuscated by crosstalk. Simultaneous measurements with two PEMs are carried out in Ghent, Belgium. The highest exposure is measured for Global System for Mobile Communication downlink (0.052 mW m(-2) on average), while the lowest exposure is found for Universal Mobile Telecommunications System uplink (0.061 ?W m(-2) on average). The authors recommend the use of a combination of multiple PEMs and, considering the multivariate data, to provide the mean vector and the covariance matrix next to the commonly listed univariate summary statistics, in future PEM studies. PMID:24729592

Thielens, Arno; Agneessens, Sam; Verloock, Leen; Tanghe, Emmeric; Rogier, Hendrik; Martens, Luc; Joseph, Wout

2015-01-01

381

Workgroup report: base stations and wireless networks-radiofrequency (RF) exposures and health consequences.  

PubMed

Radiofrequency (RF) waves have long been used for different types of information exchange via the air waves--wireless Morse code, radio, television, and wireless telephone (i.e., construction and operation of telephones or telephone systems). Increasingly larger numbers of people rely on mobile telephone technology, and health concerns about the associated RF exposure have been raised, particularly because the mobile phone handset operates in close proximity to the human body, and also because large numbers of base station antennas are required to provide widespread availability of service to large populations. The World Health Organization convened an expert workshop to discuss the current state of cellular-telephone health issues, and this article brings together several of the key points that were addressed. The possibility of RF health effects has been investigated in epidemiology studies of cellular telephone users and workers in RF occupations, in experiments with animals exposed to cell-phone RF, and via biophysical consideration of cell-phone RF electric-field intensity and the effect of RF modulation schemes. As summarized here, these separate avenues of scientific investigation provide little support for adverse health effects arising from RF exposure at levels below current international standards. Moreover, radio and television broadcast waves have exposed populations to RF for > 50 years with little evidence of deleterious health consequences. Despite unavoidable uncertainty, current scientific data are consistent with the conclusion that public exposures to permissible RF levels from mobile telephone and base stations are not likely to adversely affect human health. PMID:17431492

Valberg, Peter A; van Deventer, T Emilie; Repacholi, Michael H

2007-03-01

382

Short-duration exposure to radiofrequency electromagnetic radiation alters the chlorophyll fluorescence of duckweeds (Lemna minor).  

PubMed

Plants growing in natural environments are exposed to radiofrequency electromagnetic radiation (EMR) emitted by various communication network base stations. The environmental concentration of this radiation is increasing rapidly with the congested deployment of base stations. Although numerous scientific studies have been conducted to investigate the effects of EMR on the physiology of humans and animals, there have been few attempts to investigate the effects of EMR on plants. In this study, we attempted to evaluate the effects of EMR on photosynthesis by investigating the chlorophyll fluorescence (ChF) parameters of duckweed fronds. During the experiment, the fronds were tested with 2, 2.5, 3.5, 5.5 and 8?GHz EMR frequencies, which are not widely studied even though there is a potentially large concentration of these frequencies in the environment. The duckweed fronds were exposed to EMR for 30?min, 1?h and 24?h durations with electric field strength of 45-50?V/m for each frequency. The results indicated that exposure to EMR causes a change in the non-photochemical quenching of the duckweeds. The changes varied with the frequency of the EMR and were time-varying within a particular frequency. The temperature remained unchanged in the duckweed fronds upon exposure to EMR, which confirms that the effect is non-thermal. PMID:24131393

Senavirathna, Mudalige Don Hiranya Jayasanka; Takashi, Asaeda; Kimura, Yuichi

2014-12-01

383

Caudal Epidural of Pulsed Radiofrequency in Post Herpetic Neuralgia (PHN); Report of Three Cases  

PubMed Central

Introduction: Postherpetic neuralgia (PHN) is a frequently occurring neuropathic pain, its pathophysiology is not fully understood. There are only few evidence based therapeutic options; sympathetic nerve block can be considered for patients with PHN refractory to conservative treatment, but long-term effects are poor. Application of pulsed radiofrequency was effective to treat a variety of pain syndromes without neurological complications or other sequelae. Case Presentation: We observed a remarkable long-lasting pain relief in patients with post herpetic neuralgia (PHN) treated with caudal epidural PRF. We described the technique of caudal epidural PRF and three case reports. Conclusions: The mode of action of PRF is far from being completely elucidated. The high frequency current induces an electric field that in turn seems to influence the immunity, the inflammation and other pain conducting mechanisms. Our findings suggest an effect distal from the application of the current. It reaches targets that are difficultly attainable by any other means of current application. The observations of pain relief in the difficult to treat patients with PHN justifies further investigation. PMID:25237634

Rohof, Olav Jacobus Johannes Maria

2014-01-01

384

Thermoregulatory responses of rats exposed to 9. 3-GHz radio-frequency radiation  

SciTech Connect

Ketamine-anesthetized Sprague-Dawley rats were exposed in H orientation to far-field 9.3-GHz continuous-wave (CW) and pulsed (2 microseconds 500 pps) radiofrequency radiation (RFR) at average power densities of 30 and 60 mW/sq. cm (whole-body average specific absorption rates of 9.3 and 18.6 W/kg, respectively). Irradiation was conducted to cyclicly increase colonic temperature from 38.5 to 39.5 C. Colonic, tympanic, and subcutaneous temperatures, ECG, blood pressure, and respiratory rate were continuously recorded during experimentation. At both power densities, the subcutaneous and tympanic temperature increases significantly exceeded the colonic temperature increase. At both exposure levels, heart rate increased significantly during irradiation and returned to baseline when exposure was discontinued. Blood pressure and respiratory rate did not significantly change during irradiation. There were no significant differences between the effects of CW and pulsed RFR exposure. The levels of subcutaneous heating and heart rate change were greater, and the times required to achieve and to recover from a 1 C colonic temperature increase were longer than in previous studies conducted at 2.8 GHz. Results of these studies indicate that the carrier frequency used during irradiation markedly affects the pattern of heat distribution and the physiological responses of RF-irradiated animals.

Frei, M.R.; Jauchem, J.R.; Heinmets, F.

1987-10-15

385

Deep hyperthermia with radiofrequencies in patients with liver metastases from colorectal cancer.  

PubMed

Patients at advanced stage of colorectal cancer with liver metastases have been treated with deep hyperthermia alone or in combination with chemotherapy (5-FU + FA + MMC). Hyperthermia was achieved by arrangements of capacitive electrodes with a radiofrequency field of 13.56 MHz (RF-DHT). This prospective open single-arm clinical study with 80 patients suffering from liver metastases from colorectal cancer gives some first hints, that deep RF-hyperthermia alone may have a substantial beneficial effect on overall survival time of patients with liver metastases from colorectal cancer. Long lasting no-change, partial and even some complete remissions could be observed. The overall median survival time from progression of metastases or relapse was 24.5 months and survival rates at 1, 2 or 3 years from first diagnosis of metastases or progression were twice as high as expected from patients treated with chemotherapy. The combination of hyperthermia with delayed chemotherapy did not change overall survival time. These encouraging results deserve to be confirmed in randomized clinical studies. PMID:10629627

Hager, E D; Dziambor, H; Höhmann, D; Gallenbeck, D; Stephan, M; Popa, C

1999-01-01

386

Workgroup Report: Base Stations and Wireless Networks—Radiofrequency (RF) Exposures and Health Consequences  

PubMed Central

Radiofrequency (RF) waves have long been used for different types of information exchange via the airwaves—wireless Morse code, radio, television, and wireless telephony (i.e., construction and operation of telephones or telephonic systems). Increasingly larger numbers of people rely on mobile telephone technology, and health concerns about the associated RF exposure have been raised, particularly because the mobile phone handset operates in close proximity to the human body, and also because large numbers of base station antennas are required to provide widespread availability of service to large populations. The World Health Organization convened an expert workshop to discuss the current state of cellular-telephone health issues, and this article brings together several of the key points that were addressed. The possibility of RF health effects has been investigated in epidemiology studies of cellular telephone users and workers in RF occupations, in experiments with animals exposed to cell-phone RF, and via biophysical consideration of cell-phone RF electric-field intensity and the effect of RF modulation schemes. As summarized here, these separate avenues of scientific investigation provide little support for adverse health effects arising from RF exposure at levels below current international standards. Moreover, radio and television broadcast waves have exposed populations to RF for > 50 years with little evidence of deleterious health consequences. Despite unavoidable uncertainty, current scientific data are consistent with the conclusion that public exposures to permissible RF levels from mobile telephony and base stations are not likely to adversely affect human health. PMID:17431492

Valberg, Peter A.; van Deventer, T. Emilie; Repacholi, Michael H.

2007-01-01

387

Optical fiber sensors-based temperature distribution measurement in ex vivo radiofrequency ablation with submillimeter resolution.  

PubMed

Radiofrequency thermal ablation (RFTA) induces a high-temperature field in a biological tissue having steep spatial (up to 6°C?mm) and temporal (up to 1°C?s) gradients. Applied in cancer care, RFTA produces a localized heating, cytotoxic for tumor cells, and is able to treat tumors with sizes up to 3 to 5 cm in diameter. The online measurement of temperature distribution at the RFTA point of care has been previously carried out with miniature thermocouples and optical fiber sensors, which exhibit problems of size, alteration of RFTA pattern, hysteresis, and sensor density worse than 1 sensor?cm. In this work, we apply a distributed temperature sensor (DTS) with a submillimeter spatial resolution for the monitoring of RFTA in porcine liver tissue. The DTS demodulates the chaotic Rayleigh backscattering pattern with an interferometric setup to obtain the real-time temperature distribution. A measurement chamber has been set up with the fiber crossing the tissue along different diameters. Several experiments have been carried out measuring the space-time evolution of temperature during RFTA. The present work showcases the temperature monitoring in RFTA with an unprecedented spatial resolution and is exportable to in vivo measurement; the acquired data can be particularly useful for the validation of RFTA computational models. PMID:25388811

Macchi, Edoardo Gino; Tosi, Daniele; Braschi, Giovanni; Gallati, Mario; Cigada, Alfredo; Busca, Giorgio; Lewis, Elfed

2014-01-01

388

Optical fiber sensors-based temperature distribution measurement in ex vivo radiofrequency ablation with submillimeter resolution  

NASA Astrophysics Data System (ADS)

Radiofrequency thermal ablation (RFTA) induces a high-temperature field in a biological tissue having steep spatial (up to 6°C/mm) and temporal (up to 1°C/s) gradients. Applied in cancer care, RFTA produces a localized heating, cytotoxic for tumor cells, and is able to treat tumors with sizes up to 3 to 5 cm in diameter. The online measurement of temperature distribution at the RFTA point of care has been previously carried out with miniature thermocouples and optical fiber sensors, which exhibit problems of size, alteration of RFTA pattern, hysteresis, and sensor density worse than 1 sensor/cm. In this work, we apply a distributed temperature sensor (DTS) with a submillimeter spatial resolution for the monitoring of RFTA in porcine liver tissue. The DTS demodulates the chaotic Rayleigh backscattering pattern with an interferometric setup to obtain the real-time temperature distribution. A measurement chamber has been set up with the fiber crossing the tissue along different diameters. Several experiments have been carried out measuring the space-time evolution of temperature during RFTA. The present work showcases the temperature monitoring in RFTA with an unprecedented spatial resolution and is exportable to in vivo measurement; the acquired data can be particularly useful for the validation of RFTA computational models.

