Note: This page contains sample records for the topic non-ionizing radiofrequency fields from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

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

2012-09-27

2

Non-ionizing electromagnetic fields - biological effects terminology. A tutorial  

Microsoft Academic Search

Uniform standards or preferred practices for non-ionizing electromagnetic field biological effects are not yet widely accepted and applied. However, those involved in environmental impact studies and the preparation of environmental impact statements require a familiarity with the terminology and methodology used in the development of the basic data. Non-ionizing electromagnetic waves are often confused with ionizing radiation. Nonionizing waves do

Valentino

1979-01-01

3

Measurement of radiofrequency fields  

SciTech Connect

We are literally surrounded by radiofrequency (RFR) and microwave radiation, from both natural and man-made sources. The identification and control of man-made sources of RFR has become a high priority of radiation safety professionals in recent years. For the purposes of this paper, we will consider RFR to cover the frequencies from 3 kHz to 300 MHz, and microwaves from 300 MHz to 300 GHz, and will use the term RFR interchangeably to describe both. Electromagnetic radiation and field below 3 kHz is considered Extremely Low Frequency (ELF) and will not be discussed in this paper. Unlike x- and gamma radiation, RFR is non-ionizing. The energy of any RFR photon is insufficient to produce ionizations in matter. The measurement and control of RFR hazards is therefore fundamentally different from ionizing radiation. The purpose of this paper is to acquaint the reader with the fundamental issues involved in measuring and safely using RFR fields. 23 refs.

Leonowich, J.A.

1992-05-01

4

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

5

Electromagnetic and heat transfer computations for non-ionizing radiation dosimetry  

Microsoft Academic Search

Reliable information on the heat distribution inside biological tissues is essential for the planning and optimization of experiments which aim to study the effects of non-ionizing radiation (NIR). In electrodynamics, the finite-difference time-domain (FDTD) technique has become the dominant technique for radiofrequency dosimetry. In order to obtain the electromagnetic field and heat distributions within the same simulation run without changing

T. Samaras; P. Regli; N. Kuster

2000-01-01

6

Occupational exposure to radiofrequency fields in antenna towers.  

PubMed

Exposure of workers to radiofrequency fields was assessed in two medium-sized antenna towers. Towers had transmitting antennas from different networks, e.g. mobile phone networks, radio and digital TV sub-stations and amateur radio. The levels of radiofrequency fields were measured close to the ladders of the towers. All measured values were below ICNIRP occupational reference levels. PMID:17166878

Alanko, T; Hietanen, M

2006-12-13

7

Assessment of outdoor radiofrequency electromagnetic field exposure through hotspot localization using kriging-based sequential sampling.  

PubMed

In this study, a novel methodology is proposed to create heat maps that accurately pinpoint the outdoor locations with elevated exposure to radiofrequency electromagnetic fields (RF-EMF) in an extensive urban region (or, hotspots), and that would allow local authorities and epidemiologists to efficiently assess the locations and spectral composition of these hotspots, while at the same time developing a global picture of the exposure in the area. Moreover, no prior knowledge about the presence of radiofrequency radiation sources (e.g., base station parameters) is required. After building a surrogate model from the available data using kriging, the proposed method makes use of an iterative sampling strategy that selects new measurement locations at spots which are deemed to contain the most valuable information-inside hotspots or in search of them-based on the prediction uncertainty of the model. The method was tested and validated in an urban subarea of Ghent, Belgium with a size of approximately 1km(2). In total, 600 input and 50 validation measurements were performed using a broadband probe. Five hotspots were discovered and assessed, with maximum total electric-field strengths ranging from 1.3 to 3.1V/m, satisfying the reference levels issued by the International Commission on Non-Ionizing Radiation Protection for exposure of the general public to RF-EMF. Spectrum analyzer measurements in these hotspots revealed five radiofrequency signals with a relevant contribution to the exposure. The radiofrequency radiation emitted by 900MHz Global System for Mobile Communications (GSM) base stations was always dominant, with contributions ranging from 45% to 100%. Finally, validation of the subsequent surrogate models shows high prediction accuracy, with the final model featuring an average relative error of less than 2dB (factor 1.26 in electric-field strength), a correlation coefficient of 0.7, and a specificity of 0.96. PMID:23759207

Aerts, Sam; Deschrijver, Dirk; Verloock, Leen; Dhaene, Tom; Martens, Luc; Joseph, Wout

2013-06-05

8

Sensitivity of Neurotransmitter Release to Radiofrequency Fields.  

National Technical Information Service (NTIS)

Exploring the interactions between radiofrequency (RF) radiation and biological systems is essential for developing RF-based non-lethal stunning/immobilizing weaponry. To this end a research effort was initiated to identify RF parameters potentially capab...

G. L. Craviso I. Chatterjee

2005-01-01

9

Radiofrequency fields, transthyretin, and Alzheimer's disease.  

PubMed

Radiofrequency field (RF) exposure provided cognitive benefits in an animal study. In Alzheimer's disease (AD) mice, exposure reduced brain amyloid-beta (Abeta) deposition through decreased aggregation of Abeta and increase in soluble Abeta levels. Based on our studies on humans on RF from wireless phones, we propose that transthyretin (TTR) might explain the findings. In a cross-sectional study on 313 subjects, we used serum TTR as a marker of cerebrospinal fluid TTR. We found a statistically significantly positive beta coefficient for TTR for time since first use of mobile phones and desktop cordless phones combined (P=0.03). The electromagnetic field parameters were similar for the phone types. In a provocation study on 41 persons exposed for 30 min to an 890-MHz GSM signal with specific absorption rate of 1.0 Watt/kg to the temporal area of the brain, we found statistically significantly increased serum TTR 60 min after exposure. In our cross-sectional study, use of oral snuff also yielded statistically significantly increased serum TTR concentrations and nicotine has been associated with decreased risk for AD and to upregulate the TTR gene in choroid plexus but not in the liver, another source of serum TTR. TTR sequesters Abeta, thereby preventing the formation of Abeta plaques in the brain. Studies have shown that patients with AD have lowered TTR concentrations in the cerebrospinal fluid and have attributed the onset of AD to insufficient sequestering of Abeta by TTR. We propose that TTR might be involved in the findings of RF exposure benefit in AD mice. PMID:20164553

Söderqvist, Fredrik; Hardell, Lennart; Carlberg, Michael; Mild, Kjell Hansson

2010-01-01

10

Optimized radiofrequency resonators for high field NMR clinical imaging  

Microsoft Academic Search

In high field (>4 Tesla) magnetic resonance imaging (MRI) systems, a major challenge is the design of radiofrequency (RF) coils that exhibit a good signal to noise ratio, tangential magnetic field (B 1) uniformity, and low specific absorption rate (SAR) in the biological tissues. As the static magnetic field increases, the frequency of operation rises and consequently the electrical dimensions

T. S. Ibrahim; R. Lee; B. B. Baertlein; P. M. L. Robitaille

2000-01-01

11

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

12

Occupational exposure to radio-frequency electromagnetic fields  

SciTech Connect

The paper considers occupational exposure to radio-frequency (RF) electromagnetic (EM) fields in industrial processes in near-field situations where electric and magnetic field strengths are monitored to assess the health hazard. Plastic materials are joined by an RF machine whose electrodes are not shielded and which may produce high level RF fields in the immediate vicinity, exceeding the ANSI standard. A physiotherapist may be exposed to high E and H fields using RF shortwave therapy, the maintenance personnel in FM/TV broadcast towers are subject to intense RF fields, and induction heating equipment used for forging, annealing and brazing can expose operators' hands to magnetic fields.

Mild, K.H.

1980-01-01

13

Radiofrequency field-induced thermal cytotoxicity in cancer cells treated with fluorescent nanoparticles  

PubMed Central

Background Non-ionizing radiation, such as radiofrequency (RF) field and near infrared laser, induces thermal cytotoxicity in cancer cells treated with gold nanoparticles (AuNP). Quantum dots (QD) are fluorescent semiconducting nanoparticles that we hypothesize will induce similar injury following RF field irradiation. Methods AuNP and two types of QD (cadmium-selenide and indium-gallium-phosphide) conjugated to cetuximab (C225), a monoclonal antibody against human epidermal growth factor receptor (EGFR-1), demonstrated concentration-dependent heating in a RF field. We investigated the effect of RF field exposure after targeted nanoparticle treatment in a co-culture of two human cancer cell lines that have differential EGFR-1 expression (a high expressing pancreatic carcinoma, Panc-1, and a low expressing breast carcinoma, Cama-1). Results RF exposed Panc-1 or Cama-1 cells not containing AuNP or QD had a viability greater than 92%. The viability of Panc-1 cells exposed to the RF field after treatment with 50 nM Au-C225 was 39.4% ± 8.3% without injury to bystander Cama-1 cells (viability was 93.7% ± 1.0%, p ~ 0.0006). Panc-1 cells treated with targeted Cd-Se QD were only 47.5% viable after RF field exposure (p < 0.0001 compared to RF only Panc-1 control cells). Targeted InGaP QD decreased Panc-1 viability to 58.2% ± 3.4% after RF field exposure (p ~ 0.0004 compared to Cama-1 and Panc-1 controls). Conclusion We selectively induced RF field cytotoxicity in Panc-1 cells without injury to bystander Cama-1 cells utilizing EGFR-1 targeted nanoparticles, and demonstrated an interesting bifunctionality of fluorescent nanoparticles as agents for both cancer cell imaging and treatment.

Glazer, Evan S.; Curley, Steven A.

2010-01-01

14

Electromagnetic Field Measurement in Presence of Radiofrequency Wideband Digital Signals  

Microsoft Academic Search

This paper describes an experimental research carried out to evaluate the efficiency of traditional exposure assessment procedures when applied to the measurement of radiofrequency electromagnetic field radiated by digital wideband signal transmitters (802.11x, 802.16x, DVB-x). For this purpose, it was analysed both the performance of wideband measuring procedures based on the use of wideband field probes and the behaviour of

Daniele Trinchero; Benedetta Fiorelli; Riccardo Stefanelli; Laura Anglesio; Alberto Benedetto; Stefano Trinchero; Giovanni d'Amore; Michele Borsero; Giuseppe Vizio

15

Genetic, carcinogenic and teratogenic effects of radiofrequency fields.  

PubMed

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 in particular, are not genotoxic: they do not induce genetic effects in vitro and in vivo, at least under non-thermal exposure conditions, and do not seem to be teratogenic or to induce cancer. Yet, some investigations gave rather alarming results that should be confirmed and completed by further experiments. Among them the investigation of synergistic effects and of possible mechanisms of action should be emphasised. PMID:9637234

Verschaeve, L; Maes, A

1998-04-01

16

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

SciTech Connect

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.

Roeoesli, Martin [Institute of Social and Preventive Medicine, Department of Social and Preventive Medicine, University of Bern, Finkenhubelweg 11, CH-3012 Bern (Switzerland)], E-mail: Roeoesli@ispm.unibe.ch

2008-06-15

17

Far field radio-frequency sheath modeling  

NASA Astrophysics Data System (ADS)

Recent probe data on Alcator C-Mod suggests that fast wave propagation to regions far from the antenna can produce large rf sheaths (˜ 100 V). This data provides a good test case for 1D and 2D models of far field sheath generation. The 1D model [D. D'Ippolito et al., Phys. Plasmas 15, 102501 (2008)] shows that coupling between the fast and slow waves at the limiter can drive sheath potentials when rapid spatial variation (associated with the limiter geometry) is assumed. Using the rfSOL code [H. Kohno et al., Phys. Plasmas 19, 012508 (2012)] a new 2D simulation shows that rapid spatial variation in the magnetic field direction relative to the limiter can produce slow waves and rf sheath potentials varying rapidly along the sheath. While neither of these models treats the actual experimental geometry, they provide support for the idea that the observed potentials are driven by fast wave -- slow wave coupling at the limiter. Understanding this physics is important for minimizing rf-enhanced impurities in rf experiments.

D'Ippolito, D. A.; Myra, J. R.; Kohno, H.; Ochoukov, R.; Whyte, D. G.

2012-10-01

18

Pancreatic carcinoma cells are susceptible to non-invasive radiofrequency fields after treatment with targeted gold nanoparticles  

PubMed Central

Background Gold and carbon nanoparticles absorb non-ionizing radiofrequency (RF) energy and release heat. Solid gold nanoparticles are delivered to cancer cells via conjugation with targeting antibodies. Here, 20 nm gold particles were conjugated to cetuximab, an epidermal growth factor recpetor-1 (EGFR-1) antibody. Methods A pancreatic carcinoma cell line that highly expresses EGFR-1, Panc-1, and a breast carcinoma cell line that minimally expresses EGFR-1, Cama-1, were treated with 100 nM cetuximab-conjugated gold nanoparticles for 3 hours (n = 4). Thirty-six hours later, the dishes were placed in an RF field with a generator power of 200 W for 5 minutes. After another 36 hours, cell injury and death were evaluated with flow cytometry. Results The targeted cell line, Panc-1, had a viability of 45.5% ± 11.7% while Cama-1 cell had a viability of 91.7% ± 1.6% after RF field exposure (p < 0.008). Transmission electron microscopy showed gold nanoparticle uptake in Panc-1 cells, but negligible uptake by Cama-1 cells. Non-targeted cells do not internalize a sufficient amount of antibody-conjugated gold nanoparticles to induce injury in a noninvasive RF field. Conclusion This technique could be useful in cancer treatment provided a cancer-specific antibody is utilized to localize gold nanoparticles to malignant cells.

Glazer, E. S.; Massey, K. L.; Zhu, C.; Curley, S. A.

2010-01-01

19

Remotely triggered cisplatin release from carbon nanocapsules by radiofrequency fields.  

PubMed

The efficacy of nanoparticle-mediated drug delivery is limited by its peri-vascular sequestration, thus necessitating a strategy to trigger drug release from such intra-tumoral nanocarrier-drug depots. In our efforts to explore remotely-activated nanocarriers, we have developed carbon nanocapsules comprised of an ultra-short carbon nanotube shell (US-tubes) loaded with cisplatin (CDDP@US-tubes) and covered with a Pluronic surfactant wrapping to minimize passive release. We demonstrate here that non-invasive radiofrequency (RF) field activation of the CDDP@US-tubes produces heat that causes Pluronic disruption which triggers cisplatin release in an RF-dependent manner. Furthermore, release-dependent cytotoxicity is demonstrated in human hepatocellular carcinoma cell lines. PMID:23228421

Raoof, Mustafa; Cisneros, Brandon T; Guven, Adem; Phounsavath, Sophia; Corr, Stuart J; Wilson, Lon J; Curley, Steven A

2012-12-08

20

Second harmonic acoustic responses induced in matter by quasi continuous radiofrequency fields  

NASA Astrophysics Data System (ADS)

We subjected conductive matter and tissue to intermittent continuous-wave radiofrequency fields and investigated whether acoustic responses could be recorded. By placing samples in the near-field of the excitation, we observed frequency-domain acoustic responses from tissues responding to CW radiofrequency excitation. Frequency analysis revealed the generation of 2nd harmonic mechanical waves. This discovery of non-linear responses can lead to alternative measurement concepts of CW radiofrequency deposition in matter and tissues. We offer the theoretical mainframe and discuss sensing applications involving the direct measurement of second harmonic responses representative of CW RF energy deposition in matter.

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

2013-10-01

21

Radiofrequency Field Exposure of Cultured Lymphocytes from 'Macaca mulatta'.  

National Technical Information Service (NTIS)

Exposure of cultured lymphocytes, obtained from Macaca mulatta, to 500 V/m, 30-MHz radiofrequency radiation provided no evidence of cell death, damage, or interference with mitotic activity, whether stimulated by PHA or unstimulated, immediately following...

R. H. Lovely T. J. Sparks A. W. Guy C. K. Chou

1979-01-01

22

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

23

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

24

Calculation of radiofrequency electromagnetic fields and their effects in MRI of human subjects.  

PubMed

Radiofrequency magnetic fields are critical to nuclear excitation and signal reception in magnetic resonance imaging. 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 magnetic resonance imaging techniques and technology have evolved through the years, so to have the requirements for meaningful interpretation of calculation results. Here, we review the basic physics of radiofrequency electromagnetics in magnetic resonance imaging and discuss a variety of ways radiofrequency field calculations are used in magnetic resonance imaging 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

2011-03-04

25

Relaxation-stimulated resonances in Mössbauer absorption spectra under radiofrequency magnetic field excitation  

Microsoft Academic Search

A new type of resonant phenomena in the Mössbauer spectroscopy of soft magnetic materials in radiofrequency (rf) magnetic fields is predicted for the rf field frequencies related to those of components of the magnetic hyperfine structure via the parametric resonance condition. Resonant effects of this kind are still unknown in physics; they are realized not at frequencies of transitions between

A. M. Afanas'ev; M. A. Chuev; J. Hesse

2000-01-01

26

Mobile phones, radiofrequency fields, and health effects in children – Epidemiological studies  

Microsoft Academic Search

In 2004, when WHO organized a workshop on children's sensitivity to electromagnetic fields, very few studies on radiofrequency fields were available. With the recent increase in mobile phone use among children and adolescents, WHO has identified studies on health effects in this age-group as a high priority research area. There are no empirical data supporting the notion that children and

Maria Feychting

27

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

Microsoft Academic Search

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

John E. H Tattersall; Iain R Scott; Sebastien J Wood; Julia J Nettell; Michael K Bevir; Zhou Wang; Nalinda P Somasiri; Xiaodong Chen

2001-01-01

28

Comment on enhancement of forbidden nuclear beta decay by high-intensity radio-frequency fields  

Microsoft Academic Search

A recent claim that forbidden nuclear beta decay can, by the application of a high-intensity radio-frequency field, be enhanced by many orders of magnitude is contested. The effect is shown to be nonexistent, at least within the theoretical model which has been adopted thus far.

W. Becker; R. R. Schlicher; M. O. Scully

1984-01-01

29

Concepts Relating to the Development of Modern Exposure Guidelines for Radiofrequency Fields  

Microsoft Academic Search

The determination of levels of safe exposure of humans to radiofrequency fields is based principally on relating the threshold for harmful effects in exposed animals to the whole-body mass averaged absorbed energy density or specific absorption rate (SAR). The SAR, given in units of watts per kilogram, is a complex function of the source configuration, shape, and size of the

Arthur W. Guy

1996-01-01

30

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

Microsoft Academic Search

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

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

2011-01-01

31

Multiple-quantum radio-frequency spectroscopy of atoms: Application to the metrology of geomagnetic fields  

Microsoft Academic Search

The evolution of the radio-frequency magnetic resonance spectrum of optically oriented potassium atoms in terrestrial magnetic\\u000a fields as a function of the amplitude of the alternating magnetic field H\\u000a 1 is investigated theoretically and experimentally. It is shown that among the set of observed n-quantum resonances which satisfy the selection rules ?F=0 and ?m\\u000a Fn (n is an integer), there

E. B. Aleksandrov; M. V. Balabas; A. K. Vershovskii; A. S. Pazgalev

1999-01-01

32

Radio-frequency transmission properties of carbon nanotubes in a field-effect transistor configuration  

Microsoft Academic Search

In this letter, the radio-frequency (RF) transmission properties of single-walled carbon nanotubes (CNTs) have been characterized up to the frequency of 12 GHz in a carbon nanotube field-effect transistor (CNFET) configuration using a two-port S-parameter method for the first time. The RF characteristics of the CNTs were measured from the drain to the source of the CNFET. A resistance, inductance,

Min Zhang; Xiao Huo; Philip C. H. Chan; Q. Liang; Z. K. Tang

2006-01-01

33

Size-dependent joule heating of gold nanoparticles using capacitively coupled radiofrequency fields  

Microsoft Academic Search

Capacitively coupled shortwave radiofrequency fields (13.56 MHz) resistively heat low concentrations (?1 ppm) of gold nanoparticles\\u000a with a thermal power dissipation of ?380 kW\\/g of gold. Smaller diameter gold nanoparticles (< 50 nm) heat at nearly twice\\u000a the rate of larger diameter gold nanoparticles (?50 nm), which is attributed to the higher resistivity of smaller gold nanostructures.\\u000a A Joule heating

Christine H. Moran; Sean M. Wainerdi; Tonya K. Cherukuri; Carter Kittrell; Benjamin J. Wiley; Nolan W. Nicholas; Steven A. Curley; John S. Kanzius; Paul Cherukuri

2009-01-01

34

Mechanisms of biological effects of radiofrequency electromagnetic fields: an overview  

Microsoft Academic Search

Manmade sources of electromagnetic (EM) fields, and therefore human exposures to them, continue to increase. Public concerns stem from the effects reported in the literature, the visibility of the sources, and somewhat from confusion between EM fields and ionizing radiation. Protecting humans from the real hazards and allaying groundless fears requires a self-consistent body of scientific data concerning effects of

Erwin

1988-01-01

35

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:24092143

Guo, Xuemei; Zhai, Fei; Nan, Qun

2013-01-01

36

Present knowledge about specific absorption rates inside a human body exposed to radiofrequency electromagnetic fields  

SciTech Connect

We have compiled results of scientific investigations about the relationship between external field-strengths and specific absorption rates inside the human body. The data were normalized to SAR-values that form the basis for current safety standards. Results were compared to exposure limits given in these standard. This comparison should serve as a reference for the selection of reliable reference levels for personal protection against thermal effects in radiofrequency electromagnetic fields. The need to measure and monitor ankle/wrist currents to protect some exposed workers is explained. The study has also highlighted a scarcity of dosimetric data at frequencies below 3 MHz. 20 refs., 7 figs.

Garn, J. [Austrian Research centre Seibersdorf (Australia); Gabriel, C. [King`s College, London (United Kingdom)

1995-02-01

37

[On one term (translation of SAR) in the dosimetry of radiofrequency electromagnetic fields].  

PubMed

Uncertainties in the use of some terms in the dosimetry of radiofrequency electromagnetic fields are discussed. We have come to the conclusion that the term conventionally applied in the Russian literature to describe the absorbed energy is an incorrect translation of the international term "Specific Absorption Rate" (SAR). The main error in the Russian term is that the energy rather than the rate is absorbed. More precise Russian definition for this term is suggested by analogy with the dosimetry of ionizing radiation. In this case, the dimension of this parameter remains without any change. PMID:23227718

Petin, V G; Grigor'ev, O A; Merkulov, A V; Grigor'ev, Iu G; Trukhanov, K A

38

Field reversals in electrically asymmetric capacitively coupled radio-frequency discharges in hydrogen  

NASA Astrophysics Data System (ADS)

In this paper, we present a simulation study of electrically asymmetric capacitively coupled radio-frequency hydrogen discharges using the hybrid plasma equipment model operated at the combined frequencies of 10 and 20 MHz. We find that, in such discharges, field reversals cause ionization near the electrodes during the sheath collapse. In the case of the investigated asymmetric voltage waveforms, the field reversals are asymmetrically distributed over the sheaths, which causes asymmetric ionization and density profiles. The asymmetry of these profiles can be controlled by the phase angle between the two frequencies. As a result, the possibility to control the ion energy independently from the ion flux via the electrical asymmetry effect (EAE) is reduced in discharges displaying strong field reversals, as the asymmetric field reversals compensate the electrically induced asymmetry. The reason for this is understood by an analytical model. Furthermore, we demonstrate, that the EAE can be restored by the addition of specific gases to a pure hydrogen discharge.

Mohr, Sebastian; Schüngel, Edmund; Schulze, Julian; Czarnetzki, Uwe

2013-10-01

39

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

NASA Astrophysics Data System (ADS)

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

2013-08-01

40

Fractional kinetics of glioma treatment by a radio-frequency electric field  

NASA Astrophysics Data System (ADS)

A realistic model for estimation of the medical effect of brain cancer (glioma) treatment by a radio-frequency (RF) electric field is suggested. This low intensity, intermediate-frequency alternating electric field is known as the tumor-treating field (TTF). The model is based on a construction of 3D comb model for a description of the cancer cells dynamics, where the migration-proliferation dichotomy becomes naturally apparent, and the outer-invasive region of glioma cancer is considered as a fractal composite embedded in the 3D space. In the framework of this model, the interplay between the TTF and the migration-proliferation dichotomy of cancer cells is considered, and the efficiency of this TTF is estimated. It is shown that the efficiency of the medical treatment by the TTF depends essentially on the mass fractal dimension of the cancer in the outer-invasive region.

Iomin, A.

2013-09-01

41

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.

Collins, Christopher M.; Wang, Zhangwei

2011-01-01

42

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

43

Separation of components of a 1H NMR composite signal by nutation experiments under low amplitude radio-frequency fields. Application to the water signal in clays  

Microsoft Academic Search

NMR nutation experiment consists in probing the evolution of nuclear magnetization perpendicularly to a radio-frequency field applied for a variable time. It is shown theoretically and experimentally that, under weak radio-frequency field conditions, the nutation frequency depends on relaxation rates. The Fourier transform of the nutation curve, which is obtained by plotting the signal amplitude as a function of the

Gregory Trausch; Daniel Canet; Anthony Cadène; Pierre Turq

2006-01-01

44

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

45

Radio-frequency heating of sloshing ions in a straight field line mirror  

SciTech Connect

A scenario to sustain a sloshing ion population with radio-frequency heating in a newly proposed mirror device, the straight field line mirror, is examined. The possibilities of ion cyclotron heating in two-ion species plasma have been analyzed and a scheme with longitudinal wave conversion and fundamental harmonic heating of deuterium ions in tritium plasma has been investigated. This scheme provides efficient ion heating for high deuterium 'minority' concentration without substantial conversion to slow waves and heating of the electrons. Numerical calculations carried out for a reactor-scale device show that conversion of the fast magnetosonic wave to the fast Alfven wave occurs. For reasons of strong cyclotron absorption of the fast Alfven wave, only a small portion of the wave energy transits through the cyclotron layer and penetrates to the central part of the trap. The power deposition is peaked at the plasma core. The amount of deposited power does not depend sensitively on the parameters of the discharge. The study uses numerical three-dimensional calculations for the time-harmonic boundary problem for Maxwell's equations. For radio-frequency heating in this scheme, a simple efficient strap antenna is proposed. It has low Q antenna and operates in the regime of global resonance overlapping.

Moiseenko, V.E.; Aagren, O. [Division of Electricity and Lightning Research, Angstroem Laboratory, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden)

2005-10-01

46

Suppression of ionization instability in a magnetohydrodynamic plasma by coupling with a radio-frequency electromagnetic field  

NASA Astrophysics Data System (ADS)

We describe the suppression of ionization instability and the control of a magnetohydrodynamic electrical power-generating plasma by coupling with a radio-frequency (rf) electromagnetic field. The rf heating stabilizes the unstable plasma behavior and homogenizes the nonuniform plasma structure, whereby the power-generating performance is significantly improved.

Murakami, Tomoyuki; Okuno, Yoshihiro; Yamasaki, Hiroyuki

2005-05-01

47

Retarding field analyzer for ion energy distribution measurements at a radio-frequency biased electrode  

SciTech Connect

A retarding field energy analyzer designed to measure ion energy distributions impacting a radio-frequency biased electrode in a plasma discharge is examined. The analyzer is compact so that the need for differential pumping is avoided. The analyzer is designed to sit on the electrode surface, in place of the substrate, and the signal cables are fed out through the reactor side port. This prevents the need for modifications to the rf electrode--as is normally the case for analyzers built into such electrodes. The capabilities of the analyzer are demonstrated through experiments with various electrode bias conditions in an inductively coupled plasma reactor. The electrode is initially grounded and the measured distributions are validated with the Langmuir probe measurements of the plasma potential. Ion energy distributions are then given for various rf bias voltage levels, discharge pressures, rf bias frequencies - 500 kHz to 30 MHz, and rf bias waveforms - sinusoidal, square, and dual frequency.

Gahan, D.; Hopkins, M. B. [National Centre for Plasma Science and Technology, Dublin City University, Glasnevin, Dublin 9 (Ireland); Dolinaj, B. [Impedans Ltd., Invent Centre, Dublin City University, Glasnevin, Dublin 9 (Ireland)

2008-03-15

48

Retarding field analyzer for ion energy distribution measurements at a radio-frequency biased electrode.  

PubMed

A retarding field energy analyzer designed to measure ion energy distributions impacting a radio-frequency biased electrode in a plasma discharge is examined. The analyzer is compact so that the need for differential pumping is avoided. The analyzer is designed to sit on the electrode surface, in place of the substrate, and the signal cables are fed out through the reactor side port. This prevents the need for modifications to the rf electrode--as is normally the case for analyzers built into such electrodes. The capabilities of the analyzer are demonstrated through experiments with various electrode bias conditions in an inductively coupled plasma reactor. The electrode is initially grounded and the measured distributions are validated with the Langmuir probe measurements of the plasma potential. Ion energy distributions are then given for various rf bias voltage levels, discharge pressures, rf bias frequencies--500 kHz to 30 MHz, and rf bias waveforms--sinusoidal, square, and dual frequency. PMID:18377005

Gahan, D; Dolinaj, B; Hopkins, M B

2008-03-01

49

Wide-bandwidth charge sensitivity with a radio-frequency field-effect transistor  

NASA Astrophysics Data System (ADS)

We demonstrate high-speed charge detection at room temperature with single-electron resolution by using a radio-frequency field-effect transistor (RF-FET). The RF-FET combines a nanometer-scale silicon FET with an impedance-matching circuit composed of an inductor and capacitor. Driving the RF-FET with a carrier signal at its resonance frequency, small signals at the transistor's gate modulate the impedance of the resonant circuit, which is monitored at high speed using the reflected signal. The RF-FET driven by high-power carrier signals enables a charge sensitivity of 2 × 10-4 e/Hz0.5 at a readout bandwidth of 20 MHz.

Nishiguchi, Katsuhiko; Yamaguchi, Hiroshi; Fujiwara, Akira; van der Zant, Herre S. J.; Steele, Gary A.

2013-09-01

50

Assessment of SAR in the tissues near a cochlear implant exposed to radiofrequency electromagnetic fields.  

PubMed

Cochlear implants (CI) are electronic devices used to restore partial hearing to people with severe hearing impairment. This paper aims to investigate if the introduction of a CI has an effect on SAR distribution in a head model exposed to radiofrequency electromagnetic fields (RF EMF) at mobile communication frequencies. The head model was obtained by image segmentation, the implant was modelled as a geometric structure and the exposure source was modelled as a uniform plane wave at 900 MHz, 1750 MHz and 1950 MHz, incident on the side of the head with the CI. Vertical and horizontal polarizations were simulated. Results show that the presence of a CI inside the cochlea produces negligible variations in the averaged SAR values, both in the head and in the cochlear tissues, although very localized differences in point SAR were found in the cochlea. Globally, these results suggest that finding harmful effects in the cochlear tissues will be unlikely. PMID:19321926

Sibella, F; Parazzini, M; Paglialonga, A; Ravazzani, P

2009-03-25

51

Entanglement under equilibrium establishing in spin systems subjected to radiofrequency field  

NASA Astrophysics Data System (ADS)

We study the entanglement evolution in a dipolar-coupled spin system irradiated by a radiofrequency (RF) field in quasi-equilibrium state characterized by a two-temperature density matrix. Process of the establishment of equilibrium is in the equalization of these temperatures. The method of the nonequilibrium statistical operator in a rotating frame is used to describe the evolution of the spin system. It is shown that the equilibrium establishment has nonexponential character, and the time needed for this establishment depends strongly on the RF field strength. Particularly, the weak RF irradiation increases the lifetime of entanglement. Temporal and temperature dependencies of the concurrence of spin pairs are obtained and discussed. It is shown that application of RF field increases the time of the equilibrium establishment (up to order of 1,000 times) and lifetime of the existence of entangled states (up to order of 1,000 times). Thus, with the help of RF irradiation, we can govern the relaxation process and control entanglement in the system. The obtained results can be used for analysis of more complex spin systems because dipole-dipole interaction decreases proportionally to inverse third power of the distance between the spins, and influence of far way spins can be negligible.

Furman, Gregory B.; Meerovich, Victor M.; Sokolovsky, Vladimir L.

2013-10-01

52

Radiofrequency field exposure and cancer: what do the laboratory studies suggest?  

PubMed Central

Significant concern has been raised about possible health effects from exposure to radiofrequency (RF) electromagnetic fields, especially after the rapid introduction of mobile telecommunications systems. Parents are especially concerned with the possibility that children might develop cancer after exposure to the RF emissions from mobile telephone base stations erected in or near schools. These questions have followed scientific reports suggesting that residence near high voltage power lines may to be associated with an increased childhood leukemia risk. Epidemiologic studies have been plagued by poor RF exposure assessment and differences in methodology. There are no high-quality epidemiologic studies that can be used to evaluate health risks from RF exposure. Laboratory studies in this area have been somewhat confusing. Some animal studies suggest that RF fields accelerate the development of sarcoma colonies in the lung, mammary tumors, skin tumors, hepatomas, and sarcomas. A substantial RF-induced increase in lymphoma incidence in transgenic mice exposed for up to 18 months has also been reported. In contrast, other studies have not found carcinogenic effects. These conflicting results indicate the need for more well-conducted studies on laboratory animals, supplemented with high-quality in vitro studies to identify effects that need further research in vivo, and to characterize any acting mechanisms, especially at low RF field levels. This paper provides a review of the laboratory studies and indicates what conclusions about RF-induced cancer can be drawn.

Repacholi, M H

1997-01-01

53

Analytic model of near-field radio-frequency sheaths. II. Full plasma dielectric  

SciTech Connect

An analytic model is derived for electromagnetic radio-frequency (rf) wave propagation in a plasma-filled waveguide with rf sheath boundary conditions. The model gives a simplified description of the rf fields and sheath potentials near an ion cyclotron range of frequencies antenna under certain conditions. The present work lifts the restriction to a low density plasma ('tenuous plasma model') described in a previous paper [D. A. D'Ippolito and J. R. Myra, Phys. Plasmas 16, 022506 (2009)] to include the full plasma dielectric tensor with the ordering epsilon{sub perpendicular}approxepsilon{sub x}approx1, epsilon{sub ||}>>1 for the case where the magnetic field is well aligned with the antenna. It is shown that retaining epsilon{sub x}approx1 provides an additional drive term for the rf sheath. This effect is shown to be negligible in most practical situations suggesting that the tenuous plasma model does not miss any essential finite-density effects. The condition to recover the tenuous plasma result is derived. Expressions for the sheath voltage and sheath power dissipation are given in the arbitrary density limit, and a comparison of several mechanisms for dissipating power in rf sheaths is discussed.

D'Ippolito, D. A.; Myra, J. R. [Lodestar Research Corporation, 2400 Central Avenue, Boulder, Colorado 80301 (United States)

2010-07-15

54

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.

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

2010-01-01

55

Synthesis and characterization of Fe 3 O 4 magnetic nanoparticles and their heating effects under radiofrequency capacitive field  

Microsoft Academic Search

Fe3O4 magnetic nanoparticles with diameters varying from 10 to 426 nm were synthesized and characterized. Heating effects of Fe3O4 magnetic nanoparticles under radiofrequency capacitive field (RCF) with frequency of 27.12 MHz and power of 60–150 W were\\u000a investigated. When the power of RCF is lower than 90 W, temperatures of Fe3O4 magnetic nanoparticles (75–150 mg\\/mL) can be raised and maximal

Xu-hong Li; Zhi-ming Feng; Wei-wei Ouyang; Xiao-xue Xie; Yu-ping Liao; Jin-tian Tang

2010-01-01

56

Effects of 1800MHz Radiofrequency Fields on Circadian Rhythm of Plasma Melatonin and Testosterone in Male Rats  

Microsoft Academic Search

Radiofrequency fields (RF) at 1800 MHz are known to affect melatonin (MEL) and testosterone in male rats, but it remains to be determined whether RF affected circadian rhythm of these plasma hormones. Male Sprague-Dawley rats were exposed to 1800-MHz RF at 208 ?w\\/cm power density (SAR: 0.5762 W\\/kg) at different zeitgeber (ZT) periods of the day, including 0 (ZT0), 4

Fenju Qin; Jie Zhang; Honglong Cao; Cao Yi; Jian Xiang Li; Jihua Nie; Li Li Chen; Jiajun Wang; Jian Tong

2012-01-01

57

FAST TRACK COMMUNICATION: Discharge features of radio-frequency, atmospheric-pressure cold plasmas under an intensified local electric field  

Microsoft Academic Search

In this paper, stable atmospheric-pressure argon, nitrogen or air glow discharges driven by a radio-frequency power supply with water-cooled, bare copper electrodes are obtained by employing a newly-designed plasma generator. Due to the existence of the intensified local electric field by using an insulated tungsten wire between the two bare copper electrodes, which is also verified by the modelling results,

Guo Li; He-Ping Li; Wen-Ting Sun; Sen Wang; Zhe Tian; Cheng-Yu Bao

2008-01-01

58

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

59

Effects of multi-polar radiofrequency and pulsed electromagnetic field treatment in Koreans: case series and survey study.  

PubMed

Background: Recently, a novel combined multi-polar radiofrequency and pulsed electromagnetic field device was developed for non-ablative skin tightening. However, little is known about the clinical effects of this device. Objectives: The present study evaluated the clinical efficacy and safety of the multi-polar radiofrequency and pulsed electromagnetic field device. Materials and Methods: Ten Korean patients underwent eight treatment sessions over 6 weeks. Clinical photographs of the skin were taken before and after the treatment at each week of treatment. Satisfaction score (0; dissatisfied, 5; neutral, 10; very satisfied) and pain score (0; no pain, 10; too painful) was determined using weekly questionnaires. A dermatologist evaluated the improvement of facial skin aging, including laxity, nasolabial fold, facial contour, skin texture, and skin color tone. Results:The mean satisfaction score was high (>8) and the mean pain score was low (1.5). Improved skin laxity, nasolabial fold, and facial contour were observed in four, one, and three patients, respectively. Skin texture and skin color tone improved in 90% and 70% of the patients, respectively. Conclusion: The novel combined multi-polar radiofrequency and pulsed electromagnetic field device is safe and effective for rejuvenating aged skin in Korean subjects. PMID:22812649

Lee, Young Bok; Eun, Young Sun; Lee, Ji Hae; Cheon, Min Seok; Cho, Baik Kee; Park, Hyun Jeong

2012-09-19

60

Young's modulus reconstruction for radio-frequency ablation electrode-induced displacement fields: a feasibility study.  

PubMed

Radio-frequency (RF) ablation is a minimally invasive treatment for tumors in various abdominal organs. It is effective if good tumor localization and intraprocedural 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 2-D 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, Christopher L; Madsen, Ernest L; Hall, Timothy J; Bharat, Shyam; Hobson, Maritza A; Zagzebski, James A; Lee, Fred T

2009-02-27

61

Calibration and uncertainties in personal exposure measurements of radiofrequency electromagnetic fields.  

PubMed

In the past 5 years radiofrequency personal exposure meters have been used to characterize the exposure during daily activities. We found from calibration tests for the 12 frequency bands of the EME Spy 121 exposimeter in a Gigahertz Transverse Electromagnetic cell and an Open Area Test Site, that these measurements tend to underestimate the actual exposure. Therefore, a maximum frequency-dependent correction factor of 1.1-1.6 should be applied to the electric field. This correction factor consists of three multipliers correcting for calibration, elevation arrival angle, and influence of the body. The calibration correction factor should be determined per exposimeter, as the maximum range of response between exposimeters in a frequency band is 2.4 dB. Since the range of response for different elevation angles could reach 10.2?dB, a strict protocol for wearing the exposimeter during fieldwork should be followed to be able to compare and combine measurements made by different persons in the same microenvironments. Because the influence of the body depends on the azimuth angle of arrival, it may lead to an over- or underestimation. Thus, the body correction factor is an average over the angles and should only be applied in activities involving movement through the full 360° range of random angles of arrival. PMID:21544843

Bolte, John F B; van der Zande, Gerard; Kamer, Jos

2011-05-04

62

Human brain wave activity during exposure to radiofrequency field emissions from mobile phones.  

PubMed

The aim of this study was to determine whether there is an effect of mobile phone electromagnetic field emissions on the human electroencephalograph (EEG). EEG recordings from ten awake subjects were taken during exposure to radiofrequency (RF) emissions from a mobile phone positioned behind the head. Two experimental trials were conducted. In the first trial, RF exposures were generated by a GSM mobile phone with the speaker disabled and configured to transmit at full-radiated power. During the second trial, exposures were generated by a non-modified GSM mobile phone in active standby mode. For each trial, subjects were exposed in five minute intervals to a randomized, interrupted sequence of five active and five sham exposures. The experiment was conducted under single-blind conditions. The average EEG band power in active exposure recordings was compared to corresponding sham recordings. Statistical tests indicated significant difference in the full-power mode trial within the EEG alpha (8-13 Hz) and beta (13-32 Hz) bands. A subsequent statistical analysis of median spectral power in discrete EEG rhythms revealed significant differences in 7 of the 32 distinct frequencies overall. In conclusion, the results of this study lend support to EEG effects from mobile phones activated in talk-mode. PMID:14995060

D'Costa, H; Trueman, G; Tang, L; Abdel-rahman, U; Abdel-rahman, W; Ong, K; Cosic, I

2003-12-01

63

Fast 3D radiofrequency field mapping using echo-planar imaging.  

