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1

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

PubMed Central

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

Cao, Yi; Tong, Jian

2014-01-01

2

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

PubMed

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

Vo?chuk, S I

2014-01-01

3

Bio-effects of non-ionizing electromagnetic fields in context of cancer therapy.  

PubMed

Bio-effects mediated by non-ionizing electromagnetic fields (EMF) have become a hot topic of research in the last decades. This interest has been triggered by a growing public concern about the rapid expansion of telecommunication devices and possible consequences of their use on human health. Despite a feasibility study of potential negative impacts, the therapeutic advantages of EMF could be effectively harnessed for the treatment of cancer and other diseases. This review aims to examine recent findings relating to the mechanisms of action underlying the bio-effects induced by non-ionizing EMF. The potential of non-thermal and thermal effects is discussed in the context of possible applications for the induction of apoptosis, formation of reactive oxygen species, and increase of membrane permeability in malignant cells. A special emphasis has been put on the combination of EMF with magnetic nano-particles and ultrasound for cancer treatment. The review encompasses both human and animal studies. PMID:24389151

Saliev, Timur; Tachibana, Katsuro; Bulanin, Denis; Mikhalovsky, Sergey; Whitby, Ray D L

2014-01-01

4

Radiofrequency electromagnetic fields: properties, quantities and units, biophysical interaction, and measurements  

SciTech Connect

This report marks the debut of NCRP into the field of non-ionizing radiation. The purpose of this report is to discuss radiofrequency (RF) electromagnetic interaction mechanisms and the measurement of external radiation fields. The primary emphasis of this report is on the physical parameters and mechanisms of radiofrequency interaction with matter. Base units are specified and defined in a manner similar to that adopted in the International System of Units (SI). (KRM)

Not Available

1981-01-01

5

78 FR 33633 - Human Exposure to Radiofrequency Electromagnetic Fields  

Federal Register 2010, 2011, 2012, 2013

...Exposure to Radiofrequency Electromagnetic Fields; Reassessment of Exposure to Radiofrequency Electromagnetic Fields Limits and Policies; Final...Exposure to Radiofrequency Electromagnetic Fields AGENCY: Federal...

2013-06-04

6

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

Microsoft Academic Search

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

Martin Röösli

2008-01-01

7

Superconducting surface impedance under radiofrequency field  

NASA Astrophysics Data System (ADS)

Based on BCS theory with moving Cooper pairs, the electron states distribution at 0 K and the probability of electron occupation with finite temperature have been derived and applied to anomalous skin effect theory to obtain the surface impedance of a superconductor under radiofrequency (RF) field. We present the numerical results for Nb and compare these with representative RF field-dependent effective surface resistance measurements from a 1.5 GHz resonant structure.

Xiao, B. P.; Reece, C. E.; Kelley, M. J.

2013-07-01

8

Non-ionizing radiation with nanosecond pulsed electric fields as a cancer treatment: in vitro studies.  

PubMed

Cancer continues to be a major risk to the health and well being among populations around the world. A new method using ion-ionizing radiation with nanosecond pulsed electric fields (nsPEFs) provides a novel means to treat cancer at local sites. NsPEFs promote cell death in several cell types and here we investigated mechanisms for cell death induction. In murine B16f10 melanoma, murine E4 squamous carcinoma, murine Hep1-6 and human HepG2 hepatocellular carcinoma, nsPEFs induced cell death in 90-95% of cells. Cell death coincides with decreases in the mitochondria membrane potential, increases in YO-PRO-1 uptake and active caspases in the presence or absence of cytochrome c release. The results indicate that nsPEFs induced cell death by multiple apoptosis mechanisms that involve mitochondrial responses, but not necessarily through cytochrome c release. Further, these in vitro studies suggest a potential to induce cell death that bypasses cancer mechanisms that evade apoptosis. PMID:19964169

Beebe, Stephen J; Ford, Wentia E; Ren, Wei; Chen, Xinhua; Schoenbach, Karl H

2009-01-01

9

Fundamentals of Ion Motion in Electric Radiofrequency Multipole Fields.  

National Technical Information Service (NTIS)

The fundamentals of ion motion in electromagnetic fields are reviewed in detail with a special emphasis on electric radiofrequency (RF) fields which are used frequently in dynamic mass spectrometry. Forces and effects on ions in electromagnetic fields whi...

M. H. Friedman A. L. Yergey J. E. Campana L. Kelner

1981-01-01

10

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 1 km2. 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 3.1 V/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 900 MHz 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

2013-10-01

11

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

SciTech Connect

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 1 km{sup 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 3.1 V/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 900 MHz 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 2 dB (factor 1.26 in electric-field strength), a correlation coefficient of 0.7, and a specificity of 0.96. -- Highlights: • We present an iterative measurement and modeling method for outdoor RF-EMF exposure. • Hotspots are rapidly identified, and accurately characterized. • An accurate graphical representation, or heat map, is created, using kriging. • Random validation shows good correlation (0.7) and low relative errors (2 dB)

Aerts, Sam, E-mail: sam.aerts@intec.ugent.be; Deschrijver, Dirk; Verloock, Leen; Dhaene, Tom; Martens, Luc; Joseph, Wout

2013-10-15

12

Adaptive Response in Mice Exposed to 900 MHz Radiofrequency Fields: Primary DNA Damage  

PubMed Central

The phenomenon of adaptive response (AR) in animal and human cells exposed to ionizing radiation is well documented in scientific literature. We have examined whether such AR could be induced in mice exposed to non-ionizing radiofrequency fields (RF) used for wireless communications. Mice were pre-exposed to 900 MHz RF at 120 µW/cm2 power density for 4 hours/day for 1, 3, 5, 7 and 14 days and then subjected to an acute dose of 3 Gy ?-radiation. The primary DNA damage in the form of alkali labile base damage and single strand breaks in the DNA of peripheral blood leukocytes was determined using the alkaline comet assay. The results indicated that the extent of damage in mice which were pre-exposed to RF for 1 day and then subjected to ?-radiation was similar and not significantly different from those exposed to ?-radiation alone. However, mice which were pre-exposed to RF for 3, 5, 7 and 14 days showed progressively decreased damage and was significantly different from those exposed to ?-radiation alone. Thus, the data indicated that RF pre-exposure is capable of inducing AR and suggested that the pre-exposure for more than 4 hours for 1 day is necessary to elicit such AR.

Zhou, Zhen; Zhang, Jie; Tong, Jian; Cao, Yi

2012-01-01

13

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

14

Ionization of N2 in radio-frequent electric field  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

15

The Effect of Combined Exposure of 900 MHz Radiofrequency Fields and Doxorubicin in HL-60 Cells  

PubMed Central

Human promyelocytic leukemia HL-60 cells were pre-exposed to non-ionizing 900 MHz radiofrequency fields (RF) at 12 µW/cm2 power density for 1 hour/day for 3 days and then treated with a chemotherapeutic drug, doxorubicin (DOX, 0.125 mg/L). Several end-points related to toxicity, viz., viability, apoptosis, mitochondrial membrane potential (MMP), intracellular free calcium (Ca2+) and Ca2+-Mg2+ -ATPase activity were measured. The results obtained in un-exposed and sham-exposed control cells were compared with those exposed to RF alone, DOX alone and RF+DOX. The results indicated no significant differences between un-exposed, sham-exposed control cells and those exposed to RF alone while treatment with DOX alone showed a significant decrease in viability, increased apoptosis, decreased MMP, increased Ca2+ and decreased Ca2+-Mg2+-ATPase activity. When the latter results were compared with cells exposed RF+DOX, the data showed increased cell proliferation, decreased apoptosis, increased MMP, decreased Ca2+ and increased Ca2+-Mg2+-ATPase activity. Thus, RF pre-exposure appear to protect the HL-60 cells from the toxic effects of subsequent treatment with DOX. These observations were similar to our earlier data which suggested that pre-exposure of mice to 900 MHz RF at 120 µW/cm2 power density for 1 hours/day for 14 days had a protective effect in hematopoietic tissue damage induced by subsequent gamma-irradiation.

Jiang, Bingcheng; Zhou, Zhen; Tong, Jian; Cao, Yi

2012-01-01

16

Biological effects and exposure criteria for radiofrequency electromagnetic fields  

SciTech Connect

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

Not Available

1986-01-01

17

78 FR 33654 - Reassessment of Exposure to Radiofrequency Electromagnetic Fields Limits and Policies  

Federal Register 2010, 2011, 2012, 2013

...Exposure to Radiofrequency Electromagnetic Fields Limits and Policies AGENCY...for human exposure to RF electromagnetic fields. The Commission's further...Commission's exposure limits for RF electromagnetic fields. The Commission...

2013-06-04

18

Radiofrequency fields associated with the Itron smart meter.  

PubMed

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

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

2012-08-01

19

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

20

Remotely Triggered Cisplatin Release from Carbon Nanocapsules by Radiofrequency Fields  

PubMed Central

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 ultrashort 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.

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

2013-01-01

21

Effects of radiofrequency electromagnetic fields on the human nervous system.  

PubMed

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). This is not corroborated, however, by the results from studies on evoked potentials. Although there is some evidence emerging that there may be an effect of exposure to a GSM-type signal on sleep EEG, results are still variable. In summary, exposure to a GSM-type signal may result in minor effects on brain activity, but such changes have never been found to relate to any adverse health effects. No consistent significant effects on cognitive performance in adults have been observed. If anything, any effect is small and exposure seems to improve performance. Effects in children did not differ from those in healthy adults. Studies on auditory and vestibular function are more unequivocal: neither hearing nor the sense of balance is influenced by short-term exposure to mobile phone signals. Subjective symptoms over a wide range, including headaches and migraine, fatigue, and skin itch, have been attributed to various radiofrequency sources both at home and at work. However, in provocation studies a causal relation between EMF exposure and symptoms has never been demonstrated. There are clear indications, however, that psychological factors such as the conscious expectation of effect may play an important role in this condition. PMID:20183535

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

2009-10-01

22

MR Detection of Mechanical Vibrations Using a Radiofrequency Field Gradient  

NASA Astrophysics Data System (ADS)

A new method for NMR characterization of mechanical waves, based upon radiofrequency field gradient for motion encoding, is proposed. A binomial B1 gradient excitation scheme was used to visualize the mobile spins undergoing a periodic transverse mechanical excitation. A simple model was designed to simulate the NMR signal as a function of the wave frequency excitation and the periodicity of the NMR pulse sequence. The preliminary results were obtained on a gel phantom at low vibration frequencies (0-200 Hz) by using a ladder-shaped coil generating a nearly constant RF field gradient along a specific known direction. For very small displacements and/or B1 gradients, the NMR signal measured on a gel phantom was proportional to the vibration amplitude and the pulse sequence was shown to be selective with respect to the vibration frequency. A good estimation of the direction of vibrations was obtained by varying the angle between the motion direction and the B1 gradient. The method and its use in parallel to more conventional MR elastography techniques are discussed. The presented approach might be of interest for noninvasive investigation of elastic properties of soft tissues and other materials.

Baril, Nathalie; Lewa, Czeslaw Jozef; de Certaines, Jacques Donald; Canioni, Paul; Franconi, Jean-Michel; Thiaudière, Eric

2002-01-01

23

Statistical analysis of personal radiofrequency electromagnetic field measurements with nondetects.  

PubMed

Exposimeters are increasingly applied in bioelectromagnetic research to determine personal radiofrequency electromagnetic field (RF-EMF) exposure. The main advantages of exposimeter measurements are their convenient handling for study participants and the large amount of personal exposure data, which can be obtained for several RF-EMF sources. However, the large proportion of measurements below the detection limit is a challenge for data analysis. With the robust ROS (regression on order statistics) method, summary statistics can be calculated by fitting an assumed distribution to the observed data. We used a preliminary sample of 109 weekly exposimeter measurements from the QUALIFEX study to compare summary statistics computed by robust ROS with a naïve approach, where values below the detection limit were replaced by the value of the detection limit. For the total RF-EMF exposure, differences between the naïve approach and the robust ROS were moderate for the 90th percentile and the arithmetic mean. However, exposure contributions from minor RF-EMF sources were considerably overestimated with the naïve approach. This results in an underestimation of the exposure range in the population, which may bias the evaluation of potential exposure-response associations. We conclude from our analyses that summary statistics of exposimeter data calculated by robust ROS are more reliable and more informative than estimates based on a naïve approach. Nevertheless, estimates of source-specific medians or even lower percentiles depend on the assumed data distribution and should be considered with caution. PMID:18421711

Röösli, Martin; Frei, Patrizia; Mohler, Evelyn; Braun-Fahrländer, Charlotte; Bürgi, Alfred; Fröhlich, Jürg; Neubauer, Georg; Theis, Gaston; Egger, Matthias

2008-09-01

24

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

25

Probing the fundamental limit of niobium in high radiofrequency fields by dual mode excitation in superconducting radiofrequency cavities  

SciTech Connect

We have studied thermal breakdown in several multicell superconducting radiofrequency cavity by simultaneous excitation of two TM{sub 010} passband modes. Unlike measurements done in the past, which indicated a clear thermal nature of the breakdown, our measurements present a more complex picture with interplay of both thermal and magnetic effects. JLab LG-1 that we studied was limited at 40.5 MV/m, corresponding to B{sub peak} = 173 mT, in 8{pi}/9 mode. Dual mode measurements on this quench indicate that this quench is not purely magnetic, and so we conclude that this field is not the fundamental limit in SRF cavities.