Macchi, Edoardo Gino; Tosi, Daniele; Braschi, Giovanni; Gallati, Mario; Cigada, Alfredo; Busca, Giorgio; Lewis, Elfed

2014-11-01

389

Development of a novel radio-frequency negative hydrogen ion source in conically converging configuration.  

PubMed

Volume-produced negative ion source still requires enhancement of current density with lower input RF (radio-frequency) power in lower operating pressure for various applications. To confirm recent observation of efficient negative ion production with a short cylindrical chamber with smaller effective plasma size, the RF-driven transformer-coupled plasma H(-) ion source at Seoul National University is modified by adopting a newly designed quartz RF window to reduce the chamber length. Experiments with the reduced chamber length show a few times enhancement of H(-) ion beam current compared to that extracted from the previous chamber design, which is consistent with the measured H(-) ion population. Nevertheless, decrease in H(-) ion beam current observed in low pressure regime below ?5 mTorr owing to insufficient filtering of high energy electrons in the extraction region needs to be resolved to address the usefulness of electron temperature control by the change of geometrical configuration of the discharge chamber. A new discharge chamber with conically converging configuration has been developed, in which the chamber diameter decreases as approaching to the extraction region away from the planar RF antenna such that stronger filter magnetic field can be utilized to prohibit high energy electrons from transporting to the extraction region. First experimental results for the H(-) ion beam extraction with this configuration show that higher magnetic filter field makes peak negative beam currents happen in lower operating pressure. However, overall decrease in H(-) ion beam current due to the change of chamber geometry still requires further study of geometrical effect on particle transport and optimization of magnetic field in this novel configuration. PMID:24593552

Jung, B K; Dang, J J; An, Y H; Chung, K J; Hwang, Y S

2014-02-01

390

The Effects of Non-Invasive Radiofrequency Treatment and Hyperthermia on Malignant and Nonmalignant Cells  

PubMed Central

Background: Exposure of biological subjects to electromagnetic fields with a high frequency is associated with temperature elevation. In our recent studies, we reported that non-invasive radiofrequency (RF) treatment at 13.56 MHz with the field ranging from 1 KeV to 20 KeV/m2 inhibits tumor progression in animals with abdominal tumor xenografts and enhances the anticancer effect of chemotherapy. The RF treatment was followed by temperature elevation in tumors to approximately 46 °C during 10 min of exposure. In contrast, the temperature of normal tissues remained within a normal range at approximately 37 °C. Whether all biological effects of RF treatment are limited to its hyperthermic property remains unclear. Here, we compared how RF and hyperthermia (HT) treatments change the proliferation rate, oxygen consumption and autophagy in malignant and nonmalignant cells. Methods: In the current study, cancer and nonmalignant cells of pancreatic origin were exposed to the RF field or to conventional HT at 46 °C, which was chosen based on our previous in vivo studies of the tumor-specific RF-induced hyperthermia. Results: Only RF treatment caused declines in cancer cell viability and proliferation. RF treatment also affected mitochondrial function in cancer cells more than HT treatment did and, unlike HT treatment, was followed by the elevation of autophagosomes in the cytoplasm of cancer cells. Importantly, the effects of RF treatment were negligible in nonmalignant cells. Conclusion: The obtained data indicate that the effects of RF treatment are specific to cancer cells and are not limited to its hyperthermic property. PMID:25192147

Curley, Steven A.; Palalon, Flavio; Sanders, Kelly E.; Koshkina, Nadezhda V.

2014-01-01

391

Radiofrequency identification and medical devices: the regulatory framework on electromagnetic compatibility. Part II: active implantable medical devices.  

PubMed

The number and the types of electromagnetic emitters to which patients with active implantable medical devices (AIMD) are exposed to in their daily activities have proliferated over the last decade. Radiofrequency identification (RFID) is an example of wireless technology applied in many fields. The interaction between RFID emitters and AIMD is an important issue for patients, industry and regulators, because of the risks associated with such interactions. The different AIMDs refer to different standards that address the electromagnetic immunity issue in different ways. Indeed, different test setups, immunity levels and rationales are used to guarantee that AIMDs are immune to electromagnetic nonionizing radiation. In this article, the regulatory framework concerning electromagnetic compatibility between RFID systems and AIMDs is analyzed to understand whether and how the application of the current AIMD standards allows for the effective control of the possible risks associated with RFID technology. PMID:22702260

Mattei, Eugenio; Censi, Federica; Triventi, Michele; Bartolini, Pietro; Calcagnini, Giovanni

2012-05-01

392

Formation of spatially periodic fronts of high-energy electrons in a radio-frequency driven surface microdischarge  

SciTech Connect

The generation of spatially periodic fronts of high-energy electrons (>13.48 eV) has been investigated in a radio-frequency surface microdischarge in atmospheric-pressure argon. Optical emission spectroscopy is used to study the Ar I 2p{sub 1}-1s{sub 2} transition surrounding a filamentary microdischarge, both spatially and with respect to the phase of the applied voltage. The formation of excitation fronts, which remain at a constant propagation distance throughout the RF cycle and for the duration of the pulse, may be explained by a localized increase in the electric field at the tip of surface-charge layers that are deposited during the extension phase.

Dedrick, J.; Boswell, R. W.; Charles, C. [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, Australian National University, ACT 0200 (Australia)] [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, Australian National University, ACT 0200 (Australia); O'Connell, D.; Gans, T. [York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom)] [York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom)

2013-01-21

393

Wireless Chalcogenide Nanoionic-Based Radio-Frequency Switch  

NASA Technical Reports Server (NTRS)

A new nonvolatile nanoionic switch is powered and controlled through wireless radio-frequency (RF) transmission. A thin layer of chalcogenide glass doped with a metal ion, such as silver, comprises the operational portion of the switch. For the switch to function, an oxidizable electrode is made positive (anode) with respect to an opposing electrode (cathode) when sufficient bias, typically on the order of a few tenths of a volt or more, is applied. This action causes the metal ions to flow toward the cathode through a coordinated hopping mechanism. At the cathode, a reduction reaction occurs to form a metal deposit. This metal deposit creates a conductive path that bridges the gap between electrodes to turn the switch on. Once this conductive path is formed, no further power is required to maintain it. To reverse this process, the metal deposit is made positive with respect to the original oxidizable electrode, causing the dissolution of the metal bridge thereby turning the switch off. Once the metal deposit has been completely dissolved, the process self-terminates. This switching process features the following attributes. It requires very little to change states (i.e., on and off). Furthermore, no power is required to maintain the states; hence, the state of the switch is nonvolatile. Because of these attributes the integration of a rectenna to provide the necessary power and control is unique to this embodiment. A rectenna, or rectifying antenna, generates DC power from an incident RF signal. The low voltages and power required for the nanoionic switch control are easily generated from this system and provide the switch with a novel capability to be operated and powered from an external wireless device. In one realization, an RF signal of a specific frequency can be used to set the switch into an off state, while another frequency can be used to set the switch to an on state. The wireless, miniaturized, and nomoving- part features of this switch make it suitable for applications such as integration into garments, RFID (radio-frequency identification) tags, and conformal structures (e.g., aircraft wings, sounding rockets contours, etc). In the case of RFID tags the innovation will provide countermeasures to attempts for identity theft and other uninvited attempts for retrieval of information. It could also be applicable to the automotive industry as well as the aerospace industry for collision avoidance and phased array radar systems, respectively

Nessel, James; Miranda, Felix

2013-01-01

394

Radio-frequency plasma transducer for use in harsh environments.  

PubMed

We describe a compact transducer used to generate and modulate low-intensity radio-frequency atmospheric pressure plasma (RF-APP) for high temperature gap measurement and generation of air-coupled ultrasound. The new transducer consists of a quarter-wave transmission line where the ground return path is a coaxial solenoid winding. The RF-APP is initiated at the open end of the transmission line and stabilized by passive negative feedback between the electrical impedance of the plasma and the energy stored in the solenoid. The electrical impedance of the plasma was measured at the lower-voltage source end of the transducer, eliminating the need to measure kilovolt-level voltages near the discharge. We describe the use of a 7 MHz RF-APP prototype as a harsh-environment clearance sensor to demonstrate the suitability of plasma discharges for a common nondestructive inspection application. Clearance measurements of 0-5 mm were performed on a rotating calibration target with a measurement precision of 0.1 mm and a 20 kHz sampling rate. PMID:17979443

May, Andrew; Andarawis, Emad

2007-10-01

395

[Radiofrequency ablation of type I atrial flutter. Personal experience].  

PubMed

The cause of Afl-I is macroentry in the right atrium. The critical site of reentry is the narrow anatomical space in the isthmic region between the posterior part of the annulus of the tricuspid valve and the vena cava inferior (isthmus TA-IVC). Radiofrequency ablation (RF) of the isthmus TA-IVC is successful on average in 90% of patients. The best criterium for evaluation of short-term and long-term effect of RF ablation is a two-way block of conduction in the TA-IVC insthmus, created by RF ablation. In case of a relapse it is possible to repeat ablation. Although a proarrhythmic effect of ablation is not assumed, the cause of the higher frequency of atrial fibrillation is not known. The authors present their own experience with the treatment of Afl-I by RF ablation of the TA-IVC isthmus in a group of 18 patients. RF ablation was successful in 83.3% patients of the group, no complications were recorded. Late relapses of Afl-1 in three patients were resolved by repeated RF ablation which was successful. The results are comparable with results in other departments. Based on their own experience the authors consider ablation treatment of Afl-1 a safe and effective therapeutic method in a selected group of patients. PMID:10422524

Szentiványi, M; Kaliská, G

1999-01-01

396

Recent progress in radiofrequency ablation therapy for hepatocellular carcinoma.  

PubMed

In order to attain better ablation and more effective management of hepatocellular carcinoma (HCC), new approaches and devices in radiofrequency ablation (RFA) therapy were presented and discussed in a workshop at the 50th Annual Meeting of the Liver Cancer Study Group of Japan. A novel bipolar RFA apparatus was introduced in Japan in January 2013. Hundreds of subjects with HCC were treated with multipolar RFA with varied devices and plans. Among these, no-touch ablation was one of the most useful procedures in the treatment of HCC with the apparatus. In RFA therapy, a few assisting devices and techniques were applied for convenience and improvement of the thermal ablation procedure. Contrast-enhanced ultrasonography and three-dimensional fusion imaging technique using volume data of CT or MRI could improve exact targeting and shorten the treatment time for RFA procedures under ultrasonographic guidance. A more complicated method using a workstation was also reported as being helpful in planning the ablated shape and volume in multineedle RFA. The effective use of sedatives and antianalgesics as well as a novel microwave apparatus with a cooled-tip electrode was also discussed. PMID:25427736

Ikeda, Kenji; Osaki, Yukio; Nakanishi, Hiroyuki; Nasu, Akihiro; Kawamura, Yusuke; Jyoko, Koji; Sano, Takatomo; Sunagozaka, Hajime; Uchino, Koji; Minami, Yasunori; Saito, Yu; Nagai, Kazumasa; Inokuchi, Ryosuke; Kokubu, Shigehiro; Kudo, Masatoshi

2014-01-01

397

Atrio-oesophageal fistula after transcatheter radiofrequency ablation.  