PubMed

An inhomogeneous radiofrequency (RF) magnetic field is an essential source of error for the quantification of MRI and MRS parameters. To correct for effects of RF inhomogeneities in 3D data sets, it is necessary to have knowledge of the 3D RF distribution in the sample. In this paper a method for fast 3D RF mapping is presented. The method is based on the simultaneous acquisition of a spin echo (SE) and a stimulated echo (STE) using echo-planar imaging (EPI). The acquisition of the 3D RF map using 64 partitions and TR = 500 ms requires 1.5 min. The use of the sequence in vivo is demonstrated by the calculation of the RF maps in the human brain at 3T. The comparison of calculated flip angles with the flip angles obtained by fitting signal behavior in the 3D stimulated-echo acquisition mode (STEAM)-EPI sequence and the analysis of errors due to spatially dependent T(1) values in the brain show that the accuracy of the calculated flip angles in the human brain is about 2 degrees. PMID:17089359

Jiru, F; Klose, U

2006-12-01

64

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.

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

2012-01-01

65

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

PubMed Central

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

2012-01-01

66

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

PubMed

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. PMID:22991480

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

2012-08-24

67

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

68

Exposure to extremely-low-frequency electromagnetic fields and radiofrequency radiation: cardiovascular effects in humans.  

PubMed

Cardiovascular changes in humans exposed to nonionizing radiation [including extremely-low-frequency electromagnetic fields (ELF EMFs) and radiofrequency radiation (RFR)] are reviewed. Both acute and long-term effects have been investigated. In general, if heating does not occur during exposure, current flow appears to be necessary for major cardiovascular effects to ensue, such as those due to electric shock. Whereas most studies have revealed no acute effect of static or time-varying ELF EMFs on the blood pressure, heart rate, or electrocardiogram waveform, others have reported subtle effects on the heart rate. The possible health consequences of these results are unknown. Regarding long-term effects of ELF EMFs, reports from the former Soviet Union in the early 1960s indicated arrhythmias and tachycardia in high-voltage-switchyard workers. Subsequent studies in Western countries, however, did not confirm these findings. These studies are limited by uncertainties regarding exposure durations and appropriate control groups. Investigations of acute cardiovascular changes in humans purposely exposed to RFR have been limited to studies of magnetic resonance imaging (which, in addition to RFR, involves static and time-varying magnetic fields). It has been concluded that such exposures, as presently performed, are not likely to cause adverse cardiovascular effects. Reports of hypertension in workers potentially exposed to high levels of RFR during accidents are considered to be incidental (due to anxiety and posttraumatic stress). Soviet investigators have also indicated that long-term RFR exposure may result in hypotension and bradycardia or tachycardia. Other researchers, however, have been incapable of replicating these results, and some scientists have attributed the effects to chance variations and mishandling of data. In summary, studies have not yielded any obvious cardiovascular-related hazards of acute or long-term exposures to ELF EMFs or RFR at levels below current exposure standards. PMID:9258703

Jauchem, J R

1997-01-01

69

In vitro effects of GSM modulated radiofrequency fields on human immune cells.  

PubMed

Despite the important role of the immune system in defending the body against infections and cancer, only few investigations on possible effects of radiofrequency (RF) radiation on function of human immune cells have been undertaken. Aim of the present investigation was therefore to assess whether GSM modulated RF fields have adverse effects on the functional competence of human immune cells. Within the frame of the multidisciplinary project "Biological effects of high frequency electromagnetic fields (EMF)" sponsored by the National Occupation Hazard Insurance Association (AUVA) in vitro investigations were carried out on human blood cells. Exposure was performed at GSM Basic 1950 MHz, an SAR of 1 mW/g in an intermittent mode (5 min "ON", 10 min "OFF") and a maximum Delta T of 0.06 degrees C for the duration of 8 h. The following immune parameters were evaluated: (1) the intracellular production of interleukin-2 (IL-2) and interferon (INF) gamma in lymphocytes, and IL-1 and tumor necrosis factor (TNF)-alpha in monocytes were evaluated with monoclonal antibodies. (2) The activity of immune-relevant genes (IL 1-alpha and beta, IL-2, IL-2-receptor, IL-4, macrophage colony stimulating factor (MCSF)-receptor, TNF-alpha, TNF-alpha-receptor) and housekeeping genes was analyzed with real time PCR. (3) The cytotoxicity of lymphokine activated killer cells (LAK cells) against a tumor cell line was determined in a flow cytometric test. For each parameter, blood samples of at least 15 donors were evaluated. No statistically significant effects of exposure were found and there is no indication that emissions from mobile phones are associated with adverse effects on the human immune system. PMID:16342197

Tuschl, Helga; Novak, Waltraud; Molla-Djafari, Hamid

2006-04-01

70

[Ionizing and non-ionizing radiation (comparative risk estimations)].  

PubMed

The population has widely used mobile communication for already more than 15 years. It is important to note that the use of mobile communication has sharply changed the conditions of daily exposure of the population to EME We expose our brain daily for the first time in the entire civilization. The mobile phone is an open and uncontrollable source of electromagnetic radiation. The comparative risk estimation for the population of ionizing and non-ionizing radiation was carried out taking into account the real conditions of influence. Comparison of risks for the population of ionizing and non-ionizing radiation leads us to a conclusion that EMF RF exposure in conditions of wide use of mobile communication is potentially more harmful than ionizing radiation influence. PMID:22690585

Grigor'ev, Iu G

71

Radio-frequency amplification property of the MgO-based magnetic tunnel junction using field-induced ferromagnetic resonance  

NASA Astrophysics Data System (ADS)

The radio-frequency (RF) voltage amplification property of a tunnel magnetoresistance device driven by an RF external-magnetic-field-induced ferromagnetic resonance was studied. The proposed device consists of a magnetic tunnel junction and an electrically isolated coplanar waveguide. The input RF voltage applied to the waveguide can excite the resonant dynamics in the free layer magnetization, leading to the generation of an output RF voltage under a DC bias current. The dependences of the RF voltage gain on the static external magnetic field strength and angle were systematically investigated. The design principles for the enhancement of the gain factor are also discussed.

Konishi, K.; Dixit, D. K.; Tulapurkar, A. A.; Miwa, S.; Nozaki, T.; Kubota, H.; Fukushima, A.; Yuasa, S.; Suzuki, Y.

2013-04-01

72

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.

Mohler, Evelyn; Frei, Patrizia; Frohlich, Jurg; Braun-Fahrlander, Charlotte; Roosli, Martin

2012-01-01

73

Pulsed radiofrequency electromagnetic field therapy: a potential novel treatment of plantar fasciitis.  

PubMed

Plantar fasciitis is a common cause of heel pain, and although treatments are usually conservative, they can take up to 2 years to achieve resolution. A double-blind, multicenter, randomized, placebo-controlled study was used to evaluate a small, wearable, extended-use pulsed radiofrequency electromagnetic field (PRFE) device as a treatment of plantar fasciitis. A total of 70 subjects diagnosed with plantar fasciitis were enrolled in the present study. The subjects were randomly assigned a placebo or active PRFE device. The subjects were instructed to wear the PRFE device overnight, record their morning and evening pain using a 0- to 10-point visual analog scale (VAS), and log any medication use. The primary outcome measure for the present study was morning pain, a hallmark of plantar fasciitis. The study group using the active PRFE device showed progressive decline in morning pain. The day 7 AM-VAS score was 40% lower than the day 1 AM-VAS score. The control group, in comparison, showed a 7% decline. A significantly different decline was demonstrated between the 2 groups (p = .03). The PM-VAS scores declined by 30% in the study group and 19% in the control group, although the difference was not significant. Medication use in the study group also showed a trend downward, but the use in the control group remained consistent with the day 1 levels. PRFE therapy worn on a nightly basis appears to offer a simple, drug-free, noninvasive therapy to reduce the pain associated with plantar fasciitis. PMID:22297104

Brook, Joel; Dauphinee, Damien M; Korpinen, Jaryl; Rawe, Ian M

2012-01-31

74

Effects of chronic exposure to radiofrequency electromagnetic fields on energy balance in developing rats.  

PubMed

The effects of radiofrequency electromagnetic fields (RF-EMF) on the control of body energy balance in developing organisms have not been studied, despite the involvement of energy status in vital physiological functions. We examined the effects of chronic RF-EMF exposure (900 MHz, 1 V?m(-1)) on the main functions involved in body energy homeostasis (feeding behaviour, sleep and thermoregulatory processes). Thirteen juvenile male Wistar rats were exposed to continuous RF-EMF for 5 weeks at 24 °C of air temperature (T a) and compared with 11 non-exposed animals. Hence, at the beginning of the 6th week of exposure, the functions were recorded at T a of 24 °C and then at 31 °C. We showed that the frequency of rapid eye movement sleep episodes was greater in the RF-EMF-exposed group, independently of T a (+42.1 % at 24 °C and +31.6 % at 31 °C). The other effects of RF-EMF exposure on several sleep parameters were dependent on T a. At 31 °C, RF-EMF-exposed animals had a significantly lower subcutaneous tail temperature (-1.21 °C) than controls at all sleep stages; this suggested peripheral vasoconstriction, which was confirmed in an experiment with the vasodilatator prazosin. Exposure to RF-EMF also increased daytime food intake (+0.22 g?h(-1)). Most of the observed effects of RF-EMF exposure were dependent on T a. Exposure to RF-EMF appears to modify the functioning of vasomotor tone by acting peripherally through ?-adrenoceptors. The elicited vasoconstriction may restrict body cooling, whereas energy intake increases. Our results show that RF-EMF exposure can induce energy-saving processes without strongly disturbing the overall sleep pattern. PMID:23143821

Pelletier, Amandine; Delanaud, Stéphane; Décima, Pauline; Thuroczy, Gyorgy; de Seze, René; Cerri, Matteo; Bach, Véronique; Libert, Jean-Pierre; Loos, Nathalie

2012-11-10

75

47 CFR 1.1310 - Radiofrequency radiation exposure limits.  

Code of Federal Regulations, 2010 CFR

...radiofrequency (RF) radiation as specified...Guidelines for Human Exposure to Radiofrequency Radiation.â Note to...National Council on Radiation Protection and...Biological Effects and Exposure...Radiofrequency Electromagnetic Fields...with Respect to Human Exposure to...

2010-10-01

76

47 CFR 1.1310 - Radiofrequency radiation exposure limits.  

Code of Federal Regulations, 2010 CFR

...radiofrequency (RF) radiation as specified...Guidelines for Human Exposure to Radiofrequency Radiation.â Note to...National Council on Radiation Protection and...Biological Effects and Exposure...Radiofrequency Electromagnetic Fields...with Respect to Human Exposure to...

2009-10-01

77

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

Microsoft Academic Search

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

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

1988-01-01

78

p25/CDK5 is partially involved in neuronal injury induced by radiofrequency electromagnetic field exposure.  

PubMed

Abstract Purpose: Several studies suggest that radiofrequency electromagnetic field (RF-EMF) exposure can induce neuronal injury. The aim of the present work was to investigate whether the cyclin-dependent kinase 5 (CDK5) pathway is involved in neuronal injury induced by RF-EMF exposure. Materials and methods: Newborn Sprague-Dawley rats' primary cultured cortical neurons were exposed to pulsed 2.45 GHz RF-EMF for 10 min. The cellular viability was assessed using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The apoptosis was assessed by Hoechst 33342 and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling co-staining. The protein expressions of CDK5, p35, p25, and phosphorylated tau at Ser(404) were examined by Western blot analysis. The CDK5 activity was detected using a histone-H1 kinase assay. Results: The cellular viability of neurons was significantly decreased (p < 0.01, Partial Eta Squared [?p(2)]: 0.554), and the percentage of apoptotic nuclei (p < 0.01, ?p(2) = 0.689), activity of CDK5 (p < 0.05, ?p(2) = 0.589), ratio of p25 and p35 (p < 0.05, ?p(2 =) 0.670), levels of tau phosphorylation at Ser(404) (p < 0.01, ?p(2) = 0.896) were significantly increased after RF-EMF exposure. No significant change was detected in CDK5 expression after RF-EMF exposure. Pretreatment with Roscovitine (a CDK5 inhibitor) significantly blocked the RF-EMF-induced decrease of cellular viability (p < 0.05, ?p(2) = 0.398) and tau hyperphosphorylation at Ser(404) (p < 0.01, ?p(2 =) 0.917), but did not significantly block the RF-EMF-induced apoptosis (p > 0.05, ?p(2) = 0.130). Conclusions: These results suggest that abnormal activity of p25/CDK5 is partially involved in primary cultured cortical neuron injury induced by RF-EMF exposure. PMID:23786497

Zhang, Yanwen; She, Fei; Li, Li; Chen, Chunhai; Xu, Shangcheng; Luo, Xue; Li, Min; He, Mindi; Yu, Zhengping

2013-07-29

79

Non-ionizing radiation protection training manual for radiation control. Lectures, demonstrations, laboratories and tours on the course on non-ionizing radiations. Final report  

Microsoft Academic Search

In late 1974, consultation with the National Training Coordination Committee of the Conference of Radiation Control Program Directors determined that State personnel needed training in order to fulfill their responsibility with respect to the growing number of non-ionizing radiation sources. A contract was awarded to the Georgia Institute of Technology to develop materials for a training program on non-ionizing radiation

K. Z. Morgan; R. L. Burkhart

1976-01-01

80

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

81

EDITORIAL: The interaction of radio-frequency fields with fusion plasmas: the JET experience The interaction of radio-frequency fields with fusion plasmas: the JET experience  

NASA Astrophysics Data System (ADS)

The JET Task Force Heating is proud to present this special issue. It is the result of hard and dedicated work by everybody participating in the Task Force over the last four years and gives an overview of the experimental and theoretical results obtained in the period 2008-2010 with radio frequency heating of JET fusion plasmas. Topics studied and reported in this issue are: investigations into the operation of lower hybrid heating accompanied by new modeling results; new experimental results and insights into the physics of various ion cyclotron range of frequencies (ICRF) heating scenarios; progress in studies of intrinsic and ion cyclotron wave-induced plasma rotation and flows; a summary of the developments over the last years in designing an ion cyclotron radiofrequency heating (ICRH) system that can cope with the presence of fast load variations in the edge, as e.g. caused by pellets or edge localized modes (ELMs) during H-Mode operation; an overview of the results obtained with the ITER-like antenna operating in H-Mode with a packed array of straps and power densities close to those of the projected ITER ICRH antenna; and, finally, a summary of the results obtained in applying ion cyclotron waves for wall conditioning of the tokamak. This issue would not have been possible without the strong motivation and efforts (sometimes truly heroic) of all colleagues of the JET Task Force Heating. A sincere word of thanks, therefore, to all authors and co-authors involved in the experiments, analysis and compilation of the papers. It was a special privilege to work with all of them during the past very intense years. Thanks also to all other European and non-European scientists who contributed to the JET scientific programme, the operations team of JET and the colleagues of the Close Support Unit in Culham. Thanks also to the editors, Editorial Board and referees of Plasma Physics and Controlled Fusion, together with the publishing staff of IOPP, who have not only supported but also contributed very substantially to this initiative. Without their dedication this issue would not have been possible in its present form. A special word of thanks to Marie-Line Mayoral and Joelle Mailloux for their precious help and very active support in running the JET Task Force Heating over the last years. Without Joelle and Marie-Line itwould have been a much more daunting task to prepare JET operations, monitor progress during the experiments and edit the papers that are compiled here.

Ongena, Jef

2012-07-01

82

Effects of micro- and macro-plasma-sheath electric fields on carbon nanotube growth in a cross-field radio-frequency discharge  

SciTech Connect

Effects of magnetic-field introduction and micro/macroelectric fields in a plasma sheath on the carbon nanotube growth are investigated by employing a cylindrical magnetron-type radio-frequency (rf) plasma-enhanced chemical-vapor deposition method. The cross-field magnetic-field application is accompanied by the high-density plasma generation and the reduction of direct impinge of high-energy ions to a rf electrode substrate, achieving the carbon nanotube formation without harmful sputtering phenomenon. It is found that microelectric fields in the plasma sheath are useful in the sense of substrate pretreatment and macroelectric fields have to be optimized in order to obtain well-aligned and refined nanotube structures in a large area. These experimental results lead to putting into practice of quite simple methods for the site-selected carbon nanotube growth in a relatively large area, so-called substrate-scratching method and mesh-masking method.

Hatakeyama, R.; Jeong, G.-H.; Kato, T.; Hirata, T. [Department of Electronic Engineering, Tohoku University, Sendai 980-8579 (Japan)

2004-12-01

83

Radio-Frequency, Atmospheric-Pressure Glow Discharges: Producing Methods, Characteristics and Applications in Bio-Medical Fields  

NASA Astrophysics Data System (ADS)

Radio-frequency (RF), atmospheric-pressure glow discharge (APGD) plasmas with bare metallic electrodes have shown their promising prospects in different fields. In this paper, based on the induced gas discharge approach, the discharge characteristics of RF, APGD plasmas using helium/oxygen mixture as the plasma working-gas are presented. The bio-medical effects of the helium RF APGD plasma jet acting on the gfp DNA and E. coli are also reported. Studies concerning the lethal and sub-lethal effects of the RF APGDs on the molecular and cell levels, which are related with the characteristics of the plasmas and their operation conditions are necessary in the future work based on a closer cooperation between the researchers in the field of the plasma science & technology and of the bio-medical science.

Li, He-Ping; Li, Guo; Sun, Wen-Ting; Wang, Sen; Bao, Cheng-Yu; Wang, Liyan; Huang, Ziliang; Ding, Nan; Zhao, Hongxin; Xing, Xin-Hui

2008-02-01

84

Water dissociation in a radio-frequency electromagnetic field with ex situ electrodes—modelling of discharge initiation  

NASA Astrophysics Data System (ADS)

Applying a new experimental design with a capillary glass reactor and plate electrodes outside of the reactor allowed the initiation of discharges in aqueous electrolytes under the influence of a radio-frequency (RF) electromagnetic field. This study focused on the mechanism leading to the initiation of such discharges in the restriction of a glass tube. The light emission correlated with discharges was analysed with optical emission spectroscopy. Electrons with energies between 20 and 45 eV were responsible for the dissociation of water molecules into (excited) OH, H and O radicals. Current-voltage characteristics were measured before and under discharge conditions. Modelling of the experimental setup and simulation of electrical field strength distribution support the hypothesis of the origin of discharges in general and experimental findings such as ring-shaped discharges and a minimum solution conductivity of about 1 S m-1 required for discharge initiation with RF voltages of 2 kV.

Schneider, Jens; Holzer, Frank; Rabe, Carsten; Häupl, Tilmann; Kopinke, Frank-Dieter; Roland, Ulf

2013-04-01

85

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

2012-12-31

86

[Dependence of the non-thermal radiofrequency electromagnetic field bioeffects on the typological features of electroencephalogram in humans].  

PubMed

In researches with participation of volunteers bioeffects of short-term non-thermal radiofrequency electromagnetic field (RF EMF) exposure were studied. The basic form of brain's reaction was the amplification of energy in a-range in electroencephalogram (EEG) spectra. Dependence of these changes, not only due to the changes of the exposure parameters, but also due to personal EEG typological features was shown. Moderate degree of the alpha frequencies domination in the background promoted development of reaction of a brain to the RF EMF exposure. To a lesser degree it was shown at hyperactivity of this range and, practically, was absent in the conditions of theta- or beta2-range domination in the EEG background with the open and closed eyes. The combination of RF EMF exposure and monotonous activity has authentically strengthened result, keeping the basic form of reaction (energy amplification in the alpha range of EEG spectrum) and dependence on EEG typological features. PMID:21434398

Luk'ianova, S N; Grigor'ev, Iu G; Grigor'ev, O A; Merkulov, A V

87

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

88

Biophysical evaluation of radiofrequency electromagnetic field effects on male reproductive pattern.  

PubMed

There are possible hazardous health effects of exposure to radiofrequency electromagnetic radiations emitted from mobile phone on the human reproductive pattern. It is more effective while keeping mobile phones in pocket or near testicular organs. Present review examines the possible concern on radio frequency radiation interaction and biological effects such as enzyme induction, and toxicological effects, including genotoxicity and carcinogenicity, testicular cancer, and reproductive outcomes. Testicular infertility or testicular cancer due to mobile phone or microwave radiations suggests an increased level of reactive oxygen species (ROS). Though generation of ROS in testis has been responsible for possible toxic effects on physiology of reproduction, the reviews of last few decades have well established that these radiations are very harmful and cause mutagenic changes in reproductive pattern and leads to infertility. The debate will be focused on bio-interaction mechanism between mobile phone and testicular cancer due to ROS formation. This causes the biological damage and leads to several changes like decreased sperm count, enzymatic and hormonal changes, DNA damage, and apoptosis formation. In the present review, physics of mobile phone including future research on various aspects has been discussed. PMID:22926544

Kesari, Kavindra Kumar; Kumar, Sanjay; Nirala, Jayprakash; Siddiqui, Mohd Haris; Behari, Jitendra

2013-03-01

89

Luciferase-based protein-denaturation assay for quantification of radiofrequency field-induced targeted hyperthermia: developing an intracellular thermometer  

PubMed Central

Background Several studies have reported targeted hyperthermia at the cellular level using remote activation of nanoparticles by radiofrequency waves. To date, methods to quantify intracellular thermal dose have not been reported. In this report we study the relationship between radio wave exposure and luciferase denaturation with and without intracellular nanoparticles. The findings are used to devise a strategy to quantify targeted thermal dose in a primary human liver cancer cell line. Methods Water-bath or non-invasive external RF generator (600W, 13.56 MHz) was used for hyperthermia exposures. Luciferase activity was measured using a bioluminescence assay and viability was assessed using Annexin V-FITC and Propidium iodide staining. Heat shock proteins were analyzed using western-blot analysis Results Duration-dependent luciferase denaturation was observed in SNU449 cells exposed to RF field that preceded measurable loss in viability. Loss of luciferase activity was higher in cetuximab-conjugated gold nanoparticle (C225-AuNP) treated cells. Using a standard curve from water-bath experiments, the intracellular thermal dose was calculated. Cells treated with C225-AuNP accumulated 6.07 times higher intracellular thermal dose than the untreated controls over initial 4 minutes of RF exposure. Conclusions Cancer cells when exposed to an external RF field exhibit dose-dependent protein denaturation. Luciferase denaturation assay can be used to quantify thermal dose delivered after RF exposures to cancer cells with and without nanoparticles.

Raoof, Mustafa; Zhu, Cihui; Kaluarachchi, Warna D.; Curley, Steven A.

2013-01-01

90

Effects of 1.8 GHz radiofrequency field on DNA damage and expression of heat shock protein 70 in human lens epithelial cells  

Microsoft Academic Search

To investigate the DNA damage, expression of heat shock protein 70 (Hsp70) and cell proliferation of human lens epithelial cells (hLEC) after exposure to the 1.8GHz radiofrequency field (RF) of a global system for mobile communications (GSM). An Xc-1800 RF exposure system was used to employ a GSM signal at 1.8GHz (217Hz amplitude-modulated) with the output power in the specific

Sun Lixia; Ke Yao; Wang Kaijun; Lu Deqiang; Hu Huajun; Gao Xiangwei; Wang Baohong; Zheng Wei; Lou Jianling; Wu Wei

2006-01-01

91

ROS release and Hsp70 expression after exposure to 1,800 MHz radiofrequency electromagnetic fields in primary human monocytes and lymphocytes  

Microsoft Academic Search

The aim of this study is to investigate if 1,800 MHz radiofrequency electromagnetic fields (RF-EMF) can induce reactive oxygen species (ROS) release and\\/or changes in heat shock protein 70 (Hsp70) expression in human blood cells, using different exposure and co-exposure conditions. Human umbilical cord blood-derived monocytes and lymphocytes were used to examine ROS release after exposure to continuous wave or different

M. Lantow; M. Lupke; J. Frahm; M. O. Mattsson; N. Kuster; M. Simko

2006-01-01

92

Impact of one's own mobile phone in stand-by mode on personal radiofrequency electromagnetic field exposure.  

PubMed

When moving around, mobile phones in stand-by mode periodically send data about their positions. The aim of this paper is to evaluate how personal radiofrequency electromagnetic field (RF-EMF) measurements are affected by such location updates. Exposure from a mobile phone handset (uplink) was measured during commuting by using a randomized cross-over study with three different scenarios: disabled mobile phone (reference), an activated dual-band phone and a quad-band phone. In the reference scenario, uplink exposure was highest during train rides (1.19?mW/m(2)) and lowest during car rides in rural areas (0.001?mW/m(2)). In public transports, the impact of one's own mobile phone on personal RF-EMF measurements was not observable because of high background uplink radiation from other people's mobile phone. In a car, uplink exposure with an activated phone was orders of magnitude higher compared with the reference scenario. This study demonstrates that personal RF-EMF exposure is affected by one's own mobile phone in stand-by mode because of its regular location update. Further dosimetric studies should quantify the contribution of location updates to the total RF-EMF exposure in order to clarify whether the duration of mobile phone use, the most common exposure surrogate in the epidemiological RF-EMF research, is actually an adequate exposure proxy. PMID:23093102

Urbinello, Damiano; Röösli, Martin

2012-10-24

93

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. Bioelectromagnetics. 34:542-548. © 2013 Wiley Periodicals, Inc. PMID:23720062

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

2013-05-29

94

Combined functional data from multispectral non-ionizing and non-invasive brain imaging  

Microsoft Academic Search

Ongoing research during the past few years, envisions the development of an integrated functional imaging methodology to study brain function in-vivo and ex-vivo through a multi-modal, multi-spectral approach using non-ionizing radiation to provide combined functional information from molecule to tissue level. The scope of this research is threefold: (a) provide non-invasive, non-ionizing functional imaging comprising combined blood flow and neural

Irene S. Karanasiou

2009-01-01

95

Pulsed radiofrequency for chronic pain  

Microsoft Academic Search

Pulsed radiofrequency (PRF), a technology related to continuous radiofrequency, is unique in that it provides pain relief\\u000a without causing significant damage to nervous tissue. The mechanism by which PRF controls pain is unclear, but it may involve\\u000a a temperature-independent pathway mediated by a rapidly changing electrical field. Although much anecdotal evidence exists\\u000a in favor of PRF, there are few quality

David Byrd; Sean Mackey

2008-01-01

96

The light reflection from semiconductor heterostructures modulated by a double polarized radiofrequency field  

Microsoft Academic Search

An rf modulation optical spectroscopy method for the study of semiconductor heterostructures is suggested which employs the\\u000a effect of the light reflection coefficient modulation under the action of two rf fields with different configurations. The\\u000a dependence of the rf-modulated light reflection spectra at the fundamental absorption edge of a semiconductor on the rf field\\u000a polarization allows various layers of the

A. O. Volkov; O. A. Ryabushkin; M. S. Povolotskyi

2001-01-01

97

Model for initiation of quality factor degradation at high accelerating fields in superconducting radio-frequency cavities  

NASA Astrophysics Data System (ADS)

A model for the onset of the reduction in superconducting radio-frequency (SRF) cavity quality factor, the so-called Q-drop, at high accelerating electric fields is presented. Since magnetic fields at the cavity equator are tied to accelerating electric fields by a simple geometric factor, the onset of magnetic flux penetration determines the onset of Q-drop. We consider breakdown of the surface barrier at triangular grooves to predict the magnetic field of first flux penetration Hpen. Such defects were argued to be the worst case by Buzdin and Daumens (1998 Physica C 294 257), whose approach, moreover, incorporates both the geometry of the groove and local contamination via the Ginzburg-Landau parameter ?. Since previous Q-drop models focused on either topography or contamination alone, the proposed model allows new comparisons of one effect in relation to the other. The model predicts equivalent reduction of Hpen when either roughness or contamination were varied alone, so smooth but dirty surfaces limit cavity performance about as much as rough but clean surfaces do. Still lower Hpen was predicted when both effects were combined, i.e. contamination should exacerbate the negative effects of roughness and vice versa. To test the model with actual data, coupons were prepared by buffered chemical polishing and electropolishing, and stylus profilometry was used to obtain distributions of angles. From these data, curves for surface resistance generated by simple flux flow as a function of magnetic field were generated by integrating over the distribution of angles for reasonable values of ?. This showed that combined effects of roughness and contamination indeed reduce the Q-drop onset field by ~ 20%, and that contamination contributes to Q-drop as much as roughness. The latter point may be overlooked by SRF cavity research, since access to the cavity interior by spectroscopy tools is very difficult, whereas optical images have become commonplace. The model was extended to fit cavity test data, which indicated that reduction of the superconducting gap by contaminants may also play a role in Q-drop.

Dzyuba, A.; Romanenko, A.; Cooley, L. D.

2010-12-01

98

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.

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

99

Genotoxic effects of exposure to radiofrequency electromagnetic fields (RF-EMF) in HL-60 cells are not reproducible.  

PubMed

Conflicting results have been published regarding the induction of genotoxic effects by exposure to radiofrequency electromagnetic fields (RF-EMF). Various results indicating a genotoxic potential of RF-EMF were reported by the collaborative EU-funded REFLEX (Risk Evaluation of Potential Environmental Hazards From Low Energy Electromagnetic Field Exposure Using Sensitive in vitro Methods) project. There has been a long-lasting scientific debate about the reliability of the reported results and an attempt to reproduce parts of the results obtained with human fibroblasts failed. Another part of the REFLEX study was performed in Berlin with the human lymphoblastoid cell line HL-60; genotoxic effects of RF-EMF were measured by means of the comet assay and the micronucleus test. The plausibility and reliability of these results were also questioned. In order to contribute to a clarification of the biological significance of the reported findings, a repeat study was performed, involving scientists of the original study. Comet-assay experiments and micronucleus tests were performed under the same experimental conditions that had led to genotoxic effects in the REFLEX study. Here we report that the attempts to reproduce the induction of genotoxic effects by RF-EMF in HL-60 cells failed. No genotoxic effects of RF-EMF were measured in the repeat experiments. We could not find an explanation for the conflicting results. However, the negative repeat experiments suggest that the biological significance of genotoxic effects of RF-EMF reported by the REFLEX study should be re-assessed. PMID:23817106

Speit, Günter; Gminski, Richard; Tauber, Rudolf

2013-06-28

100

Detection of radio-frequency magnetic fields using nonlinear magneto-optical rotation  

SciTech Connect

We describe a room-temperature alkali-metal atomic magnetometer for detection of small, high-frequency magnetic fields. The magnetometer operates by detecting optical rotation due to the precession of an aligned ground state in the presence of a small oscillating magnetic field. The resonance frequency of the magnetometer can be adjusted to any desired value by tuning the bias magnetic field. Based on experimentally measured signal-to-noise ratio, we demonstrate a sensitivity of 100 pG/{radical}(Hz) (rms) in a 3.5-cm-diameter paraffin coated cell. Assuming detection at the photon shot-noise limit, we project a sensitivity as low as 25 pG/{radical}(Hz) (rms)

Ledbetter, M. P.; Acosta, V. M.; Rochester, S. M.; Budker, D.; Pustelny, S.; Yashchuk, V. V. [Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300 (United States); Centrum Badan Magnetooptycznych, Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, Reymonta 4, 30-059 Krakow (Poland); Advanced Light Source Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2007-02-15

101

Influence of radio-frequency electromagnetic field on optical characteristics of cast-iron surface  

NASA Astrophysics Data System (ADS)

Variations in spectral coefficients of specular reflection and Raman scattering spectra were detected during exposure of a cast-iron surface to an electromagnetic field in the radio-wave range. The observed variations were supposed to be caused by both field-induced changes in the surface morphological structure, density, and crystalline state and ordering of the carbon structures accompanied by a reduction in the amount of defects. Spectral reflectometry and Raman scattering methods were shown to be applicable to nondestructive remote monitoring of the morphological state of the cast-iron surface and changes in the structure and size of its microcrystalline graphite inclusions.

Azharonok, V. V.; Krat'koa, L. E.; Anisovich, A. G.; Bislukb, L. V.

2012-11-01

102

1H nutation experiments under low-amplitude radiofrequency fields. Quantitative analysis of a complex NMR signal arising from water in clays and including a Pake doublet.  

PubMed

It is shown theoretically and experimentally that, under weak radiofrequency (RF) field conditions, nutation frequency depends on relaxation times. The Fourier transform of a nutation curve, which is obtained by plotting signal amplitude as a function of RF field application time, yields separate bands corresponding to the components of an unresolved composite signal. This can be effectively achieved provided that these components possess different relaxation characteristics. Using proton nuclear magnetic resonance, this new method is applied to the study of water in clays and leads to the proportion of different types of water. The case where one water species appears in the form of a Pake doublet is considered. PMID:17466779

Trausch, Grégory; Canet, Daniel

2007-01-16

103

Water dissociation in a radio-frequency electromagnetic field with ex situ electrodes—process characterization  

NASA Astrophysics Data System (ADS)

A new type of water dissociation at ambient pressure initiated by the irradiation of aqueous electrolytes using an electromagnetic field with a frequency of 13.56 MHz is described in this study. A special reactor design allows the use of ex situ electrodes to form in situ electrical discharges in water vapour bubbles. The observed formation of molecular hydrogen (H2) and oxygen (O2) combined with the emission of light (‘burning water’ phenomenon) originates from a non-thermal plasma in water vapour bubbles. The influences of type of electrolyte, its concentration, pH value and external RF voltage on the gas formation rate as well as on the gas composition are presented.

Schneider, Jens; Holzer, Frank; Kraus, Markus; Kopinke, Frank-Dieter; Roland, Ulf

2013-02-01

104

Conduct of a personal radiofrequency electromagnetic field measurement study: proposed study protocol  

PubMed Central

Background The development of new wireless communication technologies that emit radio frequency electromagnetic fields (RF-EMF) is ongoing, but little is known about the RF-EMF exposure distribution in the general population. Previous attempts to measure personal exposure to RF-EMF have used different measurement protocols and analysis methods making comparisons between exposure situations across different study populations very difficult. As a result, observed differences in exposure levels between study populations may not reflect real exposure differences but may be in part, or wholly due to methodological differences. Methods The aim of this paper is to develop a study protocol for future personal RF-EMF exposure studies based on experience drawn from previous research. Using the current knowledge base, we propose procedures for the measurement of personal exposure to RF-EMF, data collection, data management and analysis, and methods for the selection and instruction of study participants. Results We have identified two basic types of personal RF-EMF measurement studies: population surveys and microenvironmental measurements. In the case of a population survey, the unit of observation is the individual and a randomly selected representative sample of the population is needed to obtain reliable results. For microenvironmental measurements, study participants are selected in order to represent typical behaviours in different microenvironments. These two study types require different methods and procedures. Conclusion Applying our proposed common core procedures in future personal measurement studies will allow direct comparisons of personal RF-EMF exposures in different populations and study areas.

2010-01-01

105

Theranostic applications: Non-ionizing cellular and molecular imaging through innovative nanosystems for early diagnosis and therapy  

PubMed Central

Modern medicine is expanding the possibilities of receiving “personalized” diagnosis and therapies, providing minimal invasiveness, technological solutions based on non-ionizing radiation, early detection of pathologies with the main objectives of being operator independent and with low cost to society. Our research activities aim to strongly contribute to these trends by improving the capabilities of current diagnostic imaging systems, which are of key importance in possibly providing both optimal diagnosis and therapies to patients. In medical diagnostics, cellular imaging aims to develop new methods and technologies for the detection of specific metabolic processes in living organisms, in order to accurately identify and discriminate normal from pathological tissues. In fact, most diseases have a “molecular basis” that detected through these new diagnostic methodologies can provide enormous benefits to medicine. Nowadays, this possibility is mainly related to the use of Positron Emission Tomography, with an exposure to ionizing radiation for patients and operators and with extremely high medical diagnostics costs. The future possible development of non-ionizing cellular imaging based on techniques such as Nuclear Magnetic Resonance or Ultrasound, would represent an important step towards modern and personalized therapies. During the last decade, the field of nanotechnology has made important progress and a wide range of organic and inorganic nanomaterials are now available with an incredible number of further combinations with other compounds for cellular targeting. The availability of these new advanced nanosystems allows new scenarios in diagnostic methodologies which are potentially capable of providing morphological and functional information together with metabolic and cellular indications.

Casciaro, Sergio

2011-01-01

106

Characteristics of Electron Conduction in a Gas under a Quadrupole Magnetic Field and Radio-Frequency Electric Fields  

NASA Astrophysics Data System (ADS)

Electron conduction in CF4 under a simplified model quadrupole magnetic field (QMF) and rf electric fields at f = 13.56, 27.12, and 40.68 MHz was analyzed using a Monte Carlo method, following the manner of electron swarm analyses. This field configuration simulated current paths of magnetic neutral loop discharge plasmas used for dry etching. The electron conduction therein was focused on as an elemental process of plasma power deposition. The electrons formed a star-shaped distribution with four rays along the separatrices of the QMF. The effective electron conductivity quantified as the amplitude of mean electron velocity was high around the central axis. The time-averaged mean electron velocities in the four regions of the QMF were biased under a rectification effect of the magnetic field. With increasing f, the high-conductivity region expanded and ionization was promoted. An enhancement of plasma power deposition under high driving frequencies was indicated.

Sugawara, Hirotake

2013-05-01

107

GPU-accelerated FDTD modeling of radio-frequency field-tissue interactions in high-field MRI.  

PubMed

The analysis of high-field RF field-tissue interactions requires high-performance finite-difference time-domain (FDTD) computing. Conventional CPU-based FDTD calculations offer limited computing performance in a PC environment. This study presents a graphics processing unit (GPU)-based parallel-computing framework, producing substantially boosted computing efficiency (with a two-order speedup factor) at a PC-level cost. Specific details of implementing the FDTD method on a GPU architecture have been presented and the new computational strategy has been successfully applied to the design of a novel 8-element transceive RF coil system at 9.4?T. Facilitated by the powerful GPU-FDTD computing, the new RF coil array offers optimized fields (averaging 25% improvement in sensitivity, and 20% reduction in loop coupling compared with conventional array structures of the same size) for small animal imaging with a robust RF configuration. The GPU-enabled acceleration paves the way for FDTD to be applied for both detailed forward modeling and inverse design of MRI coils, which were previously impractical. PMID:21335302

Chi, Jieru; Liu, Feng; Weber, Ewald; Li, Yu; Crozier, Stuart

2011-02-17

108

Measurement and analysis of radiofrequency radiations from some mobile phone base stations in Ghana.  

PubMed

A survey of the radiofrequency electromagnetic radiation at public access points in the vicinity of 50 cellular phone base stations has been carried out. The primary objective was to measure and analyse the electromagnetic field strength levels emitted by antennae installed and operated by the Ghana Telecommunications Company. On all the sites measurements were made using a hand-held spectrum analyser to determine the electric field level with the 900 and 1800 MHz frequency bands. The results indicated that power densities at public access points varied from as low as 0.01 microW m(-2) to as high as 10 microW m(-2) for the frequency of 900 MHz. At a transmission frequency of 1800 MHz, the variation of power densities is from 0.01 to 100 microW m(-2). The results were found to be in compliant with the International Commission on Non-ionizing Radiological Protection guidance level but were 20 times higher than the results generally obtained for such a practice elsewhere. There is therefore a need to re-assess the situation to ensure reduction in the present level as an increase in mobile phone usage is envisaged within the next few years. PMID:19584141

Amoako, J K; Fletcher, J J; Darko, E O

2009-07-07

109

Radiofrequency-induced Heating near Fixed Orthodontic Appliances in High Field MRI Systems at 3.0 Tesla  

Microsoft Academic Search

\\u000a Abstract\\u000a \\u000a \\u000a Objective:\\u000a   To assess radiofrequency (RF)-induced heating of\\u000a fixed orthodontic appliances during acquisition of three different\\u000a sequences in magnetic resonance imaging (MRI) at 3 Tesla.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and Methods:\\u000a   Ten commonly used fixed orthodontic\\u000a appliances were investigated utilizing a phantom head and simulating\\u000a the in vivo intraoral situation. A 3 Tesla MRI system (Intera,\\u000a Philips Medical Systems, Best, The Netherlands) was

Marc Regier; Jörn Kemper; Michael G. Kaul; Markus Feddersen; Gerhard Adam; Bärbel Kahl-Nieke; Arndt Klocke

2009-01-01

110

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

111

Application of amplitude-modulated radiofrequency fields to the magic-angle spinning NMR of spin-7/2 nuclei  

NASA Astrophysics Data System (ADS)

We report pulse sequences for the sensitivity enhancement of magic-angle spinning and multiple-quantum magic-angle spinning spectra of spin-7/2 systems. Sensitivity enhancement is obtained with the use of fast amplitude-modulated (FAM) radiofrequency pulses. In one-dimensional magic-angle spinning experiments, signal enhancement of 3 is obtained by a FAM pulse followed by a soft 90° pulse. In two-dimensional multiple-quantum magic-angle spinning experiments, FAM pulses are used for both the excitation of multiple-quantum coherences and for their conversion into observable single-quantum coherences. The observed signal enhancements are 2.2 in 3Q experiments, 3.1 in 5Q experiments, and 4.1 in 7Q experiments, compared to the conventional two-pulse scheme. The pulse schemes are demonstrated on the 45Sc NMR of Sc2(SO4)3/.5H2O and the 139La NMR of LaAlO3. We also demonstrate the generation of FAM pulses by double-frequency irradiation.