Eremeev, Grigory; Geng, Rongli; Palczewski, Ari

2011-07-01

26

68 FR 52879 - Exposure to Radiofrequency Electromagnetic Fields  

Federal Register 2010, 2011, 2012, 2013

...Federal Communications Commission...Regarding Human Exposure to Radiofrequency...evaluate the effects of their actions...Permissible Exposure (MPE...partial-body exposures. The Commission's...with the RF exposure guidelines...evaluate the effects of their actions...r) of the Communications Act of...

2003-09-08

27

Assessment of physiotherapists' occupational exposure to radiofrequency electromagnetic fields from shortwave and microwave diathermy devices: a literature review.  

PubMed

We reviewed studies reporting the strength of radiofrequency (RF) electromagnetic fields (EMF) in physiotherapists' occupational environment. Studies from academic journals published from January 1990 to June 2010 were identified in nine online bibliographic databases. EMF strength was compared with occupational exposure limits (OELs) recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). In the reviewed studies, EMFs were measured at different distances (range 0.2 m to 6 m) from the console of diathermy devices, electrodes, and cables. For continuous shortwave diathermy (CSWD) (27.12 megahertz, MHz), measurements of EMFs at < 1 m, 1 m, 1.1-1.5 m, and 2 m reported the maximum E field strength as 8197%, 1639%, 295%, and 69%, respectively, and the maximum H field strength as 6250%, 681%, 213%, and 56%, respectively, of the ICNIRP limits for E and H fields for occupational exposure. For pulsed shortwave diathermy (PSWD) (27.12 MHz), EMF measurements at < 1 m, 1 m, and, 1.1-1.5 m showed the maximum E field intensity as 1639%, 175%, and 32%, and the maximum H field strength as 1175%, 968%, and 28%, respectively, of the ICNIRP limits for E and H fields for occupational exposure. For microwave diathermy (MWD) (2.45 gigahertz, GHz), the maximum power density measured at < 1 m, 1 m, 1.1-1.5 m, and 2 m was 200%, <30%, 0.76%, and 0.82%, respectively, of the ICNIRP limit for occupational exposure. RF EMF emissions measured from continuous and pulsed electrotherapeutic diathermy devices may well be higher than OELs at specific distances, i.e., at 1 m, which is currently designated to be a safe distance for physiotherapists. The minimum safe distance for physiotherapists should be revised to at least 2 m for CSWD and 1.5 m for PSWD. The reviewed studies did not provide evidence of exceeding the ICNIRP's reference levels for occupational exposure at 1 m from MWD devices. PMID:23570423

Shah, Syed Ghulam Sarwar; Farrow, Alexandra

2013-01-01

28

Effects of vane-tip geometry on the electric fields in radio-frequency quadrupole linacs  

NASA Astrophysics Data System (ADS)

Five types of vane-tip geometries for radio-frequency quadrupole linacs are described. Tables show the peak surface field and the eight lowest order multipole coefficients as a function of cell length and modulation parameter. The method used to obtain the data in the tables is discussed.

Crandall, K. R.

1983-04-01

29

Effects of Vane-Tip Geometry on the Electric Fields in Radio-Frequency Quadrupole Linacs.  

National Technical Information Service (NTIS)

This report describes five types of vane-tip geometries for radio-frequency quadrupole linacs and presents in tabular form the peak surface field and the eight lowest order multipole coefficients as a function of cell length and modulation parameter. A br...

K. R. Crandall

1983-01-01

30

Effects of vane-tip geometry on the electric fields in radio-frequency quadrupole linacs  

SciTech Connect

This report describes five types of vane-tip geometries for radio-frequency quadrupole linacs and presents in tabular form the peak surface field and the eight lowest order multipole coefficients as a function of cell length and modulation parameter. A brief description is given of the method used to obtain the results given in the tables.

Crandall, K.R.

1983-04-01

31

Effects of vane-tip geometry on the electric fields in radio-frequency quadrupole linacs  

Microsoft Academic Search

Five types of vane-tip geometries for radio-frequency quadrupole linacs are described. Tables show the peak surface field and the eight lowest order multipole coefficients as a function of cell length and modulation parameter. The method used to obtain the data in the tables is discussed.

K. R. Crandall

1983-01-01

32

Effects of Field Orientation during 700-MHz Radiofrequency Irradiation of Rats.  

National Technical Information Service (NTIS)

Ketamine-anesthetized Sprague-Dawley rats were exposed to far-field 700-MHz continuous-wave radiofrequency radiation (RFR) in both E and H orientations. Irradiation was conducted at whole-body average specific absorption rates (SARs) of 9.2 and 13.0 W/kg ...

M. R. Frei J. R. Jauchem J. M. Padilla

1989-01-01

33

Exposure to radio-frequency electromagnetic fields and behavioural problems in Bavarian children and adolescents  

Microsoft Academic Search

Only few studies have so far investigated possible health effects of radio-frequency electromagnetic fields (RF EMF) in children\\u000a and adolescents, although experts discuss a potential higher vulnerability to such fields. We aimed to investigate a possible\\u000a association between measured exposure to RF EMF fields and behavioural problems in children and adolescents. 1,498 children\\u000a and 1,524 adolescents were randomly selected from

Silke Thomas; Sabine Heinrich; Rüdiger von Kries; Katja Radon

2010-01-01

34

Energy Distribution of Ions Incident on Radio-Frequency Biased Electrodes in External Magnetic Field  

NASA Astrophysics Data System (ADS)

A radio-frequency (rf) plasma sheath model in an oblique magnetic field is established and the energy distribution of ions (IED) incident on the rf sheath biased electrodes is numerically investigated. The simulation results reveal that the external magnetic field can have a decisive impact on the ion flux and energy distribution of the sheath. The ion energy can be transferred between the perpendicular and parallel components under the action of a magnetic field.

Zou, Xiu; Feng, Xiaobing; Qiu, Minghui; Liu, Jinyuan; Gong, Ye

2010-02-01

35

Citation Index for Foreign Language Reports on Biological Effects of Radio-Frequency Electro-Magnetic Fields.  

National Technical Information Service (NTIS)

A citation index is presented for foreign language documents selected from an extensive literature collection in the subject field of biological effects of radio-frequency electromagnetic fields, with emphasis on the microwave range. Also included is a li...

J. Healer R. Smiley

1969-01-01

36

Tunable Atomic Magnetometer for Detection of Radio-Frequency Magnetic Fields  

Microsoft Academic Search

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\\/Hz¹² at a frequency of 99 kHz with a resonance width of

I. M. Savukov; S. J. Seltzer; M. V. Romalis; K. L. Sauer

2005-01-01

37

Tunable Atomic Magnetometer for Detection of Radio-Frequency Magnetic Fields  

Microsoft Academic Search

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\\/Hz1\\/2 at a frequency of 99 kHz with a resonance width of

I. M. Savukov; S. J. Seltzer; M. V. Romalis; K. L. Sauer

2005-01-01

38

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

Microsoft Academic Search

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

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

2012-01-01

39

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

Microsoft Academic Search

Cardiovascular changes in humans exposed to nonionizing radiation [including extremely-low-frequency electromagnetic fields\\u000a (ELF EMFs) and radiofrequency radiation (RFR)] are reviewed. Both acute and long-term effects have been investigated. In general,\\u000a if heating does not occur during exposure, current flow appears to be necessary for major cardiovascular effects to ensue,\\u000a such as those due to electric shock. Whereas most studies have

James R. Jauchem

1997-01-01

40

Sense and sensibility in the context of radiofrequency electromagnetic field exposure  

Microsoft Academic Search

The association between radiofrequency exposure (RF-EMF) and non-specific health complaints in electromagnetic hypersensitive (EHS) individuals was investigated in a prospective cohort study conducted between 2008 and 2009 in Switzerland. Exposure to environmental far-field RF-EMF sources was modelled and cordless and mobile phone use was also considered in the analyses. About 8% (n=130) of the study population declared to be EHS.

Martin Röösli; Evelyn Mohler; Patrizia Frei

2010-01-01

41

Radio-frequency and microwave energies, magnetic and electric fields  

NASA Technical Reports Server (NTRS)

The biological effects of radio frequency, including microwave, radiation are considered. Effects on body temperature, the eye, reproductive systems, internal organs, blood cells, the cardiovascular system, and the central nervous system are included. Generalized effects of electric and magnetic fields are also discussed. Experimentation with animals and clinical studies on humans are cited, and possible mechanisms of the effects observed are suggested.

Michaelson, S. M.

1975-01-01

42

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

43

Human exposure to radiofrequency electromagnetic fields. Final rule.  

PubMed

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

2013-06-01

44

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

SciTech Connect

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

Tong Wang

2002-09-18

45

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

NASA Astrophysics Data System (ADS)

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

Glazer, Evan Scott

46

Radiofrequency field inhomogeneity compensation in high spatial resolution magnetic resonance spectroscopic imaging.  

PubMed

Clinical magnetic resonance spectroscopy imaging (MRSI) is a non-invasive functional technique, whose mathematical framework falls into the category of linear inverse problems. However, its use in medical diagnostics is hampered by two main problems, both linked to the Fourier-based technique usually implemented for spectra reconstruction: poor spatial resolution and severe blurring in the spatial localization of the reconstructed spectra. Moreover, the intrinsic ill-posedness of the MRSI problem might be worsened by (i) spatially dependent distortions of the static magnetic field (B0) distribution, as well as by (ii) inhomogeneity in the power deposition distribution of the radiofrequency magnetic field (B1). Among several alternative methods, slim (Spectral Localization by IMaging) and bslim (B0 compensated slim) are reconstruction algorithms in which a priori information concerning the spectroscopic target is introduced into the reconstruction kernel. Nonetheless, the influence of the B1 field, particularly when its operating wavelength is close to the size of the human organs being studied, continues to be disregarded. starslim (STAtic and Radiofrequency-compensated slim), an evolution of the slim and bslim methods, is therefore proposed, in which the transformation kernel also includes the B1 field inhomogeneity map, thus allowing almost complete 3D modelling of the MRSI problem. Moreover, an original method for the experimental determination of the B1 field inhomogeneity map specific to the target under evaluation is also included. The compensation capabilities of the proposed method have been tested and illustrated using synthetic raw data reproducing the human brain. PMID:24828836

Passeri, Alessandro; Mazzuca, Stefano; Bene, Veronica Del

2014-06-21

47

Radiofrequency field inhomogeneity compensation in high spatial resolution magnetic resonance spectroscopic imaging  

NASA Astrophysics Data System (ADS)

Clinical magnetic resonance spectroscopy imaging (MRSI) is a non-invasive functional technique, whose mathematical framework falls into the category of linear inverse problems. However, its use in medical diagnostics is hampered by two main problems, both linked to the Fourier-based technique usually implemented for spectra reconstruction: poor spatial resolution and severe blurring in the spatial localization of the reconstructed spectra. Moreover, the intrinsic ill-posedness of the MRSI problem might be worsened by (i) spatially dependent distortions of the static magnetic field (B0) distribution, as well as by (ii) inhomogeneity in the power deposition distribution of the radiofrequency magnetic field (B1). Among several alternative methods, slim (Spectral Localization by IMaging) and bslim (B0 compensated slim) are reconstruction algorithms in which a priori information concerning the spectroscopic target is introduced into the reconstruction kernel. Nonetheless, the influence of the B1 field, particularly when its operating wavelength is close to the size of the human organs being studied, continues to be disregarded. starslim (STAtic and Radiofrequency-compensated slim), an evolution of the slim and bslim methods, is therefore proposed, in which the transformation kernel also includes the B1 field inhomogeneity map, thus allowing almost complete 3D modelling of the MRSI problem. Moreover, an original method for the experimental determination of the B1 field inhomogeneity map specific to the target under evaluation is also included. The compensation capabilities of the proposed method have been tested and illustrated using synthetic raw data reproducing the human brain.