PubMed

A 68-year-old woman presented 3?weeks following unsuccessful transcatheter radiofrequency ablation (TcRFA) for treatment of her chronic atrial fibrillation. Neurological signs manifested on day 2 of admission with generalised tonic-clonic seizures and reduced Glasgow Coma Score. She was treated for presumed central nervous system (CNS) infection, intubated and transferred to the intensive care unit. CT of the head showed bilateral oedema secondary to acute embolic stroke. Blood cultures grew Streptococcus viridans, and lumbar puncture findings were consistent with CNS infection. Echocardiography showed only a septostomy puncture from the atrial fibrillation ablation procedure. Thoracic CT demonstrated air in the left atrium, consistent with the diagnosis of atrio-oesophageal fistula, a rarely reported iatrogenic complication of TcRFA. MRI of the head showed significant neurological injury with innumerable embolic infarcts. After discussion with her family regarding the significant neurological insult, and with no signs of any clinical improvement, the patient died on day 8 of admission. PMID:25564583

Moss, Caroline E; Fernandez-Caballero, Sandra; Walker, David

2015-01-01

398

Quality Improvement Guidelines for Radiofrequency Ablation of Liver Tumours  

SciTech Connect

The development of image-guided percutaneous techniques for local tumour ablation has been one of the major advances in the treatment of liver malignancies. Among these methods, radiofrequency ablation (RFA) is currently established as the primary ablative modality at most institutions. RFA is accepted as the best therapeutic choice for patients with early-stage hepatocellular carcinoma (HCC) when liver transplantation or surgical resection are not suitable options [1, 2]. In addition, RFA is considered a viable alternate to surgery (1) for inoperable patients with limited hepatic metastatic disease, especially from colorectal cancer, and (2) for patients deemed ineligible for surgical resection because of extent and location of the disease or concurrent medical conditions [3]. These guidelines were written to be used in quality-improvement programs to assess RFA of HCC and liver metastases. The most important processes of care are (1) patient selection, (2) performing the procedure, and (3) monitoring the patient. The outcome measures or indicators for these processes are indications, success rates, and complication rates.

Crocetti, Laura, E-mail: l.crocetti@med.unipi.i [University of Pisa, Division of Diagnostic Imaging and Intervention, Department of Hepatology, Liver Transplants, and Infectious Diseases (Italy); Baere, Thierry de [Institut de Cancerologie Gustave Roussy, Department of Interventional Radiology (France); Lencioni, Riccardo [University of Pisa, Division of Diagnostic Imaging and Intervention, Department of Hepatology, Liver Transplants, and Infectious Diseases (Italy)

2010-02-15

399

Pulsed radiofrequency treatment in a case of Eagle's syndrome.  

PubMed

Eagle (Arch Otolaryngol. 1937;25:584 and Arch Otolaryngol. 1949;49:490) first identified elongation of the styloid process and ossification of the stylohyoid ligament as a cause of orofacial pain. The elongated styloid process presses on the internal carotid artery and adjacent structures, including branches of the glossopharyngeal nerve and this produce orofacial pain. Some authors define an elongated styloid process as longer than 4?cm because this length is associated with an increase in the incidence of Eagle's syndrome. The syndrome is diagnosed by exclusion (Walkman SD. Atlas of Uncommon Pain Syndromes. Philadelphia: Elsevier Science; 2003), and the diagnosis is confirmed by radiological studies and computed tomography. Treatment can be divided into medical, interventional, and surgical techniques. We report a patient with symptoms of glossopharyngeal neuralgia, who was diagnosed with Eagle's syndrome on the basis of diagnostic imaging. The length of the stylohyoid process was 63?mm on the left side and 64?mm on the right. Treatment was performed by applying pulsed radiofrequency to the glossopharyngeal nerve with satisfactory results. The technique was performed twice on an outpatient basis, produced no complications or side effects, and proved effective in the short and medium term in decreasing the intensity of pain. PMID:23057728

Mollinedo, Fernando T; Esteban, Sonia L T; Vega, Cristina G; Orcasitas, Ana C; Maguregi, Antón A

2013-06-01

400

Software-assisted post-interventional assessment of radiofrequency ablation  

NASA Astrophysics Data System (ADS)

Radiofrequency ablation (RFA) is becoming a standard procedure for minimally invasive tumor treatment in clinical practice. Due to its common technical procedure, low complication rate, and low cost, RFA has become an alternative to surgical resection in the liver. To evaluate the therapy success of RFA, thorough follow-up imaging is essential. Conventionally, shape, size, and position of tumor and coagulation are visually compared in a side-by-side manner using pre- and post-interventional images. To objectify the verification of the treatment success, a novel software assistant allowing for fast and accurate comparison of tumor and coagulation is proposed. In this work, the clinical value of the proposed assessment software is evaluated. In a retrospective clinical study, 39 cases of hepatic tumor ablation are evaluated using the prototype software and conventional image comparison by four radiologists with different levels of experience. The cases are randomized and evaluated in two sessions to avoid any recall-bias. Self-confidence of correct diagnosis (local recurrence vs. no local recurrence) on a six-point scale is given for each case by the radiologists. Sensitivity, specificity, positive and negative predictive values as well as receiver operating curves are calculated for both methods. It is shown that the software-assisted method allows physicians to correctly identify local tumor recurrence with a higher percentage than the conventional method (sensitivity: 0.6 vs. 0.35), whereas the percentage of correctly identified successful ablations is slightly reduced (specificity: 0.83 vs. 0.89).

Rieder, Christian; Geisler, Benjamin; Bruners, Philipp; Isfort, Peter; Na, Hong-Sik; Mahnken, Andreas H.; Hahn, Horst K.

2014-03-01

401

Radiofrequency ablation of osseous metastases for the palliation of pain  

PubMed Central

A number of different methods have been proposed for pain relief in cancer patients with bone metastases, each with different indications, contraindications and complications (systemic analgesics, bisphosphonates, antitumor chemotherapy, radiotherapy, systemic radio-isotopes, local surgery and vertebroplasty). The ideal treatment has to be fast, safe, effective and tolerable for the patient. CT-guided radiofrequency (RF) ablation may fulfill these criteria. Our experience in the treatment of 30 patients (34 lesions) with painful bone metastases using RF ablation was assessed. There was a significant decrease in the mean past-24-h Brief Pain Inventory (BPI) score for worst pain, for average pain and for pain interference during daily life (4.7, 4.8 and 5.3 units respectively) 4 and 8 weeks after treatment. There was a marked decrease (3 out of 30 patients 4 and 8 weeks after treatment) in the use of analgesics. CT-guided RF ablation appears to be effective for treatment of painful bone metastases. PMID:18030464

Mylona, S.; Galani, P.; Tzavoulis, D.; Kalioras, V.; Tanteles, S.; Pomoni, M.

2007-01-01

402

Radiofrequency Ablation: A Minimally Invasive Approach in Kidney Tumor Management  

PubMed Central

The management and diagnosis of renal tumors have changed significantly over the last decade. Due to advances in imaging techniques, more than 50% of kidney tumors are discovered incidentally and many of them represent an early stage lesion. This has stimulated the development of nephron-sparing surgery and of the minimally invasive treatment options including ablative techniques, i.e., radiofrequency ablation (RFA) and cryoablation. The objective of the minimally invasive approach is to preserve the renal function and to lower the perioperative morbidity. RFA involves inducing the coagulative necrosis of tumor tissue. Being probably one of the least invasive procedures in kidney tumor management, RFA may be performed percutaneously under ultrasound (US), computed tomography (CT) or magnetic resonance (MR) guidance. Most of the studies show that the RFA procedure is efficient, safe and has a low complication rate. Due to the still limited data on the oncological outcome of RFA, the indication for this intervention remains limited to selected patients with small organ-confined renal tumors and contraindication to surgery or who have a solitary kidney. The aim of our study is to review the literature on RFA of kidney tumors. PMID:24281207

Salagierski, Maciej; Salagierski, Marek S.

2010-01-01

403

Towards ultrasound cardiac image segmentation based on the radiofrequency signal.  

PubMed

In echocardiography, the radio-frequency (RF) image is a rich source of information about the investigated tissues. Nevertheless, very few works are dedicated to boundary detection based on the RF image, as opposed to envelope image. In this paper, we investigate the feasibility and limitations of boundary detection in echocardiographic images based on the RF signal. We introduce two types of RF-derived parameters: spectral autoregressive parameters and velocity-based parameters, and we propose a discontinuity adaptive framework to perform the detection task. In classical echographic cardiac acquisitions, we show that it is possible to use the spectral contents for boundary detection, and that improvement can be expected with respect to traditional methods. Using the system approach, we study on simulations how the spectral contents can be used for boundary detection. We subsequently perform boundary detection in high frame rate simulated and in vivo cardiac sequences using the variance of velocity, obtaining very promising results. Our work opens the perspective of a RF-based framework for ultrasound cardiac image segmentation and tracking. PMID:12946474

Dydenko, Igor; Friboulet, Denis; Gorce, Jean-Marie; D'hooge, Jan; Bijnens, Bart; Magnin, Isabelle E

2003-09-01

404

Nanoscale radiofrequency impedance sensors with unconditionally stable tuning  

PubMed Central

Impedance sensors perform an important role in a number of biosensing applications, including particle counting, sizing, and velocimetry. Detection of nanoparticles, or changes in, e.g., the interfacial Debye–Hückel layer, can also be performed using nanoscale impedance sensors. One method for monitoring changes in the local impedance is to use radiofrequency reflectometry, which when combined with an impedance-matched sensor can afford very high sensitivity with very large detection bandwidth. Maintaining sensitivity and dynamic range, however, requires continuous tuning of the impedance matching network. Here we demonstrate a dual feedback tuning circuit, which allows us to maintain near-perfect impedance matching, even in the presence of long-term drifts in sensor impedance. We apply this tuning technique to a nanoscale interdigitated impedance sensor, designed to allow the direct detection of nanoparticles or real-time monitoring of molecular surface binding. We demonstrate optimal performance of the nanoscale sensor and tuned impedance network both when modulating the concentration of saline to which the sensor is exposed and when electronically switching between sensors configured in a two-element differential array, achieving a stabilization response time of <20 ms. PMID:19902001

Requa, M. V.; Fraikin, J.-L.; Stanton, M. A.; Cleland, A. N.