Madhu, P. K.; Johannessen, Ole G.; Pike, Kevin J.; Dupree, Ray; Smith, Mark E.; Levitt, Malcolm H.

2003-08-01

112

Effects of magnetic field on pulse wave forms in plasma immersion ion implantation in a radio-frequency, inductively coupled plasma  

NASA Astrophysics Data System (ADS)

The time-dependent current wave forms measured using a pulse biased planar electrode in hydrogen radio-frequency (rf), inductively coupled plasma, plasma immersion ion implantation experiments are observed to vary in the presence of an external magnetic field B. Results further indicate that the magnitude of the pulse current is related to the strength and direction of the magnetic field, rf power, and pressure, but the pulse current curves can be primarily correlated with B. The plasma discharges are enhanced in all cases due to magnetic confinement of the electrons, enlargement of the plasma generation volume, and increase in the rf power absorbing efficiency. The plasma density diagnosed by Langmuir probe diminishes in front of the sample chuck with B, whereas the plasma is confined nearby the sidewall of the vacuum chamber at high magnetic field. The high degree of plasma density nonuniformity at high B in front of the sample chuck is not desirable for the processing of planar samples such as silicon wafers and must be compensated. The reduction in the plasma density and plasma density gradient in the sheath can be accounted for by the changes in the pulse current wave forms.

Tong, Honghui; Fu, Ricky K. Y.; Tang, Deli; Zeng, Xuchu; Chu, Paul K.

2002-09-01

113

Radiofrequency and microwave radiation  

SciTech Connect

This paper deals with the controversy and disagreement surrounding the issue of harm from radiofrequency (RF) and microwaves. The radiation standards adopted by different countries are quite divergent with the least strict standard for microwave exposure differing from the most strict by a factor of 100. Among the most powerful sources of RF and microwave radiation are radar systems used for tracking and guidance purposes, as well as transmiters used in satellite communication systems. RF and microwaves are nonionizing because the energy of each photon is relatively low. Biological systems exposed to RF and microwaves acquire induced electric and magnetic fields which can be focused by a combination of high refractive index within an animal and convex body contours. The effects on animals and humans are summarized. (KRM)

Hileman, B.

1982-08-01

114

Sensitive model with which to detect athermal effects of non-ionizing electromagnetic radiation  

SciTech Connect

To clarify the potential of non-ionizing electromagnetic radiation to cause biological effects by athermal mechanisms, and to initiate elucidation of those mechanisms, a model system amenable to scrutiny at the molecular level has been designed and characterized. Assessment of beta-galactosidase activity in E. coli JM101 containing the plasmid pUC8 provides a sensitive assay with many important advantages. The ability to examine at the molecular level each of the processes involved in producing beta-galactosidase should permit elucidation of the molecular mechanism(s) that give rises to an observed effect.

Saffer, J.D.; Profenno, L.A. (Jackson Laboratory, Bar Harbor, ME (USA))

1989-01-01

115

Increased protein synthesis by cells exposed to a 1,800-MHz radio-frequency mobile phone electromagnetic field, detected by proteome profiling  

PubMed Central

Purpose To investigate whether or not low intensity radio frequency electromagnetic field exposure (RF-EME) associated with mobile phone use can affect human cells, we used a sensitive proteome analysis method to study changes in protein synthesis in cultured human cells. Methods Four different cell kinds were exposed to 2 W/kg specific absorption rate in medium containing 35S-methionine/cysteine, and autoradiography of 2D gel spots was used to measure the increased synthesis of individual proteins. Results While short-term RF-EME did not significantly alter the proteome, an 8-h exposure caused a significant increase in protein synthesis in Jurkat T-cells and human fibroblasts, and to a lesser extent in activated primary human mononuclear cells. Quiescent (metabolically inactive) mononuclear cells, did not detectably respond to RF-EME. Since RF exposure induced a temperature increase of less than 0.15°C, we suggest that the observed cellular response is a so called “athermal” effect of RF-EME. Conclusion Our finding of an association between metabolic activity and the observed cellular reaction to low intensity RF-EME may reconcile conflicting results of previous studies. We further postulate that the observed increased protein synthesis reflects an increased rate of protein turnover stemming from protein folding problems caused by the interference of radio-frequency electromagnetic fields with hydrogen bonds. Our observations do not directly imply a health risk. However, vis-a-vis a synopsis of reports on cells stress and DNA breaks, after short and longer exposure, on active and inactive cells, our findings may contribute to the re-evaluation of previous reports. Electronic supplementary material The online version of this article (doi:10.1007/s00420-010-0513-7) contains supplementary material, which is available to authorized users.

Gerner, Christopher; Haudek, Verena; Schandl, Ulla; Bayer, Editha; Gundacker, Nina; Hutter, Hans Peter

2010-01-01

116

[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

117

A surprising answer in the search for a comprehensive health protection exposure metric for radiofrequency (RF) fields  

NASA Astrophysics Data System (ADS)

Matter can interact with light in 3 different ways (known by 1910): by absorption of energy [thermal hazard] or by absorption of linear momentum (radiation pressure) or of angular momentum (torque) or of both [nonthermal hazards].^1,2 The same is true for RF fields; indeed, microwave wattmeters may operate on a momentum absorption principle.^3,4 But most RF health protection standards today are based solely on thermal effects, ignoring nonthermal effects. Formal expressions for scientifically valid exposure metrics will be presented. It will be shown that nonthermal effects depend on field frequency, polarization and spatial configuration as well as on field strength, so a general metric valid for all fields may not exist. But with some approximations, the magnetic induction current may constitute an adequate practical exposure metric for RF fields. ^1M. Lundquist, BAPS 50(1):620(2005). ^2 M. Lundquist, BAPS 50(1):1178(2005). ^3A. L. Cullen, Proc. IEE 99Pt4(2):100-110(Apr 1952). ^4A. L. Cullen & I. M. Stephenson, Proc. IEE 99Pt4(4):294-301(Dec 1952).

Lundquist, Marjorie

2006-03-01

118

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

119

Association between exposure to radiofrequency electromagnetic fields assessed by dosimetry and acute symptoms in children and adolescents: a population based cross-sectional study  

PubMed Central

Background The increase in numbers of mobile phone users was accompanied by some concern that exposure to radiofrequency electromagnetic fields (RF EMF) might adversely affect acute health especially in children and adolescents. The authors investigated this potential association using personal dosimeters. Methods A 24-hour exposure profile of 1484 children and 1508 adolescents was generated in a population-based cross-sectional study in Germany between 2006 and 2008 (participation 52%). Personal interview data on socio-demographic characteristics, self-reported exposure and potential confounders were collected. Acute symptoms were assessed twice during the study day using a symptom diary. Results Only few of the large number of investigated associations were found to be statistically significant. At noon, adolescents with a measured exposure in the highest quartile during morning hours reported a statistically significant higher intensity of headache (Odd Ratio: 1.50; 95% confidence interval: 1.03, 2.19). At bedtime, adolescents with a measured exposure in the highest quartile during afternoon hours reported a statistically significant higher intensity of irritation in the evening (4th quartile 1.79; 1.23, 2.61), while children reported a statistically significant higher intensity of concentration problems (4th quartile 1.55; 1.02, 2.33). Conclusions We observed few statistically significant results which are not consistent over the two time points. Furthermore, when the 10% of the participants with the highest exposure are taken into consideration the significant results of the main analysis could not be confirmed. Based on the pattern of these results, we assume that the few observed significant associations are not causal but rather occurred by chance.

2010-01-01

120

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

121

A review of the effects of non-ionizing electromagnetic radiation on human body and exposure standards  

Microsoft Academic Search

Recent studies and investigations revealed that the effect of non-ionizing electromagnetic radiation on the human body may not be restricted to thermal effects only but it may help to explain some of the unsolved important biological activities to closely examine whether continuous or occupational exposure to electromagnetic radiation causes or aggravates any adverse health conditions, directly or indirectly. This paper

S. Mukhopadhyay; ASHIS SANYAL

1997-01-01

122

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

123

ROS release and Hsp70 expression after exposure to 1,800 MHz radiofrequency electromagnetic fields in primary human monocytes and lymphocytes.  

PubMed

The aim of this study is to investigate if 1,800 MHz radiofrequency electromagnetic fields (RF-EMF) can induce reactive oxygen species (ROS) release and/or changes in heat shock protein 70 (Hsp70) expression in human blood cells, using different exposure and co-exposure conditions. Human umbilical cord blood-derived monocytes and lymphocytes were used to examine ROS release after exposure to continuous wave or different GSM signals (GSM-DTX and GSM-Talk) at 2 W/kg for 30 or 45 min of continuous or intermittent (5 min ON/5 min OFF) exposure. The cells were exposed to incubator conditions, to sham, to RF-EMF, or to chemicals in parallel. Cell stimulation with the phorbol ester phorbol-12-myristate-13-acetate (PMA; 1 microM) was used as positive control for ROS release. To investigate the effects on Hsp70 expression, the human monocytes were exposed to the GSM-DTX signal at 2 W/kg for 45 min, or to heat treatment (42 degrees C) as positive control. ROS production and Hsp70 expression were determined by flow cytometric analysis. The data were compared to sham and/or to control values and the statistical analysis was performed by the Student's t-test (P<0.05). The PMA treatment induced a significant increase in ROS production in human monocytes and lymphocytes when the data were compared to sham or to incubator controls. After continuous or intermittent GSM-DTX signal exposure (2 W/kg), a significantly different ROS production was detected in human monocytes if the data were compared to sham. However, this significant difference appeared due to the lowered value of ROS release during sham exposure. In human lymphocytes, no differences could be detected if data were compared either to sham or to incubator control. The Hsp70 expression level after 0, 1, and 2 h post-exposure to GSM-DTX signal at 2 W/kg for 1 h did not show any differences compared to the incubator or to sham control. PMID:16552570

Lantow, M; Lupke, M; Frahm, J; Mattsson, M O; Kuster, N; Simko, M

2006-03-22

124

Hsp70 expression and free radical release after exposure to non-thermal radio-frequency electromagnetic fields and ultrafine particles in human Mono Mac 6 cells  

Microsoft Academic Search

The contemporary urban environment has become increasingly complex in its composition, leading to discussions regarding possible novel health effects. Two factors that recently have received considerable attention are ultrafine particles (UFP; <0.1?m) produced by combustion processes and emissions from wireless communication devices like mobile phones that emit in the radio-frequency (RF) part of the spectrum. Several studies have shown biological

M. Simkó; C. Hartwig; M. Lantow; M. Lupke; M.-O. Mattsson; Q. Rahman; J. Rollwitz

2006-01-01

125

Radiofrequency Ablation of Cancer  

Microsoft Academic Search

Radiofrequency ablation (RFA) has been used for over 18 years for treatment of nerve-related chronic pain and cardiac arrhythmias. In the last 10 years, technical developments have increased ablation volumes in a controllable, versatile, and relatively inexpensive manner. The host of clinical applications for RFA have similarly expanded. Current RFA equipment, techniques, applications, results, complications, and research avenues for local

Marc Friedman; Igor Mikityansky; Anthony Kam; Steven K. Libutti; McClellan M. Walther; Ziv Neeman; Julia K. Locklin; Bradford J. Wood

2004-01-01

126

Radiofrequency and microwave radiation  

Microsoft Academic Search

This paper deals with the controversy and disagreement surrounding the issue of harm from radiofrequency (RF) and microwaves. The radiation standards adopted by different countries are quite divergent with the least strict standard for microwave exposure differing from the most strict by a factor of 100. Among the most powerful sources of RF and microwave radiation are radar systems used

Hileman

1982-01-01

127

The study of the effects of ionizing and non-ionizing radiations on birth weight of newborns to exposed mothers  

PubMed Central

Objectives: Life evolved in an environment filled with a wide variety of ionizing and non-ionizing radiation. It was previously reported that medical exposures to pregnant women increases the risk of low birth weight. This study intends to investigate the relationship between exposure to ionizing and non-ionizing radiation and the risk of low birth weight. Materials and Methods: One thousand two hundred mothers with their first-term labor (vaginal or cesarean) whose newborns’ history had been registered in neonates’ screening program in Shiraz were interviewed and surveyed. Data collection was performed by the assessment of mother's history of radiography before and during pregnancy, physical examination of the mother for height and weight and weighing and examining the newborn for any diagnosis of disease and anomalies. Results: There were no statistical significant differences between the mean weight of newborns whose mothers had been exposed to some common sources of ionizing and non-ionizing radiations such as dental or non dental radiographies, mobile phone, cordless phone and cathode ray tube (CRT) and those of non-exposed mothers. Conclusions: The findings of this study cast doubt on previous reports, which indicated that exposure to ionizing radiation during pregnancy increased the risk of low birth weight.

Mortazavi, S. M. J.; Shirazi, K. R.; Mortazavi, G.

2013-01-01

128

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

129

[Osteoid osteoma and radiofrequency].  

PubMed

Osteoid osteoma and radiofrequency Osteoid osteoma relates to a benign skeletal neoplasm, smaller than 2 cm in diameter, composed of osteoid, highly vascularized connective tissue and surrounded by a ring of bone sclerosis. Its aetiology remains unknown. It affects twice more males than female patients and occurs usually between 5 and 40 years old. Long bones and spine are the most involved areas but the whole skeleton can be involved. Clinical manifestations can include local pain (increased at night and decreased by activity) and relief with salicylates administration. CT guided radiofrequency ablation of osteoid osteoma is in comparison to surgery less invasive, time saving and economic technique with excellent long term results. PMID:16429972

Theumann, N; Hauser, P; Schmidt, S; Schnyder, P; Leyvraz, P-F; Mouhsine, E

2005-12-21

130

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

Code of Federal Regulations, 2010 CFR

...2.1093 Radiofrequency radiation exposure evaluation: portable...Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz...by the National Council on Radiation Protection and Measurements...Criteria for Radiofrequency Electromagnetic Fields,â NCRP...

2009-10-01

131

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

Code of Federal Regulations, 2010 CFR

...2.1093 Radiofrequency radiation exposure evaluation: portable...Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz...by the National Council on Radiation Protection and Measurements...Criteria for Radiofrequency Electromagnetic Fields,â NCRP...

2010-10-01

132

Radiofrequency Ablation of Cancer  

SciTech Connect

Radiofrequency ablation (RFA) has been used for over 18 years for treatment of nerve-related chronic pain and cardiac arrhythmias. In the last 10 years, technical developments have increased ablation volumes in a controllable, versatile, and relatively inexpensive manner. The host of clinical applications for RFA have similarly expanded. Current RFA equipment, techniques, applications, results, complications, and research avenues for local tumor ablation are summarized.

Friedman, Marc; Mikityansky, Igor; Kam, Anthony [National Institutes of Health, Diagnostic Radiology Department, Special Procedures Division (United States); Libutti, Steven K. [National Cancer Institute, National Institutes of Health, Surgery Branch (United States); Walther, McClellan M. [National Cancer Institute, National Institutes of Health, Urologic Oncology Branch (United States); Neeman, Ziv; Locklin, Julia K.; Wood, Bradford J. [National Institutes of Health, Diagnostic Radiology Department, Special Procedures Division (United States)], E-mail: bwood@nih.gov

2004-09-15

133

Evaluation of non-ionizing radiation around the shortwave diathermy devices  

Microsoft Academic Search

Short wave and microwave equipment are used for treatment purpose in physiotherapy units. Such equipments' stray fields can affect around them in the near field region. This fact has been stressed in current studies. In this way, some \\

U. Ozen; S. Comlekci; O. Cerezci; A. U. Onural

2003-01-01

134

Radiofrequency exposure near high-voltage lines.  

PubMed Central

Many epidemiologic studies suggest a relationship between incidence of diseases like cancer and leukemia and exposure to 50/60 Hz magnetic fields. Some studies suggest a relationship between leukemia incidence in populations residing near high-voltage lines and the distance to these lines. Other epidemiologic studies suggest a relationship between leukemia incidence and exposure to 50/60 Hz magnetic fields (measured or estimated) and distance from the main system (220 or 120 V). The present work does not question these results but is intended to draw attention to a possible concurrent cause that might also increase the incidence of this disease; the presence on an electric grid of radiofrequency currents used for communications and remote control. These currents have been detected on high- and medium-voltage lines. In some cases they are even used on the main system for remote reading of electric meters. This implies that radiofrequency (RF) magnetic fields are present near the electric network in addition to the 50/60 Hz fields. This intensity of these RF fields is low but the intensity of currents induced in the human body by exposure to magnetic fields increases with frequency. Because scientific research has not yet clarified whether the risk is related to the value of magnetic induction or to the currents this kind of exposure produces in the human body, it is reasonable to suggest that the presence of the RF magnetic fields must be considered in the context of epidemiologic studies. Images Figure 3. Figure 4. Figure 5.

Vignati, M; Giuliani, L

1997-01-01

135

Radiofrequency exposure near high-voltage lines.  

PubMed

Many epidemiologic studies suggest a relationship between incidence of diseases like cancer and leukemia and exposure to 50/60 Hz magnetic fields. Some studies suggest a relationship between leukemia incidence in populations residing near high-voltage lines and the distance to these lines. Other epidemiologic studies suggest a relationship between leukemia incidence and exposure to 50/60 Hz magnetic fields (measured or estimated) and distance from the main system (220 or 120 V). The present work does not question these results but is intended to draw attention to a possible concurrent cause that might also increase the incidence of this disease; the presence on an electric grid of radiofrequency currents used for communications and remote control. These currents have been detected on high- and medium-voltage lines. In some cases they are even used on the main system for remote reading of electric meters. This implies that radiofrequency (RF) magnetic fields are present near the electric network in addition to the 50/60 Hz fields. This intensity of these RF fields is low but the intensity of currents induced in the human body by exposure to magnetic fields increases with frequency. Because scientific research has not yet clarified whether the risk is related to the value of magnetic induction or to the currents this kind of exposure produces in the human body, it is reasonable to suggest that the presence of the RF magnetic fields must be considered in the context of epidemiologic studies. PMID:9467084

Vignati, M; Giuliani, L

1997-12-01

136

Studies on the Effect of Radio-Frequency Waves in Biological Macromolecules.  

National Technical Information Service (NTIS)

The effect of radio-frequency electric fields on various biologic materials was examined. Particularly, the effects on alcohol dehydrogenase and DNA were carefully investigated. To avoid the effects of heating, a pulsed electric field was used, and sample...

S. Takashima

1965-01-01

137

[Instrumental radiofrequency electromagnetic radiation dosimetry: general principals and modern methodology].  

PubMed

The modern experimental radiofrequency electromagnetic field dosimetry approach has been considered. The main principles of specific absorbed rate measurement are analyzed for electromagnetic field biological effect assessment. The general methodology of specific absorbed rate automated dosimetry system applied to establish the compliance of radiation sources with the safety standard requirements (maximum permissible levels and base restrictions) is described. PMID:22891551

Perov, S Iu; Kudriashov, Iu B; Rubtsova, N B

138

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

139

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

140

Biological effects of non-ionizing radiations: cellular properties and interactions.  

PubMed

The Lauriston Taylor lectures honor the founder of the National Committee on Radiation Protection and Measurement, soon to be followed by the corresponding international organization. These standard setting bodies had a vast influence on proper recognition of radiation hazards. The 10th Taylor lecture is the first to deal with nonionizing radiations and may be, therefore, of particular interest to the bioengineer. During early history biophysics and bioengineering were primarily concerned with ionizing radiation bioeffects and electrophysiology. The nonionizing part of the radiation field and electrophysiology are closely related. Biomedical observation, biophysical and bioengineering efforts in the nonionizing radiation field are defined and complement each other. Topics concentrate on the relevant biophysical and bioengineering efforts of the author and his colleagues. They include: electrical properties of biological systems; established electrical field interactions (excitation, macromolecular responses and cellular responses); problems of dosimetry (macroscopic and microscopic considerations); conclusions about relative merits of various research approaches. PMID:3400907

Schwan, H P

1988-01-01

141

Questions and answers about biological effects and potential hazards of radiofrequency radiation (third edition)  

SciTech Connect

The Federal Communications Commission (FCC) is responsible for licensing or authorizing many of the transmitting devices in the United States that use radio-frequency (RF) radiation to provide a variety of important telecommunications services. Because of its responsibilities in this regard, the FCC often receives inquiries concerning potential health risks from exposure to the RF radiation emitted by these transmitters. The expanding use of RF technology has resulted in speculation concerning the alleged 'electromagnetic pollution' of the environment and the potential dangers of exposure to non-ionizing radiation. The publication is written in a question and answer format and is designed to provide factual information to the public by answering some of the most commonly asked questions about this complex and often misunderstood topic. Information is included on such topics as the differences between non-ionizing and ionizing radiation; the biological effects of RF energy; health and safety standards; federal responsibilities; and RF exposure from specific types of transmitters. The bulletin is an updated version of the previous (second) edition published in 1983.

Not Available

1989-01-01

142

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

Microsoft Academic Search

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

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

2007-01-01

143

24. IMPROVED TECHNIQUE FOR SIMPLIFYING STANDARDS-COMPLIANT TESTS OF NON-IONIZING ELECTROMAGNETIC RADIATION  

Microsoft Academic Search

Summary Typically the compliance with Standards for personal safety in electromagnetic fields under complex exposure situations was measured by experts with specific equipment. Recently, measuring instruments became more sophisticated. This enables also less educated staff to carry out the measurements. Inexperienced workers can be fitted with personal monitors. Ease of use was improved in three points. The frequency response shaping

Rainer Bitzer; Helmut Keller

144

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

145

Laser Initiation and Radiofrequency Sustainment of Seeded Air Plasmas  

NASA Astrophysics Data System (ADS)

Seeded gas plasmas and air constituents have been created by a 193 nm laser and radiofrequency sources. We have obtained 10^14/cm^3 plasma densities with initial electron temperatures of 0.3 eV in TMAE (tetrakis (dimethylamino) ethylene) by laser photoionization. We developed a fast Langmuir probe analysis of plasma decay independent of ion species mix. Langmuir probe and optical emission data illustrating the density and temperature decay with TMAE mixed with nitrogen is presented. Simulations of antenna coupling, wave frequencies, wave propagation, and power absorption are compared with experimental observations for radiofrequency plasma sources. The source produces plasma densities of 2 × 10^13/cm^3in an 8500 cm^3 volume at electron temperatures of 5 eV in 10 mTorr Ar in a nonuniform magnetic field. Radiofrequency plasma production at pressures from 2-760 Torr using Ar and laser initiated TMAE plasmas as seeds will be discussed.

Scharer, J.; Ding, G.; Gui, H.; Kelly, K.; Paller, E.

1999-11-01

146

Radiofrequency conical emission from femtosecond filaments in air  

SciTech Connect

We show that the broadband conical emission associated with filaments in air extends down to the radiofrequency region. This rf emission which originates from the longitudinal oscillation of charged ions formed during filamentation is strongly enhanced by the presence of a longitudinal static electric field.

Forestier, B.; Houard, A.; Durand, M.; Andre, Y. B.; Prade, B.; Mysyrowicz, A. [Laboratoire d'Optique Appliquee, ENSTA ParisTech, CNRS UMR 7639, Ecole Polytechnique, 91761 Palaiseau (France); Dauvignac, J.-Y.; Perret, F.; Pichot, Ch. [Laboratoire d'Electronique, Antennes et Telecommunications, CNRS UMR 6071, Universite Nice-Sophia Antipolis, 250 rue Albert Einstein, 06560 Valbonne (France); Pellet, M. [Ministere de la Defense, F-00457 Armees (France)

2010-04-05

147

Superconducting radiofrequency window assembly  

DOEpatents

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) is brazed to eyelet (50) which is then electron beam welded to frame (30). 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.

Phillips, Harry L. (Seaford, VA); Elliott, Thomas S. (Yorktown, VA)

1997-01-01

148

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 (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) is brazed to eyelet (50) which is then electron beam welded to frame (30). 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.

Phillips, Harry Lawrence (Seaford, VA); Elliott, Thomas S. (Yorktown, VA)

1998-01-01

149

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...

150

A Streamline-Upwind Petrov-Galerkin Finite Element Scheme for the Thermochemical Nonequilibrium Navier-Stokes Equations Part I: Non-Ionized Flows  

Microsoft Academic Search

This paper considers the streamline-upwind Petrov-Galerkin (SUPG) method applied to the thermochemical nonequilibrium Navier-Stokes equations in conservation-variable form. The governing equations for a non- ionized reacting mixture of perfect gases in thermal nonequilibrium are reviewed. The spatial discretization, time discretization, and solution scheme are briefly discussed. The performance of the formulation is then investigated by considering a number of classical

Benjamin S. Kirk; Steven W. Bova

151

Effects of ionizing and non-ionizing radiation on the growth and development of plants. Final report, May 1959November 1982  

Microsoft Academic Search

A summary of research to investigate the effects of ionizing and non-ionizing radiation on the growth and development of plants is presented. Included in this report are summaries of studies on the interaction of visible radiant energy with x-ray-induced chromosomal aberrations, an investigation of the biochemical and biophysical mechanisms by which plants detect and react to external radiation across the

1985-01-01

152

Computational modelling of temperature rises in the eye in the near field of radiofrequency sources at 380, 900 and 1800 MHz  

NASA Astrophysics Data System (ADS)

This paper reports calculations of the temperature rises induced in the eye and lens by near-field exposure to radiation from communication handsets, using the finite difference time domain method and classical bioheat equation. Various models are compared, including the analytic solution for a sphere, a finite element model of an isolated eye and a modern model of the whole head. The role of the blood supply to the choroid in moderating temperature is discussed. Three different frequencies are considered, namely 380 MHz (used by TETRA), and 900 and 1800 MHz (used by GSM mobile phones). At 380 MHz, monopole and helical antennas are compared. An 'equivalent blood flow' is derived for the choroid in order to facilitate comparison of the whole head and isolated eye models. In the whole head model, the heating of the lens receives a significant contribution from energy absorbed outside the eye. The temperature rise in the lens is compared to the ICNIRP-recommended average specific energy absorption rate (SAR) and the SAR averaged over the eye alone. The temperature rise may reach 1.4 °C at the ICNIRP occupational exposure limit if an antenna is placed less than 24 mm from the eye and the exposure is sufficiently prolonged.

Wainwright, P. R.

2007-07-01

153

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.

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

2013-01-01

154

Radiofrequency treatment of peripheral nerves.  

PubMed

Treatment of chronic refractory pain in which peripheral nerves are involved has proven to be difficult. Neurolysis by surgical, chemical, cryogenic, or thermal means may be considered as an option on seldom occasions, because of the risk of neuritis and deafferentation pain, motor deficit, and potential unintentional damage to nontargeted tissue. To our knowledge, there is only 1 report concerning selective radiofrequency (RF) treatment of the obturator and femoral nerves that was published. The introduction of the non-neurodestructive pulsed radiofrequency technique has provided new possibilities for the treatment of peripheral nerves. Today there is some experience with the management of chronic shoulder pain and additional case reports on other indications. PMID:17147740

Rohof, O J J M

2002-09-01

155

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

156

47 CFR 1.1310 - Radiofrequency radiation exposure limits.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Radiofrequency radiation exposure limits. 1.1310 Section...of 1969 § 1.1310 Radiofrequency radiation exposure limits. The criteria listed...human exposure to radiofrequency (RF) radiation as specified in §...

2012-10-01

157

Radiofrequency Tumor Ablation in Children  

Microsoft Academic Search

Percutaneous image-guided radiofrequency (RF) tumor ablation continues to gain momentum in adult patients as a viable and\\u000a effective therapeutic option in the treatment of solid tumors in a variety of locations including the skeleton, liver, spleen,\\u000a kidney, adrenal gland, and lung (1–6). In all these areas, the basic concept of RF tumor ablation is similar: localized and contained heat generation

William E. Shiels; Stephen D. Brown

158

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

159

Radiofrequency and Pulsed Radiofrequency Treatment of Chronic Pain Syndromes: The Available Evidence  

Microsoft Academic Search

Abstract: There are currently 6 reviews on (pulsed) radiofrequency for the management of spinal pain. Two reviews on interventional pain management techniques in general also discuss radiofrequency. The outcomes of those reviews depend on the type of studies included and the opinion of the reviewers, which may result in different evidence levels. Radiofrequency denervation on the cervical and lumbar level

Koen van Boxem; Maarten van Eerd; Tjinta Brinkhuize; Jacob Patijn; Maarten van Kleef; Jan van Zundert

2008-01-01

160

Radiofrequency treatment of cervicogenic headache  

PubMed Central

Objectives: In the clinical management of facial pain, a possible cervical origin must be considered. A clinical exploration is therefore essential. The disorder originates in the intimate connections between the cranial portion of the spinal cord and the trigeminal system. Although solid evidence supporting the use of radiofrequency (RF) treatment is lacking, it remains one of the management options to be taken into account. The present study evaluates the efficacy of RF in application to cervicogenic headache. Study design: We present three cases of severe facial pain arising from different cervical structures. Results: In two cases the pain originated in cervical roots C2 and C3, while in the third patient the trigger point was located at the level of the atlantoaxial joint. Pulsed RF was applied for 4 minutes at the dorsal ganglion of C2 and C3 in the first two cases, and for 8 minutes at intraarticular level in the third patient. The pain gradually subsided during the first month in all cases. The first two patients reported 70% improvement after one month, 60% improvement after 6 months, and 30-50% after one year, versus baseline. The third patient reported complete pain resolution lasting approximately 5 months, after which the pain reappeared with the same intensity as before. Conclusions: Radiofrequency is a satisfactory treatment option, affording adequate analgesia, though the effects are sometimes temporary. Key words:Cervicogenic headache, pulsed radiofrequency, analgesia.

Penarrocha, Miguel; Penarrocha, Maria; Calvo, Ana; Jimenez, Alejandro; March, Rafael

2013-01-01

161

Radiofrequency exposure and mammalian cell toxicity, genotoxicity, and transformation  

Microsoft Academic Search

Thepublishedinvitroliteraturerelevanttotheissueofthepossibleinductionoftoxicity,genotoxicity, and transformation of mammalian cells due to radiofrequency field (RF) exposure is examined. In some instances, information about related in vivo studies is presented. The review is from the perspective of technical merit and also biological consistency, especially with regard to those publicationsreportingapositiveeffect.Theweightofevidenceavailableindicatesthat,foravarietyof frequenciesandmodulationswithbothshortandlongexposuretimes,atexposurelevelsthatdonot(or in some instances do) heat the biological sample such that there is a measurable increase

Martin L. Meltz

2003-01-01

162

Auditory response to pulsed radiofrequency energy  

Microsoft Academic Search

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

J. A. Elder; C. K. Chou

2003-01-01

163

Radio-Frequency Magnetometry Using a Single Electron Spin  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate a simple and robust protocol for the detection of weak radio-frequency magnetic fields using a single electron spin in diamond. Our method relies on spin locking, where the Rabi frequency of the spin is adjusted to match the MHz signal frequency. In a proof-of-principle experiment we detect a 7.5 MHz magnetic probe field of ˜40nT amplitude with <10kHz spectral resolution. Rotating-frame magnetometry may provide a direct and sensitive route to high-resolution spectroscopy of nanoscale nuclear spin signals.

Loretz, M.; Rosskopf, T.; Degen, C. L.

2013-01-01

164

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

Code of Federal Regulations, 2012 CFR

... 2012-10-01 false Radiofrequency radiation exposure evaluation: mobile devices...Authorization Procedures Radiofrequency Radiation Exposure § 2.1091 Radiofrequency radiation exposure evaluation: mobile...

2012-10-01

165

21 CFR 880.6300 - Implantable radiofrequency transponder system for patient identification and health information.  

Code of Federal Regulations, 2010 CFR

... false Implantable radiofrequency transponder system for patient identification and...6300 Implantable radiofrequency transponder system for patient identification and...Identification . An implantable radiofrequency transponder system for patient...

2010-04-01

166

21 CFR 880.6300 - Implantable radiofrequency transponder system for patient identification and health information.  

Code of Federal Regulations, 2010 CFR

... false Implantable radiofrequency transponder system for patient identification and...6300 Implantable radiofrequency transponder system for patient identification and...Identification . An implantable radiofrequency transponder system for patient...

2009-04-01

167

Laser Initiation and Radiofrequency Sustainment of Seeded Air Plasmas  

NASA Astrophysics Data System (ADS)

Seeded gas plasmas and air constituents have been created by a 193 nm laser and radiofrequency sources. We have obtained 1014/cm3 plasma densities with initial electron temperatures of 0.3 eV in TMAE (tetrakis (dimethylamino) ethylene) by laser photoionization. We developed a fast Langmuir probe analysis of plasma decay independent of ion species mix. Langmuir probe and optical emission data illustrating the density and temperature decay with TMAE mixed with nitrogen is presented showing the existence of superexcited seed gas states which reduce the effective recombination rate. Simulations of antenna coupling, wave frequencies, wave propagation, and power absorption are compared with experimental observations for radiofrequency plasma sources. The source produces plasma densities of 2 x 1013/cm3 in an 8500 cm cm3 volume at electron temperatures of 5 eV in 10 mTorr Ar in a nonuniform magnetic field. Radiofrequency plasma sustainment at pressures from 2-760 Torr using Ar and laser initiated TMAE plasmas as seeds will be discussed.

Kelly, K.; Scharer, J.; Cao, R.; Ding, G.; Paller, E.

2000-10-01

168

Further observations on tissue heating patterns using an invasive ground probe with radiofrequency hyperthermia system.  

PubMed

Critical modifications have been made in the grounded elements of a previously reported hybrid radiofrequency heating system with inductive, capacitive, and grounded elements designed for deep focal heating. These modifications facilitate introduction of the ground probe, the single invasive element of the system, into animals and humans. The modified grounded elements also enable monitoring and optimization of ground point current, thereby improving control of heating rate, and greatly increase the volume of tissue that can be heated using a single invasive grounding element, embedded in a lossy dielectric field in the near field of the radiofrequency hyperthermia system. PMID:6493095

Yamanashi, W S; Boddie, A W; Frazer, J W; McBride, C M; Martin, R G

169

Radiofrequency Ablation: A Nursing Perspective  

PubMed Central

Radiofrequency ablation (RFA) has emerged as a safe and predictable technology for treating certain patients with cancer who otherwise have few treatment options. Nurses need to be familiar with all phases of the RFA procedure to create an optimal environment for patients. This article offers a brief review of the RFA procedure and nurses' responsibilities in caring for these patients. Before RFA, nurses should focus on patient education and aggressive hydration. During the procedure, nurses can prevent injury by placing grounding pads appropriately, monitoring vital signs, and medicating patients as needed. After RFA, nurses should assess the skin puncture site, provide adequate pain relief, and, again, hydrate patients. Nurses who care appropriately for RFA recipients may help to improve patient outcomes and make an otherwise frightening procedure more comfortable.

Locklin, Julia K.; Wood, Bradford J.

2008-01-01

170

Radiofrequency Catheter Ablation: Indications and Complications  

Microsoft Academic Search

.   Radiofrequency catheter ablation was first described in pediatric patients in the early 1990s. Since then, multiple advances\\u000a in the technology and understanding of radiofrequency ablation have allowed this technique to blossom into one of the most\\u000a powerful therapeutic tools available to the pediatric electrophysiologist. This treatment has, in the majority of cases, replaced\\u000a arrhythmia surgery as the definitive cure

A. M. Dubin; G. F. Van Hare

2000-01-01

171

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.

2004-01-01

172

Comparison of pulsed radiofrequency with conventional radiofrequency in the treatment of idiopathic trigeminal neuralgia  

Microsoft Academic Search

The aim of this prospective, randomized, double-blinded study was to evaluate the effect of pulsed radiofrequency (PRF) in comparison with conventional radiofrequency (CRF) in the treatment of idiopathic trigeminal neuralgia. A total of 40 patients with idiopathic trigeminal neuralgia were included. The 20 patients in each group were randomly assigned to one of the two treatment groups. Each patient in

Serdar Erdine; Nuri Suleyman Ozyalcin; Ali Cimen; Mehmet Celik; Gul Koknel Talu; Rian Disci

2007-01-01

173

Radiofrequency microcoils for magnetic resonance imaging and spectroscopy.  

PubMed

Small radiofrequency coils, often termed "microcoils", have found extensive use in many areas of magnetic resonance. Their advantageous properties include a very high intrinsic sensitivity, a high (several MHz) excitation and reception bandwidth, the fact that large arrays can fit within the homogeneous volume of the static magnetic field, and the very high resonance frequencies (several GHz) that can be achieved. This review concentrates on recent developments in the construction of single and multiple RF microcoil systems, and new types of experiments that can be performed using such assemblies. PMID:23142002

Webb, A G

2012-10-26

174

Effects of Simultaneous Radiofrequency Radiation and Chemical Exposure of Mammalian Cells. Volume 2.  

National Technical Information Service (NTIS)

A circulating water-bath exposure system has been designed for in vitro radiofrequency radiation (RFR) exposure studies in the 915 to 2450 MHz range. A continuously rotating styrofoam float, holding ten T-25 tissue culture flasks, averages out field heter...

M. L. Meltz V. Ciaravino J. J. Kerbacher P. Eagan

1988-01-01

175

Effects from 884 MHz mobile phone radiofrequency on brain electrophysiology, sleep, cognition, and well-being  

Microsoft Academic Search

There is an increasing concern about possible neurobiological effects from radiofrequency fields (RF) emitted from cell phones. In a double-blind laboratory exposure study, we assessed the effects on electrophysiological, cognitive, and self-rated measures from 3 hour exposure to 884 MHz. RF exposure resulted in prolonged time to reach deep (Stage 3) and shortened deep (Stages 3 and 4) sleep, enhanced

Bengt B. Arnetz; Lena Hillert; Torbjörn Åkerstedt; Arne Lowden; Niels Kuster; Sven Ebert; Scott Douglas Moffat; Clairy Wiholm

176

Interactions of Radiofrequency Radiation with NITELLA: Electrical Excitation and Perturbation of the Control of Cytoplasmic Streaming.  

National Technical Information Service (NTIS)

Radiofrequency radiation (RFR) of 0.5 Hz - 2.5 GHz, at field strengths on the order of 10 v/cm, has been shown to interact with isolate Nitella internodal cells in two separate and frequency dependent manners. At frequencies up to ca. 10 KHz, RFR acts to ...

L. S. Wong

1982-01-01

177

Percutaneous Tumor Ablation with Radiofrequency  

PubMed Central

BACKGROUND Radiofrequency thermal ablation (RFA) is a new minimally invasive treatment for localized cancer. Minimally invasive surgical options require less resources, time, recovery, and cost, and often offer reduced morbidity and mortality, compared with more invasive methods. To be useful, image-guided, minimally invasive, local treatments will have to meet those expectations without sacrificing efficacy. METHODS Image-guided, local cancer treatment relies on the assumption that local disease control may improve survival. Recent developments in ablative techniques are being applied to patients with inoperable, small, or solitary liver tumors, recurrent metachronous hereditary renal cell carcinoma, and neoplasms in the bone, lung, breast, and adrenal gland. RESULTS Recent refinements in ablation technology enable large tumor volumes to be treated with image-guided needle placement, either percutaneously, laparoscopically, or with open surgery. Local disease control potentially could result in improved survival, or enhanced operability. CONCLUSIONS Consensus indications in oncology are ill-defined, despite widespread proliferation of the technology. A brief review is presented of the current status of image-guided tumor ablation therapy. More rigorous scientific review, long-term follow-up, and randomized prospective trials are needed to help define the role of RFA in oncology.

Wood, Bradford J.; Ramkaransingh, Jeffrey R.; Fojo, Tito; Walther, McClellan M.; Libutti, Stephen K.

2008-01-01

178

Radiofrequency Ablation Beyond the Liver  

PubMed Central

Radiofrequency ablation (RFA) has begun to show promise for extrahepatic indications. Although much of the reported work on image-guided RFA of liver neoplasms is quite promising, it is even earlier in the evaluation and validation process for extrahepatic RFA, with few short-term and no long-term studies reported. Although there are much more data for liver RFA with almost 3,000 cases reported in the literature, there are a number of ongoing investigations of RFA for tumors in the kidney, lung, bone, breast, bone, and adrenal gland. Debulking and pain control with RFA present palliative options becoming increasingly popular weapons in the interventionalist's oncology arsenal. Metastatic disease with a wide variety of primary histologies in a myriad of locations may be treated with RFA after a careful consideration of the risk-to-benefit ratio balance. The RFA technique can be slightly different outside the liver. Specifically, differing dielectric tissue characteristics may markedly alter the RFA treatment. Each different RFA system has a unique risk and advantage profile. Extrahepatic indications and contraindications will be suggested. Treatment tips and the unique complications and considerations will be introduced for some of the more common extrahepatic locations.

Neeman, Ziv; Wood, Bradford J.