Passeri, Alessandro; Mazzuca, Stefano; Del Bene, Veronica

2014-06-01

48

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

PubMed

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

2009-10-01

49

Diffusion tensor in electron transport in gases in a radio-frequency field  

SciTech Connect

Electron transport theory in gases in a radio-frequency field is developed in the hydrodynamic regime from the density gradient expansion method of the Boltzmann equation. Swarm parameters for the radio-frequency (rf) field with periodic time modulation are derived as functions of both reduced effective field strength and reduced angular frequency from the time dependent velocity distribution function. The rf electron transport in phase space is analyzed from the series of governing equations by a direct numerical procedure (DNP). Electron velocity distribution function and corresponding swarm parameters obtained from DNP agree with those of the Monte Carlo simulation in the frequency range 10{endash}200 MHz at 10 Td for Reid`s inelastic ramp model gas. The temporal modulation of the ensemble average of energy and the diffusion tensor are discussed. The appearance of the anomalous time behavior of the longitudinal diffusion coefficient is discussed in particular detail, and we provide an explanation of the observed effect. {copyright} {ital 1997} {ital The American Physical Society}

Maeda, K.; Makabe, T.; Nakano, N. [Department of Electronics, Keio University, 3-14-1 Hiyoshi, Yokohama 223 (Japan)] [Department of Electronics, Keio University, 3-14-1 Hiyoshi, Yokohama 223 (Japan); Bzenic, S.; Petrovic, Z.L. [Institute of Physics, University of Belgrade, P.O. Box 57, 11001, Belgrade (Yugoslavia)] [Institute of Physics, University of Belgrade, P.O. Box 57, 11001, Belgrade (Yugoslavia)

1997-05-01

50

Lack of teratogenicity after combined exposure of pregnant mice to CDMA and WCDMA radiofrequency electromagnetic fields.  

PubMed

Concern about the possible adverse effects of radiofrequency (RF)-field exposure on public health has increased because of the extensive use of wireless mobile phones and other telecommunication devices in daily life. The murine fetus is a very sensitive indicator of the effects of stress or stimuli in the environment. Therefore, we investigated the teratogenic effects of multi-signal radiofrequency electromagnetic fields (RF EMFs) on mouse fetuses. Pregnant mice were simultaneously exposed to two types of RF signals, single code division multiple access (CDMA) and wideband code division multiple access (WCDMA). Mice received two 45-min RF-field exposures, separated by a 15-min interval, daily throughout the entire gestation period. The whole-body average specific absorption rate (SAR) of CDMA or WCDMA was 2.0 W/kg. The animals were killed humanely on the 18th day of gestation and fetuses were examined for mortality, growth retardation, changes in head size and other morphological abnormalities. From the results, we report for the first time that simultaneous experimental exposure to CDMA and WCDMA RF EMFs did not cause any observable adverse effects on mouse fetuses. PMID:19883234

Lee, Hae-June; Lee, Jae-Seon; Pack, Jeong-Ki; Choi, Hyung-Do; Kim, Nam; Kim, Sung-Ho; Lee, Yun-Sil

2009-11-01

51

Stabilization of predissociating nitric oxide Rydberg molecules using microwave and radio-frequency fields  

NASA Astrophysics Data System (ADS)

We present three techniques for suppressing predissociation of the nitric oxide Rydberg states normally excited in pulsed-field ionization zero-kinetic-energy photoelectron spectroscopy. By applying a combination of appropriate dc and microwave fields it is possible to inhibit predissociation by resonantly mixing Stark states of adjacent principal quantum number n, with similar parabolic quantum number k. Lifetime enhancement is also obtained by using an appropriate radio-frequency field to resonantly mix Stark states of the same n. Finally, in the absence of dc fields, microwaves are used to stabilize optically excited nf Rydberg states, by inducing transitions to higher angular momentum states with longer lifetimes, specifically to the n+/-1, l>=4 states.

Murgu, Elena; Martin, J. D. D.; Gallagher, T. F.

2001-10-01

52

Induction of an adaptive response in human blood lymphocytes exposed to radiofrequency fields: influence of the universal mobile telecommunication system (UMTS) signal and the specific absorption rate.  

PubMed

The induction of an adaptive response (AR) was examined in human peripheral blood lymphocytes exposed to non-ionizing radiofrequency fields (RF). Cells from nine healthy human volunteers were stimulated for 24h with phytohaemagglutinin and then exposed for 20h to an adaptive dose (AD) of a 1950MHz RF UMTS (universal mobile telecommunication system) signal used for mobile communications, at different specific absorption rates (SAR) of 1.25, 0.6, 0.3, and 0.15W/kg. This was followed by treatment of the cells at 48h with a challenge dose (CD) of 100ng/ml mitomycin C (MMC). Lymphocytes were collected at the end of the 72h total culture period. The cytokinesis-block method was used to record the frequency of micronuclei (MN) as genotoxicity end-point. When lymphocytes from six donors were pre-exposed to RF at 0.3W/kg SAR and then treated with MMC, these cells showed a significant reduction in the frequency of MN, compared with the cells treated with MMC alone; this result is indicative of induction of AR. The results from our earlier study indicated that lymphocytes that were stimulated for 24h, exposed for 20h to a 900MHz RF GSM (global system for mobile communication) signal at 1.25W/kg SAR and then treated with 100ng/ml MMC, also exhibited AR. These overall data suggest that the induction of AR depends on RF frequency, type of the signal and SAR. Further characterization of RF-induced AR is in progress. PMID:22525361

Zeni, Olga; Sannino, Anna; Romeo, Stefania; Massa, Rita; Sarti, Maurizio; Reddy, Abishek B; Prihoda, Thomas J; Vijayalaxmi; Scarfì, Maria Rosaria

2012-08-30

53

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

54

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

55

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

56

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

57

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

PubMed Central

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

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

2014-01-01

58

Magnetic orientation of garden warblers (Sylvia borin) under 1.4 MHz radiofrequency magnetic field.  

PubMed

We report on the experiments on orientation of a migratory songbird, the garden warbler (Sylvia borin), during the autumn migration period on the Courish Spit, Eastern Baltics. Birds in experimental cages, deprived of visual information, showed the seasonally appropriate direction of intended flight with respect to the magnetic meridian. Weak radiofrequency (RF) magnetic field (190 nT at 1.4 MHz) disrupted this orientation ability. These results may be considered as an independent replication of earlier experiments, performed by the group of R. and W. Wiltschko with European robins (Erithacus rubecula). Confirmed outstanding sensitivity of the birds' magnetic compass to RF fields in the lower megahertz range demands for a revision of one of the mainstream theories of magnetoreception, the radical-pair model of birds' magnetic compass. PMID:24942848

Kavokin, Kirill; Chernetsov, Nikita; Pakhomov, Alexander; Bojarinova, Julia; Kobylkov, Dmitry; Namozov, Barot

2014-08-01

59

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

60

Exposure of biological preparations to radiofrequency electromagnetic fields under low gravity.  

PubMed

There is interest as to whether the electromagnetic fields used in mobile radiotelephony might affect biological processes. Other weak fields such as gravity intervene in a number of physical and biological processes. Under appropriate in vitro conditions, the macroscopic self-organization of microtubules, a major cellular component, is triggered by gravity. We wished to investigate whether self-organization might also be affected by radiotelephone electromagnetic fields. Detecting a possible effect requires removing the obscuring effects triggered by gravity. A simple manner of doing this is by rotating the sample about the horizontal. However, if the external field does not also rotate with the sample, its possible effect might also be averaged down by rotation. Here, we describe an apparatus in which both the sample and an applied radiofrequency electromagnetic field (1.8 GHz) are stationary with respect to one another while undergoing horizontal rotation. The electromagnetic field profile within the apparatus has been measured and the apparatus tested by reproducing the in vitro behavior of microtubule preparations under conditions of weightlessness. Specific adsorption rates of electromagnetic energy within a sample are measured from the initial temperature rise the incident field causes. The apparatus can be readily adapted to expose samples to various other external fields and factors under conditions of weightlessness. PMID:21133497

Jacquot, Jean Francois; le Bail, Jean-Luc; Bardet, Michel; Tabony, James

2010-11-01

61

Assessment of induced radio-frequency electromagnetic fields in various anatomical human body models  

NASA Astrophysics Data System (ADS)

The reference levels for testing compliance of human exposure with radio-frequency (RF) safety limits have been derived from very simplified models of the human. In order to validate these findings for anatomical models, we investigated the absorption characteristics for various anatomies ranging from 6 year old child to large adult male by numerical modeling. We address the exposure to plane-waves incident from all major six sides of the humans with two orthogonal polarizations each. Worst-case scattered field exposure scenarios have been constructed in order to test the implemented procedures of current in situ compliance measurement standards (spatial averaging versus peak search). Our findings suggest that the reference levels of current electromagnetic (EM) safety guidelines for demonstrating compliance as well as some of the current measurement standards are not consistent with the basic restrictions and need to be revised.

Kühn, Sven; Jennings, Wayne; Christ, Andreas; Kuster, Niels

2009-02-01

62

Modeling far-field radio-frequency sheaths in Alcator C-Mod  

NASA Astrophysics Data System (ADS)

This paper is motivated by the recent measurement of large (>100 V) plasma potentials in Alcator C-Mod during ion cyclotron range of frequency (ICRF) heating. The plasma potential is measured on field lines that intersect a limiter but do not pass near a powered ICRF antenna. The measured potential correlates with the local ICRF fast wave electric field and is a prime candidate to cause increased Mo sputtering from the limiter surface. In this paper, it is shown that a theory of ‘far-fieldradio-frequency (rf) sheaths can qualitatively explain this experimental observation. The theory describes rf-sheath formation when unabsorbed fast ICRF waves are incident on a conducting boundary far from the antenna. It is shown that the rf-sheath drive is sensitive to the angle between the surface normal and the equilibrium magnetic field. The main conclusion of this work is that the rapid tangential variation in the B field-limiter geometry near the tip of the limiter promotes the formation of large sheath potentials of the same order as the measured ones.

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

2013-08-01

63

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

64

Genotoxic effects of exposure to radiofrequency electromagnetic fields (RF-EMF) in cultured mammalian cells are not independently reproducible  

Microsoft Academic Search

Conflicting results have been published regarding the induction of genotoxic effects by exposure to radiofrequency electromagnetic fields (RF-EMF). Using the comet assay, the micronucleus test and the chromosome aberration test with human fibroblasts (ES1 cells), the EU-funded “REFLEX” project (Risk Evaluation of Potential Environmental Hazards From Low Energy Electromagnetic Field Exposure Using Sensitive in vitro Methods) reported clearly positive effects

Günter Speit; Petra Schütz; Heike Hoffmann

2007-01-01

65

Residential characteristics and radiofrequency electromagnetic field exposures from bedroom measurements in Germany.  

PubMed

The objectives of this study were to assess total exposure to radiofrequency electromagnetic fields (RF-EMF) in bedrooms and the contribution of different radioservices (FM radio, analogue TV and DVB-T, TETRA, GSM900 downlink, GSM1800 downlink, UMTS downlink, DECT, and wireless LAN and blue tooth) to the total exposure. Additional aims were to describe the proportion of measuring values above the detection limit of the dosimeters and to characterize the differences in exposure patterns associated with self-reported residential characteristics. Exposure to RF sources in bedrooms was measured using Antennessa(®) EME Spy 120 dosimeters in 1,348 households in Germany; 280 measures were available for each frequency band per household. Mean electrical field strengths and power flux densities were calculated. Power flux densities allow the calculation of proportions of different radioservices on total exposure. Exposure was often below the detection limit (electrical field strength: 0.05 V/m) of the dosimeter. Total exposure varied, depending on residential characteristics (urban vs. rural areas and floor of a building the measurement took place). Major sources of exposure were cordless phones (DECT standard) and wireless LAN/blue tooth contributing about 82% of total exposure (20.5 ?W/m(2)). Exposure to RF-EMF is ubiquitous, but exposure levels are-if at all measurable-very low and far below the ICNIRP's exposure reference levels. PMID:21964673

Breckenkamp, J; Blettner, M; Schüz, J; Bornkessel, C; Schmiedel, S; Schlehofer, B; Berg-Beckhoff, G

2012-03-01

66

Analysis of auditory evoked potential parameters in the presence of radiofrequency fields using a support vector machines method.  