2009-01-01

405

Complications of intraoperative radiofrequency ablation of liver metastases  

PubMed Central

Background Intraoperative radiofrequency ablation (IRFA) of liver metastases can be used to treat patients with complex tumours that are unsuitable for parenchymal resection alone. This systematic review assesses the frequency, patterns and severity of complications associated with this procedure. Methods We carried out a bibliographic search on MEDLINE focused on IRFA for liver metastases, excluding hepatocarcinomas, and on intraoperative use, excluding percutaneous application. Results Thirty papers published between 1999 and 2007 were analysed. They covered a total of 2822 patients and 1755 IRFA procedures. The indications and techniques for IRFA differ from those for percutaneous treatment, as do associated results and complications. Specific complications associated with IRFA, such as liver abscesses, biliary stenoses and vascular thromboses, are directly correlated with the indications and associated procedures. Published results should be interpreted with caution as IRFA can be used alone or combined with parenchymal resection. Conclusions Specific complications related to IRFA are rare, especially for lesions of <35 mm in size located far from a main biliary duct, when additional septic procedures are not used. A lesion-by-lesion approach based on the benefit : risk ratio should therefore be used in the process of making surgical decisions. Combining resection with IRFA leads to higher morbidity, especially in difficult patients with numerous bilateral lesions, but may be necessary to achieve R0 (microscopically negative margins) outcomes. PMID:21159099

Razafindratsira, Tsiriniaina; Isambert, Milène; Evrard, Serge

2011-01-01

406

Treatment of Acne Scars of Skin Types II to V by Sublative Fractional Bipolar Radiofrequency and Bipolar Radiofrequency Combined with Diode Laser  

PubMed Central

Objective: This study evaluated the safety and efficacy of sublative fractional bipolar radiofrequency and bipolar radio frequency combined with diode laser for the treatment of both superficial and deep acne scars in patients with skin types II to V. Design: Prospective, single-center study. Subjects received up to five treatments with sublative fractional bipolar radiofrequency and bipolar radiofrequency combined with diode laser. Treatments were directed to at least two facial (forehead, perioral, cheeks) and/or neck areas with acne scars at four-week intervals. Treatment parameters on each subject were based on skin type and on skin responses to test spots on the target area just before treatment. Setting: Physician office. Participants: Subjects (n=20, aged 40.7±10.5 years [mean ± SD], skin types II–V) with acne scars and without acne lesions enrolled in this prospective study. Measurements: Results were evaluated just before each treatment and at four and 12 weeks after the final treatment using the Goodman Scar Scale, a quantitative method of evaluating scars that attempts to reduce grading subjectivity, as well as by patient satisfaction. Results: Acne scars improved significantly one month after three treatments and improvement persisted for at least 12 weeks after the fifth treatment. Improvement was not affected by skin type. Adverse effects were limited to transient erythema and edema. Conclusion: The combination of diode laser and bipolar radiofrequency energy device in addition to fractionated sublative radiofrequency is a safe and statistically significantly effective combined modality for the treatment of both superficial and deep acne scars in patients with skin types II to V with minimal downtime and no significant side effects. PMID:22010052

Garretson, Cara Beth

2011-01-01

407

Metabolic and vasomotor responses of rhesus monkeys exposed to 225-MHz radiofrequency energy. [Macaca mulatta  

SciTech Connect

A previous study showed a substantial increase in the colonic temperature of rhesus monkeys (Macaca mulatta) exposed to radiofrequency (RF) fields at a frequency near whole-body resonance and specific absorption rates (SAR) of 2-3 W/kg. The present experiments were conducted to determine the metabolic and vasomotor responses during exposures to similar RF fields. We exposed five adult male rhesus monkeys to 225 MHz radiation (E orientation) in an anechoic chamber. Oxygen consumption and carbon dioxide production were measured before, during, and after RF exposure. Colonic, tail and leg skin temperatures were continuously monitored with RF-nonperturbing probes. The monkeys were irradiated at two carefully-controlled ambient temperatures, either cool (20 degrees C) or thermoneutral (26 degrees C). Power densities ranged from 0 (sham) to 10.0 mW/cm2 with an average whole-body SAR of 0.285 (W/kg)/(mW/cm2). We used two experimental protocols, each of which began with a 120-min pre-exposure equilibration period. One protocol involved repetitive 10-min RF exposures at successively higher power densities with a recovery period between exposures. In the second protocol, a 120-min RF exposure permitted the measurement of steady-state thermoregulatory responses. Metabolic and vasomotor adjustments in the rhesus monkey exposed to 225 MHz occurred during brief or sustained exposures at SARs at or above 1.4 W/kg. The SAR required to produce a given response varied with ambient temperature. Metabolic and vasomotor responses were coordinated effectively to produce a stable deep body temperature. The results show that the thermoregulatory response of the rhesus monkey to an RF exposure at a resonant frequency limits storage of heat in the body. However, substantial increases in colonic temperature were not prevented by such responses, even in a cool environment.

Lotz, W.G.; Saxton, J.L.

1987-01-01

408

Reconfigurable radio-frequency arbitrary waveforms synthesized in a silicon photonic chip.  

PubMed

Photonic methods of radio-frequency waveform generation and processing can provide performance advantages and flexibility over electronic methods due to the ultrawide bandwidth offered by the optical carriers. However, bulk optics implementations suffer from the lack of integration and slow reconfiguration speed. Here we propose an architecture of integrated photonic radio-frequency generation and processing and implement it on a silicon chip fabricated in a semiconductor manufacturing foundry. Our device can generate programmable radio-frequency bursts or continuous waveforms with only the light source, electrical drives/controls and detectors being off-chip. It modulates an individual pulse in a radio-frequency burst within 4?ns, achieving a reconfiguration speed three orders of magnitude faster than thermal tuning. The on-chip optical delay elements offer an integrated approach to accurately manipulating individual radio-frequency waveform features without constraints set by the speed and timing jitter of electronics, and should find applications ranging from high-speed wireless to defence electronics. PMID:25581847

Wang, Jian; Shen, Hao; Fan, Li; Wu, Rui; Niu, Ben; Varghese, Leo T; Xuan, Yi; Leaird, Daniel E; Wang, Xi; Gan, Fuwan; Weiner, Andrew M; Qi, Minghao

2015-01-01

409

Reconfigurable radio-frequency arbitrary waveforms synthesized in a silicon photonic chip  

NASA Astrophysics Data System (ADS)

Photonic methods of radio-frequency waveform generation and processing can provide performance advantages and flexibility over electronic methods due to the ultrawide bandwidth offered by the optical carriers. However, bulk optics implementations suffer from the lack of integration and slow reconfiguration speed. Here we propose an architecture of integrated photonic radio-frequency generation and processing and implement it on a silicon chip fabricated in a semiconductor manufacturing foundry. Our device can generate programmable radio-frequency bursts or continuous waveforms with only the light source, electrical drives/controls and detectors being off-chip. It modulates an individual pulse in a radio-frequency burst within 4?ns, achieving a reconfiguration speed three orders of magnitude faster than thermal tuning. The on-chip optical delay elements offer an integrated approach to accurately manipulating individual radio-frequency waveform features without constraints set by the speed and timing jitter of electronics, and should find applications ranging from high-speed wireless to defence electronics.

Wang, Jian; Shen, Hao; Fan, Li; Wu, Rui; Niu, Ben; Varghese, Leo T.; Xuan, Yi; Leaird, Daniel E.; Wang, Xi; Gan, Fuwan; Weiner, Andrew M.; Qi, Minghao

2015-01-01

410

Radiofrequency energy delivery to the gastric cardia inhibits triggering of transient lower esophageal sphincter relaxation and gastroesophageal reflux in dogs  

Microsoft Academic Search

Background: Delivery of radiofrequency energy to the lower esophageal sphincter and gastric cardia is a new endoluminal technique proposed for the treatment of reflux disease. The mechanisms by which it achieves its effects are unclear. The study assessed the effect of radiofrequency energy delivery to the gastric cardia on the triggering of transient lower esophageal sphincter relaxations and gastroesophageal reflux

Michael S. Kim; Richard H. Holloway; John Dent; David S. Utley

2003-01-01

411

Biophysical characteristics of radiofrequency lesion formation in vivo: Dynamics of catheter tip–tissue contact evaluated by intracardiac echocardiography  

Microsoft Academic Search

During clinical radiofrequency catheter ablation a wide range of delivered power may be necessary to achieve success despite an apparently stable catheter position on fluoroscopy. The purpose of this study was to use intracardiac echocardiography to characterize the relation between catheter tip–tissue contact and the efficiency of heating during applications of radiofrequency energy in vivo and to determine whether intracardiac

Jonathan M. Kalman; Adam P. Fitzpatrick; Jeffrey E. Olgin; Michael C. Chin; Randall J. Lee; Melvin M. Scheinman; Michael D. Lesh

1997-01-01

412

Tumor Recurrence After Radiofrequency Thermal Ablation of Hepatic Tumors: Spectrum of Findings on Dual-Phase Contrast Enhanced CT  

Microsoft Academic Search

OBJECTIVE. We conducted this study to determine the spectrum of CT findings of tumor recurrence after radiofrequency ablation of primary and secondary malignant hepatic tumors. MATERIALS AND METHODS. Twenty-five patients, 10 with hepatocellular carcinoma (HCC) and 15 patients with metastases who developed tumor recurrence after radiofrequency ab- lation of hepatic neoplasms, formed the study population. Three observers reviewed the CT

Shailendra Chopra; Gerald D. Dodd III; Kedar N. Chintapalli; John R. Leyendecker; Okkes I. Karahan; Hyunchul Rhim

413

Characterization of buried glands before and after radiofrequency ablation by using 3-dimensional optical coherence tomography (with videos)  

PubMed Central

Background Radiofrequency ablation (RFA) is an endoscopic technique used to eradicate Barrett’s esophagus (BE). However, such ablation can commonly lead to neosquamous epithelium overlying residual BE glands not visible by conventional endoscopy and may evade detection on random biopsy samples. Objective To demonstrate the capability of endoscopic 3-dimensional optical coherence tomography (3D-OCT) for the identification and characterization of buried glands before and after RFA therapy. Design Cross-sectional study. Setting Single teaching hospital. Patients Twenty-six male and 1 female white patients with BE undergoing RFA treatment. Interventions 3D-OCT was performed at the gastroesophageal junction in 18 patients before attaining complete eradication of intestinal metaplasia (pre–CE-IM group) and in 16 patients after CE-IM (post–CE-IM group). Main Outcome Measurements Prevalence, size, and location of buried glands relative to the squamocolumnar junction. Results 3D-OCT provided an approximately 30 to 60 times larger field of view compared with jumbo and standard biopsy and sufficient imaging depth for detecting buried glands. Based on 3D-OCT results, buried glands were found in 72% of patients (13/18) in the pre–CE-IM group and 63% of patients (10/16) in the post–CE-IM group. The number (mean [standard deviation]) of buried glands per patient in the post–CE-IM group (7.1 [9.3]) was significantly lower compared with the pre–CE-IM group (34.4 [44.6]; P = .02). The buried gland size (P = .69) and distribution (P = .54) were not significantly different before and after CE-IM. Limitations A single-center, cross-sectional study comparing patients at different time points in treatment. Lack of 1-to-1 coregistered histology for all OCT data sets obtained in vivo. Conclusion Buried glands were frequently detected with 3D-OCT near the gastroesophageal junction before and after radiofrequency ablation. PMID:22482920