2008-01-01

179

21 CFR 882.4400 - Radiofrequency lesion generator.  

Code of Federal Regulations, 2013 CFR

...generator. (a) Identification. A radiofrequency lesion generator is a device used to produce lesions in the nervous system or other tissue by the direct application of radiofrequency currents to selected sites. (b)...

2013-04-01

180

47 CFR 2.801 - Radiofrequency device defined.  

Code of Federal Regulations, 2012 CFR

...radiofrequency device is any device which in its operation is...other means. Radiofrequency devices include, but are not limited...communication transmitting devices described throughout this chapter...industrial, scientific, and medical equipment described in...

2012-10-01

181

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.

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

2011-01-01

182

Radio-frequency characteristics of graphene oxide  

NASA Astrophysics Data System (ADS)

We confirm graphene oxide, a two-dimensional carbon structure at the nanoscale level can be a strong candidate for high-efficient interconnector in radio-frequency range. In this paper, we investigate high frequency characteristics of graphene oxide in range of 0.5-40 GHz. Radio-frequency transmission properties were extracted as S-parameters to determine the intrinsic ac transmission of graphene sheets, such as the impedance variation dependence on frequency. The impedance and resistance of graphene sheets drastically decrease as frequency increases. This result confirms graphene oxide has high potential for transmitting signals at gigahertz ranges.

Kim, Whan Kyun; Jung, Young Mo; Cho, Joon Hyong; Kang, Ji Yoong; Oh, Ju Yeong; Kang, Hosung; Lee, Hee-Jo; Kim, Jae Hun; Lee, Seok; Shin, H. J.; Choi, J. Y.; Lee, S. Y.; Kim, Y. C.; Han, I. T.; Kim, J. M.; Yook, Jong-Gwan; Baik, Seunghyun; Jun, Seong Chan

2010-11-01

183

Electromagnetic radiofrequency interference with Doppler equipment.  

PubMed

Doppler ultrasound equipments incorporate radiofrequency (RF) receivers operating at the microvolt level and are liable to interference from radiated fields and mains disturbances. The most significant interference routes are: radiation from radio broadcast, paging, communication and diathermy picked up on the transducer and patient acting as an aerial; and mains disturbances from diathermy, x-ray sets, motors and thyristor controls, etc, reaching the equipment interior. Direct mains interference can be reduced by proper design incorporating a mains filter, a low RF leakage enclosure, a ground plane, careful layout and further screening of the receiver circuits. Pick-up via the transducer occurs even if the signal leads are completely screened because an RF potential can exist between transducer and equipment enclosure due to the considerable impedance at RF of any wire or cable, typically 70 omega at 5 MHz for 2 m. This potential, reduced by about 50-60 dB, appears at the receiver input because of imperfect common mode rejection of the coupling cable. As a result, induced voltages above 100-300 microV may cause problems. It is shown that such levels can easily result from the interfering field strengths of 1 mV m-1 or more that may be experienced in a hospital environment. On the other hand, field strengths of 300 microV m-1, as generally allowed by regulatory standards at 3 m from interfering sources, should not cause much effect. Other interference can arise from modulation of a strong RF signal by mains frequency power components in the Doppler equipment and from associated computer circuits. These require careful layout to reduce electric and magnetic coupling, decoupling and filtering of power supplies and components, screening of RF circuits and particular attention to the reduction of power and computer signal currents flowing in RF signal earth paths. Finally, some initial simple acceptance tests for interference susceptibility are proposed, based on the application of 300 microV of RF signal between transducer body and equipment enclosure and 10 mV to the mains supply. PMID:1754615

Follett, D H

1991-11-01

184

14N Pulsed nuclear quadrupole resonance. 2. Effect of a single radio-frequency pulse in the general case  

Microsoft Academic Search

A novel theory, based on density operator calculations, is provided for assessing the nuclear quadrupole resonance behaviour of a spin 1 (14N) subjected to a single radio-frequency pulse. It is for a powder sample in zero magnetic field for an electric field gradient tensor without symmetry. A complete set of equations is obtained for the quantities of interest. It is

Daniel Canet; Lionel Merlat; Benoit Cordier; Denis Grandclaude; Alain Retournard; Maude Ferrari

2006-01-01

185

Metabolic and vasomotor responses of rhesus monkeys exposed to 225MHz radiofrequency energy  

Microsoft Academic Search

A previous study showed a substantial increase in the colonic temperature of rhesus monkeys (Macaca mulatta) exposed to radio-frequency (RF) fields at a frequency near whole-body resonance and specific absorption rates (SAR) of 2 to 3 W\\/kg. The present experiments were conducted to determine the metabolic and vasomotor responses during exposures to similar RF fields. Five adult male rhesus monkeys

W. Gregory Lotz; Jack L. Saxton

1987-01-01

186

Metabolic and vasomotor responses of rhesus monkeys exposed to 225MHz radiofrequency energy. [Macaca mulatta  

Microsoft Academic Search

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

W. G. Lotz; J. L. Saxton

1987-01-01

187

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

188

Percutaneous Radiofrequency Ablation of Nodal Metastases  

SciTech Connect

We report our experience with percutaneous image-guided radiofrequency (RF) ablation to treat isolated nodal metastases. Four patients underwent image-guided percutaneous RF ablation of metastatic disease involving retrocrural nodes,retroperitoneal nodes, or pelvic nodes. Coagulation necrosis was achieved in all cases.

Gervais, Debra A.; Arellano, Ronald S.; Mueller, Peter R. [Department of Radiology, Massachusetts GeneralHospital, White 270, Boston, MA 02114 (United States)

2002-12-15

189

Mapping and radiofrequency ablation of ventricular tachycardia  

Microsoft Academic Search

Radiofrequency catheter ablation has become the nonpharmacologic treatment of choice in patients with a variety of supraventricular arrhythmias. Small discrete lesions are produced by delivering 20-40 W of unmodulated 500 kHz RF energy to the tip of a standard 4 mm electrode catheter. Resistive heating of cardiac tissue occurs at the point of tissue contact. Successful treatment of these arrhythmias

A. J. Greenspon

1997-01-01

190

Unexplained liver laceration after metastasis radiofrequency ablation  

Microsoft Academic Search

Many studies have established the role of radiofrequency (RF) ablation as a minimally invasive treatment for liver metastases. Although relatively safe, several complications have been reported with the increased use of RF ablation. We describe here a case of unexplained liver laceration after a RF procedure. A woman who presented a solitary metachronous liver metastasis underwent RF ablation treatment for

Esther Uña; Javier Trueba; Jose Manuel Montes

2009-01-01

191

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

192

Physics of Radio-Frequency Plasmas  

NASA Astrophysics Data System (ADS)

1. Introduction; 2. Plasma dynamics and equilibrium; 3. Bounded plasmas; 4. Radiofrequency sheaths; 5. Single frequency capacitively-coupled plasmas; 6. Multi-frequency capacitively-coupled plasmas; 7. Inductively-coupled plasmas; 8. Helicon plasmas; 9. Real plasmas; 10. Electrical measurements; Index.

Chabert, Pascal; Braithwaite, Nicholas

2011-02-01

193

MICROWAVE AND RADIO-FREQUENCY POWER APPLICATIONS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The potential for agricultural applications of radio-frequency (RF) energy for the solution of various problems in agricultural production, crop handling and storage, and product preservation and conditioning has been considered for many years. With the development of economical microwave power equ...

194

Radiofrequency map of an NMR coil by imaging.  

PubMed

We propose a new imaging method to obtain a map of the radiofrequency (RF) field amplitude over a sample. The sequence contains three RF pulses (alpha, 2 alpha, and alpha) and produces two images by a classical spin echo and a stimulated echo. A third image is computed and gives the distribution of the flip angle alpha, and so the RF amplitude, over the sample. The accuracy of the flip angle determination is verified on an homogeneous sample and results show a good correlation between experimental and theoretical flip angles in the range of 50 degrees to 130 degrees. Experiments with a surface coil and a resonator show the method is available in an inhomogeneous RF field. Images obtained on the calf of a volunteer confirms the independence of the computed RF distribution from proton density, T1, or T2 contrast. PMID:8505878

Akoka, S; Franconi, F; Seguin, F; Le Pape, A

1993-01-01

195

Laser and Radiofrequency Production of Seeded Air Plasmas  

NASA Astrophysics Data System (ADS)

Seeded gas plasmas and air constituents have been created by a 193 nm laser and by a radiofrequency source. We have obtained 10^14/cm^3 plasma densities with initial electron temperatures of 0.3 eV in TMAE (tetrakis (dimethylamino) ethylene) by laser photoionization. We developed a fast Langmuir probe analysis of plasma decay independent of ion species mix. Langmuir probe and optical emission data illustrating the density and temperature decay with TMAE mixed with nitrogen is presented. Simulations of antenna coupling, wave frequencies, wave propagation, and power absorption are compared with experimental observations for radiofrequency plasma sources. The source produces plasma densities of 2 × 10^13/cm^3in an 8500 cm^3 volume at electron temperatures of 5 eV in 10 mTorr Ar with 1 kW coupled power levels in a nonuniform magnetic field. Plasmas production at pressures from 2-760 Torr using Ar and laser initiated TMAE plasmas as seeds will be discussed.

Scharer, J.; Ding, G.; Gui, H.; Kelly, K.; Paller, E.

1999-10-01

196

Percutaneous ultrasound-guided radiofrequency thermal ablation of malignant osteolyses.  

PubMed

Metastases are the most common neoplastic pathology involving the skeletal system. The hallmark of skeletal metastases is pain that often compromises the patient's quality of life. Radiotherapy, surgery and chemotherapy are the cornerstones of the treatment, but these techniques are not completely effective. Radiofrequency thermal ablation (RFA) may offer an alternative to conventional therapies for pain control. At present, the main field of application of RFA is the treatment of primary or secondary tumors of the liver but, recently, the technique has been effectively used to treat various other tumors in organs such as the prostate, kidney, lung, brain, pancreas and breast and to control pain caused by osteoid osteomas. Five patients with six painful bone metastases underwent RFA. The patients were three women and two men, aged 40-77 years (mean: 63.4). The radiofrequency system consists of an insulated 18-gauge needle electrode attached to a 500-kHz RF generator (Radionics, Burlington, Mass, USA). Four of our five patients rapidly obtained pain relief. One patient was completely pain free within 48 hours of the procedure and the control of pain persisted for 88 weeks. Another three patients obtained at least fifty percent pain reduction that lasted, on average, 12 weeks. Our preliminary results confirm that ultrasound-guided RFA is a simple and safe technique for treating painful superficial bone metastases. PMID:14981955

Poggi, Guido; Gatti, Carlo; Melazzini, Mario; Bernardo, Giovanni; Strada, Mariarosa; Teragni, Cristina; Delmonte, Angelo; Tagliaferri, Carlo; Bonezzi, Cesare; Barbieri, Massimo; Bernardo, Antonio; Fratino, Pietro

197

Children and adults exposed to low-frequency magnetic fields at the ICNIRP reference levels: theoretical assessment of the induced electric fields  

Microsoft Academic Search

To avoid potentially adverse health effects, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined reference levels for time varying magnetic fields. Restrictions on the electric fields induced in the human body are provided based on biological response data for peripheral nerve stimulation and the induction of phosphenes. Numerical modeling is commonly used to assess the induced electric fields

J F Bakker; M M Paulides; E Neufeld; A Christ; X L Chen; N Kuster; G C van Rhoon

2012-01-01

198

B1-based specific energy absorption rate determination for nonquadrature radiofrequency excitation.  

PubMed

The current gold standard to estimate local and global specific energy absorption rate for MRI involves numerically modeling the patient and the transmit radiofrequency coil. Recently, a patient-individual method was presented, which estimated specific energy absorption rate from individually measured B(1) maps. This method, however, was restricted to quadrature volume coils due to difficulties distinguishing phase contributions from radiofrequency transmission and reception. In this study, a method separating these two phase contributions by comparing the electric conductivity reconstructed from different transmit channels of a parallel radiofrequency transmission system is presented. This enables specific energy absorption rate estimation not only for quadrature excitation but also for the nonquadrature excitation of the single elements of the transmit array. Though the contributions of the different phases are known, unknown magnetic field components and tissue boundary artifacts limit the technique. Nevertheless, the high agreement between simulated and experimental results found in this study is promising. B(1)-based specific energy absorption rate determination might become possible for arbitrary radiofrequency excitation on a patient-individual basis. PMID:22374804

Katscher, Ulrich; Findeklee, Christian; Voigt, Tobias

2012-02-28

199

Bilateral vision loss associated with radiofrequency exposure  

PubMed Central

A 57-year-old otherwise healthy woman presented with painless binocular vision loss 1 week after direct application of radiofrequency energy to her orbits. She had no light perception bilaterally. Pupils were dilated and not reactive to light. Fundoscopic exam initially showed optic disc swelling in the right eye and a normal-appearing disc in the left eye. Magnetic resonance imaging of the brain and orbits showed gadolinium enhancement of both intraorbital optic nerves. She underwent a course of high-dose steroid treatment without recovery of vision. Optic discs were pale 11 weeks after injury. With exclusion of other possible causes, this represents a unique case of irreversible binocular optic nerve damage and blindness secondary to radiofrequency exposure.

Liu, Dianna; Cruz, Franz Marie; Subramanian, Prem S

2012-01-01

200

Radio-frequency dressed atoms beyond the linear Zeeman effect  

NASA Astrophysics Data System (ADS)

We evaluate the impact that nonlinear Zeeman shifts have on resonant radio-frequency (RF) dressed traps in an atom-chip configuration. The degeneracy of the resonance between Zeeman levels is lifted at large intensities of a static field, modifying the spatial dependence of the atomic adiabatic potential. In this context, we find effects that are important for the next generation of atom chips with tight trapping: in particular, that the vibrational frequency of the atom trap is sensitive to the RF frequency and, depending on the sign of the Landé factor, can produce significantly weaker, or tighter trapping when compared to the linear regime of the Zeeman effect. We take 87Rb as an example and find that it is possible for the trapping frequency on F = 1 to exceed that of the F = 2 hyperfine manifold.

Sinuco-León, G.; Garraway, B. M.

2012-12-01

201

[Effects of mobile phones and radar radiofrequencies on the eye].  

PubMed

The increasing applications of microwaves, mainly in mobile phones and radar, induce a higher rate of exposed people, sometimes cause of worry. Eyeballs are hotspots of radiofrequency field radiation because of their anatomy and composition. We propose a review of the various effects on the eye. The studies are hardly comparable because the exposure systems, power densities and dosimetries are different. While the thermal effects on the eye are well known including cataracts, corneal edema, endothelial cell loss and retinal degeneration, the non-thermal effects are still controversial. Cell cycle abnormalities, early apoptosis were reported in experimental conditions likely due to oxidative stress, but the studies could not show any significant effect on human eyes when exposed to long-term and low-dose radiation. Next studies need to be closer to human exposure. PMID:19036534

Vignal, R; Crouzier, D; Dabouis, V; Debouzy, J-C

2008-11-25

202

Radiofrequency Volumetric Reduction for Masseteric Hypertrophy  

Microsoft Academic Search

Masseteric hypertrophy occurs frequently among Asians, including Koreans, because of racial characteristics and dietary habits.\\u000a It is thought to be an unpleasant feature, especially because of its strong and masculine impression. Recently, the authors\\u000a developed a method for the volumetric reduction of hypertrophied masseter muscles using radiofrequency energy to correct the\\u000a squared facial appearance caused by the hypertrophy. This study

Young Jin Park; Yong Woo Jo; Sa Ik Bang; Hyung Joon Kim; So Young Lim; Goo Hyun Mun; Won Sok Hyon; Kap Sung Oh

2007-01-01

203

Radiofrequency Treatment for Obstructive Tonsillar Hypertrophy  

Microsoft Academic Search

Objective: To evaluate the safety and efficacy of in- office, temperature-controlled radiofrequency submu- cosal tissue volume reduction using the Somnoplasty pro- cedure for the treatment of symptomatic chronic obstructive tonsillar hypertrophy. Design: A prospective, nonrandomized, 3-phase pro- tocol using in vitro and in vivo studies associated with operative tonsillectomy and clinical procedures per- formed in-office. Setting: Hospital operating room and

Lionel M. Nelson

2000-01-01

204

Radiofrequency ablation of colorectal carcinoma liver metastases  

Microsoft Academic Search

Hepatic metastases affect many patients with colorectal cancer. Resection remains the first choice for treatment, but many\\u000a patients do not have disease amenable to resection or are physically unable to undergo an operation. Radiofrequency ablation\\u000a is a viable option for patients who cannot undergo resection. Effective destruction of tumors can be achieved with minimal\\u000a complications or risk of death. Emerging

Michael B. Nicholl; Anton J. Bilchik

2007-01-01

205

Comparison between pulsed and continuous radiofrequency delivery  

Microsoft Academic Search

Introduction  Potentials arising in the pulmonary veins (PV) have been proposed to be a trigger of atrial fibrillation. Percutaneously,\\u000a the best results for curative treatment of atrial fibrillation have been achieved by segmental or circumferential isolation\\u000a of the PV. The purpose of our study was to determine the feasibility of ostial pulmonary vein isolation and to compare continuous\\u000a radiofrequency (RF) with

Ali Erdogan; Eiko Walleck; Sebastian Rueckleben; Thomas Neumann; Harald H. Tillmanns; Bernd Waldecker; Hans Hoelschermann; Martin Heidt

2007-01-01

206

Radiofrequency and microwave radiation in the microelectronics industry  

SciTech Connect

The microscopic precision required to produce minute integrated circuits is dependent on several processes utilizing radiofrequency and microwave radiation. This article provides a review of radiofrequency and microwave exposures in microelectronics and of the physical and biologic properties of these types of radiation; summarizes the existing, relevant medical literature; and provides the clinician with guidelines for diagnosis and treatment of excessive exposures to microwave and radiofrequency radiation. 12 references.

Cohen, R.

1986-01-01

207

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

208

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

209

Radiofrequency volumetric reduction for masseteric hypertrophy.  

PubMed

Masseteric hypertrophy occurs frequently among Asians, including Koreans, because of racial characteristics and dietary habits. It is thought to be an unpleasant feature, especially because of its strong and masculine impression. Recently, the authors developed a method for the volumetric reduction of hypertrophied masseter muscles using radiofrequency energy to correct the squared facial appearance caused by the hypertrophy. This study was performed to investigate the effects of radiofrequency applied to reduce hypertrophied masseter muscles of patients who sought an aesthetic alternative for a slim, smooth, and feminine-looking lower facial contour. A total of 340 patients were treated. The patients usually recognized the volume change 3 to 6 weeks after treatment, and an objective volume reduction was observed within 3 months of the operation. The range of the reduction in the masseter thickness, as measured by ultrasonic examination at a 6-month postoperative follow-up visit, was 10% to 60% (mean, 27%). Most of the patients could eat a nearly normal diet after 4 weeks and were satisfied with the improved aesthetic contour lines of their lower face. Radiofrequency-induced coagulation tissue necrosis of the masseter did not cause any infections or limitations of mouth opening, and the clinical improvement was well maintained after the treatment. PMID:17235460

Jin Park, Young; Woo Jo, Yong; Bang, Sa Ik; Kim, Hyung Joon; Lim, So Young; Mun, Goo Hyun; Hyon, Won Sok; Oh, Kap Sung

210

Characteristics of a 13.56 MHz radiofrequency-driven multicusp ion source  

Microsoft Academic Search

The characteristics of a radiofrequency (rf)-driven multicusp ion source are investigated. The ion source is an Nd-Fe-B magnetic multicusp type operated at 13.56 MHz with an internal quartz covered antenna. The source has been diagnosed by an rf-compensated Langmuir probe for uniformity, density and electron temperature. A retarding field energy analyser, and a multi-wire beam profile monitor and quadrupole magnet

D. Boonyawan; N. Chiraphatpimol; T. Vilaithong

2002-01-01

211

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.

Schilling, C J

1997-01-01

212

Problems of human exposure in electromagnetic fields and radiation  

Microsoft Academic Search

Recent technological applications with radio waves induced public fear about possible adverse effects. A brief and simple overview and classification of the effects when exposed to non ionizing electromagnetic fields and radiation is presented. Basics are given of the actual guidelines to protect people and some discrepancies are discussed. The introduction of safety factors (SF) and health factors (HF) is

V. L. Walter

2008-01-01

213

Issledovanie proniknoveniya radiochastotnogo ehlektromagnitnogo polya po mezhzerennym svyazyam VTSP v kriticheskom sostoyanii. (Study of the radio-frequency electromagnetic fields penetration via high-T(sub c) intergranular bounds in the critical state).  

National Technical Information Service (NTIS)

The experimental results obtained in studies of the temperature region of the electromagnetic field total penetration through the intergranular cluster of high Tc ceramic materials are given. This region is between the temperature of origination of the in...

V. V. Chabanenko

1991-01-01

214

Biofilms on tuff stones at historical sites: identification and removal by nonthermal effects of radiofrequencies.  

PubMed

A methodology aiming at identifying and removing biofilms from cultural heritage was applied to stones from tuff walls in historical sites. Identification of phototrophic encrusting microorganisms was carried out by optical and electron microscopy, as well as by molecular techniques (DNA analyses and denaturing gradient gel electrophoresis (DGGE)). In all sites, the examination of microbial components of biofilms resulted in the identification of 17 species belonging to Cyanobacteria, Rhodophyta, Bacillariophyta and Chlorophyta, with Cyanobacteria being the dominant components in all biofilms. In order to remove the biofilms, an innovative technique based on the use of nonthermal effects of radiofrequencies was adopted. The source of the electromagnetic fields was a signal generator connected to a horn antenna through an amplifier to provide the power boost required to generate the target field amplitude. Seven days after exposure to radiofrequency electromagnetic field, about 50 % reduction of biofilm was observed; after 14 days, biofilm extension was reduced by about 90 %. DGGE analyses performed after 14 days confirmed these visual inspections. Also, DGGE analyses carried out before and 14 days after treatments showed that 12 out of 17 identified species disappeared. A complete visual disappearance of biofilms was observed a month after the beginning of treatments. DGGE repeated at this time confirmed the total disappearance of biofilm-forming species. Treated stones, when transferred back to their original sites, did not show any microorganism re-growing after 6 months. No alteration in the color and structural consistency of tuff substrata was observed after radiofrequency treatments. PMID:23740199

Cennamo, P; Caputo, P; Giorgio, A; Moretti, A; Pasquino, N

2013-06-06

215

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

216

High-resolution MRI encoding using radiofrequency phase gradients.  

PubMed

Although MRI offers highly diagnostic medical imagery, patient access to this modality worldwide is very limited when compared with X-ray or ultrasound. One reason for this is the expense and complexity of the equipment used to generate the switched magnetic fields necessary for MRI encoding. These field gradients are also responsible for intense acoustic noise and have the potential to induce nerve stimulation. We present results with a new MRI encoding principle which operates entirely without the use of conventional B0 field gradients. This new approach - 'Transmit Array Spatial Encoding' (TRASE) - uses only the resonant radiofrequency (RF) field to produce Fourier spatial encoding equivalent to conventional MRI. k-space traversal (image encoding) is achieved by spin refocusing with phase gradient transmit fields in spin echo trains. A transmit coil array, driven by just a single transmitter channel, was constructed to produce four phase gradient fields, which allows the encoding of two orthogonal spatial axes. High-resolution two-dimensional-encoded in vivo MR images of hand and wrist were obtained at 0.2 T. TRASE exploits RF field phase gradients, and offers the possibility of very low-cost diagnostics and novel experiments exploiting unique capabilities, such as imaging without disturbance of the main B0 magnetic field. Lower field imaging (<1 T) and micro-imaging are favorable application domains as, in both cases, it is technically easier to achieve the short RF pulses desirable for long echo trains, and also to limit RF power deposition. As TRASE is simply an alternative mechanism (and technology) of moving through k space, there are many close analogies between it and conventional B0 -encoded techniques. TRASE is compatible with both B0 gradient encoding and parallel imaging, and so hybrid sequences containing all three spatial encoding approaches are possible. Copyright © 2013 John Wiley & Sons, Ltd. PMID:24019215

Sharp, Jonathan C; King, Scott B; Deng, Qunli; Volotovskyy, Vyacheslav; Tomanek, Boguslaw

2013-09-06

217

Ultrasonography guided percutaneous radiofrequency ablation for hepatic cavernous hemangioma  

Microsoft Academic Search

AIM: Hepatic cavernous hemangioma (HCH) is the most common benign tumor of the liver and its management is still controversial. Recent success in situ radiofrequency ablation of hepatic malignancies has led us to consider using this technique in patients with HCH. This study was to assess the efficacy, safety, and complications of percutaneous radiofrequency ablation (PRFA) under ultrasonography guidance in

Yan Cui; Li-Yan Zhou; Man-Ku Dong; Ping Wang; Min Ji; Xiao-Ou Li; Chang-Wei Chen; Zi-Pei Liu; Yong-Jie Xu; Hong-Wen Zhang

2003-01-01

218

The longer term effect of pulsed radiofrequency for neuropathic pain  

Microsoft Academic Search

Pulse radiofrequency has been recently described as a technique to apply a relatively high voltage near a nerve but with out the usual effects of a rise in temperature or subsequent nerve injury. In this set of case reports, the effect of pulsed radiofrequency (PRF) is described in patients with neuropathic pain syndromes which have been poorly controlled with other

Rajesh Munglani

1999-01-01

219

Radiofrequency Lesion Generation and lts Effect on Tissue Impedance  

Microsoft Academic Search

The method of radiofrequency heat lesion generation is reviewed with specific reference to the dorsal root entry zone. Experimental data on the impedance of electrolytic media as a function of temperature are reported, and their relation to what should be observed during radiofrequency lesioning in the body is commented upon. The future utility of impedance monitoring is discussed as well

Eric R. Cosman; William J. Rittman; Blaine S. Nashold; Thad T. Makachinas

1988-01-01

220

Determining the influence of population variation on compliance with radiofrequency exposure limits: proposed study.  

PubMed

Currently, compliance with safety limits for human exposure to radiofrequency (RF) fields is demonstrated by methods that rely on certain assumptions and approximations, which include among other things, human anatomical features, tissue types and the dielectric properties of these tissues. This paper reviews some of the available data and outlines a proposal for an encompassing study to investigate which of these assumptions are appropriate; what approximation can be used in physical and computational modeling of humans for specific energy absorption rate (SAR) calculations (a key compliance metric); and what trade-offs can be made between accuracy and modeling requirements for practical considerations. Key issues to be investigated are how SAR varies between children and adults, between males and females, and how to model SAR in the fetus of pregnant females. It is hoped that the proposed study will produce models and methods which allow for faster, more accurate and more efficient compliance with radiofrequency exposure limits. PMID:17282864

Sauren, Maia; McKenzie, Ray; Cosic, Irena

2005-01-01

221

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.

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

2013-01-01

222

T1 and T2 effects during radio-frequency pulses in spoiled gradient echo sequences  

NASA Astrophysics Data System (ADS)

Finite pulse durations in diverse pulse schemes lead to the reduction of the magnitude of the magnetization vector due to T1 and T2 effects during the radio-frequency pulses. This paper presents an analysis of the steady state signal in the presence of relaxation effects during radio-frequency pulses in MRI spoiled gradient echo sequences. It is shown that minor attenuations of the magnetization vector can have dramatic consequences on the measured signal, and may thus entail a loss in SNR benefits at high static magnetic fields if a careful analysis is not performed. It is emphasized that it is the time-integrated magnetization vector trajectory that matters for these effects and not only the pulse duration. Some experimental results obtained on a phantom at 3 T verify this analysis.

Boulant, Nicolas

2009-04-01

223

Laparoscopic radiofrequency ablation of hepatic cavernous hemangioma  

Microsoft Academic Search

Background  \\u000a Radiofrequency ablation (RFA), currently used extensively for liver tumors, also has been applied successfully to hepatic\\u000a cavernous hemangioma (HCH) percutaneously. The aim of this study was to assess the feasibility, safety, and efficacy of laparoscopic\\u000a RFA for patients with HCHs.\\u000a \\u000a \\u000a \\u000a Methods  Between March 2001 and March 2004, 27 patients with symptomatic and rapid-growth lesions were treated by laparoscopic RFA\\u000a using

R.-F. Fan; F.-L. Chai; G.-X. He; L.-X. Wei; R.-Z. Li; W.-X. Wan; M.-D. Bai; W.-K. Zhu; M.-L. Cao; H.-M. Li; S.-Z. Yan

2006-01-01

224

Laparoscopic radiofrequency ablation of unresectable hepatic malignancies  

Microsoft Academic Search

Background  Radiofrequency ablation (RFA) of hepatic malignancies has been performed successfully via a percutaneous route or at laparotomy.\\u000a We analyzed the efficacy and utility of laparoscopic intraoperative ultrasound and RFA in patients with unresectable hepatic\\u000a malignancies.\\u000a \\u000a \\u000a \\u000a Methods  Between November 1997 and November 1999, 27 patients with unresectable hepatic malignancies and no evidence of extrahepatic\\u000a disease were entered in a phase 2 trial

M. H. Chung; T. F. Wood; G. J. Tsioulias; D. M. Rose; A. J. Bilchik

2001-01-01

225

Evaporative cooling in a radio-frequency trap  

SciTech Connect

A theoretical investigation for implementing a scheme of forced evaporative cooling in radio-frequency (rf) adiabatic potentials is presented. Supposing the atoms to be trapped in a combination of a dc magnetic field and a rf field at frequency {omega}{sub 1}, the cooling procedure is facilitated using a second rf source at frequency {omega}{sub 2}. This second rf field produces a controlled coupling between the spin states dressed by {omega}{sub 1}. The evaporation is then possible in a pulsed or continuous mode. In the pulsed case, atoms with a given energy are transferred into untrapped dressed states by abruptly switching off the {omega}{sub 2} coupling. In the continuous case, it is possible for energetic atoms to adiabatically follow the doubly dressed states and escape out of the trap. Our results also show that when {omega}{sub 1} and {omega}{sub 2} are separated by at least the Rabi frequency associated with {omega}{sub 1}, additional evaporation zones appear which can make this process more efficient.

Garrido Alzar, Carlos L.; Perrin, Helene; Lorent, Vincent [Laboratoire de Physique des Lasers, CNRS-Universite Paris 13, Villetaneuse (France); Garraway, Barry M. [Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH (United Kingdom)

2006-11-15

226

Operating a radio-frequency plasma source on water vapor.  

PubMed

A magnetically enhanced radio-frequency (rf) plasma source operating on water vapor has an extensive list of potential applications. In this work, the use of a rf plasma source to dissociate water vapor for hydrogen production is investigated. This paper describes a rf plasma source operated on water vapor and characterizes its plasma properties using a Langmuir probe, a residual gas analyzer, and a spectrometer. The plasma source operated first on argon and then on water vapor at operating pressures just over 300 mtorr. Argon and water vapor plasma number densities differ significantly. In the electropositive argon plasma, quasineutrality requires n(i) approximately = n(e), where n(i) is the positive ion density. But in the electronegative water plasma, quasineutrality requires n(i+) = n(i-) + n(e). The positive ion density and electron density of the water vapor plasma are approximately one and two orders of magnitude lower, respectively, than those of argon plasma. These results suggest that attachment and dissociative attachment are present in electronegative water vapor plasma. The electron temperature for this water vapor plasma source is between 1.5 and 4 eV. Without an applied axial magnetic field, hydrogen production increases linearly with rf power. With an axial magnetic field, hydrogen production jumps to a maximum value at 500 W and then saturates with rf power. The presence of the applied axial magnetic field is therefore shown to enhance hydrogen production. PMID:19725651

Nguyen, Sonca V T; Foster, John E; Gallimore, Alec D

2009-08-01

227

Endoscopic-guided percutaneous radiofrequency cordotomy.  

PubMed

The authors present the first clinical implementation of an endoscopic-assisted percutaneous anterolateral radiofrequency cordotomy. The aim of this article is to demonstrate the intradural endoscopic visualization of the cervical spinal cord via a percutaneous approach to refine the spinal target for anterolateral cordotomy, avoiding undesired trauma to the spinal tissue or injury to blood vessels. Initially, a lateral puncture of the spinal canal in the C1-2 interspace is performed, guided by fluoroscopy. As soon as CSF is reached by the guide cannula (17-gauge needle), the endoscope can be inserted for visualization of the spinal cord and its surrounding structures. The endoscopic visualization provided clear identification of the pial surface of the spinal cord, arachnoid membrane, dentate ligament, dorsal and ventral root entry zone, and blood vessels. The target for electrode insertion into the spinal cord was determined to be the midpoint from the dentate ligament and the ventral root entry zone. The endoscopic guidance shortened the fluoroscopy usage time and no intrathecal contrast administration was needed. Cordotomy was performed by a standard radiofrequency method after refining of the neurophysiological target. Satisfactory analgesia was provided by the procedure with no additional complications or CSF leak. The initial use of this technique suggests that a percutaneous endoscopic procedure may be useful for particular manipulation of the spinal cord, possibly adding a degree of safety to the procedure and improving its effectiveness. PMID:20433282

Fonoff, Erich Talamoni; de Oliveira, Ywzhe Sifuentes Almeida; Lopez, William Omar Contreras; Alho, Eduardo Joaquim Lopes; Lara, Nilton Alves; Teixeira, Manoel Jacobsen

2010-09-01

228

Laser and Radiofrequency Air Plasma Sources  

NASA Astrophysics Data System (ADS)

We are carrying out plasma source research utilizing 193 nm laser ionization of an organic gas in constituents of air and other gas (He, Ar, Xe) components. Microwave scattering, fast Langmuir probe and photodiode measurements are used to diagnose the plasma formation and decay. Initial peak plasma densities of 10^14/cm^3 are obtained with volumes of 10 cm × 100 cm × 2 cm. Results of these measurements with an emphasis on the role of the addition of air and other gas constituents on plasma lifetime will be presented. A comparison of the experimental results with simulations will be discussed. We have constructed a plasma radiofrequency source to examine highly collisional plasma production and sustainment of a laser produced plasma. Wave modelling results utilizing the ANTENA II and MAXEB(Y. Mouzouris and J. Scharer, IEEE Trans. Plasma Science PS-24, 152 (1996); Y. Mouzouris and J. Scharer, "Wave Propagation and Absorption Simulations for Helicon Sources," submitted to Physics of Plasmas, 1998.) codes in the 2-200 MHz range illustrate the wave character. We examine the role of metastable atoms for our 1-3 kW radiofrequency plasma source experiments for different gas components. Initial wave data in 2 × 10^13/cm^3 Ar plasmas are discussed.

Scharer, J.; Ding, G.; Gui, H.; Guo, X.; Kelly, K.; Louis, L.; Mouzouris, Y.

1998-11-01

229

Fast slice-selective radio-frequency excitation pulses for mitigatingB+1 inhomogeneity in the human brain at 7 Tesla  

Microsoft Academic Search

A novel radio-frequency (RF) pulse design algorithm is pre- sented that generates fast slice-selective excitation pulses that mitigate B1 inhomogeneity present in the human brain at high field. The method is provided an estimate of the B1 field in an axial slice of the brain and then optimizes the placement of sinc-like \\

Adam C. Zelinski; Lawrence L. Wald; Kawin Setsompop; Vijayanand Alagappan; Borjan A. Gagoski; Vivek K. Goyal; Elfar Adalsteinsson

2008-01-01

230

Impact of monopolar radiofrequency energy on subchondral bone viability  

PubMed Central

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 µm 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 µm at 44 days (P < .01), to 281 µm at 66 days (P < .01) and to 133 µm 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.

Kuhn, Anke; Weigel, Arwed; Walde, Tim A.; Ferlemann, Keno G.; Sturmer, Klaus M.; Frosch, Karl-Heinz

2009-01-01

231

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

232

Cooled radiofrequency application for treatment of sacroiliac joint pain  

Microsoft Academic Search

Background  The unavailability of an effective and long-lasting treatment for sacroiliac-based pain has led researchers to study the efficacy\\u000a of radiofrequency in denervation. In this study, we aimed to investigate the efficacy and safety of novel cooled radiofrequency\\u000a application for sacral lateral-branch denervation.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Patients experiencing chronic sacroiliac pain were selected for our observational study. Fluoroscopy guidance cooled radiofrequency\\u000a denervation was applied

Haktan Karaman; Gönül Ölmez Kavak; Adnan Tüfek; Feyzi Çelik; Zeynep Baysal Y?ld?r?m; Mehmet Salim Akdemir; Orhan Tokgöz

2011-01-01

233

Estimating radiofrequency power deposition in body NMR imaging.  

PubMed

Simple theoretical estimates of the average, maximum, and spatial variation of the radiofrequency power deposition (specific absorption rate) during hydrogen nuclear magnetic resonance imaging are deduced for homogeneous spheres and for cylinders of biological tissue with a uniformly penetrating linear rf field directed axially and transverse to the cylindrical axis. These are all simple scalar multiples of the expression for the cylinder in an axial field published earlier (Med. Phys. 8, 510 (1981]. Exact solutions for the power deposition in the cylinder with axial (Phys. Med. Biol. 23, 630 (1978] and transversely directed rf field are also presented, and the spatial variation of power deposition in head and body models is examined. In the exact models, the specific absorption rates decrease rapidly and monotonically with decreasing radius despite local increases in rf field amplitude. Conversion factors are provided for calculating the power deposited by Gaussian and sinc-modulated rf pulses used for slice selection in NMR imaging, relative to rectangular profiled pulses. Theoretical estimates are compared with direct measurements of the total power deposited in the bodies of nine adult males by a 63-MHz body-imaging system with transversely directed field, taking account of cable and NMR coil losses. The results for the average power deposition agree within about 20% for the exact model of the cylinder with axial field, when applied to the exposed torso volume enclosed by the rf coil. The average values predicted by the simple spherical and cylindrical models with axial fields, the exact cylindrical model with transverse field, and the simple truncated cylinder model with transverse field were about two to three times that measured, while the simple model consisting of an infinitely long cylinder with transverse field gave results about six times that measured. The surface power deposition measured by observing the incremental power as a function of external torso radius was comparable to the average value. This is consistent with the presence of a variable thickness peripheral adipose layer which does not substantially increase surface power deposition with increasing torso radius. The absence of highly localized intensity artifacts in 63-MHz body images does not suggest anomalously intense power deposition at localized internal sites, although peak power is difficult to measure. PMID:4094551

Bottomley, P A; Redington, R W; Edelstein, W A; Schenck, J F

1985-08-01

234

Radiofrequency Ablation Therapy for Solid Tumors  

ScienceCinema

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.

235

Optical generation of radio-frequency power  

SciTech Connect

An optical technique for high-power radio-frequency (RF) signal generation is described. The technique uses a unique photodetector based on a traveling-wave design driven by an appropriately modulated light source. The traveling-wave photodetector (TWPD) exhibits simultaneously a theoretical quantum efficiency approaching 100 % and a very large electrical bandwidth. Additionally, it is capable of dissipating the high-power levels required for the RF generation technique. The modulated light source is formed by either the beating together of two lasers or by the direct modulation of a light source. A system example is given which predicts RF power levels of 100`s of mW`s at millimeter wave frequencies with a theoretical ``wall-plug`` efficiency approaching 34%.

Hietala, V.M.; Vawter, G.A.; Brennan, T.M.; Hammons, B.E.; Meyer, W.J.

1994-11-01

236

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

237

Comparison of Renal Ablation with Monopolar Radiofrequency and Hypertonic-Saline-Augmented Bipolar Radiofrequency: In Vitro and In Vivo Experimental Studies  

Microsoft Academic Search

OBJECTIVE. We sought to determine whether hypertonic-saline (HS)-augmented bipolar radiofrequency ablation has advantages over monopolar radiofrequency ablation for creating larger areas of coagulation necrosis in the kidney. MATERIALS AND METHODS. Using a 200-W generator and bipolar perfused-cooled electrodes or a monopolar cooled-tip electrode, we performed 14 radiofrequency ablations in explanted bovine kidneys. Radiofrequency was applied in standard monopolar (n =

Jeong Min Lee; Joon Koo Han; Seung Hong Choi; Se Hyung Kim; Jae Young Lee; Kyung Sook Shin; Chang Jin Han; Byung Ihn Choi; Lee JM; Choi SH; Kim SH; Lee JY; Shin KS; Han CJ; Choi BI

238

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

239

Experimental Investigation of the Bennett Type Radio-Frequency Spectrometer.  

National Technical Information Service (NTIS)

Authors conducted experiments to study the static characteristics of a Bennett radio-frequency (RF) mass spectrometer. Bennett RF mass spectrometer is used to determine individual constituent contents in gaseous mixtures. The gaseous mixture is ionized by...

C. Zeng-tsu C. Shao-chiang R. Hua-chi Y. Cheng-an

1967-01-01

240

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

241

21 CFR 882.4725 - Radiofrequency lesion probe.  

Code of Federal Regulations, 2013 CFR

...probe is a device connected to a radiofrequency (RF) lesion generator to deliver the RF energy to the site within the nervous system where a lesion is desired. (b) Classification. Class II (performance...

2013-04-01

242

Stabilization of Magnetohydrodynamic Modes by Applied Radiofrequency Waves.  