PubMed

The paper presents a study of global system for mobile (GSM) phone radiofrequency effects on human cerebral activity. The work was based on the study of auditory evoked potentials (AEPs) recorded from healthy humans and epileptic patients. The protocol allowed the comparison of AEPs recorded with or without exposure to electrical fields. Ten variables measured from AEPs were employed in the design of a supervised support vector machines classifier. The classification performance measured the classifier's ability to discriminate features performed with or without radiofrequency exposure. Most significant features were chosen by a backward sequential selection that ranked the variables according to their pertinence for the discrimination. Finally, the most discriminating features were analysed statistically by a Wilcoxon signed rank test. For both populations, the N100 amplitudes were reduced under the influence of GSM radiofrequency (mean attenuation of -0.36 microV for healthy subjects and -0.60 microV for epileptic patients). Healthy subjects showed a N100 latency decrease (-5.23 ms in mean), which could be consistent with mild, localised heating. The auditory cortical activity in humans was modified by GSM phone radiofrequencies, but an effect on brain functionality has not been proven. PMID:15320468

Maby, E; Le Bouquin Jeannès, R; Liégeois-Chauvel, C; Gourevitch, B; Faucon, G

2004-07-01

67

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

PubMed Central

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

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

2013-01-01

68

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

69

Resonant Mode Reduction in Radiofrequency Volume Coils for Ultrahigh Field Magnetic Resonance Imaging.  

PubMed

In a multimodal volume coil, only one mode can generate homogeneous Radiofrequency (RF) field for Magnetic Resonance Imaging. The existence of other modes may increase the volume coil design difficulties and potentially decreases coil performance. In this study, we introduce common-mode resonator technique to high and ultrahigh field volume coil designs to reduce the resonant mode while maintain the homogeneity of the RF field. To investigate the design method, the common-mode resonator was realized by using a microstrip line which was split along the central to become a pair of parallel transmission lines within which common-mode currents exist. Eight common-mode resonators were placed equidistantly along the circumference of a low loss dielectric cylinder to form a volume coil. Theoretical analysis and comparison between the 16-strut common-mode volume coil and a conventional 16-strut volume coil in terms of RF field homogeneity and efficiency was performed using Finite-Difference Time-Domain (FDTD) method at 298.2 MHz. MR imaging experiments were performed by using a prototype of the common-mode volume coil on a whole body 7 Tesla scanner. FDTD simulation results showed the reduced number of resonant modes of the common-mode volume coil over the conventional volume coil, while the RF field homogeneity of the two type volume coils was kept at the same level. MR imaging of a water phantom and a kiwi fruit showing the feasibility of the proposed method for simplifying the volume coil design is also presented. PMID:22081791

Pang, Yong; Xie, Zhentian; Li, Ye; Xu, Duan; Vigneron, Daniel; Zhang, Xiaoliang

2011-07-28

70

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

PubMed Central

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

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

2013-01-01

71

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

SciTech Connect

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

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

1989-01-01

72

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

SciTech Connect

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

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

1989-01-01

73

Optimization and Validation of Methods for Mapping of the Radiofrequency Transmit Field at 3T  

PubMed Central

MRI techniques such as quantitative imaging and parallel transmit require precise knowledge of the radio-frequency transmit field (). Three published methods were optimized for robust mapping at 3T in the human brain: three-dimensional (3D) actual flip angle imaging (AFI), 3D echo-planar imaging (EPI), and two-dimensional (2D) stimulated echo acquisition mode (STEAM). We performed a comprehensive comparison of the methods, focusing on artifacts, reproducibility, and accuracy compared to a reference 2D double angle method. For the 3D AFI method, the addition of flow-compensated gradients for diffusion damping reduced the level of physiological artifacts and improved spoiling of transverse coherences. Correction of susceptibility-induced artifacts alleviated image distortions and improved the accuracy of the 3D EPI imaging method. For the 2D STEAM method, averaging over multiple acquisitions reduced the impact of physiological noise and a new calibration method enhanced the accuracy of the maps. After optimization, all methods yielded low noise maps (below 2 percentage units), of the nominal flip angle value (p.u.) with a systematic bias less than 5 p.u. units. Full brain coverage was obtained in less than 5 min. The 3D AFI method required minimal postprocessing and showed little sensitivity to off-resonance and physiological effects. The 3D EPI method showed the highest level of reproducibility. The 2D STEAM method was the most time-efficient technique. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.

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

2010-01-01

74

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

SciTech Connect

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

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

1990-12-01

75

Young's Modulus Reconstruction for Radio-Frequency Ablation Electrode-Induced Displacement Fields: A Feasibility Study  

Microsoft Academic Search

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

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

2009-01-01

76

[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

2012-01-01

77

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

NASA Astrophysics Data System (ADS)

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, the experimental measurements show that stable glow discharges of argon, nitrogen or air can be obtained following a local breakdown process in the vicinity of the tungsten wire under lower applied voltages between the electrodes.

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

2008-10-01

78

Does Exposure to a Radiofrequency Electromagnetic Field Modify Thermal Preference in Juvenile Rats?  

PubMed Central

Some studies have shown that people living near a mobile phone base station may report sleep disturbances and discomfort. Using a rat model, we have previously shown that chronic exposure to a low-intensity radiofrequency electromagnetic field (RF-EMF) was associated with paradoxical sleep (PS) fragmentation and greater vasomotor tone in the tail. Here, we sought to establish whether sleep disturbances might result from the disturbance of thermoregulatory processes by a RF-EMF. We recorded thermal preference and sleep stage distribution in 18 young male Wistar rats. Nine animals were exposed to a low-intensity RF-EMF (900 MHz, 1 V.m?1) for five weeks and nine served as non-exposed controls. Thermal preference was assessed in an experimental chamber comprising three interconnected compartments, in which the air temperatures (Ta) were set to 24°C, 28°C and 31°C. Sleep and tail skin temperature were also recorded. Our results indicated that relative to control group, exposure to RF-EMF at 31°C was associated with a significantly lower tail skin temperature (?1.6°C) which confirmed previous data. During the light period, the exposed group preferred to sleep at Ta?=?31°C and the controls preferred Ta?=?28°C. The mean sleep duration in exposed group was significantly greater (by 15.5%) than in control group (due in turn to a significantly greater amount of slow wave sleep (SWS, +14.6%). Similarly, frequency of SWS was greater in exposed group (by 4.9 episodes.h?1). The PS did not differ significantly between the two groups. During the dark period, there were no significant intergroup differences. We conclude that RF-EMF exposure induced a shift in thermal preference towards higher temperatures. The shift in preferred temperature might result from a cold thermal sensation. The change in sleep stage distribution may involve signals from thermoreceptors in the skin. Modulation of SWS may be a protective adaptation in response to RF-EMF exposure.

Pelletier, Amandine; Delanaud, Stephane; de Seze, Rene; Bach, Veronique; Libert, Jean-Pierre; Loos, Nathalie

2014-01-01

79

Paternal occupational exposure to radiofrequency electromagnetic fields and risk of adverse pregnancy outcome  

Microsoft Academic Search

Background:\\u000a   During the last decades, public concern that radiofrequency radiation (RFR) may be related to adverse reproductive outcomes has been emerging. Our objective was to assess associations between paternal occupational exposure to RFR and adverse pregnancy outcomes including birth defects using population-based data from Norway.\\u000a Methods:\\u000a   Data on reproductive outcomes derived from the Medical Birth Registry of Norway were linked

Geir Mjøen; Dag Ottar Sætre; Rolv T. Lie; Tore Tynes; Karl Gerhard Blaasaas; Merete Hannevik; Lorentz M. Irgens

2006-01-01

80

A practical guide to the determination of human exposure to radiofrequency fields  

SciTech Connect

This report provides a comprehensive collection of information on various radiofrequency (RF) radiation sources, and a straight-forward `how-to` guide for estimating the exposure associated with these sources by providing a framework for health and safety personnel to access individual sources of RF and microwave radiation. It also provides an overview of RF radiation safety as it exists today. Extensive information on levels of RF exposure for occupational workers and the general public is included.

NONE

1993-12-31

81

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

82

A radio-frequency source using direct digital synthesis and field programmable gate array for nuclear magnetic resonance.  

PubMed

A radio-frequency (rf) source for nuclear magnetic resonance (NMR) is described. With the application of direct digital synthesis (DDS), the rf source has the ability to yield rf pulses with short switching time and high resolution in frequency and phase. To facilitate the generation of a soft pulse, a field programmable gate array (FPGA) cooperating with a pulse programmer is used as the auxiliary controller of the DDS chip. Triggered by the pulse programmer, the FPGA automatically controls the DDS to generate soft pulse according to predefined parameters, and the operation mode of the pulse programmer is optimized. The rf source is suitable for being used as transmitter in low-field (<1 T) NMR applications, for example, magnetic resonance imaging and relaxation measurement. As a compact and low-cost module, the rf source is of general use for constructing low-field NMR spectrometer. PMID:20059160

Liang, Xiao; Weimin, Wang

2009-12-01

83

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

84

Effect of the transverse nonuniformity of the radiofrequency field on the start current and efficiency of gyrodevices with confocal mirrors  

SciTech Connect

The theory is developed for analyzing the effect of transverse nonuniformity of the radiofrequency (rf) field on the starting conditions and efficiency of such gyrotron oscillators as gyromonotrons and gyro-backward-wave oscillators (gyro-BWO). The formalism allows one to study this effect in oscillators operating in the regimes of soft and hard self-excitation. Results obtained for a device with a confocal waveguide (or resonator) are compared with the results for conventional gyrodevices where the rf field acting on electrons with different guiding centers is the same. It is shown how to use results of the classical small-signal theory of backward-wave oscillators driven by linear electron beams for calculating the start currents in gyro-BWOs. The effect of the wave attenuation in waveguide walls on the start current is analyzed, which is important for the design of frequency-tunable gyro-backward-wave oscillators in the THz (and sub THz) frequency range.

Nusinovich, Gregory S.; Chainani, Samir; Granatstein, Victor L. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742-3511 (United States)

2008-10-15

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

2013-05-01

86

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

NASA Astrophysics Data System (ADS)

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

Verduijn, J.; Vinet, M.; Rogge, S.

2014-03-01

87

[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

2010-01-01

88

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

89

A COMPARATIVE STUDY OF RADIOFREQUENCIES FIELD LEVELS OF SOME BASE STATIONS IN MAKURDI AND ITS ENVIRONS IN BENUE STATE, NORTH CENTRAL NIGERIA  

Microsoft Academic Search

A comparative study of radiofrequencies field levels of some base stations in Makurdi and its environs was carried out in Makurdi, Benue State, North central Nigeria. Electromagnetic field tester (EMF 827 Lutron) was used for measurement at distances ranging from 5.00, 10.00, 15.00 and 20.00 meters away from the base stations at the North, South, West and East directions. Electric

J. T Iortile; L. Alumuku

2014-01-01

90

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

PubMed Central

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

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

2013-01-01

91

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

92

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

93

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

2013-01-01

94

TROMBONE: T1-Relaxation-Oblivious Mapping of Transmit Radio-Frequency Field (B1) for MRI at High Magnetic Fields  

PubMed Central

Fast, 3D radio-frequency transmit field (B1) mapping is important for parallel transmission, spatially-selective pulse design and quantitative MRI applications. It has been shown that AFI — two interleaved spoiled gradient recalled echo (SPGR) images acquired in steady state with two very short time delays (T R1, T R2) — is an attractive method of B1 mapping. Herein, we describe the TROMBONE method which efficiently integrates AFI with EPI imaging, alleviates very short T R requirement of AFI and through their synergy yields up to 16 times higher precision in B1 estimation in the same experimental time. High precision of TROMBONE can be traded for faster scans. The map of B1 reconstructed from the ratio of intensities of two images is insensitive to longitudinal relaxation time (T1) in the physiologically relevant range. A table of the optimal acquisition protocol parameters for various target experimental conditions is provided.