Zhou, Chao; Tsai, Tsung-Han; Lee, Hsiang-Chieh; Kirtane, Tejas; Figueiredo, Marisa; Tao, Yuankai K.; Ahsen, Osman O.; Adler, Desmond C.; Schmitt, Joseph M.; Huang, Qin; Fujimoto, James G.; Mashimo, Hiroshi

2012-01-01

414

Evidence for thermal boundary resistance effects on superconducting radiofrequency cavity performances  

NASA Astrophysics Data System (ADS)

The majority of the literature on superconducting cavities for particle accelerators concentrates on the interaction of a radiofrequency (RF) electromagnetic field with a superconductor cooled in liquid helium, generally either at a fixed temperature of 4.2 K or 1.8 K, basing the analysis of experimental results on the assumption that the superconductor is at the same temperature as the infinite reservoir of liquid helium. Only a limited number of papers have extended their analysis to the more complex overall system composed of an RF field, a superconductor and liquid helium. Only a few papers have analyzed, for example, the problem of the Kapitza resistance, i.e. the thermal boundary resistance between the superconductor and the superfluid helium. Among them, the general conclusion is that the Kapitza resistance, one of the most controversial and less understood topics in physics, is generally negligible, or not relevant for the performance enhancement of cavities. In our work presented here, studying the performance of 6 GHz niobium (Nb) test cavities, we have discovered and studied a new effect consisting of an abrupt change in the surface resistance versus temperature at the superfluid helium lambda transition T?. This abrupt change (or ‘jump’) clearly appears when the RF measurement of a cavity is performed at constant power rather than at a constant field. We have correlated this jump to a change in the thermal exchange regime across the lambda transition, and, through a simple thermal model and further reasonable assumptions, we have calculated the thermal boundary resistance between niobium and liquid helium in the temperature range between 4.2 K and 1.8 K. We find that the absolute values of the thermal resistance both above and below the lambda point are fully compatible with the data reported in the literature for heat transfer to pool boiling helium I (HeI) above T? and for the Kapitza interface resistance (below T?) between a polished metal surface and superfluid HeII. Finally, based on the well-documented evidence that the surface status of metal to liquid helium influences the heat exchange towards the fluid, and specifically the Kapitza resistance below T?, we have tested an anodization process external to the cavity, comparing the performances of the cavity before and after external anodization. The tests were done without breaking the vacuum inside the cavity or modifying the inner superconducting layer in any way, and were repeated on different samples. The results show that when the cavity is externally anodized, both the Q-factor and the maximum accelerating field increase. Again, when the oxide layer is removed, the Q-factor shifts towards a lower level and the maximum accelerating field is also reduced.

Palmieri, Vincenzo; Rossi, Antonio Alessandro; Stark, Sergey Yu; Vaglio, Ruggero

2014-08-01

415

Hydrogen production in a radio-frequency plasma source operating on water vapor  

NASA Astrophysics Data System (ADS)

The global energy and climate challenges have motivated development of innovative techniques to satisfy energy demand while minimizing emissions. To this end, hydrogen as an alternative energy carrier in the transportation sector is an attractive option. In addition, there is already a great need for hydrogen gas in several industrial processes such as hydro-cracking of crude oil to produce gasoline and production of ammonia and methanol. The current dominant methods of hydrogen production from fossil fuels are well-developed and have reached relatively high energy efficiencies (up to 85%), but these methods rely on non-renewable natural resources and produce carbon dioxide emissions. This work investigates the feasibility of hydrogen production by dissociating water molecules in a radio-frequency (RF) plasma discharge. In addition to the widespread usage of hydrogen gas, applications of water plasma have permeated in many areas of research, and information on basic behaviors of a water plasma discharge will provide fruitful insights for other researchers. An RF plasma source equipped with a double-helix antenna (m = 1 mode) and an applied axial magnetic field is designed to operate on water vapor. It is shown that water molecules are being dissociated in the discharge. Experimental results show that the rate of hydrogen production increases linearly with RF power in the absence of the applied axial magnetic field. With the magnetic field, the rate of hydrogen production increases from 250 to 500 W, and begins to saturate with RF power. Despite this saturation, it is shown that hydrogen increases with magnetic field strength at a fixed RF power. Further, the rate of hydrogen production increases with water input flow rate up to 100 sccm for a fixed RF power level, and begins to decrease at 125 sccm. This dissertation characterizes the rate of hydrogen production and plasma properties as a function of RF power, applied B-field strength, and water input flow rate. A zero-dimensional kinetics model is used to determine the theoretical energy efficiency.

Nguyen, Son-Ca Viet Thi

416

Energy Saving Glass Lamination via Selective Radio-Frequency Heating  

SciTech Connect

This Inventions and Innovations program supported the technical and commercial research and development needed to elevate Ceralink's energy saving process for flat glass lamination from bench scale to a self-supporting technology with significant potential for growth. Radio-frequency heating was any un-explored option for laminating glass prior to this program. With significant commercial success through time and energy savings in the wood, paper, and plastics industries, RF heating was found to have significant promise for the energy intensive glass lamination industry. A major technical goal of the program was to demonstrate RF lamination across a wide range of laminate sizes and materials. This was successfully accomplished, dispelling many skeptics' concerns about the abilities of the technology. Ceralink laminated panels up to 2 ft x 3 ft, with four sets processed simultaneously, in a 3 minute cycle. All major categories of interlayer materials were found to work with RF lamination. In addition to laminating glass, other materials including photovoltaic silicon solar cells, light emitting diodes, metallized glass, plastics (acrylic and polycarbonate), and ceramics (alumina) were found compatible with the RF process. This opens up a wide range of commercial opportunities beyond the initially targeted automotive industry. The dramatic energy savings reported for RF lamination at the bench scale were found to be maintained through the scale up of the process. Even at 2 ft x 3 ft panel sizes, energy savings are estimated to be at least 90% compared to autoclaving or vacuum lamination. With targeted promotion through conference presentations, press releases and internet presence, RF lamination has gained significant attention, drawing large audiences at American Ceramic Society meetings. The commercialization success of the project includes the establishment of a revenue-generating business model for providing process development and demonstrations for potential RF lamination users. A path to industrial energy benefits and revenue through industrial equipment sales was established in a partnership with Thermex Thermatron, a manufacturer of RF equipment.

Shulman, Holly S.; Allan, Shawn M.

2009-11-11

417

Palliative Treatment of Rectal Carcinoma Recurrence Using Radiofrequency Ablation  

SciTech Connect

Purpose: To evaluate the safety and efficacy of CT-guided radiofrequency (RF) ablation for the palliative treatment of recurrent unresectable rectal tumors. Materials and Methods: Twenty-seven patients with locally recurrent rectal cancer were treated with computed tomography (CT)-guided RF ablation. Therapy was performed with the patient under conscious sedation with a seven- or a nine-array expandable RF electrode for 8-10 min at 80-110 Degree-Sign C and a power of 90-110 W. All patients went home under instructions the next day of the procedure. Brief Pain Inventory score was calculated before and after (1 day, 1 week, 1 month, 3 months, and 6 months) treatment. Results: Complete tumor necrosis rate was 77.8% (21 of a total 27 procedures) despite lesion location. BPI score was dramatically decreased after the procedure. The mean preprocedure BPI score was 6.59, which decreased to 3.15, 1.15, and 0.11 at postprocedure day 1, week 1, and month 1, respectively, after the procedure. This decrease was significant (p < 0.01 for the first day and p < 0.001 for the rest of the follow-up intervals (paired Student t test; n - 1 = 26) for all periods during follow-up. Six patients had partial tumor necrosis, and we were attempted to them with a second procedure. Although the necrosis area showed a radiographic increase, no complete necrosis was achieved (secondary success rate 65.6%). No immediate or delayed complications were observed. Conclusion: CT-guided RF ablation is a minimally invasive, safe, and highly effective technique for treatment of malignant rectal recurrence. The method is well tolerated by patients, and pain relief is quickly achieved.

Mylona, Sophia, E-mail: mylonasophia@yahoo.com; Karagiannis, Georgios, E-mail: gekaragiannis@yahoo.gr; Patsoura, Sofia, E-mail: sofia.patsoura@yahoo.gr [Hellenic Red Cross Hospital 'Korgialenio-Benakio' (Greece); Galani, Panagiota, E-mail: gioulagalani@yahoo.com [Amalia Fleming Hospital (Greece); Pomoni, Maria, E-mail: marypomoni@gmail.com [Evgenidion Hospital (Greece); Thanos, Loukas, E-mail: loutharad@yahoo.com [Sotiria Hospital (Greece)

2012-08-15

418

Radiofrequency Ablation of Hepatocellular Cancer in 110 Patients With Cirrhosis  

PubMed Central

Objective To determine the treatment efficacy, safety, local tumor control, and complications related to radiofrequency ablation (RFA) in patients with cirrhosis and unresectable hepatocellular carcinoma (HCC). Summary Background Data Most patients with HCC are not candidates for resection because of tumor size, location, or hepatic dysfunction related to cirrhosis. RFA is a technique that permits in situ destruction of tumors by means of local tissue heating. Methods One hundred ten patients with cirrhosis and HCC (Child class A, 50; B, 31; C, 29) were treated during a prospective study using RFA. Patients were treated with RFA using an open laparotomy, laparoscopic, or percutaneous approach with ultrasound guidance to place the RF needle electrode into the hepatic tumors. All patients were followed up at regular intervals to detect treatment-related complications or recurrence of disease. Results All 110 patients were followed up for at least 12 months after RFA (median follow-up 19 months). Percutaneous or intraoperative RFA was performed in 76 (69%) and 34 patients (31%), respectively. A total of 149 discrete HCC tumor nodules were treated with RFA. The median diameter of tumors treated percutaneously (2.8 cm) was smaller than that of lesions treated during laparotomy (4.6 cm). Local tumor recurrence at the RFA site developed in four patients (3.6%); recurrent HCC subsequently developed in other areas of the liver in all four. New liver tumors or extrahepatic metastases developed in 50 patients (45.5%), but 56 patients (50.9%) had no evidence of recurrence. There were no treatment-related deaths, but complications developed in 14 patients (12.7%) after RFA. Conclusions In patients with cirrhosis and HCC, RFA produces effective local control of disease in a significant proportion of patients and can be performed safely with minimal complications. PMID:10973388

Curley, Steven A.; Izzo, Francesco; Ellis, Lee M.; Nicolas Vauthey, J.; Vallone, Paolo

2000-01-01

419

Radiofrequency ablation as treatment for pulmonary metastasis of colorectal cancer.  