National Technical Information Service (NTIS)

A kinetic theory describing the nonlinear interaction of radiofrequency waves with low frequency magnetohydrodynamic modes is presented. The calculation of the nonlinear force density on a fluid element includes both ponderomotive and sideband mode coupli...

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

1986-01-01

243

Electromagnetic Field Interactions with the Human Body: Observed Effects and Theories.  

National Technical Information Service (NTIS)

The state of published knowledge about the effects of non-ionizing EM fields on humans is summarized. In addition to over 1000 written sources in-person meetings, telephone interviews and lecture tapes were used. It is indicated that there are good, bad a...

J. K. Raines

1981-01-01

244

Supercomputer Simulation of Radio-frequency Hepatic Tumor Ablation  

NASA Astrophysics Data System (ADS)

We simulate the thermal and electrical processes, involved in the radio-frequency (RF) ablation procedure. The mathematical model consists of two parts-electrical and thermal. The energy from the applied AC voltage is determined first, by solving the Laplace equation to find the potential distribution. After that, the electric field intensity and the current density are directly calculated. Finally, the heat transfer equation is solved to determine the temperature distribution. Heat loss due to blood perfusion is also accounted for. The representation of the computational domain is based on a voxel mesh. Both partial differential equations are discretized in space via linear conforming FEM. After the space discretization, the backward Euler scheme is used for the time stepping. Large-scale linear systems arise from the FEM discretization. Moreover, they are ill-conditioned, due to the strong coefficient jumps and the complex geometry of the problem. Therefore, efficient parallel solution methods are required. The developed parallel solver is based on the preconditioned conjugate gradient (PCG) method. As a preconditioner, we use BoomerAMG-a parallel algebraic multigrid implementation from the package Hypre, developed in LLNL, Livermore. Parallel numerical tests, performed on the IBM Blue Gene/P massively parallel computer are presented.

Kosturski, N.; Margenov, S.

2010-11-01

245

Fast and quiet MRI using a swept radiofrequency.  

PubMed

A novel fast and quiet method of magnetic resonance imaging (MRI) is introduced which creates new opportunities for imaging in medicine and materials science. The method is called SWIFT, sweep imaging with Fourier transformation. In SWIFT, time-domain signals are acquired in a time-shared manner during a swept radiofrequency excitation of the nuclear spins. With negligible time between excitation and signal acquisition, new possibilities exist for imaging objects consisting of spins with extremely fast transverse relaxation rates, such as macromolecules, semi-solids, and quadrupolar nuclei. The field gradient used for spatial-encoding is not pulsed on and off, but rather is stepped in orientation in an incremental manner, which results in low acoustic noise. This unique acquisition method is expected to be relatively insensitive to sample motion, which is important for imaging live objects. Additionally, the frequency-swept excitation distributes the signal energy in time and thus dynamic range requirements for proper signal digitization are reduced compared with conventional MRI. For demonstration, images of a plastic object and cortical bone are shown. PMID:16782371

Idiyatullin, Djaudat; Corum, Curt; Park, Jang-Yeon; Garwood, Michael

2006-06-19

246

Niobium and its Impact on Superconducting Radiofrequency Technology  

NASA Astrophysics Data System (ADS)

The Continuous Electron Beam Accelerator Facility at Jefferson Lab in Newport News, Virginia, was the first large-scale deployment of superconducting radiofrequency (RF) technology, and was optimized for nuclear/high energy physics research. The success of this technology led to the creation of a Free Electron Laser (FEL) facility at Jefferson Lab that has achieved world-record power, and is leading the way towards the next generation of FELs based on superconducting energy-recovery linacs. Superconducting RF technology has been adopted for other large accelerators (LEP, SNS) and is proposed for many of the future large accelerator facilities (ESS, FRIB, ILC, Project X, etc.). All these applications rely on the superconducting properties of niobium. While the performance of niobium accelerating cavities has been excellent, there are still improvements being developed, in particular, the new ingot niobium technology. This talk will provide a review of superconducting RF technology and the impact it has had, and will continue to have, on the accelerator field.

Hutton, Andrew

2011-03-01

247

Correcting radiofrequency inhomogeneity effects in skeletal muscle magnetisation transfer maps.  

PubMed

The potential of MRI to provide quantitative measures of neuromuscular pathology for use in therapeutic trials is being increasingly recognised. Magnetisation transfer (MT) imaging shows particular promise in this context, being sensitive to pathological changes, particularly in skeletal muscle, where measurements correlate with clinically measured muscle strength. Radiofrequency (RF) transmit field (B(1)) inhomogeneities can be particularly problematic in measurements of the MT ratio (MTR) and may obscure genuine muscle MTR changes caused by disease. In this work, we evaluate, for muscle imaging applications, a scheme previously proposed for the correction of RF inhomogeneity artefacts in cerebral MTR maps using B(1) information acquired in the same session. We demonstrate the theoretical applicability of this scheme to skeletal muscle using a two-pool model of pulsed quantitative MT. The correction scheme is evaluated practically in MTR imaging of the lower limbs of 28 healthy individuals and in two groups of patients with representative neuromuscular diseases: Charcot-Marie-Tooth disease type 1A and inclusion body myositis. The correction scheme was observed to reduce both the within-subject and between-subject variability in the calf and thigh muscles of healthy subjects and patient groups in histogram- and region-of-interest-based approaches. This method of correcting for RF inhomogeneity effects in MTR maps using B(1) data may markedly improve the sensitivity of MTR mapping indices as measures of pathology in skeletal muscle. PMID:21796708

Sinclair, C D J; Morrow, J M; Hanna, M G; Reilly, M M; Yousry, T A; Golay, X; Thornton, J S

2011-07-27

248

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

NASA Astrophysics Data System (ADS)

A low pressure (~0.5 mTorr in xenon and ~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.; Takahashi, K.

2013-06-01

249

Electromagnetic characterization of superconducting radio-frequency cavities for gw detection  

NASA Astrophysics Data System (ADS)

The electromagnetic properties of a prototype gravitational wave detector, based on two coupled superconducting microwave cavities, were tested. The radio-frequency (rf) detection system was carefully analysed. With the use of piezoelectric crystals small harmonic displacements of the cavity walls were induced and the parametric conversion of the electromagnetic field inside the cavities explored. Experimental results of bandwidth and sensitivity of the parametric converter versus stored energy and voltage applied to the piezoelectric crystal are reported. A rf control loop, developed to stabilize phase changes on signal paths, gave a 125 dBc rejection of the drive mode on a time scale of 1 h.

Ballantini, R.; Bernard, Ph; Chincarini, A.; Gemme, G.; Parodi, R.; Picasso, E.

2004-03-01

250

High-order maps with acceleration for optimization of electrostatic and radio-frequency ion-optical elements  

Microsoft Academic Search

A method has been developed to calculate accurate high-order ion-optical maps for electrostatic and radio-frequency accelerating elements. The method has been incorporated into the arbitrary-order map-based beam optics code COSY Infinity. The treatment is restricted to the case of negligible magnetic fields, as is typical of heavy-ion accelerating cavities, and does not include space charge. For validation purposes, the beam

Andrew A. Geraci; Teresa A. Barlow; Mauricio Portillo; Jerry A. Nolen; Kenneth W. Shepard; Kyoko Makino; Martin Berz

2002-01-01

251

Effect of 835 MHz radiofrequency radiation exposure on calcium binding proteins in the hippocampus of the mouse brain  

Microsoft Academic Search

Worldwide expansion of mobile phones and electromagnetic field (EMF) exposure has raised question of their possible biological effects on the brain and nervous system. Radiofrequency (RF) radiation might alter intracellular signaling pathways through changes in calcium (Ca2+) permeability across cell membranes. Changes in the expression of calcium binding proteins (CaBP) like calbindin D28-k (CB) and calretinin (CR) could indicate impaired

Dhiraj Maskey; Minsoo Kim; Bijay Aryal; Jonu Pradhan; In-Young Choi; Ki-Sup Park; Taeho Son; Sae-Yong Hong; Seok Bae Kim; Hyung Gun Kim; Myeung Ju Kim

2010-01-01

252

Electromagnetic noise inhibits radiofrequency radiation-induced DNA damage and reactive oxygen species increase in human lens epithelial cells  

Microsoft Academic Search

Purpose: The goal of this study was to investigate whether superposing of electromagnetic noise could block or attenuate DNA damage and intracellular reactive oxygen species (ROS) increase of cultured human lens epithelial cells (HLECs) induced by acute exposure to 1.8 GHz radiofrequency field (RF) of the Global System for Mobile Communications (GSM). Methods: An sXc-1800 RF exposure system was used

Ke Yao; Wei Wu; KaiJun Wang; LiXia Sun

2008-01-01

253

Investigations on bipolar radio-frequency current application for interstitial thermotherapy (RF-ITT)  

NASA Astrophysics Data System (ADS)

This paper discusses the feasibility of radio-frequency current in bipolar technique for interstitial thermotherapy (rf-ITT). A short survey of established methods for interstitial tissue coagulation, e.g. the interstitial laser photocoagulation (ILP) and microwave exposure are given. In addition, a new concept for interstitial application of bipolar or quasi-bipolar radio- frequency alternating current is presented. Theoretical investigations of the electrical field distribution generated by a dipole model come together in the different mechanisms of heat generation by using radio-frequency alternating current. New concepts of bipolar or quasi- bipolar coaxial layered applicators are presented. This bipolar needle electrode enables the surgeon to use a partial and homogeneous exposure of radio-frequency current for interstitial thermotherapy, e.g. for the treatment of BPH or for concha coagulation in ENT. Less power is needed due to the limited current exposition at the immediate operation site and a highly safe procedure is possible. Therefore, to determine the thermal damage of tissue, depending on the rf parameters, a computer model for a real-time simulation of the spatial electrical field distribution especially for a multiple probe application is currently being developed. This is an appropriate tool for dosimetry. A similar program for LITT, called LITCIT, developed at the Laser-Medizin-Zentrum Berlin has already shown its efficiency in clinical use. Furthermore the feasibility of a 'cross-over' applicator is discussed which combines ILP and rf-application by using metallized optical fibers for a simultaneous application of electrical energy and laser radiation.

Desinger, K.; Mueller, Gerhard J.; Stein, T.; Tschepe, Johannes

1996-01-01

254

Carbon Dust Growth in a Radiofrequency Discharge  

NASA Astrophysics Data System (ADS)

Plasma wall interactions studies are of primary importance for increasing the life time of the first wall in fusion devices. In ITER, the divertor target plates will receive on a small surface a significant part of the power during operation, and carbon materials will be used. Although carbon has several advantages than the materials used at other places of the plasma chamber (W and Be), they undergo chemical reactions with hydrogen and its isotopes used as fuel for the fusion reaction. Under ITER operating conditions, the high temperature of the wall will promote diffusion and recombination of atomic hydrogen, withholding the fuel. Moreover, carbon atoms produced by erosion may be deposited at other locations, causing further increase of the hydrogen inventory in the vessel, and encountering several subsequent major safety issues. In our experiment, carbon dust formation and growth are studied in a radiofrequency discharge. Dust particles sediment into the cathode sheath using carbon originating either from a graphite cathode in pure argon plasmas or from C2H2 mixed with argon in case where a stainless steel cathode is used. In this contribution, we present a characterization of carbon dust particles under various plasma conditions (pressure, RF power, C2H2 percentage). Dust growth is studied in situ using FTIR spectroscopy, whereas the structural properties of the dust particles are studied ex situ using TEM, SEM, and FTIR.

Peng, Y.; Hugon, R.; Brochard, F.; Vasseur, J.-L.; Lacroix, D.; Brosset, C.; Bougdira, J.

2008-03-01

255

Current oncologic applications of radiofrequency ablation therapies.  

PubMed

Radiofrequency ablation (RFA) uses high frequency alternating current to heat a volume of tissue around a needle electrode to induce focal coagulative necrosis with minimal injury to surrounding tissues. RFA can be performed via an open, laparoscopic, or image guided percutaneous approach and be performed under general or local anesthesia. Advances in delivery mechanisms, electrode designs, and higher power generators have increased the maximum volume that can be ablated, while maximizing oncological outcomes. In general, RFA is used to control local tumor growth, prevent recurrence, palliate symptoms, and improve survival in a subset of patients that are not candidates for surgical resection. It's equivalence to surgical resection has yet to be proven in large randomized control trials. Currently, the use of RFA has been well described as a primary or adjuvant treatment modality of limited but unresectable hepatocellular carcinoma, liver metastasis, especially colorectal cancer metastases, primary lung tumors, renal cell carcinoma, boney metastasis and osteoid osteomas. The role of RFA in the primary treatment of early stage breast cancer is still evolving. This review will discuss the general features of RFA and outline its role in commonly encountered solid tumors. PMID:23671734

Shah, Dhruvil R; Green, Sari; Elliot, Angelina; McGahan, John P; Khatri, Vijay P

2013-04-15

256

Errors in radio-frequency quadrupole structures  

SciTech Connect

Performance degradation caused by certain radio-frequency quadrupole (RFQ) machine errors was studied using an efficient 3-D particle-tracing simulation code for a high-brightness example. Matched beams, for which no emittance growth occurs, exist for periodic structures and were used as input beams for particle tracing in the presence of errors. We considered both slowly varying and fast (random) errors that destroy periodicity. Random dipole errors cause emittance growth because of the mismatches they introduce and also result in a motion of the beam centroid that causes a reduction in acceptance. Because of the way RFQs are manufactured, the random error amplitudes can be kept below harmful levels. More important are the slow errors, which are harmful because they reduce acceptance even though they maintain a match (up to the point of particle loss). Slow dipole errors steer the beam toward the wall, and voltage deficiencies cause instabilities in the longitudinal direction resulting in particles not being accelerated to full energy.

Lysenko, W.P.

1983-01-01

257

Radiofrequency and its effect on suture strength.  

PubMed

The use of radiofrequency-based electrocautery for hemostasis and ablation within the subacromial space and glenohumeral joint can cause damage to suture material. Prior studies have focused on the mechanical properties of sutures including their ability to withstand abrasion. The purpose of this study was to determine the effect of electrical energy on the mechanical properties of 5 different brands of #2 suture used for arthroscopic shoulder repair: FiberWire (Arthrex Inc, Naples, Florida); Orthocord (DePuy Mitek, Norwood, Massachusetts); Hi-Fi (formally Herculine; Linvatec Corp, Largo, Florida); MaxBraid (Teleflex Medical, Research Triangle Park, North Carolina); and Ethibond (Ethicon, Inc, Somerville, New Jersey). A matched pair of human deltoid muscle submerged in buffered saline solution (pH 7.4) was used as a test medium. The suture strengths were tested in 3 different scenarios. The 3 groups were as follows: control group without electrical current, coagulation group with direct introduction of electrical current on a coagulate setting for 2 seconds, and a cutting group with direct introduction of electrical current on a cut setting for 2 seconds. Hi-Fi suture seemed to be the least susceptible to damage by direct electrocautery application. Orthocord suffered the greatest loss of strength of all materials tested. This study demonstrates that exposure to electrocautery damages and weakens suture. Great care should be taken when electrocautery is used during arthroscopic repairs to prevent suture failure and preserve repair integrity. PMID:19968222

Shah, Anup A; Kang, Parminder; Deutsch, Allen

2009-12-01

258

A polyacrylamide gel phantom for radiofrequency ablation.  

PubMed

A polyacrylamide gel (PAG) containing bovine serum albumin (BSA) is introduced as a new tissue-mimicking phantom for the purpose of visualizing three-dimensional coagulation temperature distribution during radiofrequency ablation (RFA). The coagulation temperature of the phantom can be changed at the same range of biological tissue (50-60 degrees C) by adjusting the pH from 4.3 to 4.7. The phantom is transparent except in thermal coagulation regions which are ivory white. The physical properties of the phantom, such as density, electrical conductivity and specific heat capacity, are very favorable, similar to those of soft tissues. We illustrate the usefulness of the phantom in visualizing RFA lesions. This phantom has magnetic resonance properties which change drastically upon thermal coagulation, enabling its use for the characterization of RFA device, quality assurance, treatment planning and treatment verification. The PAG containing BSA, whose pH was adjusted from 4.3 to 4.7, is an attractive tissue-mimicking phantom suitable for RFA investigations. PMID:18608575

Bu-Lin, Zhang; Bing, Hu; Sheng-Li, Kuang; Huang, Ying; Rong, Wu; Jia, Li

2008-11-01

259

Characterization of tracked radiofrequency ablation in phantom.  

PubMed

In radiofrequency ablation (RFA), successful therapy requires accurate, image-guided placement of the ablation device in a location selected by a predictive treatment plan. Current planning methods rely on geometric models of ablations that are not sensitive to underlying physical processes in RFA. Implementing plans based on computational models of RFA with image-guided techniques, however, has not been well characterized. To study the use of computational models of RFA in planning needle placement, this work compared ablations performed with an optically tracked RFA device with corresponding models of the ablations. The calibration of the tracked device allowed the positions of distal features of the device, particularly the tips of the needle electrodes, to be determined to within 1.4 +/- 0.6 mm of uncertainty. Ablations were then performed using the tracked device in a phantom system based on an agarose-albumin mixture. Images of the sliced phantom obtained from the ablation experiments were then compared with the predictions of a bioheat transfer model of RFA, which used the positional data of the tracked device obtained during ablation. The model was demonstrated to predict 90% of imaged pixels classified as being ablated. The discrepancies between model predictions and observations were analyzed and attributed to needle tracking inaccuracy as well as to uncertainties in model parameters. The results suggest the feasibility of using finite element modeling to plan ablations with predictable outcomes when implemented using tracked RFA. PMID:17985649

Chen, Chun-Cheng R; Miga, Michael I; Galloway, Robert L

2007-10-01

260

Characterization of tracked radiofrequency ablation in phantom  

SciTech Connect

In radiofrequency ablation (RFA), successful therapy requires accurate, image-guided placement of the ablation device in a location selected by a predictive treatment plan. Current planning methods rely on geometric models of ablations that are not sensitive to underlying physical processes in RFA. Implementing plans based on computational models of RFA with image-guided techniques, however, has not been well characterized. To study the use of computational models of RFA in planning needle placement, this work compared ablations performed with an optically tracked RFA device with corresponding models of the ablations. The calibration of the tracked device allowed the positions of distal features of the device, particularly the tips of the needle electrodes, to be determined to within 1.4{+-}0.6 mm of uncertainty. Ablations were then performed using the tracked device in a phantom system based on an agarose-albumin mixture. Images of the sliced phantom obtained from the ablation experiments were then compared with the predictions of a bioheat transfer model of RFA, which used the positional data of the tracked device obtained during ablation. The model was demonstrated to predict 90% of imaged pixels classified as being ablated. The discrepancies between model predictions and observations were analyzed and attributed to needle tracking inaccuracy as well as to uncertainties in model parameters. The results suggest the feasibility of using finite element modeling to plan ablations with predictable outcomes when implemented using tracked RFA.

Chen, Chun-Cheng R.; Miga, Michael I.; Galloway, Robert L. [Department of Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, Nashville, Tennessee 37235 (United States)

2007-10-15

261

Radiofrequency ablation of hepatocellular carcinoma: Current status  

PubMed Central

Ablation therapy is one of the best curative treatment options for malignant liver tumors, and can be an alternative to resection. Radiofrequency ablation (RFA) of primary and secondary liver cancers can be performed safely using percutaneous, laparoscopic, or open surgical techniques, and RFA has markedly changed the treatment strategy for small hepatocellular carcinoma (HCC). Percutaneous RFA can achieve the same overall and disease-free survival as surgical resection for patients with small HCC. The use of a laparoscopic or open approach allows repeated placements of RFA electrodes at multiple sites to ablate larger tumors. RFA combined with transcatheter arterial chemoembolization will make the treatment of larger tumors a clinically viable treatment alternative. However, an accurate evaluation of treatment response is very important to secure successful RFA therapy. Since a sufficient safety margin (at least 0.5 cm) can prevent local tumor recurrences, an accurate evaluation of treatment response is very important to secure successful RFA therapy. To minimize complications of RFA, clinicians should be familiar with the imaging features of each type of complication. Appropriate management of complications is essential for successful RFA treatment.

Minami, Yasunori; Kudo, Masatoshi

2010-01-01

262

[Radiofrequency fulguration for supraventricular tachycardia in pediatrics].  

PubMed

Supraventricular tachycardias (SVT) are the most frequent cause of tachycardia in children. Its pharmacological treatment has adverse effects, is not curative, and is not always effective. During the last few years radiofrequency ablation (RF-A) has changed the treatment. The purpose of this study is to evaluate our experience in RF-A in children with SVT. Between 1990 and 1995, 92 patients (1 month to 17 years old) underwent electrophysiological study after the diagnosis of SVT. RF-A was attempted in 55 patients with accessory pathways (AP), slow-pathway of the atrioventricular node, or ectopic focus. The site of ablation was decided according to the electrical signals and the catheter position. The success of the RF-A was confirmed by the interruption of the tachycardia, the change in the sequence of activation of the intracardiac signals, the regression of the preexcitation, and the inability to reinduce tachycardia. RF-A was successful in 81% of the patients; 88% in those with a left AP, 56% in those with a right AP, and 100% in those with nodal reentry. Complications were seen in 7% of the patients: 3 with arterial obstruction, one with a minimal pneumothorax, and one with cardiac tamponade. During a follow up of 16.6 months there was no relapse nor late complications. We conclude that RF-A is a safe and effective procedure in pediatric patients with SVT. PMID:9041726

Heusser, F; Acevedo, V; Vergara, I; Fajuri, A; Neghme, R; Urcelay, G; Arnaiz, P; Cambón, A M; González, R

1996-06-01

263

Radiofrequency radiation effects on the common bean  

SciTech Connect

Our environment is bombarded daily with thousands of objects we can visually detect. However, invisible to humans are the electromagnetic waves that penetrate our environment. Electromagnetic waves consist of a large spectrum of waves including the harmful gamma rays, x-rays, and ultraviolet rays. The question that has increased tremendously is: can low energy electromagnetic waves become harmful to living organisms? The purpose of this study is to determine the effect of radiofrequency radiation on protein synthesis of the common bean. Phaseolus vulgaris (kidney bean) was surface-sterilized and allowed to germinate on Mushurage and Skoog`s medium for 1 week. Hypocotyls were wounded and placed on media to initiate callus production. Six petri dishes containing 1 g of callus were used in the experiment. Three dishes were exposed to 100kH in a Crawford cell for 24h. The remaining three petri dishes with callus were used as a control. After the exposure period, the protein from callus was extracted and analyzed by one-dimensional gel electrophoresis. The results show that hypocotyl growth was not different between control and experimental groups after 24 h. The result of one-dimensional gel electrophoresis did not show observable differences in protein synthesized by the control and experimental groups. Analysis of protein synthesis is still ongoing.

Thomkins, K.; Griggs, L.; Myles, E.L. [Tennessee State Univ., Nashville, TN (United States)] [and others

1995-07-01

264

A precautionary public health protection strategy for the possible risk of childhood leukaemia from exposure to power frequency magnetic fields  

Microsoft Academic Search

BACKGROUND: Epidemiological evidence showing a consistent association between the risk of childhood leukaemia and exposure to power frequency magnetic fields has been accumulating. This debate considers the additional precautionary intervention needed to manage this risk, when it exceeds the protection afforded by the exposure guidelines as recommended by the International Commission on Non-Ionizing Radiation Protection. METHODS: The Bradford-Hill Criteria are

Myron Maslanyj; Tracy Lightfoot; Joachim Schüz; Zenon Sienkiewicz; Alastair McKinlay

2010-01-01

265

A numerical evaluation of electromagnetic fields exposure on real human body models until 100 kHz  

Microsoft Academic Search

Purpose – The purpose of this paper is to describe how numerical models of human body have been applied for the evaluation of current density induced by strong magnetic field, to verify the respect of the basic restriction proposed by International Committee Non Ionizing Radiation Protection (ICNIRP) guidelines. Design\\/methodology\\/approach – Finite element method has been used in order to compute

F. Dughiero; M. Forzan; E. Sieni

2010-01-01

266

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

267

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

268

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

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Radiofrequency radiation for the heating of food, including microwave frequencies...THE PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency...

2013-04-01

269

Radiofrequency ablation of liver tumors (II): clinical application and outcomes.  

PubMed

Radiofrequency ablation is one of the alternatives in the management of liver tumors, especially in patients who are not candidates for surgery. The aim of this article is to review applicability of radiofrequency ablation achieving complete tumor destruction, utility of imaging techniques for patients' follow-up, indications for local ablative procedures, procedure-associated morbidity and mortality, and long-term results in patients with different tumors. The success of local thermal ablation consists in creating adequate volumes of tissue destruction with adequate "clear margin," depending on improved delivery of radiofrequency energy and modulated tissue biophysiology. Different volumes of coagulation necrosis are achieved applying different types of electrodes, pulsing energy sources, utilizing sophisticated ablation schemes. Some additional methods are used to increase the overall deposition of energy through alterations in tissue electrical conductivity, to improve heat retention within the tissue, and to modulate tolerance of tumor tissue to hyperthermia. Contrast-enhanced computed tomography, magnetic resonance imaging, ultrasound or positron emission tomography are applied to control the effectiveness of radiofrequency ablation. The long-term results of radiofrequency ablation are controversial. PMID:20440080

Vanagas, Tomas; Gulbinas, Antanas; Pundzius, Juozas; Barauskas, Giedrius

2010-01-01

270

Percutaneous pulsed radiofrequency in the treatment of cervical and lumbar radicular pain  

Microsoft Academic Search

BackgroundPrevious reports of the efficacy of percutaneous pulsed radiofrequency have been confounded by fewer case numbers, poor patient selection, and limited data on cervical or lumbar radicular pain. We used percutaneous pulsed radiofrequency for cervical and lumbar radicular pain, and the study has more than 100 cases for the analysis of the efficacy of percutaneous pulsed radiofrequency.

Shao-Ching Chao; Hsu-Tung Lee; Ting-Hsien Kao; Meng-Yin Yang; Yuang-Seng Tsuei; Chiung-Chyi Shen; Hsi-Kai Tsou

2008-01-01

271

Rapid Growth of Left Atrial Myxoma after Radiofrequency Ablation  

PubMed Central

Atrial myxoma is the most common benign tumor of the heart, but its appearance after radiofrequency ablation is very rare. We report a case in which an asymptomatic, rapidly growing cardiac myxoma arose in the left atrium after radiofrequency ablation. Two months after the procedure, cardiovascular magnetic resonance, performed to evaluate the right ventricular anatomy, revealed a 10 × 10-mm mass (assumed to be a thrombus) attached to the patient's left atrial septum. Three months later, transthoracic echocardiography revealed a larger mass, and the patient was diagnosed with myxoma. Two days later, a 20 × 20-mm myxoma weighing 37 g was excised. To our knowledge, the appearance of an atrial myxoma after radiofrequency ablation has been reported only once before. Whether tumor development is related to such ablation or is merely a coincidence is uncertain, but myxomas have developed after other instances of cardiac trauma.

Alvarez, Jose Rubio; de Alegria, Anxo Martinez; Quiroga, Juan Sierra; Nazar, Belen Adrio; Taboada, Carola Rubio; Comendador, Jose Manuel Martinez

2013-01-01

272

Arthroscopic triangular fibrocartilage complex debridement using radiofrequency probes.  

PubMed

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 was 22 (range 9-35) months. Seventeen patients experienced substantial pain relief. In three, the pain was unchanged. The mean flexion extension arc was 132 degrees , pronosupination arc 155 degrees and mean grip strength was 83% of that of the unaffected side. Using the modified Mayo wrist score, there were ten excellent, seven good and three fair results. No perioperative complications occurred. Radiofrequency probes were found to be safe and effective for use in triangular fibrocartilage complex debridement. These results compare favourably with other standard methods of treatment of this problem. PMID:16111792

Darlis, N A; Weiser, R W; Sotereanos, D G

2005-08-19

273

Rapid growth of left atrial myxoma after radiofrequency ablation.  

PubMed

Atrial myxoma is the most common benign tumor of the heart, but its appearance after radiofrequency ablation is very rare. We report a case in which an asymptomatic, rapidly growing cardiac myxoma arose in the left atrium after radiofrequency ablation. Two months after the procedure, cardiovascular magnetic resonance, performed to evaluate the right ventricular anatomy, revealed a 10 × 10-mm mass (assumed to be a thrombus) attached to the patient's left atrial septum. Three months later, transthoracic echocardiography revealed a larger mass, and the patient was diagnosed with myxoma. Two days later, a 20 × 20-mm myxoma weighing 37 g was excised. To our knowledge, the appearance of an atrial myxoma after radiofrequency ablation has been reported only once before. Whether tumor development is related to such ablation or is merely a coincidence is uncertain, but myxomas have developed after other instances of cardiac trauma. PMID:24082379

Alvarez, José Rubio; de Alegria, Anxo Martinez; Quiroga, Juan Sierra; Nazar, Belen Adrio; Taboada, Carola Rubio; Comendador, José Manuel Martinez

2013-01-01

274

High-order maps with acceleration for optimization of electrostatic and radio-frequency ion-optical elements  

NASA Astrophysics Data System (ADS)

A method has been developed to calculate accurate high-order ion-optical maps for electrostatic and radio-frequency accelerating elements. The method has been incorporated into the arbitrary-order map-based beam optics code COSY Infinity. The treatment is restricted to the case of negligible magnetic fields, as is typical of heavy-ion accelerating cavities, and does not include space charge. For validation purposes, the beam dynamics calculated for these elements is compared against ray tracing for typical beam and cavity parameters. Different from the ray-tracing approach, parameter changes of individual components typically require only recalculation of the maps of the particular components and not the entire system, and thus the method is particularly suitable for optimization. The approach developed for accurate analytical representation of the on- and off-axis electric fields of cylindrically symmetric electrostatic lenses and radio-frequency cavities is described. Some of the many possible applications for using accurate high-order map representations of Einzel lenses, electrostatic accelerating gaps, and radio-frequency accelerating structures are discussed.

Geraci, Andrew A.; Barlow, Teresa A.; Portillo, Mauricio; Nolen, Jerry A.; Shepard, Kenneth W.; Makino, Kyoko; Berz, Martin

2002-09-01

275

Numerical analysis of radio-frequency sheath-plasma interactions in the ion cyclotron range of frequencies  

SciTech Connect

A new finite element numerical scheme for analyzing self-consistent radio-frequency (RF) sheath-plasma interaction problems in the ion cyclotron range of frequencies is applied to various problems represented by simplified models for the tokamak scrape-off layer. The present code incorporates a modified boundary condition, which is called a sheath boundary condition, that couples the radio-frequency waves and sheaths at the material boundaries by treating the sheath as a thin vacuum layer. A series of numerical analyses in one- and two-dimensional domains show several important physical properties, such as the existence of multiple roots, hysteresis effects, presence and characteristics of the sheath-plasma waves, and the phase shift of a reflected slow wave, some of which are newly identified by introducing a spatially varying plasma density and background magnetic field.

Kohno, H. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Myra, J. R.; D'Ippolito, D. A. [Lodestar Research Corporation, 2400 Central Avenue P-5, Boulder, Colorado 80301 (United States)

2012-01-15

276

Histopomorphic Evaluation of Radiofrequency Mediated D?bridement 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.

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

2010-01-01

277

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.

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

2013-01-01

278

Radio frequency electromagnetic fields: mild hyperthermia and safety standards  

Microsoft Academic Search

This chapter is a short review of literature that serves as the basis for current safe exposure recommendations by ICNIRP (International Commission on Non-Ionizing Radiation Protection, 1998). and the IEEE C95.1 (IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3kHz to 300GHz, 2005) for exposure to radio frequency electromagnetic radiation (RF-EMF). Covered here

John A. D’Andrea; John M. Ziriax; Eleanor R. Adair

2007-01-01

279

Acute differential modulation of synaptic transmission and cell survival during exposure to pulsed and continuous radiofrequency energy  

Microsoft Academic Search

Pulsed radiofrequency, in which short bursts of radiofrequency energy are applied to nervous tissue, has been recently described as an alternative technique devoid of nerve injury, a subsequent side effect of thermal lesions created by continuous radiofrequency lesioning. Yet the mechanism of this effect remains unclear. In this study we compared the acute effects of pulsed versus continuous radiofrequency energy

Alex Cahana; Laszlo Vutskits; Dominique Muller

2003-01-01

280

RADIOFREQUENCY RADIATION: ACTIVITIES AND ISSUES, A 1986 PERSPECTIVE (JOURNAL VERSION)  

EPA Science Inventory

The following topics are discussed in the report: (1) environmental exposure levels of radiofrequency (RF) radiation; (2) Federal and other activities related to the control of exposure to RF radiation; (3) biological effects; (4) limitations in the knowledge of biological effect...

281

Infected sialocele: complication in masseter reduction using radiofrequency coagulation.  

PubMed

Radiofrequency coagulation was introduced to reduce the volume of masseter muscle. Radiofrequency procedure causes focal necrosis in masseter muscles, which leads to muscle hypoplasia and a slender lower face. We present a case of a 24-year-old woman who underwent radiofrequency coagulation to reduce masseter muscles. The patient experienced progressive erythematous swelling and noticed the mass around the right cheek 5 days after the procedure. On radiologic evaluation, a round cavity of 4-cm diameter containing air and fluid was observed. Incision and drainage was performed, and antibiotics were administrated intravenously. Blood-tinged purulent fluid was obtained, which was subsequently found to have a high amylase level. The swelling subsided, and there is no relapse up to 6 months after drainage. There are several complications of radiofrequency coagulation reported such as mucoserous fluid collections, late bleeding, infections, long-lasting pain, Stensen duct injury, facial nerve injuries, and limitation of temporomandibular joint movement. A well-designed operation plan and skilled technique are required to avoid these complications. PMID:22627453

Lim, Hyoseob; Lee, Il Jae; Kim, Joo Hyoung; Park, Myong Chul

2012-05-01

282

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.

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

2012-01-01

283

Radio-frequency energy in fusion power generation  

SciTech Connect

The history of radio-frequency (rf) energy in fusion experiments is reviewed, and the status of current efforts is described. Potential applications to tasks other than plasma heating are described, as are the research and development needs of rf energy technology.

Lawson, J.Q.; Becraft, W.R.; Hoffman, D.J.

1983-01-01

284

Radio-Frequency Size-Effect Line Shape for Gallium.  

National Technical Information Service (NTIS)

Study of the frequency dependence of the radio-frequency size effect line shape allows a determination of the portion of that line shape which can be interpreted as arising from extremal orbit electrons on the Fermi surface whose wave vector is simply rel...

A. Fukumoto M. W. P. Strandberg

1966-01-01

285

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.

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

2006-01-01

286

Radiofrequency Ablation in 447 Complex Unresectable Liver Tumors: Lessons Learned  

Microsoft Academic Search

Background: Radiofrequency ablation (RFA) is a promising technique for unresectable hepatic malignancies. We reviewed our RFA experience to identify variables affecting local recurrence. Methods: Patients undergoing RFA between 1997 and 2001 were reviewed for demographics, tumor size, pathology, diagnosis, recurrence, procedures, survival, and complications. Results: The 447 unresectable liver tumors were ablated in 198 procedures. The 153 patients averaged 61.9

Richard J. Bleicher; David P. Allegra; Dean T. Nora; Thomas F. Wood; Leland J. Foshag; Anton J. Bilchik

2003-01-01

287

Radiofrequency Ablation of Unresectable Hepatic Malignancies: Lessons Learned  

Microsoft Academic Search

Radiofrequency ablation (RFA) is increasingly used for the local destruction of unresectable hepatic malig- nancies. Relative contraindications include tumors in proximity to vital structures that may be injured by RFA and lesions whose size exceeds the ablation capabilities of the probe system employed. Given current technology, we believe that RFA should be cautiously utilized for lesions greater than 5 cm

ANTON J. BILCHIK; THOMAS F. W OOD

288

Unipolar radiofrequency treatment to improve the appearance of cellulite  

Microsoft Academic Search

Background: Previous studies suggest that radiofrequency (RF) energy may be effective as a treatment for cellulite. Objective: This bilateral paired blinded comparative study assesses the efficacy and safety of a unipolar RF device for improving the appearance of cellulite using a new quantitative cellulite grading system. Methods: In this randomized, blinded, split-design study, 10 individuals (aged 32-57 years) with a

Jeffrey S. Dover; Kenneth A. Arndt

2008-01-01

289

Genetic damage in subjects exposed to radiofrequency radiation.  

PubMed

Despite many research efforts and public debate there is still great concern about the possible adverse effects of radiofrequency (RF) radiation on human health. This is especially due to the enormous increase of wireless mobile telephones and other telecommunication devices throughout the world. The possible genetic effects of mobile phone radiation and other sources of radiofrequencies constitute one of the major points of concern. In the past several review papers were published on laboratory investigations that were devoted to in vitro and in vivo animal (cyto)genetic studies. However, it may be assumed that some of the most important observations are those obtained from studies with individuals that were exposed to relatively high levels of radiofrequency radiation, either as a result of their occupational activity or as frequent users of radiofrequency emitting tools. In this paper the cytogenetic biomonitoring studies of RF-exposed humans are reviewed. A majority of these studies do show that RF-exposed individuals have increased frequencies of genetic damage (e.g., chromosomal aberrations) in their lymphocytes or exfoliated buccal cells. However, most of the studies, if not all, have a number of shortcomings that actually prevents any firm conclusion. Radiation dosimetry was lacking in all papers, but some of the investigations were flawed by much more severe imperfections. Large well-coordinated multidisciplinary investigations are needed in order to reach any robust conclusion. PMID:19073278

Verschaeve, Luc

2008-11-27

290

Intraoperative radiofrequency ablation or cryoablation for hepatic malignancies  

Microsoft Academic Search

Background: The majority of patients with primary or metastatic malignancies confined to the liver are not candidates for resection because of tumor size, location, multifocality, or inadequate functional hepatic reserve. Cryoablation has become a common treatment in select groups of these patients with unresectable liver tumors. However, hepatic cryoablation is associated with significant morbidity. Radiofrequency ablation (RFA) is a technique

A. Scott Pearson; Francesco Izzo; R. Y. Declan Fleming; Lee M Ellis; Paolo Delrio; Mark S Roh; Jennifer Granchi; Steven A Curley

1999-01-01

291

Radio-Frequency Technology Division: Programs, Activities, and Accomplishments, 2001.  

National Technical Information Service (NTIS)

The Radio-Frequency Technology Division is a critical national resource for a wide range of customers. U.S. industry is the primary customer both for the Division's measurement services and for technical support on the test and measurement methodology nec...

2002-01-01

292

Towards Optimization of Probe Placement for Radio-Frequency Ablation  

Microsoft Academic Search

We present a model for the optimal placement of mono- and bipolar probes in radio-frequency (RF) ablation. The model is based on a numerical computation of the probe's electric potential and of the steady state of the heat distribution during RF ablation. The optimization is performed by minimizing a temperature based objective functional under these constraining equations. The paper discusses

Inga Altrogge; Tim Kröger; Tobias Preusser; Christof Büskens; Philippe L. Pereira; Diethard Schmidt; Andreas Weihusen; Heinz-otto Peitgen

2006-01-01

293

Operating a radio-frequency plasma source on water vapor  

Microsoft Academic Search

A magnetically enhanced radio-frequency (rf) plasma source operating on water vapor has an extensive list of potential applications. In this work, the use of a rf plasma source to dissociate water vapor for hydrogen production is investigated. This paper describes a rf plasma source operated on water vapor and characterizes its plasma properties using a Langmuir probe, a residual gas

Sonca V. T. Nguyen; John E. Foster; Alec D. Gallimore

2009-01-01

294

Stabilization of magnetohydrodynamic modes by applied radiofrequency waves  

Microsoft Academic Search

A kinetic theory describing the nonlinear interaction of radiofrequency waves with low frequency magnetohydrodynamic modes is presented. The calculation of the nonlinear force density on a fluid element includes both ponderomotive and sideband mode coupling terms and allows arbitrary rf wave polarization. Electromagnetic effects and wave-particle interactions are retained in the analysis. The influence of the nonlinear force on magnetohydrodynamic

D. A. Dippolito; J. R. Myra

1986-01-01

295

Palliation of Painful Perineal Metastasis Treated with Radiofrequency Thermal Ablation  

Microsoft Academic Search

We report a case of painful perineal metastasis from urinary bladder carcinoma in a 73-years-old woman, treated with CT-guided radiofrequency ablation (RFA). The pain was immediately relieved and follow-up at 1 and 6 months showed total necrosis of the mass. One year later, the patient has no pain and her quality of life is improved.

L. Thanos; S. Mylona; V. Kalioras; M. Pomoni; N. Batakis

2005-01-01

296

Radiofrequency Ablation in the Treatment of Breast Cancer Liver Metastases  

Microsoft Academic Search

Minimally invasive, image-guided thermal ablation is gaining acceptance for the treatment of solid tumour deposits and its use is increasing. This overview discusses one method of thermal ablation in one palliative setting; the local control of breast cancer liver metastases (BCLM) using radiofrequency ablation. Breast cancer is common and over half of all women diagnosed with metastatic disease develop BCLM.