Fleysher, Roman; Fleysher, Lazar; Inglese, Matilde; Sodickson, Daniel

2011-01-01

95

TROMBONE: T1-relaxation-oblivious mapping of transmit radio-frequency field (B1) for MRI at high magnetic fields.  

PubMed

Fast, 3D radio-frequency transmit field (B1) mapping is important for parallel transmission, spatially selective pulse design and quantitative MRI applications. It has been shown that actual flip angle imaging--two interleaved spoiled gradient recalled echo images acquired in steady state with two very short time delays (TR1, TR2)--is an attractive method of B1 mapping. Herein, we describe the TROMBONE method that efficiently integrates actual flip angle imaging with EPI imaging, alleviates very short TR requirement of actual flip angle imaging and through their synergy yields up to 16 times higher precision in B1 estimation in the same experimental time. High precision of TROMBONE can be traded for faster scans. The map of B1 reconstructed from the ratio of intensities of two images is insensitive to longitudinal relaxation time (T1) in the physiologically relevant range. A table of the optimal acquisition protocol parameters for various target experimental conditions is provided. PMID:21394765

Fleysher, Roman; Fleysher, Lazar; Inglese, Matilde; Sodickson, Daniel

2011-08-01

96

Implementation of a Prototype Data Retrieval System for Literature on Biological Effects of Radiofrequency Fields. Summary.  

National Technical Information Service (NTIS)

A prototype information-handling and retrieval system designed in a previous program for literature in the subject field of biological effects of radio frequency radiations was implemented and evaluated in preliminary tests. This system makes the informat...

J. Healer R. Smiley

1969-01-01

97

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

98

Magnetic fluid hyperthermia induced by radiofrequency capacitive field for the treatment of transplanted subcutaneous tumors in rats  

PubMed Central

Magnetic fluid hyperthermia (MFH) induced by a magnetic field has become a new heating technology for the treatment of malignant tumors due to its ability to heat the tumor tissue precisely and properly, and due to its significant therapeutic effects. In this study, MFH induced by radiofrequency capacitive field (RCF) for the treatment of transplanted subcutaneous tumors in rats, was investigated. A total of 50 rats bearing subcutaneous tumors were randomly divided into five groups, including i) a pseudo-treatment (PT) control group, ii) magnetic fluid (MF) group, iii) pure hyperthermia (PH) group, iv) magnetic fluid hyperthermia 1 (MFH1) group, and v) magnetic fluid hyperthermia 2 (MFH2) group. Tumors were irradiated for 30 min in the MFH1 group 24 h following injection of MF. Tumors were irradiated for 30 min in the MFH2 group 24 h following injection of MF, and irradiation was repeated for 30 min 72 h following injection of MF. Tumor volumes, tumor volume inhibition ratios and survival times in the rat model were examined. Temperatures of tumor cores and rims both rapidly reached the desired temperature (?50°C) for tumor treatment within 5 to 10 min in the MFH1 and MFH2 groups, and we maintained this temperature level by manually adjusting the output power (70–130 W). Tumor volumes of the MFH1 and MFH2 groups were reduced compared to those of the PT, MF and PH groups. The inhibitory effect on tumor growth in the MFH2 group (91.57%) was higher compared to that in the MFH1 group (85.21%) and the other groups. The survival time of the MFH2 group (51.62±2.28 days) and MFH1 group (43.10±1.57 days) was increased compared to that of the PH, MF and PT groups. The results obtained show that MFH induced by RCF may serve as a potential and promising method for the treatment of tumors.

LI, XU-HONG; RONG, PENG-FEI; JIN, HE-KUN; WANG, WEI; TANG, JIN-TIAN

2012-01-01

99

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

100

Pulsed Radiofrequency Procedures in Clinical Practice  

Microsoft Academic Search

\\u000a Pulsed Radiofrequency (PRF) is a relatively new use of an older procedure, conventional thermal radiofrequency. Because PRF\\u000a is reputed to be nondestructive to neural tissue, it has created a lot of interest in the pain management community. Its effect\\u000a seems to occur as a result of the electrical field generated by radiofrequency current, rather than relying on thermal injury\\u000a to

Richard M. Rosenthal

101

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

102

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

103

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

Microsoft Academic Search

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,

Martin Röösli; Patrizia Frei; John Bolte; Georg Neubauer; Elisabeth Cardis; Maria Feychting; Peter Gajsek; Sabine Heinrich; Wout Joseph; Simon Mann; Luc Martens; Evelyn Mohler; Roger C Parslow; Aslak Harbo Poulsen; Katja Radon; Joachim Schüz; György Thuroczy; Jean-François Viel; Martine Vrijheid

2010-01-01

104

Radiofrequency field absorption by carbon nanotubes embedded in a conductive host  

NASA Astrophysics Data System (ADS)

Understanding the electromagnetic response of carbon nanotubes (CNTs) in the radio frequency range is very important for experimental development of therapeutic and diagnostic CNT applications, including selective thermolysis of cancer cells and thermoacoustic imaging. In this study, we present the theory of electromagnetic wave scattering by several finite length CNT configurations, including singlewall CNT's having a surfactant coating, CNT bundles, and multiwall CNTs. Absorption cross-sections of these structures in a conductive host region are theoretically studied in the radio frequency range. Strong local field enhancement due to edge effects is predicted to be inherent to metallic singlewall CNTs in the near-field zone, providing an additional mechanism of energy dissipation in a conductive host. Due to the screening effect the application of singlewall CNTs for the enhancement of energy dissipation is more effective than the application of multiwall CNTs or CNT bundles at the same mass fraction of CNT inclusions. The presence of a lossy dielectric (surfactant) coating can significantly increase the absorption cross section of singlewall CNTs.

Shuba, Mikhail V.; Slepyan, Gregory Ya.; Maksimenko, Sergey A.; Hanson, George W.

2010-12-01

105

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

PubMed Central

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

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

2014-01-01

106

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

PubMed

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

Partsvania, B; Sulaberidze, T; Shoshiashvili, L

2013-03-01

107

New-generation radiofrequency technology.  

PubMed

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

Krueger, Nils; Sadick, Neil S

2013-01-01

108

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

109

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

PubMed

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

Guibelalde del Castillo, E

2013-12-01

110

Exposure assessment and other challenges in non-ionizing radiation studies of childhood leukaemia.  

PubMed

Studies of electromagnetic fields (EMF) and the development of childhood leukaemia face unique difficulties. EMF are imperceptible, ubiquitous, have multiple sources, and can vary greatly over time and distances. Childhood leukaemia and high average exposures to magnetic fields are both quite rare. Thus, a major challenge in EMF epidemiology is the small number of highly exposed cases and the necessity for retrospective assessment of exposure. Only studies designed to minimize bias while maximizing our ability to detect an association, should one exist, would have a potential to contribute to our understanding. New approaches are needed; the most promising in the extremely low-frequency range involves a study of a highly exposed cohort of children who have lived in apartments next to built-in transformers or electrical equipment rooms. Another promising avenue is an investigation of possible joint effects of environmental exposures and genetic co-factors. An exposure assessment methodology for residential radiofrequency fields is still in its infancy. Rapid changes in technology and exponential increases in its use make exposure assessment more difficult and urgent. PMID:18940819

Kheifets, L; Oksuzyan, S

2008-01-01

111

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

112

Temperature changes associated with radiofrequency exposure near authentic metallic implants in the head phantom--a near field simulation study with 900, 1800 and 2450 MHz dipole.  

PubMed

Along with increased use of wireless communication devices operating in the radiofrequency (RF) range, concern has been raised about the related possible health risks. Among other concerns, the interaction of medical implants and RF devices has been studied in order to assure the safety of implant carriers under various exposure conditions. In the RF range, the main established quantitative effect of electromagnetic (EM) fields on biological tissues is heating due to vibrational movements of water molecules. The temperature changes induced in tissues also constitute the basis for the setting of RF exposure limits and recommendations. In this study, temperature changes induced by electromagnetic field enhancements near passive metallic implants have been simulated in the head region. Furthermore, the effect of the implant material on the induced temperature change was evaluated using clinically used metals with the highest and the lowest thermal conductivities. In some cases, remarkable increases in maximum temperatures of tissues (as much as 8 °C) were seen in the near field with 1 W power level whereas at lower power levels significant temperature increases were not observed. PMID:20844329

Matikka Virtanen, H; Keshvari, J; Lappalainen, R

2010-10-01

113

Temperature changes associated with radiofrequency exposure near authentic metallic implants in the head phantom—a near field simulation study with 900, 1800 and 2450 MHz dipole  

NASA Astrophysics Data System (ADS)

Along with increased use of wireless communication devices operating in the radiofrequency (RF) range, concern has been raised about the related possible health risks. Among other concerns, the interaction of medical implants and RF devices has been studied in order to assure the safety of implant carriers under various exposure conditions. In the RF range, the main established quantitative effect of electromagnetic (EM) fields on biological tissues is heating due to vibrational movements of water molecules. The temperature changes induced in tissues also constitute the basis for the setting of RF exposure limits and recommendations. In this study, temperature changes induced by electromagnetic field enhancements near passive metallic implants have been simulated in the head region. Furthermore, the effect of the implant material on the induced temperature change was evaluated using clinically used metals with the highest and the lowest thermal conductivities. In some cases, remarkable increases in maximum temperatures of tissues (as much as 8 °C) were seen in the near field with 1 W power level whereas at lower power levels significant temperature increases were not observed.

Matikka (formerly Virtanen, H.; Keshvari, J.; Lappalainen, R.

2010-10-01

114

Bipolar radiofrequency for adenoidectomy  

Microsoft Academic Search

tolaryngologists have utilized bipolar radiofrequency for tonsillectomy for nearly 5 years, although many switch to a curette or suction cautery to remove the ade- noids. Since adopting Coblation bipolar radiofrequency (ArthroCare Corporation, Sunnyvale, CA) for tonsil re- moval, the author has seen patient benefits, including min- imal blood loss and less thermal damage, leading to a more thorough dissection and

J. Mark Palmer

2006-01-01

115

Changes in zeta potential of TiO 2 and CaCO 3 suspensions treated with a radiofrequency electric field as measured with a ZetaPlus instrument  

Microsoft Academic Search

Zeta potentials for titanium dioxide (Degussa, P 25) and calcium carbonate (Fluka; more than 99.0% pure) suspensions prepared in water or 0.01 M NaCl at different pH were measured after exposure to a radiofrequency (44 MHz) electric field for 5–30 min. The measurements were performed using a fully automatic ZetaPlus instrument which allowed the determination of the zeta potential at

Emil Chibowski; Lucyna Ho?ysz

1995-01-01

116

Explicit Drain-Current Model of Graphene Field-Effect Transistors Targeting Analog and Radio-Frequency Applications  

Microsoft Academic Search

We present a compact physics-based model of the current-voltage characteristics of graphene field-effect transis- tors, of especial interest for analog and RF applications where band-gap engineering of graphene could be not needed. The phys- ical framework is a field-effect model and drift-diffusion carrier transport. Explicit closed-form expressions have been derived for the drain current continuously covering all operation regions. The

David Jimenez; Oana Moldovan

2011-01-01

117

Pulsed radio-frequency electromagnetic fields: dose-dependent effects on sleep, the sleep EEG and cognitive performance.  

PubMed

To establish a dose-response relationship between the strength of electromagnetic fields (EMF) and previously reported effects on the brain, we investigated the influence of EMF exposure by varying the signal intensity in three experimental sessions. The head of 15 healthy male subjects was unilaterally exposed for 30 min prior to sleep to a pulse-modulated EMF (GSM handset like signal) with a 10 g-averaged peak spatial specific absorption rate of (1) 0.2 W kg(-1), (2) 5 W kg(-1), or (3) sham exposed in a double-blind, crossover design. During exposure, subjects performed two series of three computerized cognitive tasks, each presented in a fixed order [simple reaction time task, two-choice reaction time task (CRT), 1-, 2-, 3-back task]. Immediately after exposure, night-time sleep was polysomnographically recorded for 8 h. Sleep architecture was not affected by EMF exposure. Analysis of the sleep electroencephalogram (EEG) revealed a dose-dependent increase of power in the spindle frequency range in non-REM sleep. Reaction speed decelerated with increasing field intensity in the 1-back task, while accuracy in the CRT and N-back task were not affected in a dose-dependent manner. In summary, this study reveals first indications of a dose-response relationship between EMF field intensity and its effects on brain physiology as demonstrated by changes in the sleep EEG and in cognitive performance. PMID:17716273

Regel, Sabine J; Tinguely, Gilberte; Schuderer, Jürgen; Adam, Martin; Kuster, Niels; Landolt, Hans-Peter; Achermann, Peter

2007-09-01

118

Evaluation of Simulated Radiofrequency Heating Procedures.  