PubMed

Radiofrequency ablation (RFA) causes focal coagulation necrosis in tissue. Its first clinical application was reported in 2000, and RFA has since been commonly used in both primary and metastatic lung cancer. The procedure is typically performed using computed tomography guidance, and the techniques for introducing the electrode to the tumor are simple and resemble those used in percutaneous lung biopsy. The most common complication is pneumothorax, which occurs in up to 50% of procedures; chest tube placement for pneumothorax is required in up to 25% of procedures. Other severe complications, such as pleural effusion requiring chest tube placement, infection, and nerve injury, are rare. The local efficacy depends on tumor size, and local progression after RFA is not rare, occurring in 10% or more of patients. The local progression rate is particularly high for tumors > 3 cm. Repeat RFA may be used to treat local progression. Short- to mid-term survival after RFA appears promising and is approximately 85%-95% at 1 year and 45%-55% at 3 years. Long-term survival data are sparse. Better survival may be expected for patients with small metastasis, low carcinoembryonic antigen levels, and/or no extrapulmonary metastasis. The notable advantages of RFA are that it is simple and minimally invasive; preserves pulmonary function; can be repeated; and is applicable regardless of previous treatments. Its most substantial limitation is limited local efficacy. Although surgery is still the method of choice for treatment with curative intent, the ultimate application of RFA may be to replace metastasectomy for small metastases. Randomized trials comparing RFA with surgery are needed. PMID:24574771

Hiraki, Takao; Gobara, Hideo; Iguchi, Toshihiro; Fujiwara, Hiroyasu; Matsui, Yusuke; Kanazawa, Susumu

2014-01-28

420

Radiofrequency ablation as treatment for pulmonary metastasis of colorectal cancer  

PubMed Central

Radiofrequency ablation (RFA) causes focal coagulation necrosis in tissue. Its first clinical application was reported in 2000, and RFA has since been commonly used in both primary and metastatic lung cancer. The procedure is typically performed using computed tomography guidance, and the techniques for introducing the electrode to the tumor are simple and resemble those used in percutaneous lung biopsy. The most common complication is pneumothorax, which occurs in up to 50% of procedures; chest tube placement for pneumothorax is required in up to 25% of procedures. Other severe complications, such as pleural effusion requiring chest tube placement, infection, and nerve injury, are rare. The local efficacy depends on tumor size, and local progression after RFA is not rare, occurring in 10% or more of patients. The local progression rate is particularly high for tumors > 3 cm. Repeat RFA may be used to treat local progression. Short- to mid-term survival after RFA appears promising and is approximately 85%-95% at 1 year and 45%-55% at 3 years. Long-term survival data are sparse. Better survival may be expected for patients with small metastasis, low carcinoembryonic antigen levels, and/or no extrapulmonary metastasis. The notable advantages of RFA are that it is simple and minimally invasive; preserves pulmonary function; can be repeated; and is applicable regardless of previous treatments. Its most substantial limitation is limited local efficacy. Although surgery is still the method of choice for treatment with curative intent, the ultimate application of RFA may be to replace metastasectomy for small metastases. Randomized trials comparing RFA with surgery are needed. PMID:24574771

Hiraki, Takao; Gobara, Hideo; Iguchi, Toshihiro; Fujiwara, Hiroyasu; Matsui, Yusuke; Kanazawa, Susumu

2014-01-01

421

Single-Session Radiofrequency Ablation of Bilateral Lung Metastases  

SciTech Connect

Purpose: This retrospective study examined the feasibility and efficacy of bilateral lung radiofrequency ablation (RFA) performed in a single session. Methods: From 2002-2009, patients with bilateral lung metastases were treated by RFA, where possible in a single session under general anesthesia with CT guidance. The second lung was punctured only if no complications occurred after treatment of the first lung. Five lung metastases maximum per patient were treated by RFA and prospectively followed. The primary endpoint was the evaluation of acute and delayed complications. Secondary endpoints were calculation of hospitalization duration, local efficacy, median survival, and median time to tumor progression. Local efficacy was evaluated on CT or positron emission tomography (PET) CT. Results: Sixty-seven patients were treated for bilateral lung metastases with RFA (mean age, 62 years). Single-session treatment was not possible in 40 due to severe pneumothoraces (n = 24), bilateral pleural contact (n = 14), and operational exclusions (n = 2). Twenty-seven (41%) received single-session RFA of lesions in both lungs for 66 metastases overall. Fourteen unilateral and four bilateral pneumothoraces occurred (18 overall, 66.7%). Unilateral (n = 13) and bilateral (n = 2) chest tube drainage was required. Median hospitalization was 3 (range, 2-8) days. Median survival was 26 months (95% confidence interval (CI), 19-33). Four recurrences on RFA sites were observed (4 patients). Median time to tumor progression was 9.5 months (95% CI, 4.2-23.5). Conclusions: Although performing single-session bilateral lung RFA is not always possible due to pneumothoraces after RFA of first lung, when it is performed, this technique is safe and effective.

Palussiere, Jean, E-mail: palussiere@bergonie.org; Gomez, Fernando; Cannella, Matthieu; Ferron, Stephane; Descat, Edouard [Institut Bergonie, Department of Radiology, Regional Cancer Centre (France); Fonck, Marianne [Institut Bergonie, Department of Digestive Oncology (France); Brouste, Veronique [Institut Bergonie, Clinical and Epidemiological Research Unit (France); Avril, Antoine [Institut Bergonie, Department of Surgery (France)

2012-08-15

422

Nanoionics-Based Switches for Radio-Frequency Applications  

NASA Technical Reports Server (NTRS)

Nanoionics-based devices have shown promise as alternatives to microelectromechanical systems (MEMS) and semiconductor diode devices for switching radio-frequency (RF) signals in diverse systems. Examples of systems that utilize RF switches include phase shifters for electronically steerable phased-array antennas, multiplexers, cellular telephones and other radio transceivers, and other portable electronic devices. Semiconductor diode switches can operate at low potentials (about 1 to 3 V) and high speeds (switching times of the order of nanoseconds) but are characterized by significant insertion loss, high DC power consumption, low isolation, and generation of third-order harmonics and intermodulation distortion (IMD). MEMS-based switches feature low insertion loss (of the order of 0.2 dB), low DC power consumption (picowatts), high isolation (>30 dB), and low IMD, but contain moving parts, are not highly reliable, and must be operated at high actuation potentials (20 to 60 V) generated and applied by use of complex circuitry. In addition, fabrication of MEMS is complex, involving many processing steps. Nanoionics-based switches offer the superior RF performance and low power consumption of MEMS switches, without need for the high potentials and complex circuitry necessary for operation of MEMS switches. At the same time, nanoionics-based switches offer the high switching speed of semiconductor devices. Also, like semiconductor devices, nanoionics-based switches can be fabricated relatively inexpensively by use of conventional integrated-circuit fabrication techniques. More over, nanoionics-based switches have simple planar structures that can easily be integrated into RF power-distribution circuits.

Nessel, James; Lee, Richard

2010-01-01

423

Radiofrequency Ablation for Postoperative Recurrences of Intrahepatic Cholangiocarcinoma  

PubMed Central

Objective Most recurrent intrahepatic cholangiocarcinoma (RICC) lost the opportunity of radical resection while most nonsurgical management failed to prolong patients’ survival. The efficacy and safety of radiofrequency ablation (RFA) as a local treatment for recurrent hepatocellular carcinoma have been confirmed by many clinical studies. The purpose of this study was to evaluate the efficacy, long-term survival and complications of RFA for RICC. Methods A total of 12 patients with 19 RICCs after radical resection were included in this study. The tumors were 1.9-6.8 cm at the maximum diameter (median, 3.2±1.6 cm). All patients were treated with ultrasound guided RFA. There were two RFA approaches including percutaneous and open. Results A total of 18 RFA treatment sessions were performed. Ablation was successful (evaluated by 1-month CT after the initial RFA procedure) in 18 (94.7%) of 19 tumors. By a median follow-up period of 29.9 months after RFA, 5 patients received repeated RFA because of intrahepatic lesion recurrence. The median local recurrence-free survival period and median event-free survival period after RFA were 21.0 months and 13.0 months, respectively. The median overall survival was 30 months, and the 1- and 3-year survival rates were 87.5% and 37.5%, respectively. The complication rate was 5.6% (1/18 sessions). The only one major complication was pleural effusion requiring thoracentesis. Conclusion This study showed RFA may effectively and safely manage RICC with 3-year survival of 37.5%. It provides a treatment option for these RICC patients who lost chance for surgery. PMID:23359754

Fu, Ying; Yang, Wei; Wu, Wei; Yan, Kun; Xing, Bao-cai

2011-01-01

424

Radio-frequency spectroscopy of polarons in ultracold Bose gases  

NASA Astrophysics Data System (ADS)

Recent experimental advances enabled the realization of mobile impurities immersed in a Bose-Einstein condensate (BEC) of ultracold atoms. Here, we consider impurities with two or more internal hyperfine states, and study their radio-frequency (rf) absorption spectra, which correspond to transitions between two different hyperfine states. We calculate rf spectra for the case when one of the hyperfine states involved interacts with the BEC, while the other state is noninteracting, by performing a nonperturbative resummation of the probabilities of exciting different numbers of phonon modes. In the presence of interactions, the impurity gets dressed by Bogoliubov excitations of the BEC, and forms a polaron. The rf signal contains a ?-function peak centered at the energy of the polaron measured relative to the bare impurity transition frequency with a weight equal to the amount of bare impurity character in the polaron state. The rf spectrum also has a broad incoherent part arising from the background excitations of the BEC, with a characteristic power-law tail that appears as a consequence of the universal physics of contact interactions. We discuss both the direct rf measurement, in which the impurity is initially in an interacting state, and the inverse rf measurement, in which the impurity is initially in a noninteracting state. In the latter case, in order to calculate the rf spectrum, we solve the problem of polaron formation: a mobile impurity is suddenly introduced in a BEC, and dynamically gets dressed by Bogoliubov phonons. Our solution is based on a time-dependent variational ansatz of coherent states of Bogoliubov phonons, which becomes exact when the impurity is localized. Moreover, we show that such an ansatz compares well with a semiclassical estimate of the propagation amplitude of a mobile impurity in the BEC. Our technique can be extended to cases when both initial and final impurity states are interacting with the BEC.

Shashi, Aditya; Grusdt, Fabian; Abanin, Dmitry A.; Demler, Eugene

2014-05-01

425

Screen printed flexible radiofrequency identification tag for oxygen monitoring.  

PubMed

In this work, a radiofrequency identification (RFID) tag with an optical indicator for the measurement of gaseous oxygen is described. It consists of an O2 sensing membrane of PtOEP together with a full electronic system for RFID communication, all printed on a flexible substrate. The membrane is excited by an LED at 385 nm wavelength and the intensity of the luminescence generated is registered by means of a digital color detector. The output data corresponding to the red coordinate of the RGB color space is directly related to the concentration of O2, and it is sent to a microcontroller. The RFID tag is designed and implemented by screen printing on a flexible substrate for the wireless transmission of the measurement to a remote reader. It can operate in both active and passive mode, obtaining the power supply from the electromagnetic waves of the RFID reader or from a small battery, respectively. This system has been fully characterized and calibrated including temperature drifts, showing a high-resolution performance that allows measurement of very low values of oxygen content. Therefore this system is perfectly suitable for its use in modified atmosphere packaging where the oxygen concentration is reduced below 2%. As the reading of the O2 concentration inside the envelope is carried out with an external RFID reader using wireless communication, there is no need for perforations for probes or wires, so the packaging remains completely closed. With the presented device, a limit of detection of 40 ppm and a resolution as low as 0.1 ppm of O2 can be reached with a low power consumption of 3.55 mA. PMID:24116378

Martínez-Olmos, A; Fernández-Salmerón, J; Lopez-Ruiz, N; Rivadeneyra Torres, A; Capitan-Vallvey, L F; Palma, A J

2013-11-19

426

A nanoengineered embolic agent for precise radiofrequency ablation.  