R. Illing; A. Gillams

2010-01-01

297

Use of the radio-frequency quadrupole structure as a cyclotron axial-buncher system  

SciTech Connect

The radio-frequency quadrupole (RFQ) is a new linear accelerating structure being developed as a low-velocity linac. In this structure rf electric fields are used to simultaneously focus, bunch, and accelerate ions. The slow introduction of the accelerating field results in the adiabatic bunching of a dc ion beam with a large capture efficiency. Realistic computer simulations have shown that this new structure could also be used as a buncher in the axial injection system of a cyclotron. A description of the RFQ geometry and its general properties is given. A preliminary design is presented for a variable frequency RFQ to be used as buncher in the axial injection system of a variable energy cyclotron. The operating parameters for this RFQ are discussed.

Hamm, R.W.; Swenson, D.A.; Wangler, T.P.

1981-01-01

298

Ferromagnetism in Eu-doped ZnO films deposited by radio-frequency magnetic sputtering  

NASA Astrophysics Data System (ADS)

This paper reports that Eu-doped ZnO films were successfully deposited on silicon (100) by radio-frequency magnetic sputtering. The x-ray diffraction patterns indicate that Eu substitutes for Zn in the lattice. Ferromagnetic loops were obtained by using superconducting quantum interference device at 10 K and room temperature. No discontinuous change was found in both of the zero-field-cooled and field-cooled curves. The observed ferromagnetism in Eu-doped ZnO can be attributed to a single magnetic phase. The saturation magnetisation decreased remarkably for the Eu-doped ZnO prepared by introducing 5% of oxygen in the sputtering gas or by the post annealing in O2, suggesting that the defects play key roles in the development of ferromagnetism in Eu-doped ZnO films.

Tan, Yong-Sheng; Fang, Ze-Bo; Chen, Wei; He, Pi-Mo

2010-09-01

299

Perturbations of plant leaflet rhythms caused by electromagnetic radio-frequency radiation.  

PubMed

The minute-range up and down rhythms of the lateral leaflets of Desmodium gyrans has been studied when exposed to electromagnetic radiation in the radio-frequency (RF) range. The RF radiation was applied as homogeneous 27.12 MHz fields in specially-designed exposure cells(and in some cases as non-homogeneous radiation of 27 MHz, amplitude modulated by 50 Hz, in front of commercial diathermy equipment). All fields were applied as pulses. We report effects in the leaflet rhythms such as temporary changes in the amplitude, period, and phase. The radiation could also cause temporary or complete cessations of the rhythms. The lowest dose (8 W/cm2) used was still effective. PMID:8323575

Ellingsrud, S; Johnsson, A

1993-01-01

300

Reduction of the radiofrequency heating of metallic devices using a dual-drive birdcage coil.  

PubMed

In this work, it is demonstrated that a dual-drive birdcage coil can be used to reduce the radiofrequency heating of metallic devices during magnetic resonance imaging. By controlling the excitation currents of the two channels of a birdcage coil, the radiofrequency current that is induced near the lead tip could be set to zero. To monitor the current, the image artifacts near the lead tips were measured. The electric field distribution was controlled using a dual-drive birdcage coil. With this method, the lead currents and the lead tip temperatures were reduced substantially [<0.3 °C for an applied 4.4 W/kg SAR compared to >4.9 °C using quadrature excitation], as demonstrated by phantom and animal experiments. The homogeneity of the flip angle distribution was preserved, as shown by volunteer experiments. The normalized root-mean-square error of the flip angle distribution was less than 10% for all excitations. The average specific absorption rate increased as a trade-off for using different excitation patterns. PMID:22576183

Eryaman, Yigitcan; Turk, Esra Abaci; Oto, Cagdas; Algin, Oktay; Atalar, Ergin

2012-05-10

301

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.

Berjano, Enrique J

2006-01-01

302

Radiofrequency Ablation with the Real-Time Virtual Sonography System for Treating Hepatocellular Carcinoma Difficult to Detect by Ultrasonography  

PubMed Central

Radiofrequency ablation has been applied to treat hepatocellular carcinoma, with favorable therapeutic outcomes. Nevertheless, practitioners have approached radiofrequency ablation with some reluctance due to the difficulty of identifying isoechoic tumors and recurrent tumors. The aim of the present study is to investigate the efficacy of Real-time Virtual Sonography to treat hepatocellular carcinoma difficult to detect by conventional ultrasonography. Real-time Virtual Sonography is a system generating multiplanar reconstruction images in real-time using the Hitachi medico EUB-8500 equipped with a probe. The system included following components: 1) digital imaging and communications in medicine (DICOM) data from dynamic CT, 2) a magnetic field generator to match the multiplanar reconstruction image on the monitor and the actual ultrasonography image, 3) the cross section with the tumor displayed as a multiplanar reconstruction image. Total twenty-five nodules of twenty-one patients underwent radiofrequency ablation monitored by Real-time Virtual Sonography. All nodules difficult to detect via conventional ultrasonography were clearly visualized in real-time. The average nodule diameter was 2.4 ± 1.6 cm, and punctures and coagulation were performed an average of 2.2 and 3 times per session. Dynamic CT after session confirmed effective coagulation of each nodule. In conclusion, this study demonstrates that the present system is capable of effectively and accurately treating tumors difficult to detect by conventional ultrasonography.

Kawasoe, Hiroaki; Eguchi, Yuichiro; Mizuta, Toshihiko; Yasutake, Tsutomu; Ozaki, Iwata; Shimonishi, Tomonori; Miyazaki, Kohji; Tamai, Tsutomu; Kato, Akira; Kudo, Sho; Fujimoto, Kazuma

2007-01-01

303

Non invasive radiofrequency diagnostics of cancer. The Bioscanner — Trimprob technology and clinical applications  

NASA Astrophysics Data System (ADS)

A new paper by Pokorny, Vedruccio, Cifra, Kucera, titled Cancer physics: Diagnostics based on damped cellular elasto-electrical vibrations in microtubules, recently available on Eur. Biophys. J., discloses the mechanism of active grown cancer tissues interaction with a Non- Linear Resonance Interaction (NLRI) Bioscanner Trimprob diagnostic device that is certified and ready to be used to investigate suspected cases of disease and cancer. This technology spreads early capabilities of cancer detection by means of low level radiofrequency oscillations in UHF band. The system is based on an unique and extremely innovative non- linear radiofrequency oscillator working on 462-465 MHz plus the harmonics. The diseased tissues suspected of cancer, are irradiated by means of a handy probe near field emission, while a spectrum analyzer placed in the far field detects by means of a small antenna, the oscillator interaction within the tissues. The Bioscanner is characterized by a high dynamic range, in the order of 30 or more decibel, and is useful for detection of small cancer agglomerates, if used by a well trained operator. At the resonance, the free running oscillator locks-in on the specific interaction frequency, in a sharp frequency window centered on 462 MHz; the resulting effect is evidenced by a deep decrease of the 462 MHz spectral line propagation in the far field around the oscillator probe. The NLRI provides a selective characterization, like a sort of a electronic biopsy response of biologic tissues in support of modern imaging diagnostics. Further to existing literature describing methods for cancer detections by means of electromagnetic fields this paper shows this innovative in vivo medical diagnostic equipment and some clinical applications.

Vedruccio, Clarbruno; Ricci Vedruccio, Carla

2011-12-01

304

Determining EHV transmission line magnetic fields by applying the vector magnetic potential concept  

Microsoft Academic Search

These days renewed attention is being given to the biological effects of non-ionizing radiations from the power frequency electromagnetic fields of extra-high-voltage (EHV) transmission lines. Prior to fixing limits about the safe levels of human exposure to such radiation, it is essential to determine its field magnitudes. In this paper the concept of vector magnetic potential has been extended for

S. Shahnawaz Ahmed; Rezaul Haque; A. K. M. Rashidul Hasan; Aminul Haque Siddiqui

1995-01-01

305

Dosimetry for non-ionizing radiation  

SciTech Connect

Several commercially available phosphor-teflon dosimeters were subjected to thermal fade studies. The thermoluminescence dosimetry (TLD) tags were washed and air dried prior to each ionizing radiation pretreatment. Readings made over 3 weeks on the CaF2:Mn and CaF2:Dy TLD tags did not produce measurable thermal-fade characteristics for the 22 to 31/sup 0/C temperature range. Nonionizing radiation treatments were at 2.45 GHz. While the results obtained did demonstrate decreases in signal levels over time and temperature changes, the patterns were not smooth, making it impossible to establish differences in TLD readings as quantitative measures of temperature differences which could serve as measures of long-term exposures to nonionizing radiation. The authors concluded that, due to the irregularities that existed in the thermal fade characteristics, the dosimeter would not be suitable for quantifying exposures to nonionizing radiation. There was significant potential in the device, however, as an indicator of radiation leakage or exposure.

Fanslow, G.E.

1981-03-01

306

Members of the ad-hoc Advisory Group each briefly presented a survey of different aspects of human exposures to selected physical agents, the published evidence for an associated risk of cancer, and the current state of research on the subject. These surveys included, for ionizing radiation: exposure assessment; background radiation and cosmic radiation; medical uses of radiation; nuclear power; and testing and use of nuclear weapons  

Microsoft Academic Search

For non-ionizing radiation, these surveys included: how various exposures are defined; the nature of both occupational and environmental exposures; electromagnetic fields in static, extremely low frequency (ELF) and radiofrequency (RF) energy ranges; radar; and biological effects of various exposures. The Advisory Group also heard presentations on the IARC Monographs Programme, and discussed how inclusion of additional physical agents in the

M. Blettner; E. Cardis; J. Hall-Posner; M. Martuzzi; D. McGregor; J. Rice; J. Wilbourn; J. Mitchell; S. Reynaud

307

Adaptive radiofrequency hyperthermia-phased array system for improved cancer therapy: phantom target measurements.  

PubMed

A computer-controlled adaptive radio-frequency hyperthermia system for improved therapeutic tumour heating is experimentally investigated. Adaptive array feedback techniques are used to modify the electric-field and temperature distribution in hyperthermia experiments with homogeneous and heterogeneous phantom targets. A commercial hyperthermia phased-array antenna system at the SUNY Health Science Center in Syracuse, New York, has been modified to implement adaptive nulling and adaptive focusing algorithms. The hyperthermia system is the BSD Medical Corporation Model BSD-2000 with Sigma-60 annular phased-array antenna applicator. The transmit phased array system is made adaptive by software modifications which invoke a gradient-search feedback algorithm. The gradient-search algorithm implements the method of steepest descent for adaptive nulling (power minimization) and the method of steepest ascent for adaptive focusing (power maximization). The feedback signals are provided by electric-field short-dipole probe antennas. With an adaptive hyperthermia array using real-time measured data, it may be possible to maximize the applied electric field at a tumour position in a complex scattering target body and simultaneously minimize or reduce the electric field at target positions where undesired high-temperature regions (hot spots) occur. The measured phantom-target data indicate that adaptive nulling can reduce the electric field at one or more target positions while simultaneously focusing the electric field at a deep-seated position within the target. PMID:8064180

Fenn, A J; King, G A

308

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

309

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

310

Comparison of Two Techniques for Radio-frequency Hepatic Tumor Ablation through Numerical Simulation  

NASA Astrophysics Data System (ADS)

We simulate the thermal and electrical processes, involved in the radio-frequency ablation procedure. In this study, we take into account the observed fact, that the electrical conductivity of the hepatic tissue varies during the procedure. With the increase of the tissue temperature to a certain level, a sudden drop of the electrical conductivity is observed. This variation was neglected in some previous studies. The mathematical model consists of two parts--electrical and thermal. The energy from the applied AC voltage is determined first, by solving the Laplace equation to find the potential distribution. After that, the electric field intensity and the current density are directly calculated. Finally, the heat transfer equation is solved to determine the temperature distribution. Heat loss due to blood perfusion is also accounted for. The simulations were performed on the IBM Blue Gene/P massively parallel computer.

Kosturski, N.; Margenov, S.; Vutov, Y.

2011-11-01

311

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

312

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

313

Efficiency and safety of new radiofrequency identification system in a hospital.  

PubMed

Radiofrequency identification (RFID) applications have the capability to obtain real-time information on the location and properties of tagged people or objects. The efficiency and safety of the new RFID system (UHF band, 953 MHz) were tested in our hospital. We examined whether 1 to 4 persons and medical equipment with IC tags were captured by RFID readers in a laboratory. We next tested whether electric signals produced by RFID could affect medical devices. New radio frequency tags provided extensive patient identification and helped track capital equipment within a laboratory. Electric fields produced by the new RFID did not significantly affect medical devices in our hospital. New RFID system was safe and useful for tracking people and medical equipments in a hospital. As healthcare systems today involve increasingly complex and interrelated processes, the new RFID technologies may enhance patient safety, and wellness, and reduce staff workloads in a hospital. PMID:23920806

Saito, Yuichiro; Suzuki, Ryoji; Torikai, Kota; Hasegawa, Takashi; Sakamaki, Tetsuo

2013-01-01

314

Scientific basis for the Soviet and Russian radiofrequency standards for the general public.  

PubMed

The former Soviet Union (USSR) and the USA were the first countries to introduce standards limiting exposure to radiofrequency (RF) fields. However, the exposure limits in the USSR standards were always much lower than those in the USA and other countries. The objective of this article is to provide a history of the development of the Soviet and Russian RF standards. In addition, we summarize the scientific evidence used to develop the original USSR RF and subsequent Russian public health standards, as well as the mobile telecommunications standard published in 2003, but we do not critique them. We also describe the protective approaches used by the Soviet and Russian scientists for setting their limits. A translation of the papers of the key studies used to develop their standards is available in the online version of this publication. PMID:22753071

Repacholi, Michael; Grigoriev, Yuri; Buschmann, Jochen; Pioli, Claudio

2012-07-02

315

Non-Invasive Radiofrequency-Induced Targeted Hyperthermia for the Treatment of Hepatocellular Carcinoma  

PubMed Central

Targeted biological therapies for hepatocellular cancer have shown minimal improvements in median survival. Multiple pathways to oncogenesis leading to rapid development of resistance to such therapies is a concern. Non-invasive radiofrequency field-induced targeted hyperthermia using nanoparticles is a radical departure from conventional modalities. In this paper we underscore the need for innovative strategies for the treatment of hepatocellular cancer, describe the central paradigm of targeted hyperthermia using non-invasive electromagnetic energy, review the process of characterization and modification of nanoparticles for the task, and summarize data from cell-based and animal-based models of hepatocellular cancer treated with non-invasive RF energy. Finally, future strategies and challenges in bringing this modality from bench to clinic are discussed.

Raoof, Mustafa; Curley, Steven A.

2011-01-01

316

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

NASA Astrophysics Data System (ADS)

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.

2011-12-01

317

Radiofrequency for the treatment of stress urinary incontinence in women  

Microsoft Academic Search

Stress urinary incontinence (SUI) is a socially disabling disorder that affects a large population of women around the world.\\u000a Surgical treatments for SUI typically seek to recapitulate the support of the endopelvic fascia and reduce urethral hypermobility\\u000a or improve urethral compressive forces. Radiofrequency energy is a potent tool for such treatment, as it is in other medical\\u000a specialties. The development

Benjamin Dillon; Roger Dmochowski

2009-01-01

318

Laparoscopic Ultrasound-Guided Radiofrequency Ablation of Uterine Fibroids  

Microsoft Academic Search

Four patients with symptomatic uterine fibroids measuring less than 6 cm underwent laparoscopic ultrasound-guided radiofrequency\\u000a ablation (RFA) using multiprobe-array electrodes. Follow-up of the treated fibroids was performed with gadolinium-enhanced\\u000a magnetic resonance imaging (MRI) and patients’ symptoms were assessed by telephone interviews. The procedure was initially\\u000a technically successful in 3 of the 4 patients and MRI studies at 1 month demonstrated

Andrea Milic; Murray R. Asch; Peter A. Hawrylyshyn; Lisa M. Allen; Terence J. Colgan; John R. Kachura; Eran B. Hayeems

2006-01-01

319

Laparoscopic Ultrasound-Guided Radiofrequency Ablation of Uterine Fibroids  

Microsoft Academic Search

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

Andrea Milic; Murray R. Asch; Peter A. Hawrylyshyn; Lisa M. Allen; Terence J. Colgan; John R. Kachura; Eran B. Hayeems

2006-01-01

320

CT-guided radiofrequency ablation of a bronchogenic carcinoma  

Microsoft Academic Search

We report on the successful use of percutaneous CT-guided radiofrequency ablation (RFA) of a peripheral bronchogenic carcinoma in a 73-year-old patient. RFA was the favoured treatment option in this patient, who owing to comorbid factors was not a candidate for surgery. A 15 G LeVeen2 Needle Electrode (RadioTherapeutics, Sunnyvale, USA) with an array diameter of 3.0 cm was connected to

O Schaefer; C LOHRMANN; M LANGER

2003-01-01

321

Stereotactic Radiofrequency Ablation: Providing New Dimensions in Interventional Oncology  

Microsoft Academic Search

\\u000a Purpose: Radiofrequency ablation (RFA) has become widely accepted as the first-line local tumor therapy of surgical untreatable\\u000a primary and secondary liver malignancies. Main risk factors for residual tumor and local recurrence are tumor size (> 3cm),\\u000a imprecise probe placement and insufficient overlapping of multiple ablation spheres. Our aim was to evaluate if stereotactic\\u000a RFA may improve the results of conventional

G. Widmann; M. Haidu; L. Pallwein; P. Kovacs; W. Jaschke; R. J. Bale

322

Thermal Ablation for Benign Thyroid Nodules: Radiofrequency and Laser  

PubMed Central

Although ethanol ablation has been successfully used to treat cystic thyroid nodules, this procedure is less effective when the thyroid nodules are solid. Radiofrequency (RF) ablation, a newer procedure used to treat malignant liver tumors, has been valuable in the treatment of benign thyroid nodules regardless of the extent of the solid component. This article reviews the basic physics, techniques, applications, results, and complications of thyroid RF ablation, in comparison to laser ablation.

Lee, Jeong Hyun; Valcavi, Roberto; Pacella, Claudio M.; Rhim, Hyunchul; Na, Dong Gyu

2011-01-01

323

Radiofrequency ablation of a cervical osteoid osteoma: a transthyroid approach  

Microsoft Academic Search

We present a 16-year-old girl with an osteoid osteoma in the vertebral body of C5. Given the difficulty of surgically treating\\u000a the lesion, radiofrequency ablation was used. Percutaneous needle access to this lesion in the anterior aspect of the cervical\\u000a vertebral body was limited by the many critical adjacent structures. We present our successful treatment of this lesion utilizing\\u000a a

Sean A. Sutphen; James W. Murakami

2007-01-01

324

Interconnect Parasitic Extraction Tool for Radio-Frequency Integrated Circuits  

Microsoft Academic Search

\\u000a A tool to model interconnect parasitics in radio-frequency (RF) integrated circuits (RFICs) is presented. Accurate modeling\\u000a is achieved by combining a detailed RLC wire model together with a distributed RC substrate model. Wire geometry is fractured\\u000a to ensure accurate modeling of wave propagation as well as displacement current due to substrate losses. The wire model includes\\u000a resistance and coupled capacitance

Jérôme Lescot; François J. R. Clément

2003-01-01

325

Cosmic Radio-Frequency Radiation Near One Megacycle  

Microsoft Academic Search

Observations of cosmic radio-frequency radiation on frequencies of 2130 kc\\/sec, 1435 kc\\/sec, 900 kc\\/sec, and 520 kc\\/sec have been made, using a method of recording which effectively reduces interference from atmospherics. At these frequencies, the intensity of the radiation is approximately 10 - watt per square metre per cycle per second** per steradian. The ionospheric effects associated with observations near

Grote Reber; G. R. Ellis

1956-01-01

326

Particle simulations of radio-frequency glow discharges  

Microsoft Academic Search

Particle-in-cell (PIC) simulations are used to study the structure of radio-frequency (RF) glow discharges in helium between parallel-plate electrodes. The authors have examined a range of conditions and report on a variety of observed phenomena. Comparisons to experiment and analytical models are made, when possible. The differences between discharges in which secondary electrons play a key role in sustaining the

M. Surendra; David B. Graves

1991-01-01

327

Dynamic impedance measurements during radio-frequency heating of cornea  

Microsoft Academic Search

Hyperopia affects approximately 25% of the population. The aim of different heating modalities for the treatment of hyperopia is to steepen the central curvature of the cornea. Conductive keratoplasty (CK) involves the placement of radio-frequency (RF) lesions around a 7-mm-diameter ring concentric with the pupil of the eye. Dynamics of lesion formation during CK depend on corneal electrical impedance, which

Bernard Choi; Jihoon Kim; Ashley J. Welch; John A. Pearce

2002-01-01

328

Stabilization of magnetohydrodynamic modes by applied radio-frequency waves  

Microsoft Academic Search

A kinetic theory describing the nonlinear interaction of radio-frequency waves with low-frequency magnetohydrodynamic modes is presented. The calculation of the nonlinear force density on a fluid element includes both ponderomotive and sideband mode coupling terms and allows arbitrary rf wave polarization. Electromagnetic effects and wave--particle interactions are retained in the analysis. The influence of the nonlinear force on magnetohydrodynamic plasma

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

1986-01-01

329

Stabilization of magnetohydrodynamic modes by applied radio-frequency waves  

Microsoft Academic Search

A kinetic theory describing the nonlinear interaction of radio-frequency waves with low-frequency magnetohydrodynamic modes is presented. The calculation of the nonlinear force density on a fluid element includes both ponderomotive and sideband mode coupling terms and allows arbitrary rf wave polarization. Electromagnetic effects and wave–particle interactions are retained in the analysis. The influence of the nonlinear force on magnetohydrodynamic plasma

D. A. D’Ippolito; J. R. Myra

1986-01-01

330

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

331

Radiofrequency Catheter Ablation of Supraventricular Tachycardia in Children and Adolescents  

Microsoft Academic Search

The objective of this study is to provide results and costs of catheter ablation in children and adolescents in a low-income\\u000a country. Reports from first-world countries have demonstrated the cost-effectiveness of radiofrequency catheter ablation (RFCA)\\u000a compared to medical treatment of supraventricular tachycardia (SVT). The study included 28 patients younger than 18 years\\u000a of age with SVT in a pediatric cardiology

Vladimiro L. Vida; Gonzalo S. Calvimontes; Maximo O. Macs; Patricia Aparicio; Joaquin Barnoya; Aldo R. Castañeda

2006-01-01

332

The genotoxic effect of radiofrequency waves on mouse brain  

Microsoft Academic Search

Concerns about the health effects of radiofrequency (RF) waves have been raised because of the gradual increase in usage of\\u000a cell phones, and there are scientific questions and debates about the safety of those instruments in daily life. The aim of\\u000a this study is to evaluate the genotoxic effects of RF waves in an experimental brain cell culture model. Brain

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

333

Lung Tumor Radiofrequency Ablation: Where Do We Stand?  

Microsoft Academic Search

Today, radiofrequency ablation (RFA) of primary and metastatic lung tumor is increasingly used. Because RFA is most often\\u000a used with curative intent, preablation workup must be a preoperative workup. General anesthesia provides higher feasibility\\u000a than conscious sedation. The electrode positioning must be performed under computed tomography for sake of accuracy. The delivery\\u000a of RFA must be adapted to tumor location,

Thierry de Baère

2011-01-01

334

Ethical Implications of Implantable Radiofrequency Identification (RFID) Tags in Humans  

Microsoft Academic Search

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

Kenneth R. Foster; Jan Jaeger

2008-01-01

335

Pulsed radiofrequency treatment of the Gasserian ganglion in patients with idiopathic trigeminal neuralgia  

Microsoft Academic Search

Pulsed radiofrequency treatment has been described as a minimal invasive alternative to radiofrequency thermocoagulation for the management of chronic pain syndromes. We present here our first five high-risk patients with idiopathic trigeminal neuralgia who were treated with pulsed radiofrequency after multidisciplinary assessment; with a mean follow-up of 19.2 months (range 10–26). These patients were at high risk due to age,

Jan Van Zundert; Steven Brabant; Erik Van de Kelft; Alex Vercruyssen; Jean-Pierre Van Buyten

2003-01-01

336

Simulator for optimization of radio-frequency pulses in magnetic resonance imaging  

Microsoft Academic Search

The surface coils being driven by radio-frequency pulses are often a primary choice in magnetic resonance imaging for both radio-frequency excitation and reception of weak magnetic resonance imaging signals from the volume of interest. The advantages of the surface coils compared to the volume coils are the minimized radio-frequency power deposition in tissue and the improved detection sensitivity due to

Johanna Öberg

337

Radiofrequency catheter ablation of accessory pathways in infants.  

PubMed Central

OBJECTIVE: To evaluate the indications, results and complications of radiofrequency catheter ablation in small infants with supraventricular tachycardia due to an accessory atrioventricular pathway. METHODS: Five infants less than 9 months old underwent radiofrequency catheter ablation of accessory pathways. Ablation was done for medically refractory tachyarrhythmia associated with aborted sudden death in two patients, left ventricular dysfunction in one, failure of antiarrhythmic drugs in one, and planned cardiac surgery in one. All five patients underwent a single successful procedure. Three left free wall pathways were ablated by transseptal approach, a right posteroseptal pathway was ablated from the inferior vena cava, and a left posteroseptal pathway was approached from the inferior vena cava into the coronary sinus. A deflectable 5F bipolar electrode catheter with a 3 mm tip was used. RESULTS: A sudden increment in impedance indicative of coagulum formation was observed in two procedures. One patient developed a transient ischaemic complication after ablation of a left lateral accessory pathway by transseptal approach. This patient had mild pericardial effusion after the procedure. Moderate pericardial effusion was also noted in another patient. After a mean follow up of 18.4 months all patients are symptom free without treatment. CONCLUSIONS: Radiofrequency catheter ablation can be performed successfully in infants. Temperature monitoring in 5F ablation catheters would be desirable to prevent the development of coagulum. Echocardiography must be performed after the ablation procedure to investigate pericardial effusion. Images

Benito, F.; Sanchez, C.

1997-01-01

338

Radiofrequency ablation for hepatocellular carcinoma: use of low vs maximal radiofrequency power  

PubMed Central

Objectives To investigate whether radiofrequency (RF) ablation with low power (LP) or maximal power (MP) for hepatocellular carcinoma (HCC) can achieve optimal ablation and fewer adverse effects. Methods RF ablation was performed with MP in 101 patients (129 tumours) and with LP in 46 patients (61 tumours). MP RF ablation used power of >120 W. RF power below this was designated as LP. Clinical outcomes were also analysed in subgroups of high-risk tumours near the bile duct and blood vessels. Results Primary effectiveness was achieved in 91.8% in the LP group and 89.9% in the MP group (p=0.795). 1 and 2-year local tumour progression rates were 28% and 30%, respectively, in the LP group, and 24% and 29%, respectively, in the MP group (p=0.70). 1 and 2-year survival rates were 98% and 98%, respectively, in the LP group, and 93% and 90%, respectively, in the MP group (p=0.216). The MP group had more adverse effects, with post-RF ablation syndrome, asymptomatic pleural effusion and ascites, than the LP group (20% vs 39% in the MP group; p=0.027); however, there was no significant difference in major complication rates (6% in the MP and LP groups; p=0.497). Among the patients with high-risk tumours, RF ablation using MP vs LP was comparable in primary effectiveness (91.7% vs 95.2%; p=0.618), local tumour progression (42.9% vs 29.2%; p=0.304) and overall complications (5% vs 8%; p=0.618). Conclusion RF ablation with LP and MP are comparable in clinical outcomes but considerably fewer adverse effects were encountered in the LP group.

Macatula, T C; Lin, C-C; Lin, C-J; Chen, W-T; Lin, S-M

2012-01-01

339

Effects of simultaneous radiofrequency radiation and chemical exposure of mammalian cells. Volume 2. Final report, 2 January 1984-31 December 1986  

Microsoft Academic Search

A circulating water-bath exposure system was designed for in vitro radio-frequency radiation (RFR) exposure studies in the 915- to 2450-MHz range. A continuously rotating styrofoam float, holding ten T-25 tissue-culture flasks, averages out field heterogeneity and allows mixing in the medium in the flasks. The presence of cells in the exposure flask (as attached monolayer or cell suspension) did not

M. L. Meltz; V. Ciaravino; J. J. Kerbacher; P. Eagan

1988-01-01

340

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

341

Percutaneous radiofrequency ablation versus surgical radiofrequency-assisted nodulectomy in treatment of small single nodes of hepatocellular carcinoma: our experience.  

PubMed

Aim: Surgical resection usually represents the treatment of choice for solitary hepatocellular carcinoma (HCC) in cirrhotic patients, with well preserved liver function; local ablative strategies are the best treatment option for patients with small tumors who are not candidates for surgical resection or liver transplantation. Several studies showed that percutaneous radiofrequency ablation (RFA) has similar efficacy to surgical nodulectomy in the treatment of early-stage HCC, and is associated with lower complication rates and costs than resection. The aim of this study was to compare the effectiveness of these treatments, in terms of morbidity, overall survival, tumor recurrence and causes of death. Methods: Between January 2006 and January 2012 we observed 176 patients affected by HCC, 84 underwent curative treatment. The 40 patients presenting single HCC nodes smaller than 3 cm in diameter have been treated with radiofrequency-assisted surgical nodulectomy (N.=20) or with percutaneous radiofrequency (N.=20). Results: No perioperative mortality occurred in the two groups. Perioperative morbidity was 5% in group A (1 case of peritoneal bleeding) and 5% in group B (1 case of hepatic abscess). Disease-free survival was slightly higher in surgically treated patients, but not statistically significative differences have been demonstrated (P<0.06); no local recurrences were observed in surgically treated patients. Conclusion: RF and surgical nodulectomy can be either used in treatment of early stage hepatocellular carcinoma; no differences in terms of morbidity, overall and disease free survival were observed; nodulectomy seems to prevent from tumor local recurrence. PMID:24019044

Garavoglia, M; Oldani, A; Gentilli, S; Portigliotti, L; D'Agostino, G

2013-08-01

342

Racetrack microtron radio-frequency system  

Microsoft Academic Search

The design and construction progress of a prototype rf system to drive the Los Alamos-NBS racetrack microtron (RTM) electron accelerator is described. The rf system requires 450-kW cw at 2380 MHz from a single klystron. The output from the klystron is split three ways to drive a section, a preaccelerator section, and the main accelerator section. The fields in each

P. J. Tallerico; A. K. Mitra

1981-01-01

343

Racetrack microtron radio-frequency system  

NASA Astrophysics Data System (ADS)

The design and construction progress of a prototype RF system to drive the Los Alamos-NBS racetrack microtron electron accelerator is described. The RF system requires 450 kW CW at 2380 MHz The output from the klystron is split three ways to drive a capture section, a preaccelerator section, and the main accelerator section. The fields in each section are phase- and amplitude-controlled to tight tolerances. Temperature control of the accelerator sections also is linked to the amplitude-control system, because the system's average power is so high.

Tallerico, P. J.; Mitra, A. K.

344

Racetrack microtron radio-frequency system  

NASA Astrophysics Data System (ADS)

The design and construction progress of a prototype rf system to drive the Los Alamos-NBS racetrack microtron (RTM) electron accelerator is described. The rf system requires 450-kW cw at 2380 MHz from a single klystron. The output from the klystron is split three ways to drive a section, a preaccelerator section, and the main accelerator section. The fields in each section are phase and amplitude controlled to tight tolerances. Temperature control of the accelerator sections is linked to the amplitude control system, because the system's average power is so high.

Tallerico, P. J.; Mitra, A. K.

1981-12-01

345

Racetrack microtron radio-frequency system  

SciTech Connect

The design and construction progress of a prototype rf system to drive the Los Alamos-NBS racetrack microtron (RTM) electron accelerator is described. The rf system requires 450-kW cw at 2380 MHz from a single klystron. The output from the klystron is split three ways to drive a capture section, a preaccelerator section, and the main accelerator section. The fields in each section are phase- and amplitude-controlled to tight tolerances. Temperature control of the accelerator sections also is linked to the amplitude-control system, because the system's average power is so high.

Tallerico, P.J.; Mitra, A.K.

1981-01-01

346

Electrodynamic constraints on homogeneity and radiofrequency power deposition in multiple coil excitations.  

PubMed

The promise of increased signal-to-noise ratio and spatial/spectral resolution continues to drive MR technology toward higher magnetic field strengths. SAR management and B1 inhomogeneity correction become critical issues at the high frequencies associated with high field MR. In recent years, multiple coil excitation techniques have been recognized as potentially powerful tools for controlling specific absorption rate (SAR) while simultaneously compensating for B1 inhomogeneities. This work explores electrodynamic constraints on transmit homogeneity and SAR, for both fully parallel transmission and its time-independent special case known as radiofrequency shimming. Ultimate intrinsic SAR--the lowest possible SAR consistent with electrodynamics for a particular excitation profile but independent of transmit coil design--is studied for different field strengths, object sizes, and pulse acceleration factors. The approach to the ultimate intrinsic limit with increasing numbers of finite transmit coils is also studied, and the tradeoff between homogeneity and SAR is explored for various excitation strategies. In the case of fully parallel transmission, ultimate intrinsic SAR shows flattening or slight reduction with increasing field strength, in contradiction to the traditionally cited quadratic dependency, but consistent with established electrodynamic principles. PMID:19165885

Lattanzi, Riccardo; Sodickson, Daniel K; Grant, Aaron K; Zhu, Yudong

2009-02-01

347

Radiofrequency catheter ablation of atrial flutter after orthotopic heart transplantation: insights into the redefined critical isthmus  

Microsoft Academic Search

We report a case of successful radiofrequency catheter ablation of recurrent atrial flutter in a heart transplant recipient and discuss technical aspects of the procedure. A counterclockwise flutter circuit was defined during endocardial mapping of the donor atrium. Termination of atrial flutter was achieved by creating lines of radiofrequency lesions from the tricuspid ring to the suture line between donor

Sergio L Pinski; Audrius J Bredikis; Elaine Winkel; Richard G Trohman

1999-01-01

348

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

349

Effects of pulsed versus conventional radiofrequency current on rabbit dorsal root ganglion morphology  

Microsoft Academic Search

Lesioning using radiofrequency (RF) current has been increasingly used in clinical practice for the treatment of pain syndromes. Although formation of heat causing “thermocoagulation” of the nervous tissues is thought to be responsible of the clinical outcome, a more recent modality of RF application named pulsed radiofrequency (PRF) delivers the RF current without producing destructive levels of heat. In our

Serdar Erdine; Aysen Yucel; Ali Cimen; Salih Aydin; Aydin Sav; Ayhan Bilir

2005-01-01

350

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

SciTech Connect

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.

Patti, Jay W.; Neeman, Ziv, E-mail: zneeman@cc.hih.gov; Wood, Bradford J. [National Institutes of Health Clinical Center, Building 10, Room 1C641, Bethesda, MD 20892 (United States)

2003-08-15

351

A fatal complication due to radiofrequency ablation for atrial fibrillation: atrio-esophageal fistula.  

PubMed

Treatment of chronic atrial fibrillation with intraoperative radiofrequency ablation is gaining more acceptance in patients with rheumatic valve disease. This article reports a case of fatal atrio-esophageal fistula after radiofrequency ablation in a patient with rheumatic mitral and aortic valve disease with chronic atrial fibrillation. PMID:12842562

Sonmez, Bingur; Demirsoy, Ergun; Yagan, Naci; Unal, Mehmet; Arbatli, Harun; Sener, Deniz; Baran, Turker; Ilkova, Feryal

2003-07-01

352

High emission current density microwave-plasma-grown carbon nanotube arrays by postdepositional radio-frequency oxygen plasma treatment  

SciTech Connect

Highly stable field emission current densities of more than 6 A/ cm{sup 2} along with scalable total field emission currents of {approx}300 {mu}A per 70 {mu}m diameter carbon nanotube (CNT)-covered electron emitter dot are reported. Microwave-plasma chemical vapor deposition, along with a novel catalyst sandwich structure and postdepositional radio-frequency (rf) oxygen plasma treatment lead to well-structured vertically aligned CNTs with excellent and scalable emission properties. Scanning electron and transmission electron microscope investigations reveal that postdepositional treatment reduces not only the number but modifies the structure of the CNTs. Well-structured microwave-plasma-grown nanotubes become amorphous during rf oxygen plasma treatment and the measured work functions of CNTs change from 4.6 eV to 4.0 eV before and after treatment, respectively. Our experiments outline a novel fabrication route for structured CNT arrays with improved and scalable field emission characteristics.

Chen, Z.; Engelsen, D. den; Bachmann, P.K.; Elsbergen, V. van; Koehler, I.; Merikhi, J.; Wiechert, D.U. [School of Optoelectronic Information, University of Electronic Science and Technology of China, Jianshebei Road 4, 610054 Chengdu (China) and Philips Research Laboratories, Weisshausstrasse 2, D-52066 Aachen (Germany); School of Optoelectronic Information, University of Electronic Science and Technology of China, Jianshebei Road 4, 610054 Chengdu (China); Philips Research Laboratories, Weisshausstrasse 2, D-52066 Aachen (Germany)

2005-12-12

353

High emission current density microwave-plasma-grown carbon nanotube arrays by postdepositional radio-frequency oxygen plasma treatment  

NASA Astrophysics Data System (ADS)

Highly stable field emission current densities of more than 6 A/ cm2 along with scalable total field emission currents of ~300 ?A per 70 ?m diameter carbon nanotube (CNT)-covered electron emitter dot are reported. Microwave-plasma chemical vapor deposition, along with a novel catalyst sandwich structure and postdepositional radio-frequency (rf) oxygen plasma treatment lead to well-structured vertically aligned CNTs with excellent and scalable emission properties. Scanning electron and transmission electron microscope investigations reveal that postdepositional treatment reduces not only the number but modifies the structure of the CNTs. Well-structured microwave-plasma-grown nanotubes become amorphous during rf oxygen plasma treatment and the measured work functions of CNTs change from 4.6 eV to 4.0 eV before and after treatment, respectively. Our experiments outline a novel fabrication route for structured CNT arrays with improved and scalable field emission characteristics.

Chen, Z.; den Engelsen, D.; Bachmann, P. K.; van Elsbergen, V.; Koehler, I.; Merikhi, J.; Wiechert, D. U.

2005-12-01

354

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.

HAEMMERICH, DIETER; WOOD, BRADFORD J.

2008-01-01

355

Radiofrequency ablation in the treatment of breast cancer liver metastases.  

PubMed

Minimally invasive, image-guided thermal ablation is gaining acceptance for the treatment of solid tumour deposits and its use is increasing. This overview discusses one method of thermal ablation in one palliative setting; the local control of breast cancer liver metastases (BCLM) using radiofrequency ablation. Breast cancer is common and over half of all women diagnosed with metastatic disease develop BCLM. The mainstay of therapy remains chemotherapy and supportive care, which may prolong survival to a median of 18-24 months. Despite breast cancer being considered a systemic disease, surgical series of metastectomy for BCLM have shown a survival advantage. Despite this, surgery for BCLM is rarely practiced due to the associated morbidity for a relatively meagre survival benefit. Similarly, radiofrequency ablation has been used for local control of BCLM; the reported series show a median survival of between 30 and 60 months, with no treatment-related deaths and only three serious treatment-related adverse events in 164 patients reported. Despite this, scepticism remains over the efficacy of BCLM ablation due to the heterogeneity of patient inclusion and selective nature of reporting. Randomised trials are needed to formulate robust evidence-based recommendations and direct the necessary allocation of health care resources. Whether or not local ablative treatment of BCLM conveys a survival advantage is an important consideration. However, in this non-curative setting, it is essential that other outcome measures are carefully evaluated in conjunction with survival, including symptoms (local and constitutional), quality of life and psychological morbidity. To these ends, a randomised, multicentre trial to assess best medical therapy alone versus best medical therapy plus radiofrequency ablation in patients presenting with newly diagnosed BCLM with or without the presence of stable extra-hepatic disease will shortly be underway. PMID:20829004

Illing, R; Gillams, A

2010-09-09

356

Radiofrequency interstitial thermal ablation of hepatocellular carcinoma in liver cirrhosis  

Microsoft Academic Search

Background  The laparoscopic approach to radiofrequency interstitial thermal ablation (RITA) of hepatocellular carcinoma (HCC) with intraoperative\\u000a ultrasound guidance has been proposed with the aim of obtainning additional information for a better neoplastic staging and\\u000a a complete and effective treatment of the liver lesions in patients with a difficult percutaneous approach.\\u000a \\u000a \\u000a \\u000a Methods  In this pilot study, 29 patients with HCC in liver cirrhosis

M. Montorsi; R. Santambrogio; P. Bianchi; E. Opocher; M. Zuin; E. Bertolini; S. Bruno; M. Podda

2001-01-01

357

Radiofrequency Ablation of Thyroid Nodules: Basic Principles and Clinical Application  

PubMed Central

Radiofrequency (RF) ablation has been gaining popularity as a minimally invasive treatment for benign thyroid nodules regardless of the extent of the solid component. RF ablation of benign nodules demonstrated volume reductions of 33–58% after one month and 51–85% after six months, while solving nodule-related clinical problems. RF ablation has recently shown positive short-term results for locoregional control as well as symptom improvement in patients with recurrent thyroid cancers. This paper reviews the basic physics, indications, patient preparation, devices, procedures, clinical results, and complications of RF ablation.