National Technical Information Service (NTIS)

A method for simulating radiofrequency radiation (RFR) heating at 1.2 GHz E-field oriented in the rat using warm moist (90% relative humidity) air is presented. The method can adequately simulate the overall linear rate of internal heating in the rate and...

J. C. Burr J. H. Krupp D. A. Hamill M. E. Donahue

1980-01-01

119

Radiofrequency energy in surgery: state of the art.  

PubMed

Over a period of more than 100 years, radiofrequency energy has been introduced in many fields and applications in medicine. At present, radiofrequency constitutes the basis of numerous medical devices employed in almost all medical specialties. It is particularly applicable and valuable in various minimally invasive procedures for its locally focused effects. Radiofrequency energy is a technical term established to describe high-frequency alternating electrical currents (with a frequency ranging from 300 kHz to 3 MHz) and their impact on biological tissue. The application of RF energy causes controlled tissue heating with consequent cell protein denaturation and desiccation, which leads to cell death and tissue destruction. The primary principle of radiofrequency is that the generated heat can be used to cut, coagulate or induce metabolic processes in the target tissue. The authors of this paper offer a comprehensive and compact review of the definition, history, physics, biological principles and applications of radiofrequency energy in current surgery. PMID:23728491

Ihnát, Peter; Ihnát Rudinská, Lucia; Zon?a, Pavel

2014-06-01

120

Temperature changes associated with radiofrequency exposure near authentic metallic implants in the head phantom---a near field simulation study with 900, 1800 and 2450 MHz dipole  

Microsoft Academic Search

Along with increased use of wireless communication devices operating in the radiofrequency (RF) range, concern has been raised about the related possible health risks. Among other concerns, the interaction of medical implants and RF devices has been studied in order to assure the safety of implant carriers under various exposure conditions. In the RF range, the main established quantitative effect

J. Keshvari; R. Lappalainen

2010-01-01

121

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

PubMed

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

Bolte, John F B; Eikelboom, Tessa

2012-11-01

122

Dynamics Of Ions In A Radio-Frequency Quadrupole Trap  

NASA Technical Reports Server (NTRS)

Report describes computer-simulation study of motions of various numbers of ions in Paul trap. Study part of continuing effort to understand motions of trapped charged particles (atoms, ions, molecules, or dust particles). Motions characterized in terms of heating by radio-frequency fields, formation of crystallike structures in cold clouds of trapped particles, and other phenomena important in operation of radio-frequency traps in frequency standards.

Prestage, John D.; Williams, Angelyn P.; Maleki, Lutfollah

1994-01-01

123

Radiofrequency Ablation of Cancer  

PubMed Central

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; Libutti, Steven K.; Walther, McClellan M.; Neeman, Ziv; Locklin, Julia K.; Wood, Bradford J.

2008-01-01

124

Removal of organic pollutants by surfactant modified zeolite: comparison between ionizable phenolic compounds and non-ionizable organic compounds.  

PubMed

The aim of this study was to examine the adsorption capability and mechanism of hexadecyltrimethylammonium modified zeolite, which was synthesized from coal fly ash, for the removal of ionizable phenolic compounds (phenol, p-chlorophenol and bisphenol A, with different pK(a)) and non-ionizable organic compounds (aniline, nitrobenzene, and naphthalene, with different hydrophobicity). The obtained zeolite was identified as type Na-P1 (Na(6)Al(6)Si(10)O(32)·12H(2)O, JCPDS code 39-0219), which is classified into the gismondine group with a pore size of 3.1 Å × 4.5 Å [100] and 2.8 Å × 4.8 Å [101]. The adsorption of the two kinds of organic compounds was due to loaded surfactant bilayer because modified zeolite showed great ability for the removal of organic chemicals while little adsorption by zeolite was observed. The isotherm data of ionizable compounds fitted well to the Langmuir model but those of non-ionizable chemicals followed a linear equation. Uptake of ionizable compounds depended greatly on pH, increasing at alkaline pH conditions. In contrary, adsorption of non-ionizable chemicals was essentially the same at all pH levels studied. The adsorption of both kinds of organic compounds correlated well to k(ow) value, suggesting that more hydrophobic organic contaminants are more easily retained by modified zeolite. Based on the different adsorption behavior, the uptake of non-ionizable pollutants was thought to be a single partitioning process into the surfactant bilayer. For ionizable compounds, however, interaction of the phenol group(s) with the positively charged "head" of surfactant additionally functions. PMID:22771348

Xie, Jie; Meng, Wenna; Wu, Deyi; Zhang, Zhenjia; Kong, Hainan

2012-09-15

125

Radiofrequency in cosmetic dermatology.  

PubMed

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

Beasley, Karen L; Weiss, Robert A

2014-01-01

126

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

127

Radiofrequency attenuator and method  

DOEpatents

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

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

2009-01-20

128

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

129

A large-scale measurement of electromagnetic fields near GSM base stations in Guangxi, China for risk communication.  

PubMed

Radiofrequency (RF) electromagnetic field (EMF) exposure from wireless telecommunication base station antennae can lead to debates, conflicts or litigations among the adjacent residents if inappropriately managed. This paper presents a measurement campaign for the GSM band EMF exposure in the vicinity of 827 base station sites (totally 6207 measurement points) in Guangxi, China. Measurement specifications are designed for risk communication with the residents who previously complained of over-exposure. The EMF power densities with the global positioning system coordinate at each measured point were recorded. Compliance with the International Commission on Non-Ionizing Radiation Protection guidelines and Chinese environmental EMF safety standards was studied. The results show that the GSM band EMF level near the base stations is very low. The measurement results and the EMF risk communication procedures positively influence public perception of the RF EMF exposure from the base stations and promote the exchange of EMF exposure-related knowledge. PMID:23179188

Wu, Tongning; Shao, Qing; Yang, Lei; Qi, Dianyuan; Lin, Jun; Lin, Xiaojun; Yu, Zongying

2013-06-01

130

Nerve Regeneration After Radiofrequency Application  

Microsoft Academic Search

Background: Many patients with chronic tendinosis have experienced early pain relief after application of bipolar radiofrequency treatment. It is hypothesized that the mechanism of action may be the acute degeneration and\\/or ablation of sensory nerve fibers.Hypothesis: After ablation or degeneration by bipolar radiofrequency, nerve fibers will have the ability to regenerate with time.Study Design: Controlled laboratory study.Methods: Eighteen Sprague-Dawley rats

Nobuyasu Ochiai; James P. Tasto; Seiji Ohtori; Norimasa Takahashi; Hideshige Moriya; David Amiel

2007-01-01

131

Nonthermal effects of radiofrequency-field exposure on calcium dynamics in stem cell-derived neuronal cells: elucidation of calcium pathways.  

PubMed

Intracellular Ca(2+) spikes trigger cell proliferation, differentiation and cytoskeletal reorganization. In addition to Ca(2+) spiking that can be initiated by a ligand binding to its receptor, exposure to electromagnetic stimuli has also been shown to alter Ca(2+) dynamics. Using neuronal cells differentiated from a mouse embryonic stem cell line and a custom-built, frequency-tunable applicator, we examined in real time the altered Ca(2+) dynamics and observed increases in the cytosolic Ca(2+) in response to nonthermal radiofrequency (RF)-radiation exposure of cells from 700 to 1100 MHz. While about 60% of control cells (not exposed to RF radiation) were observed to exhibit about five spontaneous Ca(2+) spikes per cell in 60 min, exposure of cells to an 800 MHz, 0.5 W/kg RF radiation, for example, significantly increased the number of Ca(2+) spikes to 15.7+/-0.8 (P<0.05). The increase in the Ca(2+) spiking activities was dependent on the frequency but not on the SAR between 0.5 to 5 W/kg. Using pharmacological agents, it was found that both the N-type Ca(2+) channels and phospholipase C enzymes appear to be involved in mediating increased Ca(2+) spiking. Interestingly, microfilament disruption also prevented the Ca(2+) spikes. Regulation of Ca(2+) dynamics by external physical stimulation such as RF radiation may provide a noninvasive and useful tool for modulating the Ca(2+)-dependent cellular and molecular activities of cells seeded in a 3D environment for which only a few techniques are currently available to influence the cells. PMID:18302487

Rao, V S; Titushkin, I A; Moros, E G; Pickard, W F; Thatte, H S; Cho, M R

2008-03-01

132

Renal tumor radiofrequency ablation.  

PubMed

Nephron sparing surgery has become the gold standard for the treatment of small (< 4 cm) renal tumors. More recently, renal tumor ablation, destroying renal tumors with energy based modalities and leaving the tissue in situ, has gained popularity. Radiofrequency ablation (RFA) utilizes heat energy to cause cellular destruction. RFA can be applied laparoscopically, percutaneously, and as an adjunct with partial nephrectomy. A comprehensive MEDLINE search of the English literature from 1990 to present was performed to identify articles on renal RFA. RFA is an effective minimally invasive treatment alternative for small renal masses in patients with significant comorbidities that preclude extirpative surgery. Limited follow up from a number of series demonstrate a success rate of 92%. RFA has proven to be an effective ablative therapy in a number of organ systems. Over the past decade it has been applied to the treatment of small renal tumors. The short-term efficacy and minimum morbidity of RF thermal therapy for renal tumors has been encouraging. RFA provides a versatile tool to add to the urologist's armamentarium in the minimally invasive treatment of renal cancer. PMID:16247348

Slabaugh, T K; Ogan, K

2005-12-01

133

Dynamics of dust particles in a collisional radio-frequency plasma sheath  

NASA Astrophysics Data System (ADS)

In this work, we have examined the dynamics of a single dust particle in a non-ionized radio-frequency plasma sheath. For this, we have used a steady state one-dimensional time-averaged model where the electrons are considered to be in thermal equilibrium, while the positive ions are described by cold fluid equations. The interactions between ions and neutrals are considered. Numerous forces acting on the dust particles, such as electric force, gravitational force, neutral drag force and ion drag force are taken into account. The numerical results show that the ion–neutral collisions have significant effects on the properties of the motion of the dust. The dust oscillation frequency increases and the equilibrium position of the dust particle drops when the coefficient of ion collision increases.

El Kaouini, Morad; Chatei, Hassan; Bougdira, Jamal

2014-05-01

134

Radio-Frequency Plasma Probes  

NASA Astrophysics Data System (ADS)

The utility of radio-frequency probes for diagnosing low-temperature plasmas has recently been extended through the use of a network analyzer to measure the small-signal, complex probe impedance Zac as a function of applied frequency and dc bias. To interpret the results, account must be taken of the gas pressure, the plasma density, the applied frequency, and the applied magnetic field if any. In this talk four different models are presented for use in different regimes. At high gas pressure, Re(Zac) is shown to give ne0/?, where ne0 is the ambient electron density and ? is the electron-neutral collision frequency. At low pressure Re(Zac) gives not only ne0 but also ne(r) within the sheath immediately outside the probe, the plasma potential, and the electron energy distribution and temperature. Magnetized plasmas can be treated by adding an external inductance in series with the probe and operating above the upper hybrid frequency; alternatively, rf voltage can be applied between two closely-spaced planar electrodes oriented either parallel or perpendicular to the field. As will be shown, rf probes not only provide more information than Langmuir probes, but the data is easier to analyze and generally less affected by noise. Additional advantages include the following: decreased sensitivity to secondary electron emission, ions, plasma flow, and high-energy beams; clear and unequivocal determination of ne0, even in magnetized plasmas; direct utility at high pressure; multiple checks on the results; and the ability to operate in reactive and depositing gases.