PubMed

The purpose of the work is to investigate whether the electromagnetic properties of multi-walled carbon nanotubes (MWCNT) in the presence of radiofrequency (RF) energy is (1) safe, and (2) improves the precision of the therapeutic efficiency of the RF-ablation (RFA) procedure. An in vitro phantom was created for evaluating temperature near RF treated nanotubes. For the in vivo study, three baboons and six pigs were submitted for RFA procedure in superior/inferior kidney poles embolized with a non-adherent, lipophilic embolic agent (marsembol) with or without MWCNT. Tissue damage in the surrounding kill zone was assayed through caspase-3 activation. The in vitro results showed marked heat increase only in the region of the nanotubes. In vivo, necrosis/ischemic damage resulted from RFA therapy alone, RFA plus marsembol only. In marsembol + MWCNT condition, dramatic disruption of cell membranes and sub-cellular organelles was found whereas the nuclear membranes and basal cell membranes remained largely intact. The marsembol vaporized under RFA and tissue fluid filled the space. This caused the MWCNT to cluster within the new aqueous environment. RFA plus marsembol + MWCNT created a well-defined demarcation between healthy and apoptotic cells as evidenced by a marked reduction of caspase-3 expression. By contrast, there was a much less defined ablation zone in the absence of MWCNT. In conclusion, the combination of RFA plus marsembol + MWCNT embolization delineated the kill zone in vitro and in vivo. We demonstrate that MWCNTs remain in the ablation region thus minimizing their migration to the systemic circulation. PMID:24449052

Rolland, Pierre Henri; Berry, Joel L; Louis, Guillaume; Velly, Lionel; Vidal, Vincent; Brige, Pauline; Mayakonda, Vinuta; Carroll, David L

2014-05-01

427

In vivo radiofrequency ultrasound analysis of normal human heart structures.  

PubMed

Twenty young subjects were studied with a microprocessor system for quantitative analysis of backscattered radiofrequency (RF) signals from normal heart structures. This system allows an "on line" quantitative evaluation of the amplitude of the RF "native" signal, before the chain of processing and display, with the acquisition gate displayed on a conventional M-mode machine. Septum, posterior wall, and anterior mitral leaflet were analyzed. The gate length was kept at 3 microseconds (2.35 mm) for the ventricular walls (excluding endo- and epicardial reflections), and at 1 microsecond (0.8 mm) for the mitral valve. Integrated backscatter index (IBI) was calculated as the time integral of [u(t)[, where u(t) = i(t) X s(t); is the time sequence of backscattered echoes and s(t) is the time gate delimiting the thickness of the insonated tissue. The IBI was expressed in percent, normalized for the pericardial interface (the strongest reflection was assumed to be 100%). The percent IBI for the septum was found to be 22 +/- 4%; for the posterior wall it was 17 +/- 3%; for the anterior mitral leaflet it was 5 +/- 2%. A second reading of the same structures was performed by the previous observer and by a new one. Good intraobserver (r = 0.92) and interobserver (r = 0.88) correlations were obtained. In conclusion, a regional variation in echo amplitude from different heart structures can be observed in man. This set of values can be used as normal values for future studies in pathologic conditions. PMID:3134434

Lattanzi, F; Picano, E; Mazzarisi, A; Landini, L; Benassi, A; Masini, M; Distante, A; L'Abbate, A

1987-01-01

428

Lung Tumor Radiofrequency Ablation: Where Do We Stand?  

SciTech Connect

Today, radiofrequency ablation (RFA) of primary and metastatic lung tumor is increasingly used. Because RFA is most often used with curative intent, preablation workup must be a preoperative workup. General anesthesia provides higher feasibility than conscious sedation. The electrode positioning must be performed under computed tomography for sake of accuracy. The delivery of RFA must be adapted to tumor location, with different impedances used when treating tumors with or without pleural contact. The estimated rate of incomplete local treatment at 18 months was 7% (95% confidence interval, 3-14) per tumor, with incomplete treatment depicted at 4 months (n = 1), 6 months (n = 2), 9 months (n = 2), and 12 months (n = 2). Overall survival and lung disease-free survival at 18 months were, respectively, 71 and 34%. Size is a key point for tumor selection because large size is predictive of incomplete local treatment and poor survival. The ratio of ablation volume relative to tumor volume is predictive of complete ablation. Follow-up computed tomography that relies on the size of the ablation zone demonstrates the presence of incomplete ablation. Positron emission tomography might be an interesting option. Chest tube placement for pneumothorax is reported in 8 to 12%. Alveolar hemorrhage and postprocedure hemoptysis occurred in approximately 10% of procedures and rarely required specific treatment. Death was mostly related to single-lung patients and hilar tumors. No modification of forced expiratory volume in the first second between pre- and post-RFA at 2 months was found. RFA in the lung provides a high local efficacy rate. The use of RFA as a palliative tool in combination with chemotherapy remains to be explored.

Baere, Thierry de, E-mail: debaere@igr.fr [Institut Gustave Roussy, Department of Interventional Radiology (France)

2011-04-15

429

Factors governing the use of microwave/radiofrequency energies in cancer therapy  

SciTech Connect

The purpose of this review is to integrate the information on electromagnetic radiant energy so that the use of MW/RF energy in the therapy of cancer can be approached in a rational and productive manner. The frequency ranges considered in this review include 300 kHz to 300 MHz (radiofrequency) and 300 MHz to 300 GHz (microwaves). The ranges represent one of several conventions used in characterizing these energies. The limits have no particular biological significance. Although the radiofrequency (RF) range includes all frequencies below 300 GHz with the microwave domain as just part of the whole RF spectrum, the spectrum of frequencies below 300 MHz will be designated as the radiofrequency range. Sometimes a subdivision of the RF range extending from 30 to 300 MHz is termed the shortwave range.

Michaelson, S.M. (Univ. of Rochester, NY); Schwan, H.P.

1981-01-01

430

Prevention of vagotonia and pain during radiofrequency ablation of liver tumors.  

PubMed

Radiofrequency ablation (RFA) is frequently used to treat early stage hepatocellular carcinoma. Two of the most cumbersome side-effects of the ablation procedure are intractable pain and vagotonia when deep sedation is not used. We describe local injection of anesthetic into Glisson's sheath as a new technique for overcoming these problems. Lidocaine was injected into Glisson's sheath when radiofrequency ablation of hepatocellular carcinomas, which were located adjacent to Glisson's sheath, could not be continued due to severe pain (n?=?8) or bradycardia (n?=?3). In all three patients who showed vagotonia with bradycardia during the ablations, injection of lidocaine prevented bradycardia, allowing completion of the radiofrequency ablation. Pain was reduced in all eight patients who experienced pain during ablation. No side-effects were observed during the procedures. Injection of anesthetic into Glisson's sheath is simple and effective for reducing intractable pain and vagotonia associated with RFA. PMID:24593141

Nakamura, Shinichiro; Nouso, Kazuhiro; Onishi, Hideki; Kuwaki, Kenji; Hagihara, Hiroaki; Takeuchi, Yasuto; Wada, Nozomu; Morimoto, Yuki; Miyahara, Koji; Yasunaka, Tetsuya; Ikeda, Fusao; Miyake, Yasuhiro; Kobayashi, Yoshiyuki; Shiraha, Hidenori; Ishikawa, Shinichi; Takaki, Akinobu; Yamamoto, Kazuhide

2014-12-01

431

Surgical hepatic resection vs. ultrasonographic guided radiofrequency ablation in colorectal liver metastases: what should we choose?  

PubMed

Clinical evolution of the colorectal carcinoma occurs in up to 60% with colorectal liver metastases (CRLM). Although hepatic resection is considered to be the golden standard in CRLM, novel less invasive techniques have emerged, of which radiofrequency ablation has received a high credibility. When tumors are not eligible for surgery, guided radiofrequency ablation is considered an alternative. This method is appropriate when there are no more than 5 lesions with a diameter of less than 3 cm. While open surgery guarantees a more precise tumor excision, the effectiveness of ablation must be evaluated either by contrast-enhanced computer tomography, magnetic resonance, or ultrasound. This paper aim to review the current standings in radiofrequency ablation for CRLM and to compare the technique with surgical resection in order to find which one is the best treatment option. PMID:24791846

Ungureanu, Bogdan S; Sandulescu, Larisa; ?urlin, Valeriu; Spârchez, Zeno; S?ftoiu, Adrian

2014-06-01

432

Experimental and clinical studies with radiofrequency-induced thermal endometrial ablation for functional menorrhagia  

SciTech Connect

A method of ablating the endometrium has been introduced into clinical practice that uses radiofrequency electromagnetic energy to heat the endometrium, using a probe inserted through the cervix. Preliminary studies suggest that over 80% of patients treated will develop either amenorrhea or a significant reduction in flow. The advantages of radiofrequency endometrial ablation over laser ablation or resection are the avoidance of intravascular fluid absorption, simplicity (no special operative hysteroscopic skills are required), speed of operation, and reduced cost compared with the Nd:YAG laser. In this paper, we describe the experimental studies performed during development of this new technique.

Phipps, J.H.; Lewis, B.V.; Prior, M.V.; Roberts, T. (Watford General Hospital, Herts (England))

1990-11-01

433

Transcatheter Arterial Embolization for Tumor Seeding in the Chest Wall After Radiofrequency Ablation for Hepatocellular Carcinoma  

SciTech Connect

Tumor seeding in the chest wall was depicted at follow-up CT obtained 9 months after radiofrequency ablation for hepatocellular carcinoma. Transcatheter arterial embolization was successfully performed, injecting emulsion of 10 mg of epirubicin and 1 ml of iodized oil followed by gelatin sponge particles via the microcatheter placed in the right eleventh intercostal artery. The patient died of tumor growth in the liver one year after the embolization, but no progression of the tumor seeding was noted during the follow-up period. We conclude that transcatheter arterial embolization was effective for the control of tumor seeding after radiofrequency ablation for hepatocellular carcinoma.