Shin, Ji Hoon; Baek, Jung Hwan; Ha, Eun Ju; Lee, Jeong Hyun

2012-01-01

358

Single-electron transistor as a radio-frequency mixer  

NASA Astrophysics Data System (ADS)

We demonstrate the use of the single-electron transistor as a radio-frequency mixer, based on the nonlinear dependence of current on gate charge. This mixer can be used for high-frequency, ultrasensitive charge measurements over a broad and tunable range of frequencies. We demonstrate operation of the mixer, using a lithographically defined thin-film aluminum transistor, in both the superconducting and normal states of aluminum, over frequencies from 10 to 300 MHz. We have operated the device both as a homodyne detector and as a phase-sensitive heterodyne mixer. We demonstrate a charge sensitivity of <4 x10-3 e/RADICAL:[[RADICAND:[Hz

Knobel, R.; Yung, C. S.; Cleland, A. N.

2002-07-01

359

Experimental development and theoretical studies of radio-frequency absorbers  

NASA Astrophysics Data System (ADS)

A mathematical model based on the equivalence with a sequence of lossy transmission lines has been developed and applied, by numerical calculus, to the study of radio-frequency absorbers of piramidal shape, made of polyurethane foam impregnated with finely powered carbon black. The model has been used to find the expected performance of absorbers with different electrical conductivities in the microwave range of frequencies. The results agree with the measurements of reflectivity which have been previously obtained, by the arch method, during the phase of experimental development of the absorbers, when the carbon black concentration was progressively changed.

Massa, J. L. L. M.

1991-04-01

360

TOPICAL REVIEW: Radio-frequency amplifiers based on dc SQUIDs  

NASA Astrophysics Data System (ADS)

SQUIDs are an attractive candidate for the amplification of low-level rf and microwave signals. Compared to semiconductor amplifiers, they offer lower noise and much lower power dissipation. Especially at frequencies below 1 GHz, the improvement in noise temperature compared to the best cold semiconductor amplifiers can be as high as 50; noise temperatures only slightly above the quantum limit have been achieved in this frequency range. This article will review the current status of radio-frequency amplifiers based on dc SQUIDs and provide detailed discussions of amplifier noise temperature, input and output impedance, and nonlinearities.

Mück, Michael; McDermott, Robert

2010-09-01

361

Novel configurations for radiofrequency discharge excited molecular lasers  

NASA Astrophysics Data System (ADS)

Laser characteristics and beam properties of several gain medium formats including large area planar, annular, and waveguide array devices are discussed. The new configurations described offer the prospects of achieving the benefits of sealed operation, compact size, and much reduced costs at power levels up to and exceeding 1 kWt. These new laser designs use transverse radiofrequency discharges to generate either single large area discharge gain media, or multielement discharge array formats. Some of the fundamental issues relating to the discharge gain media, laser resonator configurations, and device technology are discussed.

Hall, D. R.; Baker, H. J.

362

[Serious complications after pulmonary radiofrequency ablation: report of 2 cases].  

PubMed

Radiofrequency ablation can be used to treat primary or metastatic pulmonary tumors when surgery is not indicated or involves high risk. Although this technique is less invasive than surgical resection, it is not free of risk for complications and adverse events, especially when it is used in patients with serious respiratory disease in whom comorbidity is common. We report 2 cases of serious complications. One was an intractable air leak that led to death. The other was a large hemothorax that was brought under control in the radiology procedure room. We review the literature on this technique as well as recommendations that contribute to making it as safe as possible. PMID:22141221

Hervilla Ezquerra, S; García del Valle, S; Oliver, J M; Hernández Cabrero, T; de la Cruz, R; Armijo, J E

2011-10-01

363

Torsades de pointes following radiofrequency catheter His ablation.  

PubMed

A case of polymorphic ventricular tachycardia torsade de pointes type, appearing in a 70-year-old female following radiofrequency catheter His ablation, is presented. The substrate was slow rate with ventricular bigeminy and QT prolongation which appeared after ablation. The same phenomenon reappeared after permanent VVIR pacemaker implantation with a basal rate of 55 beats/min. One episode of polymorphic ventricular tachycardia deteriorated into ventricular fibrillation, requiring a 360-J DC shock. Raising the pacemaker rate to 80 beats/min abolished the arrhythmias. PMID:9013271

Kappos, K G; Kranidis, A J; Anthopoulos, L P

1996-12-01

364

Time-domain simulation of nonlinear radiofrequency phenomena  

NASA Astrophysics Data System (ADS)

Nonlinear effects associated with the physics of radiofrequency wave propagation through a plasma are investigated numerically in the time domain, using both fluid and particle-in-cell (PIC) methods. We find favorable comparisons between parametric decay instability scenarios observed on the Alcator C-MOD experiment [J. C. Rost, M. Porkolab, and R. L. Boivin, Phys. Plasmas 9, 1262 (2002)] and PIC models. The capability of fluid models to capture important nonlinear effects characteristic of wave-plasma interaction (frequency doubling, cyclotron resonant absorption) is also demonstrated.

Jenkins, Thomas G.; Austin, Travis M.; Smithe, David N.; Loverich, John; Hakim, Ammar H.

2013-01-01

365

Radiofrequency ablation as local therapy for early breast carcinomas  

Microsoft Academic Search

Purpose  To evaluate the safety and efficacy of radiofrequency ablation (RFA) as a local therapy for early breast carcinomas, we performed\\u000a a phase I\\/II study at our institution.\\u000a \\u000a \\u000a \\u000a \\u000a Patients and methods  Fifty patients with core-needle biopsy-proven breast carcinoma that was ?3 cm in diameter on ultrasonography were enrolled\\u000a in this study. Under ultrasound (US) guidance, the tumor and surrounding breast tissue were ablated

Takayuki Kinoshita; Eriko Iwamoto; Hitoshi Tsuda; Kunihiko Seki

2011-01-01

366

Radio-frequency quadrupole: general properties and specific applications  

SciTech Connect

The radio-frequency quadrupole (RFQ) linac structure is being developed for the acceleration of low-velocity ions. Recent experimental tests have confirmed its expected performance and have led to an increased interest in a wide range of possible applications. The general properties of RFQ accelerators are reviewed and beam dynamics simulation results are presented for their use in a variety of accelerating systems. These include the low-beta sections of the Fusion Materials Irradiation Test Accelerator, a 200-MHz proton linear accelerator, and a xenon accelerator for heavy ion fusion.

Stokes, R.H.; Crandall, K.R.; Hamm, R.W.

1980-01-01

367

Architecture of the pulmonary veins: relevance to radiofrequency ablation  

PubMed Central

BACKGROUND—Radiofrequency ablation of tissues in pulmonary veins can eliminate paroxysmal atrial fibrillation.?OBJECTIVE—To explore the characteristics of normal pulmonary veins so as to provide more information relevant to radiofrequency ablation.?METHODS—20 structurally normal heart specimens were examined grossly. Histological sections were made from 65 pulmonary veins.?RESULTS—The longest myocardial sleeves were found in the superior veins. The sleeves were thickest at the venoatrial junction in the left superior pulmonary veins. For the superior veins, the sleeves were thickest along the inferior walls and thinnest superiorly. The sleeves were composed mainly of circularly or spirally oriented bundles of myocytes with additional bundles that were longitudinally or obliquely oriented, sometimes forming mesh-like arrangements. Fibrotic changes estimated at between 5% and 70% across three transverse sections were seen in 17 veins that were from individuals aged 30 to 72 years.?CONCLUSIONS—The myocardial architecture in normal pulmonary veins is highly variable. The complex arrangement, stretch, and increase in fibrosis may produce greater non-uniform anisotropic properties.???Keywords: arrhythmias; catheter ablation; fibrillation; cardiac veins

Ho, S; Cabrera, J; Tran, V; Farre, J; Anderson, R; Sanchez-Quintana, D

2001-01-01

368

Solitary Hepatic Gastrinoma Treated With Laparoscopic Radiofrequency Ablation  

PubMed Central

Background: This is a case of a solitary hepatic gastrinoma in a 65-year-old male. The patient was diagnosed with Zollinger-Ellison syndrome in 1991. He had negative radiologic and surgical explorations at that time. He was maintained on proton-pump inhibitors for the next 10 years without symptoms. Methods: A computed tomographic (CT) scan done in April 2001 demonstrated a 5-cm right hepatic lesion. Radionucleotide scanning with octreotide demonstrated intense activity in the same area in the right hepatic lobe. His serum gastrin was 317 pg/mL. He underwent laparoscopic radiofrequency ablation of the lesion. Results: Treatment resulted in a 6-cm ablative area giving a 1-cm margin on the tumor. One- and 3-month follow-up CT scans demonstrated adequate ablation of the tumor. An octreotide scan done 3 months postoperatively did not reveal any areas of abnormal uptake. Conclusion: We report success with laparoscopic radiofrequency ablation as an alternative to major hepatic resection in patients with a solitary hepatic gastrinoma.

Frezza, Eldo; DeJong, Steven; Pickleman, Jack

2003-01-01

369

Transmit/receive radiofrequency coil with individually shielded elements.  

PubMed

A novel method for decoupling coil elements of transmit/receive (transceive) arrays is reported. Each element of a coil array is shielded both concentrically and radially to reduce the magnetic flux linkage between neighboring coils; this substantially reduces the mutual inductance between coil elements and allows them to behave independently. A six-channel transceive coil was developed using this decoupling scheme and compared with two conventional decoupling schemes: the partial overlapping of adjacent elements and capacitive decoupling. The radiofrequency coils were designed to image the human head and were tested on a 7-T Varian scanner. The decoupling, transmit uniformity, transmit efficiency, signal-to-noise ratio, and geometry factors were compared between coils. The individually shielded coil achieved higher minimum isolation between elements (2.7-4.0 dB) and lower geometry factors (2-14%) than the overlapped and capacitively decoupled coils, while showing a reduction in transmit efficiency (2.8-5.9 dB) and signal-to-noise ratio (up to 34%). No difference was found in the power absorbed by the sample during a 90° radiofrequency pulse. The inset distance of coil elements within their shields was then reduced, resulting in significant improvement of the transmit efficiency (1.3 dB) and signal-to-noise ratio (28%). The greatest asset of this decoupling method lies in its versatility: transceive coils can be created with elements of arbitrary shape, size, location, and resonant frequency to produce three-dimensional conformal arrays. PMID:20648678

Gilbert, Kyle M; Curtis, Andrew T; Gati, Joseph S; Klassen, L Martyn; Villemaire, Lauren E; Menon, Ravi S

2010-07-20

370

On the imaging of radio-frequency electromagnetic data forcross-borehole mineral exploration  

NASA Astrophysics Data System (ADS)

Radio-frequency (typically from 0.1 to 20 MHz) electromagneti c methods are powerful tools for locating conductive mineralization in ore exploration and mine development. Yet data interpretation is complicated by the non-linear relationship between the observed electric and magnetic fields and the electrical parameters of the Earth. The principal means of quantifying inversion capabilities is to compute synthetic data sets using accurate numerical models and to perform the inversion under controlled conditions. Our specific interest is in locating 3-D bodies that are highly conductive relative to the host rock. An excellent approximation for this class of targets, at least at radio frequencies, is to assume that the bodies are infinitely conductive. The numerical advantage of this assumption is that inhomogeneities can be represented simply as internal boundaries where the total electric and magnetic fields are identically equal to zero. Ensuring numerical stability thus does not require excessive discretization in conductive regions since the maximum grid cell size is determined only by the electrical parameters of the host material. We use a finite-difference time-domain approach to compute the total electric and magnetic fields everywhere within the background medium and validate the code by comparisons with two analytical solutions. One common means of interpreting radio-frequency electromagnetic data is to assume linearity between the model parameters and physical response and to apply tomographic image reconstruction methods. While relatively simple and inexpensive, the limitations and applicability of tomographic imaging methods to non-linear electromagnetic data acquired in complicated, 3-D mineral exploration environments are not well understood. Our initial study involves applying the simultaneous iterative reconstruction technique to recover images of the electrical properties of a conductive inclusion. Several examples show that the structural geometry of bodies between boreholes can be reliably imaged using both frequency-doma in and time-domain data. Phase data seem more amenable to recovering geometry information from tomographic reconstruction methods than amplitude data. However, attenuation data provide better constraints on the electrical properties of the geological media and thus form an essential complement to primarily geometrical information obtained from phase tomography. Non-linear inversion methods will probably be required to incorporate the amplitude data for accurate reconstructions of the subsurface.

Yu, L.; Chouteau, M.; Boerner, D. E.; Wang, J.

1998-11-01

371

Role of Sample Temperature in the Field-Induced Alteration of Calcium Release from Brain Tissue, In vitro.  

National Technical Information Service (NTIS)

The release of calcium ions from in vitro preparations of chicken brain-tissue has been used by several investigators to demonstrate the interaction of electric and magnetic (EM) fields with biological systems. For exposures with radiofrequency radiation ...

C. F. Blackman S. G. Benane D. E. House

1989-01-01

372

Induced body currents and hot AM tower climbing: Assessing human exposure in relation to the ANSI radiofrequency protection guide  

SciTech Connect

The report documents the results of a study of the radiofrequency (RF) currents induced in individuals who climb energized AM broadcast towers for such purposes as tower maintenance. Information is needed on such currents in order to quantify the absorption of RF energy by tower climbers and to compare this absorption to levels allowed by such RF safety standards as the American National Standards Institute 1982 radiation protection guide. In the study, data on induced currents were obtained using two different AM towers, with electrical heights of 0.23 and 0.53 wavelengths, respectively. A theoretical analysis of the electric fields near the towers showed that induced body current could be correlated with the radial component of the electric field. These results were consistent with those of an earlier study performed by the FCC and the EPA. Based on the study a number of conclusions were reached relative to the question of RF absorption on live AM towers.

Tell, R.A.

1991-10-07

373

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

374

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

NASA Astrophysics Data System (ADS)

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.; Gans, T.; O'Connell, D.

2011-07-01

375

Intradiscal pulsed radiofrequency application following provocative discography for the management of degenerative disc disease and concordant pain: a pilot study.  

PubMed

The development of diagnostic criteria and the use of provocative discography allow identifying the degenerative disc as causative structure for chronic low-back pain. Unfortunately, none of the available interventional treatment options have been demonstrated to be effective over a prolonged period of time for a considerable number of patients. Pathophysiological studies indicate sprouting of sensory nerves and inflammatory processes as underlying pain mechanisms. Pulsed radiofrequency (PRF) treatment in small and larger joints was described to reduce pain and improve healing by stimulating the immunology. Earlier findings of PRF applied in the disc annulus were promising. It is assumed that PRF applied in the nucleus would change the conductivity of nerve endings and provide a clinically relevant pain reduction. The application of the electric field of PRF in the disc may also activate the immune system, thus reducing the inflammation process of chronic pain. Pulsed radiofrequency in the nucleus was studied in 76 patients with discogenic pain confirmed by magnetic resonance imaging and provocative discography. At 3-month follow-up, 38% of the patients had > 50% pain reduction, at 12 month the effect is maintained in 29%. In patients with unsatisfactory pain relief 3 months after the intervention, secondary pain sources may have been revealed. The latter were treated accordingly. Of all patients, 56% had > 50% pain reduction 1 year after first treatment. Our findings suggest that PRF in the nucleus may be considered for patients with proven discogenic pain. A randomized controlled trial to confirm our findings is justified.? PMID:22008239

Rohof, Olav

2011-10-19

376

High-voltage nanosecond pulses in a low-pressure radio-frequency discharge.  

PubMed

An influence of a high-voltage (3-17 kV) 20 ns pulse on a weakly-ionized low-pressure (0.1-10 Pa) capacitively coupled radiofrequency (RF) argon plasma is studied experimentally. The plasma evolution after pulse exhibits two characteristic regimes: a bright flash, occurring within 100 ns after the pulse (when the discharge emission increases by 2-3 orders of magnitude over the steady-state level), and a dark phase, lasting a few hundreds ?s (when the intensity of the discharge emission drops significantly below the steady-state level). The electron density increases during the flash and remains very large at the dark phase. 1D3V particle-in-cell simulations qualitatively reproduce both regimes and allow for detailed analysis of the underlying mechanisms. It is found that the high-voltage nanosecond pulse is capable of removing a significant fraction of plasma electrons out of the discharge gap, and that the flash is the result of the excitation of gas atoms, triggered by residual electrons accelerated in the electric field of immobile bulk ions. The secondary emission from the electrodes due to vacuum UV radiation plays an important role at this stage. High-density plasma generated during the flash provides efficient screening of the RF field (which sustains the steady-state plasma). This leads to the electron cooling and, hence, onset of the dark phase. PMID:23848787

Pustylnik, M Y; Hou, L; Ivlev, A V; Vasilyak, L M; Couëdel, L; Thomas, H M; Morfill, G E; Fortov, V E

2013-06-10

377

High-voltage nanosecond pulses in a low-pressure radio-frequency discharge  

NASA Astrophysics Data System (ADS)

An influence of a high-voltage (3-17 kV) 20 ns pulse on a weakly-ionized low-pressure (0.1-10 Pa) capacitively coupled radiofrequency (RF) argon plasma is studied experimentally. The plasma evolution after pulse exhibits two characteristic regimes: a bright flash, occurring within 100 ns after the pulse (when the discharge emission increases by 2-3 orders of magnitude over the steady-state level), and a dark phase, lasting a few hundreds ?s (when the intensity of the discharge emission drops significantly below the steady-state level). The electron density increases during the flash and remains very large at the dark phase. 1D3V particle-in-cell simulations qualitatively reproduce both regimes and allow for detailed analysis of the underlying mechanisms. It is found that the high-voltage nanosecond pulse is capable of removing a significant fraction of plasma electrons out of the discharge gap, and that the flash is the result of the excitation of gas atoms, triggered by residual electrons accelerated in the electric field of immobile bulk ions. The secondary emission from the electrodes due to vacuum UV radiation plays an important role at this stage. High-density plasma generated during the flash provides efficient screening of the RF field (which sustains the steady-state plasma). This leads to the electron cooling and, hence, onset of the dark phase.

Pustylnik, M. Y.; Hou, L.; Ivlev, A. V.; Vasilyak, L. M.; Couëdel, L.; Thomas, H. M.; Morfill, G. E.; Fortov, V. E.

2013-06-01

378

GPU-based real-time approximation of the ablation zone for radiofrequency ablation.  

PubMed

Percutaneous radiofrequency ablation (RFA) is becoming a standard minimally invasive clinical procedure for the treatment of liver tumors. However, planning the applicator placement such that the malignant tissue is completely destroyed, is a demanding task that requires considerable experience. In this work, we present a fast GPU-based real-time approximation of the ablation zone incorporating the cooling effect of liver vessels. Weighted distance fields of varying RF applicator types are derived from complex numerical simulations to allow a fast estimation of the ablation zone. Furthermore, the heat-sink effect of the cooling blood flow close to the applicator's electrode is estimated by means of a preprocessed thermal equilibrium representation of the liver parenchyma and blood vessels. Utilizing the graphics card, the weighted distance field incorporating the cooling blood flow is calculated using a modular shader framework, which facilitates the real-time visualization of the ablation zone in projected slice views and in volume rendering. The proposed methods are integrated in our software assistant prototype for planning RFA therapy. The software allows the physician to interactively place virtual RF applicator models. The real-time visualization of the corresponding approximated ablation zone facilitates interactive evaluation of the tumor coverage in order to optimize the applicator's placement such that all cancer cells are destroyed by the ablation. PMID:22034298

Rieder, Christian; Kröger, Tim; Schumann, Christian; Hahn, Horst K

2011-12-01

379

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

380

Intractable Hemifacial Spasm Treated by Pulsed Radiofrequency Treatment  

PubMed Central

Hemifacial spasm is defined as unilateral, involuntary, irregular twitching of all or parts of the muscles innervated by facial nerves. Here, we present a case of recurrent hemifacial spasm after microvascular decompression (MVD) treated with pulsed radiofrequency (PRF) treatment with good results. A 35-year-old woman suffered from recurrent hemifacial spasm after MVD that was refractory to medical treatment and botulinum toxin injections. We attempted a left facial nerve block twice. Then, we applied PRF at a maximum temperature of 42? for 120 sec. Some response was observed, so we applied PRF two additional times. The frequency of twitch decreased from 3-4 Hz to < 0.5 Hz, and subjective severity on a visual analogue scale also decreased from 10/10 to 2-3/10. PRF treatment might be an effective medical treatment for refractory hemifacial spasm and has fewer complications and is less invasive compared with those of surgery.

Park, Hae Lang; Lim, Seung Mo; Kim, Tae Hwa; Kang, Kyung Ho; Kang, Hyun; Jung, Yong Hun; Baek, Chong Wha; Woo, Young Cheol; Kim, Jin Yun; Koo, Gill Hoi

2013-01-01

381

Radiofrequency superconductivity applied to free-electron lasers  

SciTech Connect

Low wall losses and low wakefields inherent in superconducting radiofrequency (srf) cavities make them attractive candidates for accelerators that operate efficiently at high continuous-wave (cw) gradients. Such accelerators are desirable for free-electron lasers (FELs) that extract high-power cw light from a high-average-current electron beam, or that produce ultrashort-wavelength light from a high-energy electron beam. Efficiency is a prime consideration in the former case, while high electron-beam quality is a prime consideration in the latter case. This paper summarizes the status of FEL projects involving srf accelerators. It also introduces Jefferson Lab`s srf FEL and surveys its design because it is a new machine, with commissioning having commenced in October 1997. Once commissioning is complete, this FEL should produce tunable, cw, kW-level light at 3-6 {mu}m wavelength.

Bohn, C.L.; Benson, S.V. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

1998-01-01

382

Current status of radiofrequency ablation of hepatocellular carcinoma  

PubMed Central

Loco-regional treatments for hepatocellular carcinoma (HCC) are important alternatives to curative transplantation or resection. Among them, radiofrequency ablation (RFA) is accepted as the most popular technique showing excellent local tumor control and acceptable morbidity. The current role of RFA is well documented in the evidence-based practice guidelines of European Association of Study of Liver, American Association of Study of the Liver Disease and Japanese academic societies. Several randomized controlled trials have confirmed that RFA is superior to percutaneous ethanol injections in terms of local tumor control and survival. The overall survival after RFA is comparable to after surgical resection in a selected group of patients with smaller (< 3 cm) tumors. Currently, the clinical benefits of combined RFA with transarterial chemoembolization for intermediate stage HCC are increasingly being explored. Here we review the ongoing technical advancements of RFA and future potential.

Rhim, Hyunchul; Lim, Hyo K; Choi, Dongil

2010-01-01

383

Tumor Seeding Following Lung Radiofrequency Ablation: A Case Report  

SciTech Connect

Lung radiofrequency (RF) ablation was performed for the treatment of a primary lung cancer measuring 2.5 cm in maximum diameter in a 78-year-old man. A contrast-enhanced computed tomography (CT) study performed 3 months after RF ablation showed incomplete ablation of the lung tumor and the appearance of a chest wall tumor 4.0 cm in maximum diameter that was considered to be the result of needle-tract seeding. RF ablation was performed for the treatment of both the lung and the chest wall tumors. Although tumor enhancement was eradicated in both of the treated tumors, follow-up CT studies revealed diffuse intra-pulmonary metastases in both lungs 2 months after the second RF session. He is currently receiving systemic chemotherapy.

Yamakado, Koichiro, E-mail: yama@clinmedi.mie-u.ac.jp; Akeboshi, Masao; Nakatsuka, Atsuhiro; Takaki, Haruyuki [Mie University School of Medicine, Department of Radiology (Japan); Takao, Motoshi [Mie University School of Medicine, Department of Thoracic Surgery (Japan); Kobayashi, Hiroyasu; Taguchi, Osamu [Mie University School of Medicine, Third Department of Internal Medicine (Japan); Takeda, Kan [Mie University School of Medicine, Department of Radiology (Japan)

2005-05-15

384

Image-guided percutaneous radiofrequency ablation for osteoid osteomas.  

PubMed

The authors present a retrospective analysis of the technical and clinical successes, complications, and clinical follow-up of image-guided percutaneous radiofrequency (RF) ablation of osteoid osteomas. Nine patients with osteoid osteomas underwent image-guided localization of osteoid osteomas. Outpatient percutaneous therapy (13 procedures) was performed under general anesthesia after image-guided localization of the nidus. Initial technical success was achieved in seven of nine patients. Two initial technical and clinical failures occurred early in this experience because of failure to adequately enter the nidus with use of fluoroscopic imaging alone. Clinical success was achieved in eight of nine patients. No major immediate or delayed complications were observed. PMID:12631644

Venbrux, Anthony C; Montague, Brian J; Murphy, Kieran P J; Bobonis, Lauren A; Washington, Stanley B; Soltes, Amy P; Frassica, Frank J

2003-03-01

385

Increased susceptibility to radiofrequency radiation due to pharmacological agents  

SciTech Connect

The effects of chlorpromazine, methysergide, and propranolol on thermal responses to 2.8 GHz radiofrequency radiation were examined in anesthetized rats. During intermittent exposure at an average power density of 60 mW/sq cm (specific absorption rate, 14 W/kg), when colonic temperature was not allowed to rise above 39.5 C, none of the pharmacological agents had any significant effects on thermal responses. When exposure was continued until lethal temperatures resulted, animals which were administered chlorpromazine, methysergide, or propranolol exhibited significantly shorter survival times than saline-treated animals. Propranolol administration caused the greatest decrease in survival time and resulted in a significantly lower lethal temperature than that which occurred in saline-treated animals. 29 references.

Jauchem, J.R.; Frei, M.R.; Heinmets, F.

1984-11-01

386

Glioma proliferation modulated in vitro by isothermal radiofrequency radiation exposure  

SciTech Connect

Isothermal (37 +/- 0.2 degrees C) exposure of glioma cells (LN71) for 2 h to 27 or 2450 MHz continuous-wave radiofrequency (RF) radiation in vitro modulated the rates of DNA and RNA synthesis 1, 3, and 5 days after exposure. The alterations indicate effects on cell proliferation and were not caused by RF-induced cell heating. The dose response for either frequency of the radiation was biphasic. Exposure to specific absorption rates (SARs) of 50 W/kg or less stimulated incorporation rates of tritiated thymidine (3H-TdR) and tritiated uridine (3H-UdR), whereas higher SARs suppressed DNA and RNA synthesis. Statistically significant time-dependent alterations were detected for up to 5 days postexposure, suggesting a kinetic cellular response to RF radiation and the possibility of cumulative effects on cell proliferation. General mechanisms of effects are discussed.

Cleary, S.F.; Liu, L.M.; Merchant, R.E. (Virginia Commonwealth Univ., Richmond (USA))

1990-01-01

387

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

388

Percutaneous Radiofrequency Ablation for Treatment of Recurrent Retroperitoneal Liposarcoma  

SciTech Connect

Percutaneous CT-guided radiofrequency ablation (RFA) is becoming more and more established in the treatment of various neoplasms, including retroperitoneal tumors of the kidneys and the adrenal glands. We report the case of RFA in a patient suffering from the third relapse of a retroperitoneal liposarcoma in the left psoas muscle. After repeated surgical resection and supportive radiation therapy of a primary retroperitoneal liposarcoma and two surgically treated recurrences, including replacement of the ureter by a fraction of the ileum, there was no option for further surgery. Thus, we considered RFA as the most suitable treatment option. Monopolar RFA was performed in a single session with a 2-cm umbrella-shaped LeVeen probe. During a 27-month follow-up period the patient remained free of tumor.

Keil, Sebastian, E-mail: keil@rad.rwth-aachen.de; Bruners, Philipp [RWTH Aachen University, Department of Diagnostic Radiology, University Hospital (Germany); Brehmer, Bernhard [RWTH Aachen University, Department of Urology, University Hospital (Germany); Mahnken, Andreas Horst [RWTH Aachen University, Department of Diagnostic Radiology, University Hospital (Germany)

2008-07-15

389

[Limited resection or radiofrequency ablation for high risk patients].  

PubMed

The standard care for treatment of patients in good general conditions with stage 1 non-small cell lung cancer (NSCLC) is surgical resection by lobectomy and radical mediastinal lympadenectomy. Promising alternative treatments have been developed for high risk patients, who are (medically) inoperable due to bad general conditions. If lobe resection is not possible because of comorbidities or limited pulmonary function, we can offer less invasive surgical resection such as anatomic segmental resection or broad non-anatomic wedge resection. The results are similar to standard procedure, but the local recurrence rate is higher. Additional brachytherapy improves the outcome. Interventional radiological procedures are emerging as promising treatment options. First thermal methods such as radiofrequency ablation (RFA), microwave ablation (MWA) and kryoablation are available. In addition selective chemoembolisation by a vascular catheter-guided access allows local chemotherapy. The above-mentioned alternative treatments generate encouraging findings, but they should be applied only in clinical trials. PMID:22753292

Oesch, A; Kuster, R; Schmid, R

2012-07-01

390

Effect of the levitating microparticle cloud on radiofrequency argon plasma  

NASA Astrophysics Data System (ADS)

The effect of a levitating cloud of microparticles on the parameters of a radiofrequency (RF) plasma has been studied by means of two experimental techniques. Axial distributions of 1s excited states of argon were measured by a self-absorption method. A correction of a standard self-absorption method for the extinction of the light by the levitating microparticles is proposed. In addition the electron temperature was estimated using the optical emission spectroscopy. Measurements at the same discharge conditions in a microparticle-free discharge and discharge, containing a cloud of levitating microparticles, revealed the non-local influence of the microparticle cloud on the discharge plasma. The most probable cause of this influence is the disturbance of the ionization balance by the levitating microparticles.

Mitic, S.; Pustylnik, M. Y.; Klumov, B. A.; Morfill, G. E.

2010-06-01

391

SUPERCONDUCTING RADIO-FREQUENCY MODULES TEST FACILITY OPERATING EXPERIENCE  

SciTech Connect

Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R and 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 the SRF R and D needs. The project's first stage 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 Meson Detector Building (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. [Fermi National Accelerator Laboratory Batavia, IL, 60510 (United States)

2008-03-16

392

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

393

Intractable hemifacial spasm treated by pulsed radiofrequency treatment.  

PubMed

Hemifacial spasm is defined as unilateral, involuntary, irregular twitching of all or parts of the muscles innervated by facial nerves. Here, we present a case of recurrent hemifacial spasm after microvascular decompression (MVD) treated with pulsed radiofrequency (PRF) treatment with good results. A 35-year-old woman suffered from recurrent hemifacial spasm after MVD that was refractory to medical treatment and botulinum toxin injections. We attempted a left facial nerve block twice. Then, we applied PRF at a maximum temperature of 42? for 120 sec. Some response was observed, so we applied PRF two additional times. The frequency of twitch decreased from 3-4 Hz to < 0.5 Hz, and subjective severity on a visual analogue scale also decreased from 10/10 to 2-3/10. PRF treatment might be an effective medical treatment for refractory hemifacial spasm and has fewer complications and is less invasive compared with those of surgery. PMID:23342210

Park, Hae Lang; Lim, Seung Mo; Kim, Tae Hwa; Kang, Kyung Ho; Kang, Hyun; Jung, Yong Hun; Baek, Chong Wha; Woo, Young Cheol; Kim, Jin Yun; Koo, Gill Hoi; Shin, Hwa Yong

2013-01-04

394

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

395

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

396

Effective Treatment of Chronic Radiation Proctitis Using Radiofrequency Ablation  

PubMed Central

Endoscopic argon plasma coagulation and bipolar electrocautery are currently preferred treatments for chronic radiation proctitis, but ulcerations and strictures frequently occur. Radiofrequency ablation (RFA) has been successful for mucosal ablation in the esophagus. Here we report the efficacy of RFA with the BarRx Halo90 system in three patients with bleeding from chronic radiation proctitis. In all cases, the procedure was well tolerated and hemostasis was achieved after 1 or 2 RFA sessions. Re-epithelialization of squamous mucosa was observed over areas of prior hemorrhage. No stricturing or ulceration was seen on follow-up up to 19 months after RFA treatment. Real-time endoscopic optical coherence tomography (EOCT) visualized epithelialization and subsurface tissue microvasculature pre- and post-treatment, demonstrating its potential for follow-up assessment of endoscopic therapies.

Zhou, Chao; Adler, Desmond C.; Becker, Laren; Chen, Yu; Tsai, Tsung-Han; Figueiredo, Marisa; Schmitt, Joseph M.; Fujimoto, James G.

2009-01-01

397

Stereotactic Radiofrequency Ablation of Unresectable Intrahepatic Cholangiocarcinomas: A Retrospective Study  

SciTech Connect

Purpose: To evaluate treatment effects, complications, and outcome of percutaneous stereotactic radiofrequency ablation (SRFA) of intrahepatic cholangiocarcinoma (ICC). Patients and Methods: Eleven consecutive patients (nine men and two women) with a total of 36 inoperable ICCs (18 initial lesions, 16 lesions newly detected during follow-up, and two local recurrences) underwent SRFA between December 2004 and June 2010. Two different radiofrequency ablation (RFA) devices with internally cooled electrodes were used. Tumor diameters ranged from 0.5 to 10 cm (median 3.0 cm). A total of 23 SRFA sessions were performed. The efficacy of SRFA was evaluated by contrast-enhanced computed tomography or magnetic resonance imaging 1 month after treatment and then every 3 months. Results: Primary technical effectiveness rate was 92%. Further follow-up every 3 months revealed three local recurrences (8%), two of which were successfully retreated, resulting in a secondary technical effectiveness rate of 98%. After a total of 23 RFA sessions, three major complications occurred (13%) that could be managed interventionally. Mean follow-up time was 35 months (range 12-81 months). One- and 3-year overall survival rates were 91 and 71%, respectively. The median overall survival was 60 months (according to the life table method). Eight (73%) of 11 patients were still alive at the end of follow-up. Conclusion: SRFA is effective in the treatment of unresectable ICC even if the tumor is large and located close to major vessels. SRFA shows a survival benefit compared to other palliative treatment options and may also be considered as the first-line local treatment of ICCs in selected patients.

Haidu, Marion, E-mail: marion.haidu@i-med.ac.at [Medical University Innsbruck, Clinic of Radiology, Department of Microinvasive Therapy (SIP) (Austria); Dobrozemsky, Georg, E-mail: georg.dobroszemsky@i-med.ac.at [Medical University Innsbruck, Department of Nuclear Medicine (Austria); Schullian, Peter, E-mail: peter.schullian@i-med.ac.at; Widmann, Gerlig, E-mail: gerlig.widmann@i-med.ac.at [Medical University Innsbruck, Clinic of Radiology, Department of Microinvasive Therapy (SIP) (Austria); Klaus, Alexander, E-mail: alexander.klaus@bhs.at; Weiss, Helmut, E-mail: helmut.weiss@bbsalz.at; Margreiter, Raimund, E-mail: raimund.margreiter@i-med.ac.at [Medical University Innsbruck, Department of Surgery (Austria); Bale, Reto, E-mail: reto.bale@i-med.ac.at [Medical University Innsbruck, Clinic of Radiology, Department of Microinvasive Therapy (SIP) (Austria)

2012-10-15

398

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...

399

An adjunctive method of radiofrequency volumetric tissue reduction of the tongue for OSAS  

Microsoft Academic Search

ObjectivesTemperature-controlled radiofrequency volumetric reduction (TCRF), a minimally invasive procedure, has been used to treat tongue base obstruction in Obstructive Sleep Apnea Syndrome (OSAS). An adjunctive method was objectively evaluated.

Robert W Riley; Nelson B Powell; Kasey K Li; Edward M Weaver; Christian Guilleminault

2003-01-01

400

Percutaneous lumbar sympathectomy: A comparison of radiofrequency denervation versus phenol neurolysis  

SciTech Connect

A new percutaneous approach to sympathectomy using radiofrequency denervation has seemed to offer longer duration and less incidence of postsympathetic neuralgia as compared to phenol sympathetic blocks. To compare these techniques, 17 patients underwent either phenol lumbar sympathetic blocks (n = 9) or radiofrequency denervation (n = 8). Duration of sympathetic block was followed by a sweat test and temperature measurements. Results indicate that 89% of patients in the phenol group showed signs of sympathetic blockade after 8 weeks, as compared to 12% in the radiofrequency group (P less than 0.05). Although the incidence of post sympathetic neuralgia appears to be less with radiofrequency denervation, further refinement of needle placement to ensure complete lesioning of the sympathetic chain will be required before the technique can offer advantages over current phenol techniques.

Haynsworth, R.F. Jr.; Noe, C.E. (Baylor Univ. Medical Center, Dallas, TX (USA))

1991-03-01

401

Questions and Answers about Biological Effects and Potential Hazards of Radiofrequency Radiation (Third Edition).  

National Technical Information Service (NTIS)

The Federal Communications Commission (FCC) is responsible for licensing or authorizing many of the transmitting devices in the United States that use radio-frequency (RF) radiation to provide a variety of important telecommunications services. Because of...

1989-01-01

402

Sequential Anterograde and Retrograde Conduction Block during Radiofrequency Ablation of an Accessory Pathway  

PubMed Central

We present an interesting image showing sequential loss of anterograde, and subsequently, retrograde conduction during radiofrequency ablation of an accessory pathway. We discuss the possible mechanisms and prior literature concerning this interesting finding.

Ramasamy, Chandramohan; Ramteke, Rahul; Balachander, Jayaraman; Selvaraj, Raja

2013-01-01

403

Excessive Hyperthermic Necrosis of a Pulmonary Lobe after Hypertonic Saline-Enhanced Monopolar Radiofrequency Ablation  

SciTech Connect

Although there has been a feasibility study of saline-enhanced radiofrequency ablation of the lung in rabbits, there has been no report on hypertonic saline-enhanced radiofrequency ablation of human pulmonary tumors or its complication. We report a case in which a large necrotic cavity was produced in the lung after hypertonic saline-enhanced radiofrequency ablation of recurrent metastatic tumor from hepatocellular carcinoma. Although hypertonic saline-enhanced radiofrequency ablation is powerful and efficient in local ablation, it is difficult to predict the exact extent of ablation, especially in the lungs. This can be dangerous, as there is a high chance of producing an ablation area much larger than expected and, hence, major complications. Special attention is required not to overablate while using this technique.

Kim, Tae Sung, E-mail: tskim@smc.samsung.co.kr; Lim, Hyo K. [Sungkyunkwan University School of Medicine, Department of Radiology and Center for Imaging Science, Samsung Medical Center (Korea, Republic of); Kim, Hojoong [Sungkyunkwan University School of Medicine, Division of Pulmonary and Critical Care Medicine, The Department of Medicine, Samsung Medical Center (Korea, Republic of)

2006-02-15

404

Excessive radiofrequency application: effects on capsular tissue in an animal model.  

PubMed

Capsular attenuation has been seen after thermal capsulorrhaphy surgery. The purpose of this study was to evaluate the mechanical, histologic, and morphologic effects on capsular tissue after cumulative applications of radiofrequency energy. Ovine patellofemoral capsular tissue was treated with 1, 2, 4, or 8 applications of bipolar radiofrequency energy and then analyzed. No acute capsular ablation or destruction was seen grossly, even in the 8-application group. No definitive visual clues that excessive radiofrequency energy had been applied were seen. There was significant shrinkage and loss of tensile stiffness for all thermal application groups. Given the small sample sizes, post-application failure load, percent relaxation, and stiffness were not observed to be significantly different among the groups. Cumulative applications produced minimal further tissue shrinkage but were accompanied by larger, though not statistically significant, mechanical property losses and increased depth of tissue penetration. These findings suggest that there is no benefit to repeated applications of radiofrequency energy to capsular tissue. PMID:15789008

Wolf, Brian R; Heiner, Anneliese D; Albright, John P; Nepola, James V

405

NIOSH Comments to EPA on Radiofrequency Radiation by J. D. Millar, December 5, 1986.  

National Technical Information Service (NTIS)

The testimony concerned the opinions of NIOSH in regards to occupational exposures to radiofrequency (RF) radiation. Based on available literature the arguments for using a safety factor in recommending RF exposure limits were excellent. NIOSH argued agai...

1986-01-01

406

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

407

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

408

USAFSAM Review and Analysis of Radiofrequency Radiation Bioeffects Literature: Second Report.  

National Technical Information Service (NTIS)

The objectives of this project were to acquire, review, and analyze, on an ongoing basis, information on research pertaining to the biological effects of radiofrequency radiation (RFR), for the USAF School of Aerospace Medicine (USAFSAM). The method used ...

L. N. Heynick

1982-01-01

409

Human Exposure to Radiofrequency Radiation. A Review Pertinent to Air Force Operations.  

National Technical Information Service (NTIS)

This report presents analyses studies, research results, and other pertinent information related to investigations of human exposure to radiofrequency radiation (RFR). The topics discussed are the ANSI/IEEE RFR-exposure guidelines; environmental levels in...