Fernsler, Richard

2011-11-01

135

A Radiofrequency–Optical Modulation Spectroscope for Investigating Semiconductor Structures  

Microsoft Academic Search

A radiofrequency –optical spectroscope that makes it possible to investigate the modulation optical reflectance spectra of the various layers of a semiconductor structure is proposed and manufactured. Near the edge of the fundamental optical absorption, the light reflectance is modulated by an RF field with various spatial orientations. By using the RF–optical modulation spectroscope, new features of the electron–hole interaction

A. O. Volkov; O. A. Ryabushkin

2001-01-01

136

47 CFR 1.1310 - Radiofrequency radiation exposure limits.  

Code of Federal Regulations, 2010 CFR

...Radiation Protection and Measurements (NCRP) in âBiological Effects and Exposure Criteria...Radiofrequency Electromagnetic Fields,â NCRP Report No. 86, Sections 17.4.1...17.4.2 and 17.4.3. Copyright NCRP, 1986, Bethesda, Maryland...

2009-10-01

137

47 CFR 1.1310 - Radiofrequency radiation exposure limits.  

Code of Federal Regulations, 2010 CFR

...Radiation Protection and Measurements (NCRP) in âBiological Effects and Exposure Criteria...Radiofrequency Electromagnetic Fields,â NCRP Report No. 86, Sections 17.4.1...17.4.2 and 17.4.3. Copyright NCRP, 1986, Bethesda, Maryland...

2010-10-01

138

Principles and practice of radiofrequency neurolysis  

Microsoft Academic Search

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

Michael Hammer; William Meneese

1998-01-01

139

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...

140

South Polar in situ radio-frequency ice attenuation  

Microsoft Academic Search

We have determined the in situ electric field attenuation length Lalpha (defined as the length over which the signal amplitude diminishes by a factor 1\\/e) for radio-frequency signals broadcast vertically through South Polar ice and reflected off the underlying bed. Conservatively assuming a bedrock field reflectivity R = 1.0, we estimate Lalpha = 1450+300-150 m for f = 380 MHz,

S. Barwick; D. Besson; P. Gorham; D. Saltzberg

2005-01-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

142

Influence of non ionizing radiation of base stations on the activity of redox proteins in bovines  

PubMed Central

Background The influence of electromagnetic fields on the health of humans and animals is still an intensively discussed and scientifically investigated issue (Prakt Tierarzt 11:15-20, 2003; Umwelt Medizin Gesellschaft 17:326-332, 2004; J Toxicol Environment Health, Part B 12:572–597, 2009). We are surrounded by numerous electromagnetic fields of variable strength, coming from electronic equipment and its power cords, from high-voltage power lines and from antennas for radio, television and mobile communication. Particularly the latter cause’s controversy, as everyone likes to have good mobile reception at anytime and anywhere, whereas nobody wants to have such a basestation antenna in their proximity. Results In this experiment, the NIR has resulted in changes in the enzyme activities. Certain enzymes were disabled, others enabled by NIR. Furthermore, individual behavior patterns were observed. While certain cows reacted to NIR, others did not react at all, or even inversely. Conclusion The present results coincide with the information from the literature, according to which NIR leads to changes in redox proteins, and that there are individuals who are sensitive to radiation and others that are not. However, the latter could not be distinctly attributed – there are cows that react clearly with one enzyme while they do not react with another enzyme at all, or even the inverse. The study approach of testing ten cows each ten times during three phases has proven to be appropriate. Future studies should however set the post-exposure phase later on.

2014-01-01

143

Radiofrequency-assisted liver resection  

Microsoft Academic Search

Radiofrequency (RF)-assisted thermal ablation has been used with increasing frequency for unresectable hepatic tumors. This\\u000a new approach employs RF energy to coagulate the liver at the hepatic resection line after which hepatic resection is performed\\u000a with the use of a common scalpel. This procedure was used in three patients with hepatocellular carcinoma and in five patients\\u000a with colorectal metastasis to

Mattia Stella; Andrea Percivale; Massimo Pasqualini; Alberto Profeti; Nicola Gandolfo; Giovanni Serafini; Riccardo Pellicci

2003-01-01

144

Uniformly Distributed Wideband Metal-Oxide-Semiconductor Field-Effect Transistor Model for Complementary Metal-Oxide-Semiconductor Radio-Frequency Integrated Cirsuits Applications  

NASA Astrophysics Data System (ADS)

In this paper, a uniformly distributed wide-band metal-oxide-semiconductor field-effect transistor (MOSFET) model constructed by several same unit cells in parallel is presented. The kink phenomenon of scattering parameter S11 due to the distributed gate-resistance of MOSFETs can be fitted well by this model. Good agreement between the measured and modeled results of scattering parameters S22, current gain H21, and unilateral gain U are also demonstrated. In addition, the impact of distributed gate-resistance on cut-off frequency ( fT) and maximum oscillation frequency ( fmax) performances of single gate-finger MOSFETs with large gate-width of 20, 40, 80, 120, and 160 ?m are quantitatively characterized and analyzed.

Liang, Hsiao-Bin; Tsou, Yi-Hsun; Lin, Yo-Sheng; Chen, Chi-Chen

2008-02-01

145

47 CFR 2.801 - Radiofrequency device defined.  

Code of Federal Regulations, 2013 CFR

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

2013-10-01

146

Radiofrequency ablation: technique and clinical applications.  

PubMed

Radiofrequency ablation is the most commonly used percutaneous ablation technique and well-documented in the literature on focal therapies. It has become the image-guided ablation method of choice because of its efficacy, safety, and ease of use. Radiofrequency ablation has shown promise in treating selected solid tumors, particularly those involving the liver, kidneys, lungs, and the musculoskeletal system. It is a minimally invasive technique often used in inoperable patients with other comorbidities. Radiofrequency ablation requires a minimal hospital stay or can be performed on an outpatient basis. The aim of this article is to review radiofrequency ablation techniques and their clinical applications. PMID:22407695

Tatli, Servet; Tapan, Umit; Morrison, Paul R; Silverman, Stuart G

2012-01-01

147

Research on heating, instabilities, turbulence, and rf (radiofrequency) emission from electric-field dominated plasmas. Final report, 15 March 1986-14 May 1989  

SciTech Connect

This contract has supported four research programs: (1) a program of research on plasma turbulence; (2) a program of research on plasma heating by collisional magnetic pumping; (3) a research program on the Orbitron submillimeter maser; and (4) the initial phase of a program on plasma cloaking of military targets for protection against radar and directed microwave energy weapons. Progress in these areas is documented in the text of this final report and in the twenty archival publications included in the appendices to this report. In addition to the above four research areas, work is continuing on plasma diagnostic development, and the development of new state-of-the-art data analysis and reduction methods, including software development for on-line reduction of Langmuir probe, capacitive probe, and other diagnostic information. The authors are also developing the capability to analyze electrostatic-potential fluctuations by the methods of nonlinear dynamics. An important part of our research program has been the training of graduate and undergraduate research assistants in state-of-the-art methods in the fields of high-temperature plasma physics, plasma diagnostics, communications, and related areas.

Roth, J.R.; Alexeff, I.

1989-07-01

148

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

149

Radio-frequency quadrupole vane-tip geometries  

Microsoft Academic Search

Radio-frequency quadrupole (RFQ) linacs are becoming widely accepted in the accelerator community. They have the remarkable capability of simultaneously bunching low-energy ion beams and accelerating them to energies at which conventional accelerators can be used, accomplishing this with high-transmission efficiencies and low-emittance growths. The electric fields, used for radial focusing, bunching, and accelerating, are determined by the geometry of the

K. R. Crandall; R. S. Mills; T. P. Wangler

1983-01-01

150

Four-Sector Cylindrical Radio-Frequency Ion Trap  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

151

Predicting nurses' acceptance of radiofrequency identification technology.  

PubMed

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

Norten, Adam

2012-10-01

152

Linear octapolar radiofrequency tool for liver ablation  

Microsoft Academic Search

These work deals about the design and realization of linear octopolar radiofrequency surgical tool for liver ablation. The radiofrequency surgical technique is one of most significant methods for trauma and oncology radical therapy nowadays. This contribution deals about new surgical type design and testing with comparison of commercial present tools.

M. Penhaker; M. Hlavackova; P. Horyl; P. Vavra; L. Prokop; T. Sikora

2011-01-01

153

Evaluation of radiofrequency dielectric heaters workers exposure.  

PubMed

Radiofrequency dielectric heaters (RFDH) are widely used in the woodworking industry for gluing laminates by applying pressure and RF heating. The workers operating such equipment remain in the vicinity of the machinery all day and can therefore be exposed to considerable levels of electric and magnetic field at RFs. This work describes the method used to measure the strength of fields generated by this particular machinery. This procedure is based on current methods cited in the literature and introduces the necessary modifications to meet this specific case. In particular, as there is often a scarcity of technical data available relating to such heaters, it is suggested that a spectrum analyser be used for measurements in the frequencies domain. On the basis of the data obtained the norms of reference are established, the instrumentation to be used in successive stages determined as well as the identification of possible sources of interference from spurious signals. Furthermore, a mapping of the field strengths is presented and the means of determining the decay curve as a function of distance. This last type of measurement is done to estimate the effectiveness of grounding the machinery. The report ends with an estimate of the exposure of workers to electromagnetic fields and also some recommendations for reducing risk. PMID:17971347

Benes, M; Del Frate, S; Villalta, R

2008-01-01

154

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

Microsoft Academic Search

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

Kenneth R. Foster

2000-01-01

155

Sources of radiofrequency interference for medical devices in the non clinical environment  

Microsoft Academic Search

Radiofrequency (RF) sources in the non clinical environment can expose medical devices to field strengths that exceed several volts per meter Electric (E) field strengths were measured at typical usage sites for home or ambulatory medical devices. Isotropic, broadband E field probes and calibrated antennas with spectrum analyzers were used. Three distinct categories of RF source\\/exposure situations were identified: “Distant

Howard Bassen; Paul Ruggera; Jon Casamento; Donald Witters

1994-01-01

156

A numerical study of radiofrequency deposition in a spherical phantom using surface coils  

Microsoft Academic Search

The electromagnetic fields induced by a surface coil in a spherical phantom, having a wide range of electrical properties, is studied using numerical methods of calculation. The specific absorption rate (SAR), radiofrequency magnetic field (B1), magnetic field energy within the phantom (EB), and the volume-averaged SAR () are calculated at 10, 63, and 200 MHz. They are analyzed with respect

Richard J. Strilka; Shizhe Li; Jack T. Martin; Christopher M. Collins; Michael B. Smith

1998-01-01

157

[Laparoscopic hepatectomy with radiofrequency device].  

PubMed

Laparoscopic liver resections are gaining adherents among surgeons, as they show rapid recovery, shorter hospital stay and better cosmetic results. The use of a laparoscopic radiofrequency device was first carried out successfully in Brazil for resection of hepatocellular carcinoma of the segment VI in two cirrhotic patients. Although intraoperative bleeding remains a major challenge for the surgeon during laparoscopic liver resections, in both cases the hepatic vascular exclusion was expendable and there was no need for blood transfusion. Patients were discharged on the fourth postoperative day. PMID:23752645

Resende, Vivian; Lima, Cristiano Xavier; Lusckal, Mário Marcos; Aguiar, Milton Carlos; Gammeri, Emanuele; Habib, Nagy Adley; da Cunha-Melo, José Renan

2013-01-01

158

Radio-Frequency Strain Monitor  

NASA Technical Reports Server (NTRS)

Radio-frequency (RF) strain monitor developed to measure lengths of objects. RF waveguide or cable bonded to structure monitored. Propagation of RF signal along waveguide results in phase shift proportional to length of path traveled. Impedance mismatches placed in RF cable at nodes of structure. Records mismatches and detects overall length of line and lengths of intervals between nodes. Used to detect changes in elements of large structure with single cable. Monitor has potential for many applications, including monitoring stability of such large structures as aircraft, bridges, and buildings in Earthquake zones.

Heyman, Joseph S.; Rogowski, Robert S.; Holben, Milford S., Jr.

1988-01-01

159

Radiofrequency ablation in metastatic melanoma.  