Shibata, Toshiya, E-mail: ksj@kuhp.kyoto-u.ac.jp; Shibata, Toyomichi; Maetani, Yoji; Kubo, Takeshi [Kyoto University Graduate School of Medicine, Department of Diagnostic Imaging and Nuclear Medicine (Japan); Nishida, Naoshi [Kyoto University Graduate School of Medicine, Endocrinology (Japan); Itoh, Kyo [Kyoto University Graduate School of Medicine, Department of Diagnostic Imaging and Nuclear Medicine (Japan)

2006-06-15

434

Life-Threatening Hematuria Requiring Transcatheter Embolization Following Radiofrequency Ablation of Renal Cell Carcinoma  

SciTech Connect

Radiofrequency ablation is increasingly being acknowledged as a valid treatment for renal cell carcinoma in patients in whom definitive curative resection is deemed either undesirable or unsafe. A number of published series have shown the technique to have encouraging results and relatively low complication rates. In this article, we report a case of delayed life-threatening hematuria requiring transcatheter embolization of a bleeding intrarenal artery in a patient who had undergone imaging-guided radiofrequency ablation of a 3 cm renal cell carcinoma. To our knowledge, such a complication has not been reported previously.

Roach, H. [Bristol Royal Infirmary, Department of Radiology (United Kingdom); Whittlestone, T. [Bristol Royal Infirmary, Department of Urology (United Kingdom); Callaway, M.P. [Bristol Royal Infirmary, Department of Radiology (United Kingdom)], E-mail: Mark.Callaway@ubht.swest.nhs.uk

2006-08-15

435

Combined MRI and Fluoroscopic Guided Radiofrequency Ablation of a Renal Tumor  

SciTech Connect

Percutaneous CT- and ultrasound-guided radiofrequency ablation of renal cell carcinoma (RCC) has been shown to have very promising medium-term results. We present a unique case of recurrent RCC after partial nephrectomy in a patient with a single kidney and impaired renal function. This tumor could not be visualized either with CT or with ultrasound. A combination of magnetic resonance imaging and fluoroscopic guidance was used, to the best of our knowledge for the first time, to ablate the tumor with radiofrequency. The patient was cancer-free and off dialysis at 30-month follow up.

Fotiadis, Nikolas I., E-mail: fotiadis.nicholas@gmail.co [Royal London Hospital, Department of Interventional Radiology (United Kingdom); Sabharwal, Tarun [Guy's and St Thomas' Hospital, Interventional Radiology Department (United Kingdom); Gangi, Afshin [University Hospital of Strasbourg, Radiology Department (France); Adam, Andreas [Guy's and St Thomas' Hospital, Interventional Radiology Department (United Kingdom)

2009-01-15

436

Successful control of life-threatening polymorphic ventricular tachycardia by radiofrequency catheter ablation in an infant.  

PubMed

We present a case of a 9-month-old girl in whom malignant polymorphic ventricular tachycardia (VT) was successfully controlled by radiofrequency catheter ablation under guidance with a three-dimensional mapping system. The VTs originated from the left ventricular lateral wall, left ventricular anterior wall, and left ventricular apex. At least six types of VTs were documented during the electrophysiology study. All VTs were successfully controlled after two sessions of radiofrequency catheter ablation, and she was discharged from our hospital on propranolol, mexiletine, flecainide, and aprindine. PMID:23836069

Abe, Yuriko; Sumitomo, Naokata; Okuma, Hiromi; Nakamura, Takahiro; Fukuhara, Junji; Ichikawa, Rie; Matsumura, Masaharu; Miyashita, Michio; Kamiyama, Hiroshi; Ayusawa, Mamoru; Watanabe, Mamie; Joo, Kunitaka; Makita, Naomasa; Horie, Minoru

2014-05-01

437

Electron Spin Relaxation Time Measurements Using Radiofrequency Longitudinally Detected ESR and Application in Oximetry  

NASA Astrophysics Data System (ADS)

Longitudinally detected ESR (LODESR) involves transverse ESR irradiation with a modulated source and observing oscillations in the spin magnetization parallel to the main magnetic field. In this study, radiofrequency-LODESR was used for oximetry by measuring the relaxation times of the electron. T1e and T2e were measured by investigating LODESR signal magnitude as a function of detection frequency. We have also predicted theoretically and verified experimentally the LODESR signal phase dependence on detection frequency and relaxation times. These methods are valid even for inhomogeneous lines provided that T1e? T2e. We have also developed a new method for measuring T1e, valid for inhomogeneous spectra, for all values of T1e and T2e, based on measuring the spectral area as a function of detection frequency. We have measured T1e and T2e for lithium phthalocyanine crystals, for the nitroxide TEMPOL, and for the single line agent Triarylmethyl (TAM). Furthermore, we have collected spectra from aqueous solutions of TEMPOL and TAM at different oxygen concentrations and confirmed that T1e values are reduced with increased oxygen concentration. We have also measured the spin-lattice electronic relaxation time for degassed aqueous solutions of the same agents at different agent concentrations. T1e decreases as a function of concentration for TAM while it remains independent of free radical concentration for TEMPOL, a major advantage for oxygen mapping. This method, combined with the ability of LODESR to provide images of exogenous free radicals in vivo, presents an attractive alternative to the conventional transverse ESR linewidth based oximetry methods.

Panagiotelis, Ioannis; Nicholson, Ian; Hutchison, James M. S.

2001-03-01

438

Radiofrequency-heated enhanced confinement modes in the Alcator C-Mod tokamak  

SciTech Connect

Enhanced confinement modes up to a toroidal field of B{sub T}=8T have been studied with up to 3.5 MW of radiofrequency (rf) heating power in the ion cyclotron range of frequencies (ICRF) at 80 MHz. H-mode is observed when the edge temperature exceeds a threshold value. The high confinement mode (H-mode) with higher confinement enhancement factors (H) and longer duration became possible after boronization by reducing the radiated power from the main plasma. A quasi-steady state with high confinement (H=2.0), high normalized beta ({beta}{sub N}=1.5), low radiated power fraction (P{sub rad}{sup main}/P{sub loss}=0.3), and low effective charge (Z{sub eff}=1.5) has been obtained in Enhanced D{sub {alpha}} H-mode. This type of H-mode has enhanced levels of continuous D{sub {alpha}} emission and very little or no edge localized mode (ELM) activity, and reduced core particle confinement time relative to ELM-free H-mode. The pellet enhanced performance (PEP) mode is obtained by combining core fueling with pellet injection and core heating. A highly peaked pressure profile with a central value of 8 atmospheres was observed. The steep pressure gradient drives off-axis bootstrap current, resulting in a shear reversed safety factor (q) profile. Suppression of sawteeth appears to be important in maintaining the highly peaked pressure profile. Lithium pellets were found to be more effective than deuterium pellets in raising q{sub 0}. {copyright} {ital 1997 American Institute of Physics.}

Takase, Y.; Boivin, R.L.; Bombarda, F.; Bonoli, P.T.; Christensen, C.; Fiore, C.; Garnier, D.; Goetz, J.A.; Golovato, S.N.; Granetz, R.; Greenwald, M.; Horne, S.F.; Hubbard, A.; Hutchinson, I.H.; Irby, J.; LaBombard, B.; Lipschultz, B.; Marmar, E.; May, M.; Mazurenko, A.; McCracken, G.; OShea, P.; Porkolab, M.; Reardon, J.; Rice, J.; Rost, C.; Schachter, J.; Snipes, J.A.; Stek, P.; Terry, J.; Watterson, R.; Welch, B.; Wolfe, S. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

1997-05-01

439

Absorbed energy distribution from radiofrequency electromagnetic radiation in a mammalian cell model: Effect of membrane-bound water  

SciTech Connect

The spatial distributions of induced 27 or 2,450 MHz radiofrequency (RF) electric fields (E-fields) and specific absorption rates (SARS) in a three-component spherical cell model were determined by Mie scattering theory. The results were compared to results for the same cell model but with 0.5 nm thick of bound water on the inner and outer membrane surfaces. Induced E-fields and SARs were calculated for two bound-water characteristic frequencies and ionic conductivities. In order to estimate the dependence of the results on bound water within the membrane per se, the model was revised to include bound water within the inner and outer membrane surfaces. The results were as follows: (1) on the x-axis, the y- and z-components of the induced E-field were of insignificant magnitude compared to the x-component for an incident E-field parallel to the x-axis; (2) the ratio of transmembrane E-fields induced by 2,450 MHz vs. 27 MHz RF was 0.1; (3) for the three-component cell model, the corresponding SAR ratios in the cytoplasm and extracellular space were 1.66 and 5.0, respectively; (4) the SAR ratios for the cytoplasm and extracellular space for the five-component cell model were 1.66 and 5.0, respectively; (5) the ratio of the E-fields induced in the cytoplasmic and extracellular layers of bound water in the five-component cell model were 0.62 and 0.63, respectively; (6) the SAR ratios for the cytoplasmic and extracellular bound-water layers were 66 and 65.3, respectively; and (7) variation of bound-water characteristic frequency, ionic conductivity, or bound-water incorporation inside the membrane surfaces, per se, did not significantly affect the E-field or SAR ratios.

Liu, L.M.; Cleary, S.F. [Virginia Commonwealth Univ., Richmond, VA (United States)

1995-08-01

440

Laser nitriding for niobium superconducting radio-frequency accelerator cavities  

SciTech Connect

Particle accelerators are a key tool for scientific research ranging from fundamental studies of matter to analytical studies at light sources. Cost-forperformance is critical, both in terms of initial capital outlay and ongoing operating expense, especially for electricity. It depends on the niobium superconducting radiofrequency (SRF) accelerator cavities at the heart of most of these machines. Presently Nb SRF cavities operate near 1.9 K, well (and expensively) below the 4.2 K atmospheric boiling point of liquid He. Transforming the 40 nm thick active interior surface layer from Nb to delta NbN (Tc = 17 K instead of 9.2 K) appears to be a promising approach. Traditional furnace nitriding appears to have not been successful for this. Further, exposing a complete SRF cavity to the time-temperature history required for nitriding risks mechanical distortion. Gas laser nitriding instead has been applied successfully to other metals [P.Schaaf, Prog. Mat. Sci. 47 (2002) 1]. The beam dimensions and thermal diffusion length permit modeling in one dimension to predict the time course of the surface temperature for a range of per-pulse energy densities. As with the earlier work, we chose conditions just sufficient for boiling as a reference point. We used a Spectra Physics HIPPO nanosecond laser (l = 1064 nm, Emax= 0.392 mJ, beam spot@ 34 microns, PRF =15 – 30 kHz) to obtain an incident fluence of 1.73 - 2.15 J/cm2 for each laser pulse at the target. The target was a 50 mm diameter SRF-grade Nb disk maintained in a nitrogen atmosphere at a pressure of 550 – 625 torr and rotated at a constant speed of 9 rpm. The materials were examined by scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and x-ray diffraction (XRD). The SEM images show a sharp transition with fluence from a smooth, undulating topography to significant roughening, interpreted here as the onset of ablation. EPMA measurements of N/Nb atom ratio as a function of depth found a constant value to depths greater than the SRF active layer thickness. Certain irradiation conditions resulted in values consistent with formation of delta NbN. Under certain irradiation conditions, XRD data were consistent only with delta NbN on top of Nb metal. Funding: authored by Jefferson Science Associates LLC under US DOE Contract De-AC05-06OR23177. We are indebted to Prof. P. Schaaf (Goettingen) for the simulation code and helpful discussions.

Senthilraja Singaravelu, John Klopf, Gwyn Williams, Michael Kelley

2010-10-01