L. N. Heynick P. Polson

1996-01-01

410

Radiofrequency ablation in an infant with recurrent supraventricular tachycardia and cyanosis  

PubMed Central

We report an unusual presentation of supraventricular tachycardia, in an infant, with cyanosis. The child had atrial septal defect with hypoplastic right ventricle. Radiofrequency ablation was performed in view of drug resistant SVT

Vora, Amit; Lokhandwala, Yash; Sheth, Chirag; Dalvi, Bharat

2009-01-01

411

Histological and Ultrastructural Evaluation of the Effects of a Radiofrequency-Based Nonablative Dermal Remodeling Device  

Microsoft Academic Search

Background: Many light- and laser-based systems are used to reduce cutaneous wrinkles, and some have been shown to stimulate dermal collagen production. Using the ThermaCool TC radiofrequency device to treat bo- vine tendon and human abdominal skin, we docu- mented the cutaneous effects of a radiofrequency-based system for nonablative treatment. Observations: Electron microscopy of bovine tendon treated at varied heat

Brian D. Zelickson; David Kist; Eric Bernstein; Douglas B. Brown; Sergey Ksenzenko; Jay Burns; Suzanne Kilmer; David Mehregan; Karl Pope

2004-01-01

412

Tachycardias in Infants, Children and Adolescents: Safety and Effectiveness of Radiofrequency Catheter Ablation  

Microsoft Academic Search

Radiofrequency catheter ablations provide an effective control of a variety of supraventricular and ventricular tachycardias in adults. This study was designed to evaluate the efficacy and safety of radiofrequency catheter ablations in infants, children and adolescents. Ninty-three ablations were performed in 84 patients ranging from 5 months to 18 years of age. All but 1 patient were successfully treated (98.8%).

Sung-Jae Lee; Walter Ch. Schueller

2000-01-01

413

Radiofrequency Catheter Ablation Of Atrioventricular Nodal Reentry Tachycardia In A Patient With Inferior Vena Cava Anomaly  

PubMed Central

Curative radiofrequency catheter modification of the slow pathway is the recommended therapy for patients suffering from recurrent symptomatic atrioventricular nodal reentry tachycardia. This is usually performed via femoral vein and the inferior vena cava (IVC). Presence of venous occlusion or complex venous anomaly involving the IVC may preclude this approach. Here, we report a case with a complex venous anomaly involving the inferior vena cava, who underwent electrophysiological study and successful radiofrequency ablation by an alternative approach.

Karthigesan, Murugesan; Jayaprakash, Shenthar

2009-01-01

414

Effects of Cell Phone Radiofrequency Signal Exposure on Brain Glucose Metabolism  

PubMed Central

Context The dramatic increase in use of cellular telephones has generated concern about possible negative effects of radiofrequency signals delivered to the brain. However, whether acute cell phone exposure affects the human brain is unclear. Objective To evaluate if acute cell phone exposure affects brain glucose metabolism, a marker of brain activity. Design, Setting, and Participants Randomized crossover study conducted between January 1 and December 31, 2009, at a single US laboratory among 47 healthy participants recruited from the community. Cell phones were placed on the left and right ears and positron emission tomography with (18F)fluorodeoxyglucose injection was used to measure brain glucose metabolism twice, once with the right cell phone activated (sound muted) for 50 minutes (“on” condition) and once with both cell phones deactivated (“off” condition). Statistical parametric mapping was used to compare metabolism between on and off conditions using paired t tests, and Pearson linear correlations were used to verify the association of metabolism and estimated amplitude of radiofrequency-modulated electromagnetic waves emitted by the cell phone. Clusters with at least 1000 voxels (volume >8 cm3) and P < .05 (corrected for multiple comparisons) were considered significant. Main Outcome Measure Brain glucose metabolism computed as absolute metabolism (µmol/100 g per minute) and as normalized metabolism (region/whole brain). Results Whole-brain metabolism did not differ between on and off conditions. In contrast, metabolism in the region closest to the antenna (orbitofrontal cortex and temporal pole) was significantly higher for on than off conditions (35.7 vs 33.3 µmol/100 g per minute; mean difference, 2.4 [95% confidence interval, 0.67–4.2]; P = .004). The increases were significantly correlated with the estimated electromagnetic field amplitudes both for absolute metabolism (R = 0.95, P < .001) and normalized metabolism (R = 0.89; P < .001). Conclusions In healthy participants and compared with no exposure, 50-minute cell phone exposure was associated with increased brain glucose metabolism in the region closest to the antenna. This finding is of unknown clinical significance.

Volkow, Nora D.; Tomasi, Dardo; Wang, Gene-Jack; Vaska, Paul; Fowler, Joanna S.; Telang, Frank; Alexoff, Dave; Logan, Jean; Wong, Christopher

2011-01-01

415

Radiofrequency-assisted balloon dilatation in patients with pulmonary valve atresia and an intact ventricular septum.  

PubMed Central

OBJECTIVE--To investigate the efficacy and safety of transcatheter radiofrequency-assisted valve dilatation for infants with pulmonary valve atresia and intact ventricular septum as an alternative to the use of laser heated wires. DESIGN--Prospective clinical study. SETTING--Three paediatric cardiology centres. PATIENTS--Four children (aged 5-101 days, weight 2.8 kg) with pulmonary valve atresia and intact ventricular septum underwent percutaneous radiofrequency-assisted valve dilatation. METHODS--After delineating the atretic valve by angiography, 0.020 inch or 0.018 inch radiofrequency wires were used to perforate the atretic valve. The valve was then dilated with conventional balloon dilatation catheters up to the valve annulus diameter. RESULTS--In all four cases the radiofrequency wire perforated the atretic pulmonary valve and balloon dilatation was successful. In one patient the radiofrequency wire also passed through the anterior wall of the pulmonary artery causing tamponade which required surgical repair shortly afterwards. This patient died from sepsis six days later. One patient died three weeks after the procedure from septicaemia and a paradoxical coronary embolus. Two patients were discharged after 4 and 14 days respectively. CONCLUSIONS--Radiofrequency-assisted valve dilatation is a promising alternative to the recently developed laser wire technique. The major advantages are a reduction in cost and improved safety for the staff performing the procedure. Images

Rosenthal, E; Qureshi, S A; Chan, K C; Martin, R P; Skehan, D J; Jordan, S C; Tynan, M

1993-01-01

416

Anticancer effects on leiomyosarcoma-bearing Wistar rats after electromagnetic radiation of resonant radiofrequencies.  

PubMed

In the present study, the effects of a resonant low intensity static electromagnetic field (EMF), causing no thermal effects, on Wistar rats have been investigated. Sarcoma cell lines were isolated from leiomyosarcoma tumors induced in Wistar rats by the subcutaneous (s.c) injection of 3,4-benzopyrene. Furthermore, smooth muscle cells (SMC) were isolated from the aorta of Wistar rats and cultivated. Either leiomyosarcoma cells (LSC) or SMC were used to record a number of characteristic resonant radiofrequencies, in order to determine the specific electromagnetic fingerprint spectrum for each cell line. These spectra were used to compose an appropriate algorithm, which transforms the recorded radiofrequencies to emitted ones. The isolated LSC were cultured and then exposed to a resonant low intensity radiofrequency EMF (RF-EMF), at frequencies between 10 kHz to 120 kHz of the radiowave spectrum. The exposure lasted 45 consecutive minutes daily, for two consecutive days. Three months old female Wistar rats were inoculated with exposed and non-exposed to EMF LSC (4 x 10(6) LCS for animal). Inoculated with non-exposed to EMF cells animals were then randomly separated into three Groups. The first Group was sham exposed to the resonant EMF (control Group-CG), the second Group after the inoculation of LSC and appearance of a palpable tumor mass, was exposed to a non-resonant EMF radiation pattern, for 5 h per day till death of all animals (experimental control Group-ECG). The third Group of animals after inoculation of LSC and the appearance of a palpable tumor mass, was exposed to the resonant EMF radiation for 5 h per day, for a maximum of 60 days (experimental Group-I, EG-I). A fourth Group of animals was inoculated with LSC exposed to EMF irradiation and were not further exposed to irradiation (experimental Group-II, EG-II). Tumor induction was 100% in all Groups studied and all tumors were histologically identified as leiomyosarcomas. In the case of the EG-I, a number of tumors were completely regretted (final tumor induction: 66%). Both Groups of animals inoculated with exposed or non-exposed to the EMF LSC, (EG-I and EG-II, respectively) demonstrated a significant prolongation of the survival time and a lower tumor growth rate, in comparison to the control Group (CG) and the experimental control Group (ECG). However, the survival time of EG-I animals was found to be significantly longer and tumor growth rate significantly lower compared to EG-II animals. In conclusion, our results indicate a specific anticancer effect of resonant EMF irradiation. These results may possibly be attributed to (a) the duration of exposure of LSC and (b) the exposure of the entire animal to this irradiation. PMID:17684584

Avdikos, Antonios; Karkabounas, Spyridon; Metsios, Apostolos; Kostoula, Olga; Havelas, Konstantinos; Binolis, Jayne; Verginadis, Ioannis; Hatziaivazis, George; Simos, Ioannis; Evangelou, Angelos

417

Male reproductive health under threat: Short term exposure to radiofrequency radiations emitted by common mobile jammers  

PubMed Central

BACKGROUND: Modern life prompted man to increasingly generate, transmit and use electricity that leads to exposure to different levels of electromagnetic fields (EMFs). Substantial evidence indicates that exposure to common sources of EMF such as mobile phones, laptops or wireless internet-connected laptops decreases human semen quality. In some countries, mobile jammers are occasionally used in offices, shrines, conference rooms and cinemas to block the signal. AIMS: To the best of our knowledge, this is the first study to investigate the effect of short term exposure of human sperm samples to radiofrequency (RF) radiations emitted by common mobile jammers. SUBJECTS AND METHODS: Fresh semen samples were collected by masturbation from 30 healthy donors who had referred to Infertility Treatment Center at the Mother and Child Hospital with their wives. Female problem was diagnosed as the reason for infertility in these couples. STATISTICAL ANALYSIS: T-test and analysis of variance were used to show statistical significance. RESULTS: The motility of sperm samples exposed to jammer RF radiation for 2 or 4 h were significantly lower than those of sham-exposed samples. These findings lead us to the conclusion that mobile jammers may significantly decrease sperm motility and the couples’ chances of conception. CONCLUSION: Based on these results, it can be suggested that in countries that have not banned mobile jammer use, legislations should be urgently passed to restrict the use of these signal blocking devices in public or private places.

Mortazavi, SMJ; Parsanezhad, ME; Kazempour, M; Ghahramani, P; Mortazavi, AR; Davari, M

2013-01-01

418

Fluid modelling of capacitively coupled radio-frequency discharges: a review  

NASA Astrophysics Data System (ADS)

This paper reviews the basis and the successes with the fluid modelling of capacitively coupled radio-frequency discharges, produced within a parallel-plate cylindrical setup at (single) 13.56-80 MHz frequencies, 6 × 10-2-6 Torr pressures and 50-1000 V rf-applied voltages, in SiH4-H2, H2 and N2. The two-dimensional, time-dependent model used in the simulations accounts for the production, transport and destruction of the charged particles (via the electron and ion continuity and momentum-transfer equations, and the electron mean energy transport equations), and of the excited species and/or radicals (via their rate balance equations, including very complete kinetic descriptions with several collisional-radiative production/destruction mechanisms, coupled to the two-term electron Boltzmann equation), accounting also for the self-consistent development of the rf field (via the solution to Poisson's equation). The charged particle transport equations are solved with and without corrective flux terms (due to inertia and friction effects), whose influence on results is discussed. In the case of silane-hydrogen mixtures, the model further includes a phenomenological description of the plasma-substrate interaction to calculate the deposition rate of a-Si?:?H thin films. In general, the model gives good predictions for the self-bias voltage, the coupled power and the intensities of radiative emission transitions (both average and spatially resolved), underestimating the electron density by a factor of 3-4.

Alves, L. L.; Marques, L.

2012-12-01

419

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

420

CMOS neurostimulation ASIC with 100 channels, scaleable output, and bidirectional radio-frequency telemetry.  

PubMed

100-channel neurostimulation circuit comprising a complementary metal oxide semiconductor (CMOS), application-specific integrated circuit (ASIC) has been designed, constructed and tested. The ASIC forms a significant milestone and an integral component of a 100-electrode neurostimulation system being developed by the authors. The system comprises an externally worn transmitter and a body implantable stimulator. The purpose of the system is to communicate both data and power across tissue via radio-frequency (RF) telemetry such that externally programmable, constant current, charge balanced, biphasic stimuli may be delivered to neural tissue at 100 unique sites. An intrinsic reverse telemetry feature of the ASIC has been designed such that information pertaining to the device function, reconstruction of the stimulation voltage waveform, and the measurement of impedance may be obtained through noninvasive means. To compensate for the paucity of data pertaining to the stimulation thresholds necessary in evoking a physiological response, the ASIC has been designed with scaleable current output. The ASIC has been designed primarily as a treatment of degenerative disorders of the retina whereby the 100 channels are to be utilized in the delivery of a pattern of stimuli of varying intensity and or duty cycle to the surviving neural tissue of the retina. However, it is conceivable that other fields of neurostimulation such as cochlear prosthetics and functional electronic stimulation may benefit from the employment of the system. PMID:11296881

Suaning, G J; Lovell, N H

2001-02-01

421

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

2006-11-06

422

Bibliography of Reported Biological Phenomena ('Effects') and Clinical Manifestations Attributed to Microwave and Radio-Frequency Radiation. Supplement Number 7.  

National Technical Information Service (NTIS)

More than 350 additional references on the biological responses to radio frequency and microwave radiation, published up to May 1976, are included in this bibliography of the world literature. Particular attention has been paid to the effects of non-ioniz...

Z. R. Glaser

1976-01-01

423

Precision mass measurements of very short-lived, neutron-rich Na isotopes using a radio-frequency spectrometer  

NASA Astrophysics Data System (ADS)

Mass measurements of high precision have been performed on sodium isotopes out to 30Na using a new technique of radio-frequency excitation of ion trajectories in a homogeneous magnetic field. This method, especially suited to very short-lived nuclides, has allowed us to significantly reduce the uncertainty in mass of the most exotic Na isotopes: a relative error of 5×10-7 was achieved for 28Na having a half-life of only 30.5 ms and 9×10-7 for the weakly produced 30Na. Verifying and minimizing binding energy uncertainties in this region of the nuclear chart is important for clarification of a long-standing problem concerning the strength of the N=20 magic shell closure. These results are the fruit of the commissioning of the new experimental program MISTRAL.

Lunney, D.; Audi, G.; Doubre, H.; Henry, S.; Monsanglant, C.; de Saint Simon, M.; Thibault, C.; Toader, C.; Borcea, C.; Bollen, G.; ISOLDE Collaboration

2001-11-01

424

Ionospheric profiling through radio-frequency signals recorded by the FORTÉ satellite, with comparison to the International Reference Ionosphere  

NASA Astrophysics Data System (ADS)

Electromagnetic waves originating on Earth and recorded in space allow retrieval of ionospheric parameters. Using the FastOnboard Recording of Transient Events satellite (FORTÉ, it has been shown that traps-ionospheric pulsed radio-frequency (RF) signals carry sufficient information to infer the peak electron density of the ionosphere, in addition to the total electron content along a ray path between a source and a receiver. In this paper the detailed refractive properties of the ionosphere and the biref-ringent splitting of RF waves in the Earth's magnetic field are modeled using the Appleton-Hartree equation and an electron density profile based on the International Reference Ionosphere (IRI). Applications of this model to FORTÉ data provide additional information on the vertical profile of ionospheric plasma density at the time and place of measurement. Results of the FORTÉ observations are compared with the IRI.

Moses, Ronald W.; Jacobson, Abram R.

2004-01-01

425

Modelling for the optimization of the reaction chamber in silicon nanoparticle synthesis by a radio-frequency induction thermal plasma  

NASA Astrophysics Data System (ADS)

The optimization of the reaction chamber for the silicon nanoparticle synthesis process by a radio-frequency induction thermal plasma is addressed using a plasma thermo-fluid-dynamic model coupled with electromagnetic field equations and with a moment model for nanoparticle transport. Various reaction chamber geometries composed of two parts—a conical top and a cylindrical bottom—are evaluated in terms of the yield of the synthesis process, the presence of recirculation flow patterns that may affect the uniformity of the produced nanoparticles and the size distribution of nanoparticles at the chamber outlet. Turbulent diffusion is suggested as the physical phenomenon that leads to nanoparticle deposition onto the walls of the reaction chamber. The injection of a suitable gas along the walls of the reaction chamber at the axial position, where the nanoparticle nucleation takes place, is proven to be effective in increasing the synthesis process yield.

Colombo, V.; Ghedini, E.; Gherardi, M.; Sanibondi, P.

2012-10-01

426

Measurements of electric and magnetic fields in the Waianae, Hawaii area  

Microsoft Academic Search

During November 27 to 30, 1990, the U.S. EPA conducted a measurement survey of electric and magnetic field levels along the southwest coast of Oahu, Hawaii. These measurements were requested by the State of Hawaii to determine the levels of radiofrequency (RF) electric and magnetic fields near Naval radio transmitters at Lualualei. The objective was to determine maximum fields in

Edwin D. Mantiply

1992-01-01

427

NON-INVASIVE RADIOFREQUENCY ABLATION OF CANCER TARGETED BY GOLD NANOPARTICLES  

PubMed Central

Introduction Current radiofrequency ablation (RFA) techniques require invasive needle placement and are limited by accuracy of targeting. The purpose of this study was to test a novel non-invasive radiowave machine that uses RF energy to thermally destroy tissue. Gold nanoparticles were designed and produced to facilitate tissue heating by the radiowaves. Methods A solid state radiowave machine consisting of a power generator and transmitting/receiving couplers which transmit radiowaves at 13.56 MHz was used. Gold nanoparticles were produced by citrate reduction and exposed to the RF field either in solutions testing or after incubation with HepG2 cells. A rat hepatoma model using JM-1 cells and Fisher rats was employed using direct injection of nanoparticles into the tumor to focus the radiowaves for select heating. Temperatures were measured using a fiber-optic thermometer for real-time data. Results Solutions containing gold nanoparticles heated in a time- and power-dependent manner. HepG2 liver cancer cells cultured in the presence of gold nanoparticles achieved adequate heating to cause cell death upon exposure to the RF field with no cytotoxicity attributable to the gold nanoparticles themselves. In vivo rat exposures at 35W using gold nanoparticles for tissue injection resulted in significant temperature increases and thermal injury at subcutaneous injection sites as compared to vehicle (water) injected controls. Discussion These data show that non-invasive radiowave thermal ablation of cancer cells is feasible when facilitated by gold nanoparticles. Future studies will focus on tumor selective targeting of nanoparticles for in vivo tumor destruction.

Cardinal, Jon; Klune, John Robert; Chory, Eamon; Jeyabalan, Geetha; Kanzius, John S.; Nalesnik, Michael; Geller, David A.

2008-01-01

428

Effect of vortex hotspots on the radio-frequency surface resistance of superconductors  

NASA Astrophysics Data System (ADS)

We present detailed experimental and theoretical investigations of hotspots produced by trapped vortex bundles and their effect on the radio-frequency (rf) surface resistance Rs of superconductors at low temperatures. Our measurements of Rs, combined with the temperature mapping and laser scanning of a 2.36-mm-thick Nb plate incorporated into a 3.3-GHz Nb resonator cavity cooled by the superfluid He at 2 K, revealed spatial scales and temperature distributions of hotspots and showed that they can be moved or split by thermal gradients produced by the scanning laser beam. These results, along with the observed hysteretic field dependence of Rs which can be tuned by the scanning laser beam, show that the hotspots in our Nb sample are due to trapped vortex bundles which contain ˜106 vortices spread over regions ˜0.1-1 cm. We calculated the frequency dependence of the rf power dissipated by oscillating vortex segments trapped between nanoscale pinning centers, taking into account all bending modes and the nonlocal line tension of the vortex driven by rf Meissner currents. We also calculated the temperature distributions caused by trapped vortex hotspots, and suggested a method of reconstructing the spatial distribution of vortex dissipation sources from the observed temperature maps. Vortex hotspots can dominate the residual surface resistance at low temperatures and give rise to a significant dependence of Rs on the rf field amplitude Hp, which can have important implications for the rf resonating cavities used in particle accelerators and for thin-film structures used in quantum computing and photon detectors.

Gurevich, A.; Ciovati, G.

2013-02-01

429

Suppression of hydride precipitates in niobium superconducting radio-frequency cavities  

NASA Astrophysics Data System (ADS)

Niobium hydride is a suspected contributor to degraded niobium superconducting radio-frequency (SRF) cavity performance by Q slope and Q disease. The concentration and distribution of hydrogen atoms in niobium can be strongly affected by the cavity processing treatments. This study provides guidance for cavity processing based on density functional theory calculations of the properties of common processing impurity species—hydrogen, oxygen, nitrogen, and carbon—in the body-centered cubic (bcc) niobium lattice. We demonstrate that some fundamental properties are shared between the impurity atoms, such as anionic character in niobium. The strain field produced, however, by hydrogen atoms is both geometrically different and substantially weaker than the strain field produced by the other impurities. We focus on the interaction between oxygen and hydrogen atoms in the lattice, and demonstrate that the elastic interactions between these species and the bcc niobium lattice cause trapping of hydrogen and oxygen atoms by bcc niobium lattice vacancies. We also show that the attraction of oxygen to a lattice vacancy is substantially stronger than the attraction of hydrogen to the vacancy. Additionally, hydrogen dissolved in niobium tetrahedral interstitial sites can be trapped by oxygen, nitrogen and possibly carbon atoms dissolved in octahedral interstitial sites. These results indicate that the concentration of oxygen in the bcc lattice can have a strong impact on the ability of hydrogen to form detrimental phases. Based on our results and a literature survey, we propose a mechanism for the success of the low-temperature annealing step applied to niobium SRF cavities. We also recommend further examination of nitrogen and carbon in bcc niobium, and particularly the role that nitrogen can play in preventing detrimental hydride phase formation.

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

2013-10-01

430

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.

Requa, M. V.; Fraikin, J.-L.; Stanton, M. A.; Cleland, A. N.

2009-01-01

431

CORONARY ARTERY PATHOPHYSIOLOGY AFTER RADIOFREQUENCY CATHETER ABLATION: REVIEW AND PERSPECTIVES  

PubMed Central

Radiofrequency ablation (RFA) has proven to be an effective and safe treatment in patients with ventricular and atrial tachyarrhythmias. Among complications arising after RFA, the incidence of coronary artery (CA) injury is exceedingly low. When CA injury does occur, however, it can be clinically devastating. The proximity of CAs to common ablation sites suggests that the relationship between RFA and CA perfusion pathophysiology is important. While others have described the presentation and outcomes of patients with CA injury after ablation, a review that consolidates the mechanisms of CA injury after RFA has yet to be presented in the cardiology literature. We conducted an extensive literature search of studies published over the past thirty years that relate the biophysics of RFA with CA perfusion pathophysiology and injury. From this, we present a review of the dynamic relationship between RFA and CA perfusion. We describe RFA lesion pathology, mechanisms of CA injury from RFA, and factors that influence lesion formation such as convective cooling and the ‘shadow effect.’ Finally, we summarize methods to mitigate CA injury after RFA and propose new research avenues to optimize lesion formation and safe arrhythmia treatments when tissue is ablated in the vicinity of CAs.

Castano, Adam; Crawford, Thomas; Yamazaki, Masatoshi; Avula, Uma Mahesh R; Kalifa, Jerome

2011-01-01

432

Numerical and experimental characterization of radiofrequency ablation in perfused kidneys.  

PubMed

We develop a three-dimensional finite element model in order to predict the resulting temperature distribution of a radiofrequency ablation (RFA) treatment in human kidneys. Here, a strong cooling effect results from a high degree of blood perfusion, which is modeled via two different approaches. The influence of big blood vessels for treatments close to renal hilus is modeled by including a cylindrical cooling tube based on the renal artery (or vein) in the kidney model. The influence of the perfusion of small arterioles and capillaries is represented by Pennes' approach in the bioheat equation. The experimental validation is performed by an in vivo RFA treatment on porcine kidney. Prior to the in vivo measurements several ex vivo experiments on fresh kidneys are carried out as a plausibility check for the model. During the treatments temperature profiles are measured using thermocouples which are radially arranged around the RFA applicator trocar. The evaluated data for each sensor show a deviation between 0.01 and 12 % from the simulation results. The approach serves for the design of a preplanning tool for RFA treatment in the future. PMID:23367226

Frank, Kristian; Lindenborn, Herbert; Dahlhaus, Dirk

2012-01-01

433

Incidence and Cause of Hypertension During Adrenal Radiofrequency Ablation  

SciTech Connect

Purpose: To evaluate the incidence and cause of hypertension prospectively during adrenal radiofrequency ablation (RFA). Methods: For this study, approved by our institutional review board, written informed consent was obtained from all patients. Patients who received RFA for adrenal tumors (adrenal ablation) and other abdominal tumors (nonadrenal ablation) were included in this prospective study. Blood pressure was monitored during RFA. Serum adrenal hormone levels including epinephrine, norepinephrine, dopamine, and cortisol levels were measured before and during RFA. The respective incidences of procedural hypertension (systolic blood pressure >200 mmHg) of the two patient groups were compared. Factors correlating with procedural systolic blood pressure were evaluated by regression analysis.ResultsNine patients underwent adrenal RFA and another 9 patients liver (n = 5) and renal (n = 4) RFA. Asymptomatic procedural hypertension that returned to the baseline by injecting calcium blocker was found in 7 (38.9%) of 18 patients. The incidence of procedural hypertension was significantly higher in the adrenal ablation group (66.7%, 6/9) than in the nonadrenal ablation group (11.1%, 1/9, P < 0.0498). Procedural systolic blood pressure was significantly correlated with serum epinephrine (R{sup 2} = 0.68, P < 0.0001) and norepinephrine (R{sup 2} = 0.72, P < 0.0001) levels during RFA. The other adrenal hormones did not show correlation with procedural systolic blood pressure. Conclusion: Hypertension occurs frequently during adrenal RFA because of the release of catecholamine.

Yamakado, Koichiro, E-mail: yama@clin.medic.mie-u.ac.jp; Takaki, Haruyuki [Mie University School of Medicine, Department of Interventional Radiology (Japan); Yamada, Tomomi [Mie University School of Medicine, Department of Translational Medicine (Japan); Yamanaka, Takashi; Uraki, Junji; Kashima, Masataka; Nakatsuka, Atsuhiro; Takeda, Kan [Mie University School of Medicine, Department of Interventional Radiology (Japan)

2012-12-15

434

Radio-frequency plasma transducer for use in harsh environments  

SciTech Connect

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.

May, Andrew; Andarawis, Emad [GE Global Research, 1 Research Circle, Niskayuna, New York 12309 (United States)

2007-10-15

435

Radiofrequency ablation as a treatment for hilar cholangiocarcinoma  

PubMed Central

AIM: To explore the role of radio-frequency ablation (RFA) as a treatment for hilar cholangiocarcinoma. METHODS: Eleven patients with obstructive cholestasis underwent Computed Tomography (CT) examination, occupying lesions were observed in the hepatic hilar region in each patient. All lesions were confirmed as cholangioadenocarcinoma by biopsy and were classified as type III or IV by percutaneous transhepatic cholangiography. Patients were treated with multiple electrodes RFA combined with other adjuvant therapy. The survival rate, change of CT attenuation coefficient of the tumor and tumor size were studied in these patients after RFA. RESULTS: In a follow-up CT scan one month after RFA, a size reduction of about 30% was observed in six masses, and two masses were reduced by about 20% in size, three of the eleven masses remained unchanged. In a follow-up CT scan 6 mo after RFA, all the masses were reduced in size (overall 35%), in which the most significant size reduction was 60%. The survival follow-up among these eleven cases was 18 mo in average. Ongoing follow-up showed that the longest survival case was 30 mo and the shortest case was 10 mo. CONCLUSION: RFA is a microinvasive and effective treatment for hilar cholangiocarcinoma.

Fan, Wei-Jun; Wu, Pei-Hong; Zhang, Liang; Huang, Jin-Hua; Zhang, Fu-Jun; Gu, Yang-Kui; Zhao, Ming; Huang, Xiang-Long; Guo, Chang-Yu

2008-01-01

436

Delayed Development of Pneumothorax After Pulmonary Radiofrequency Ablation  

SciTech Connect

Acute pneumothorax is a frequent complication after percutaneous pulmonary radiofrequency (RF) ablation. In this study we present three cases showing delayed development of pneumothorax after pulmonary RF ablation in 34 patients. Our purpose is to draw attention to this delayed complication and to propose a possible approach to avoid this major complication. These three cases occurred subsequent to 44 CT-guided pulmonary RF ablation procedures (6.8%) using either internally cooled or multitined expandable RF electrodes. In two patients, the pneumothorax, being initially absent at the end of the intervention, developed without symptoms. One of these patients required chest drain placement 32 h after RF ablation, and in the second patient therapy remained conservative. In the third patient, a slight pneumothorax at the end of the intervention gradually increased and led into tension pneumothorax 5 days after ablation procedure. Underlying bronchopleural fistula along the coagulated former electrode track was diagnosed in two patients. In conclusion, delayed development of pneumothorax after pulmonary RF ablation can occur and is probably due to underlying bronchopleural fistula, potentially leading to tension pneumothorax. Patients and interventionalists should be prepared for delayed onset of this complication, and extensive track ablation following pulmonary RF ablation should be avoided.

Clasen, Stephan, E-mail: stephan.clasen@med.uni-tuebingen.d [Eberhard-Karls-University of Tuebingen, Department of Diagnostic and Interventional Radiology (Germany); Kettenbach, Joachim [Medical University of Vienna, Cardiovascular and Interventional Radiology, Department of Radiology (Austria); Kosan, Bora; Aebert, Hermann [Eberhard-Karls-University of Tuebingen, Department of Thoracic, Cardiac and Vascular Surgery (Germany); Schernthaner, Melanie [Medical University of Vienna, Cardiovascular and Interventional Radiology, Department of Radiology (Austria); Kroeber, Stefan-Martin [Eberhard-Karls-University of Tuebingen, Institute of Pathology (Germany); Boemches, Andrea [Eberhard-Karls-University of Tuebingen, Department of Thoracic, Cardiac and Vascular Surgery (Germany); Claussen, Claus D.; Pereira, Philippe L. [Eberhard-Karls-University of Tuebingen, Department of Diagnostic and Interventional Radiology (Germany)

2009-05-15

437

Radio-frequency measurement of an asymmetric single electron transistor  

NASA Astrophysics Data System (ADS)

Since the invention of the radio-frequency single-electron transistor (RF-SET) by Schoelkopf et al.,[1] most measurements have focused on the symmetric single electron transistor. It has been shown, however, that the symmetric SET has a rather low measurement efficiency in its normal working regime.[2][3] Recently, it has been pointed out that an asymmetric SET can be considerably more efficient than a symmetric SET as a quantum amplifier. In this case the measurement efficiency of the asymmetric SET becomes similar to that of the quantum point contact (QPC) detector which can approach the quantum limit. We investigate the asymmetric SET by fabricating Al/AlOx SETs with junction areas 40x40 nm^2 and 40x80nm^2 and total resistance of about 25k?. The results of RF and DC characterization of such asymmetric SETs will be discussed. [1] R. J. Schoelkopf, P. Wahlgren, A. A. Kozhevnikov, P. Delsing, D. E. Prober, Science, 280, 1242 (1998). [2] A. N. Korotkov, Phys. Rev. B, 63, 085312 (2001); 63, 115403 (2001). [3] D. Mozyrsky, I. Martin, and M. B. Hastings, Phys. Rev. Lett., 92, 018303 (2004). [4] S. A. Gurvitz and G. P. Berman, Phys. Rev. B, 72 , 073303(2005).

Ji, Zhongqing; Xue, Weiwei; Rimberg, A. J.

2007-03-01

438

Palliation of Soft Tissue Cancer Pain With Radiofrequency Ablation  

PubMed Central

The purpose of this study was to analyze the feasibility, safety, and efficacy of radiofrequency ablation (RFA) to treat pain from soft tissue neoplasms. RFA was performed on 15 painful soft tissue tumors in 14 patients. Tumors varied in histology and location and ranged in size from 2 to 20 cm. Patient pain was assessed using the Brief Pain Inventory (BPI) at baseline and 1 day, 1 week, 1 month, and 3 months post RFA. All patients had unresectable tumors or were poor operative candidates whose pain was poorly controlled by conventional treatment methods. BPI scores were divided into two categories: pain severity and interference of pain. Although not all scores were statistically significant, all mean scores trended down with increased time post ablation. Based on these outcomes, RFA appears to be a low-risk and well-tolerated procedure for pain palliation in patients with unresectable, painful soft tissue neoplasms. RFA is effective for short-term local pain control and may provide another option for failed chemotherapy or radiation therapy in patients with cancer. However, pain may transiently worsen, and relief is often temporary.

Locklin, Julia K.; Mannes, Andrew; Berger, Ann; Wood, Bradford J.

2008-01-01

439

[Permanent junction reciprocating tachycardia--treatment with radiofrequency current ablation].  

PubMed

The patients with WPW syndrome demonstrate wide scale of clinical manifestation, from asymptomatic course to sudden cardiac death. Among this patients it is possible to identify the small group of patients with rare kind of atrioventricular reentrant tachycardia named permanent junctional reciprocating tachycardia (PJRT) associated with increased risk of development tachycardia-induced cardiomyopathy. This patients should be successful treated by radiofrequency catheter ablation (RFCA). Aim of the study was assessment of efficacy and safety of RFCA procedure in patients with preexcitation syndrome and PJRT. Analyzed group consisted of 7 patients with PJRT selected from 163 consecutive patients with symptomatic WPW--syndrome undergo electrophysiological study (EPS) and RFCA. Analyzed group consist of 4 women and 3 men. Mean age of patients was 22.71 SD +/- 7.99 (from 14 to 38 years). Every patients underwent EPS and RFCA simultaneously. Success-rate in first session was 71.42% (5 patients were successful ablated). Two women underwent second ablation one who has recurrent symptomatic arrhythmia and another who initially was unsuccessfully treated in first session. This two additional procedures were successful. RFCA-duration time was average 107.85 minutes SD +/- 21.95 (min-80, max-145 min) and fluoroscopy--time amount from 28 min to 55 min average 38.58 min (SD +/- 11.14). Among analyzed patients we did not noticed any complications during ablation procedure. Patients with PJRT could be safe and successfully treated using RFCA. PMID:12412411

Kalarus, Zbigniew; Prokopczuk, Janusz; Kowalski, Oskar; Lenarczyk, Rados?aw; Pruszkowska-Skrzep, Patrycja; Sredniawa, Beata

2002-07-01

440

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

441

Radiofrequency Neurotomy of Cervical Medial Branches for Chronic Cervicobrachialgia  

PubMed Central

Chronic neck and arm pain or cervicobrachialgia commonly occurs with the degeneration of cervical spine. Authors investigated the usefulness of radiofrequency (RF) neurotomies of cervical medial branches in patients with cervicobrachialgia and analyzed the factors which can influence the treatment outcome. Demographic data, types of pain distribution, responses of double controlled blocks, electrical stimulation parameters, numbers and levels of neurotomies, and surgical outcomes were evaluated after mean follow-up of 12 months. Pain distribution pattern was not significantly correlated with the results of diagnostic blocks. Average stimulation intensity was 0.45 V, ranging from 0.3 to 0.69, to elicit pain response in cervical medial branches. The most common involvement of nerve branches was C4 (89%), followed by C5 (82%), C6 (75%), and C7 (43%). Among total of 28 patients, nineteen (68%) reported successful outcome according to outcome criteria after 6 months of follow-up (p=0.001), and eight (42%) of 19 patients reported complete relief (100%) of pain. Four patients showed recurrence of pain between 6 and 12 months. It was therefore concluded that cervical medial branch neurotomy is considered useful therapeutic modality for the management of cervicobrachialgia in selected patients, particularly in degenerative zygapophyseal disorders.

Shin, Woo-Ram; Shin, Dong-Gyu; Shin, Dong-Ah

2006-01-01

442

Radiofrequency neurotomy of cervical medial branches for chronic cervicobrachialgia.  

PubMed

Chronic neck and arm pain or cervicobrachialgia commonly occurs with the degeneration of cervical spine. Authors investigated the usefulness of radiofrequency (RF) neurotomies of cervical medial branches in patients with cervicobrachialgia and analyzed the factors which can influence the treatment outcome. Demographic data, types of pain distribution, responses of double controlled blocks, electrical stimulation parameters, numbers and levels of neurotomies, and surgical outcomes were evaluated after mean follow-up of 12 months. Pain distribution pattern was not significantly correlated with the results of diagnostic blocks. Average stimulation intensity was 0.45 V, ranging from 0.3 to 0.69, to elicit pain response in cervical medial branches. The most common involvement of nerve branches was C4 (89%), followed by C5 (82%), C6 (75%), and C7 (43%). Among total of 28 patients, nineteen (68%) reported successful outcome according to outcome criteria after 6 months of followup (p=0.001), and eight (42%) of 19 patients reported complete relief (100%) of pain. Four patients showed recurrence of pain between 6 and 12 months. It was therefore concluded that cervical medial branch neurotomy is considered useful therapeutic modality for the management of cervicobrachialgia in selected patients, particularly in degenerative zygapophyseal disorders. PMID:16479077

Shin, Woo-Ram; Kim, Hyoung-Ihl; Shin, Dong-Gyu; Shin, Dong-Ah

2006-02-01

443

Radiofrequency Ablation for Tumor-Related Massive Hematuria  

PubMed Central

To determine whether radiofrequency (RF) ablation targeting the tumor-collecting system interface has a durable effect in patients with transfusion-dependent kidney tumor-related hematuria, four patients aged 61-71 years were successfully treated with RF ablation, with a mean follow up of 12 months. Baseline creatinine levels varied from 2.0 mg/dL to 3.7 mg/dL. All patients had received red blood cell transfusions in the days and hours before RF ablation. No subsequent surgical or interventional procedures were required for management of hematuria. Gross hematuria resolved in 24-48 hours in all four patients. Two of the patients are alive with stable renal function and two died of causes unrelated to treatment. RF ablation may be an effective therapeutic option for transfusion-dependent cancer-related hematuria in patients with renal insufficiency, solitary kidney, or comorbidities, or after failed conventional therapies in patients who are not candidates for surgery.

Neeman, Ziv; Sarin, Shawn; Coleman, Jonathan; Fojo, Tito; Wood, Bradford J.

2008-01-01

444

[Ablation using radiofrequency in the treatment of ventricular tachycardia].  

PubMed

We performed radiofrequency catheter ablation in 14 consecutive patients with Ventricular Tachycardia (VT) 10 of which had healthy hearts, one patient with ischemic heart disease, one with arrhythmogenic dysplasia, one with dilated cardiomyopathy, and one with congenital heart disease. The localization of the VT was: 10 in the left posterior fascicular region, 3 in the right ventricular outflow tract (RVOT), and one patient with ischemic heart disease with the substrate in the left ventricular apex. All of them with VT refractory to pharmacological management, using an average of 2.7 drugs per patient. After all patients underwent Electrophysiological Study (EPS), an intracavitary mapping was performed, in order to locate the arrhythmogenic substrate. Later on, the RF ablation was performed, delivering an average of 15 pulses, using 40 Watts, and an average time of 25 sec. per pulse. The procedure was successful in 60% of the fascicular VT, with a 16% of recurrence; 100% of success with those originated in the RVOT with no recurrence; in the ischemic patient we achieved primary success, but with recurrence, a second session was successful with no recurrence up to date. No major complications occurred in this group. Those patients which showed no success required the use of antiarrhythmic drugs. The total success of the series is 71.4% with 10% recurrence, and no mortality. PMID:8967816

Cordero Cabra, J A; Iturralde Torres, P; Lara Vaca, S; Colín Lizalde, L; Kershenovich, S; Carvajal, A; González Hermosillo, J A

445

Radiofrequency heat ablation for lung tumors: potential applications.  

PubMed

Radiofrequency ablation (RFA) is an image guided percutaneous procedure using thermal energy that is used to treat malignant lesions in various organs including liver, breast and lungs. It has also been used bronchoscopically to treat endobronchial tumors. Current passing through tissue from the active electrode leads to ion agitation, which is converted by means of friction into heat leading to irreparable cellular damage and coagulation necrosis. The potential benefits include decreased cost and morbidity, treating patients who are not surgical candidates due to age, co-morbidity or extent of disease and the possibility of performing the procedure on an outpatient basis. The aim is usually to reduce tumor size. Whether it can be used with a curative intent in well localized primary tumors remains to be determined by well designed studies. However, caution should be exercised because selective tumor resection is not the gold standard to treat potentially resectable lung malignancies that are treated with lobectomy. Obviously, lung volume reduction surgery combined with tumor resection has challenged this approach. RFA might be the treatment of choice for multiple lung metastases that are usually approached surgically for long-term remission. A specific indication may also be bilateral pulmonary metastases. Other potential applications might be tumor size reduction by a non-surgical procedure followed by adjuvant chemotherapy. Curren