PubMed

Radiofrequency ablation (RFA) is a minimally invasive therapy that has, until recently, received limited attention in the management of metastatic melanoma. RFA is well described in the management of primary malignancies of the liver, however limited data are available on its application to metastatic deposits of melanoma occurring in the lung, liver, or adrenal glands. This article explores the basic principles of RFA, its safety, efficacy, and application to metastatic malignancies of the lung, liver and adrenal glands, with particular emphasis on melanoma. Previously published results are reviewed, and we report a small additional series of patients with liver and lung metastases treated in Sydney using RFA. PMID:24375239

Shashank, Arridh; Shehata, Mena; Morris, David L; Thompson, John F

2014-03-01

160

Inactivation of bacteriophages in water by means of non-ionizing (uv-253.7 nm) and ionizing (gamma) radiation: a comparative approach  

Microsoft Academic Search

The inactivation behaviour of the bacteriophages PHI X 174 (ssDNA virus), MS2 (ssRNA virus) and B40-8 (dsDNA) toward non-ionizing (UV-253.7nm) as well as to ionizing radiation (gamma radiation) was studied in order to evaluate their potential as viral indicators for water disinfection by irradiation. Previous findings of the high UV-253.7nm resistance of MS2 were confirmed whereas an unexpected high sensitivity

Regina Sommer; Walter Pribil; Silvia Appelt; Peter Gehringer; Helmut Eschweiler; Hermann Leth; Alexander Cabaj; Thomas Haider

2001-01-01

161

Radiofrequency Produced Air Constituent Plasmas*  

NASA Astrophysics Data System (ADS)

A high power(1-25 kW) pulsed radiofrequency source is used to create and sustain a high-density(10^11-14 /cm^3, large volume plasmas of air constituents(N_2, O_2, Ar and air mixtures) at high gas pressures. Initial experiments at 1-30 Torr reveal that a noble gas mix improves the antenna loading and is beneficial for the breakdown of air constituents. It also leads to a lower recombination rate and reduced power requirements. Radiofrequency power is coupled through various antenna configurations including a multi-turn helical antenna and a double half-turn helix, using a capacitive matching network. Research results with the new, high power pulsed units will be presented at pressures from 30 to 760 Torr with different gas mixes. Plasma density measurements which use and 105 GHz interferometer as well as network analyzer measurements of the antenna coupling impedance and spectroscopic data will be presented. These will be used to describe the chemical and physical processes and ionic constituents as well as plasma decay processes for the different gas mixtures.

Akhtar, Kamran; Scharer, John; Paller, Eric; White, Ben; Tysk, Shane

2001-10-01

162

Radiofrequency and testicular cancer (review).  

PubMed

Physical agents such as ultraviolet or ionizing radiation, heat, and repetitive trauma have been related to the causation of cancer in humans. Much less clear is the association between exposure to radiofrequency, i.e. radar and microwave radiation, emitted from television screens, antennas and detection equipment, to the development of cancer. Sporadic case reports and small series suggest that this type of radiation might lead to cancer or contribute to its evolution. The association between radiofrequency and testicular damage and cancer is unproved, but clinical and experimental data are suggestive of such possibility. We have recently encountered a case of secondary severe oligospermia, followed by seminoma, most probably induced by exposure to radar and microwave radiation, in an 18-year-old man. The population handling or repairing dangerous radar facilities is too small to be evaluated by epidemiological surveys. Even it were so, this material is handled in secrecy, either military or industrial. Arousing the alertness of the medical team in those facilities and bringing better protection to the employees is the aim of our report. PMID:21594374

Merimsky, O; Levita, M; Merimsky, E; Chaitchik, S

1996-03-01

163

Radiofrequency heating pathways for gold nanoparticles.  

PubMed

This feature article reviews the thermal dissipation of nanoscopic gold under radiofrequency (RF) irradiation. It also presents previously unpublished data addressing obscure aspects of this phenomenon. While applications in biology motivated initial investigation of RF heating of gold nanoparticles, recent controversy concerning whether thermal effects can be attributed to nanoscopic gold highlight the need to understand the involved mechanism or mechanisms of heating. Both the nature of the particle and the nature of the RF field influence heating. Aspects of nanoparticle chemistry which may affect thermal dissipation include the hydrodynamic diameter of the particle, the oxidation state and related magnetism of the core, and the chemical nature of the ligand shell. Aspects of RF which may affect thermal dissipation include power, frequency and antenna designs that emphasize relative strength of magnetic or electric fields. These nanoparticle and RF properties are analysed in the context of three heating mechanisms proposed to explain gold nanoparticle heating in an RF field. This article also makes a critical analysis of the existing literature in the context of the nanoparticle preparations, RF structure, and suggested mechanisms in previously reported experiments. PMID:24962620

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

2014-07-10

164

Radiofrequency ablation of pulmonary malignant tumors in nonsurgical candidates  

Microsoft Academic Search

Objective: Radiofrequency ablation applies thermal energy with a catheter delivery system, resulting in coagulation necrosis. Radiofrequency ablation is frequently used for hepatic malignant tumors, but few reports exist regarding its use for lung tumors. We report our experience with radiofrequency ablation for the treatment of pulmonary malignant tumors.Methods: We evaluated the results of lung radiofrequency ablation for patients not considered

Luis J. Herrera; Hiran C. Fernando; Yaron Perry; William E. Gooding; Percival O. Buenaventura; Neil A. Christie; James D. Luketich

2003-01-01

165

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

PubMed Central

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

Glazer, Evan S; Curley, Steven A

2013-01-01

166

Medical Applications of Radiofrequency-Radiation Hyperthermia.  

National Technical Information Service (NTIS)

This report provides an overview of the medical applications of radiofrequency radiation (RFR) hyperthermia. RFR has limitations in focusing and penetration but can heat tissue selectively, on the basis of water content and dielectric properties. nonioniz...

J. L. Kiel

1982-01-01

167

Hazards Evaluation of Radiofrequency and Microwave Radiation.  

National Technical Information Service (NTIS)

This manual is for Industrial Hygienists and other readers with an interest in the topic and a background in the natural sciences. The basic concepts of protecting people from radiofrequency and microwave radiation (RFMW) are presented here to help reader...

G. C. Miller

1987-01-01

168

The Radiofrequency Radiation Dosimetry Handbook: reminiscences.  

PubMed

This paper traces the history of the development of the Radiofrequency Radiation Dosimetry Handbook and its subsequent impact on radio frequency radiation exposure standards. The author's recollections are used to illustrate the behind the scenes efforts of the individuals involved in this project. The development of models at the University of Utah and confirmation of these results by various experimenters led to the publication of four editions of the Radiofrequency Radiation Dosimetry Handbook, i.e., "The RFR Experimenters Bible." PMID:10334710

Allen, S J

1999-01-01

169

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.

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

2004-01-01

170

Radiofrequency radiation leakage from microwave ovens.  

PubMed

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

Lahham, Adnan; Sharabati, Afifeh

2013-12-01

171

Characterization of superconducting radiofrequency breakdown by two-mode excitation  

SciTech Connect

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

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

2014-01-01

172

Protein adsorption enhanced radio-frequency heating of silica nanoparticles  

NASA Astrophysics Data System (ADS)

Measurements of specific-absorption-rate (SAR) of silica 30, 50, and 100 nm nanoparticles (NP) suspended in water were carried out at 30 MHz in 7 kV/m radio-frequency (rf) electric field. Size dependent, NP-suspension interface related heating of silica NP was observed. To investigate a possible mechanism of heating, bovine serum albumin was adsorbed on the surface of silica NPs in suspension. It resulted in significant enhancement of SAR when compared to bare silica NPs. A calorimetric and rf loss model was used to calculate effective conductivity of silica NP with/without adsorbed albumin as a function of silica size and albumin concentration.

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

2013-07-01

173

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

174

Radiofrequency ablation for hepatocellular carcinoma.  

PubMed

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related mortality worldwide. Unfortunately, only 20% of HCC patients are amenable to curative therapy (liver transplantation or surgical resection). Locoregional therapies such as radiofrequency ablation (RFA), percutaneous ethanol injection, microwave coagulation therapy, and transcatheter arterial chemoembolisation play a key role in the management of HCC. The choice of the treatment modality depends on the size of the tumour, tumour location, anatomic considerations and the number of tumours present and liver function. RFA therapy for HCC can be performed safely using a percutaneous, laparoscopic, or an open approach, even in patients with poor functional reserve. Since the introduction of RFA, several randomised controlled trials and non-randomised studies comparing RFA and other therapies for HCC have been conducted. In addition, in the last decade there have been technical advances in RFA therapy for HCC, resulting in significant improvement in the prognosis of HCC patients treated with this modality. In this review, we primarily focus on percutaneous RFA therapy for HCC and refer to current knowledge and future perspectives for this therapy. We also discuss new emerging ablation techniques. PMID:23937321

Nishikawa, Hiroki; Kimura, Toru; Kita, Ryuichi; Osaki, Yukio

2013-09-01

175

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

176

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

177

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

Microsoft Academic Search

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

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

2008-01-01

178

Personal radio-frequency dosimeter with cumulative-dose recording capabilities.  

National Technical Information Service (NTIS)

The radio-frequency (rf) dosimeter developed by the Oak Ridge National Laboratory is a portable, pocket-sized cumulative-dose recording device designed to detect and record the strengths and durations of electric fields present in the work areas of naval ...

R. W. Rochelle M. R. Moore R. S. Thomas P. D. Ewing R. A. Hess

1990-01-01

179

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

180

ASSESSMENT OF RADIOFREQUENCY RADIATION DISTRIBUTION AROUND MOBILE BASE STATIONS IN MAKURDI, BENUE STATE  

Microsoft Academic Search

The radiofrequency field levels of selected MTN and ZAIN base stations in Makurdi were measured using electromagnetic field tester (EMF 827, Lutron). Measurements were done at distances of approximately 5.00, 10.00, 15.00 and 20.00 metres for each base station at the North, South, West, and East directions. Results shows that the average magnetic field levels of MTN and ZAIN base

J. T. Iortile; E. H. Agba

2014-01-01

181

Tracking Inmates and Locating Staff with Active Radio-Frequency Identification (RFID): Early Lessons Learned in One U.S. Correctional Facility.  

National Technical Information Service (NTIS)

This report is the result of National Institute of Justice's (NIJ's) interest in helping inform the correctional field about the potential implications of the use of active radio-frequency identification (RFID) technology in correctional facilities. The f...

E. Wells L. J. Hickman L. M. Davis M. Eisman

2010-01-01

182

A practical method to evaluate radiofrequency exposure of mast workers.  

PubMed

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

Alanko, Tommi; Hietanen, Maila

2008-01-01

183

Extremely Low Frequency (ELF) Communications Program Non-Ionizing Electromagnetic Radiation Literature Evaluation and Assessment; 1977-1986 Literature Review.  

National Technical Information Service (NTIS)

Chapter I of this report presents brief summaries for nine different and, in our opinion, the most important issue areas associated with the ELF electric and magnetic field bioeffects. These general issue areas are: Physical Hazards Including Electric Sho...

1986-01-01

184

Complications of radiofrequency ablation in hepatocellular carcinoma  

Microsoft Academic Search

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

H. Rhim

2005-01-01

185

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

186

Complications of radiofrequency coagulation of liver tumours  

Microsoft Academic Search

Background: Radiofrequency coagulation (RFC) is being promoted as a novel technique with a low morbidity rate in the treatment of liver tumours. The purpose of this study was to assess critically the complication rates of RFC in centres with both large and limited initial experience, and to establish causes and possible means of prevention and treatment. Methods: This is an

S. Mulier; P. Mulier; Y. Ni; Y. Miao; B. Dupas; G. Marchal; I. De Wever; L. Michel

2002-01-01

187

The use of radiofrequency in cancer  

Microsoft Academic Search

Radiofrequency ablation (RFA) provides an effective technique for minimally invasive tissue destruction. An alternating current delivered via a needle electrode causes localised ionic agitation and frictional heating of the tissue around the needle. Image-guided, percutaneous ablation techniques have been developed in most parts of the body, but the most widely accepted applications are for the treatment of hepatocellular carcinoma (HCC)

A R Gillams

2005-01-01

188

Radiofrequency Ablation in Barrett's Esophagus with Dysplasia  

Microsoft Academic Search

Background Barrett's esophagus, a condition of intestinal metaplasia of the esophagus, is associ- ated with an increased risk of esophageal adenocarcinoma. We assessed whether endoscopic radiofrequency ablation could eradicate dysplastic Barrett's esophagus and decrease the rate of neoplastic progression. Methods In a multicenter, sham-controlled trial, we randomly assigned 127 patients with dys- plastic Barrett's esophagus in a 2:1 ratio to

Nicholas J. Shaheen; Prateek Sharma; Bergein F. Overholt; Herbert C. Wolfsen; Richard E. Sampliner; Kenneth K. Wang; Joseph A. Galanko; Mary P. Bronner; John R. Goldblum; Ana E. Bennett; Blair A. Jobe; Glenn M. Eisen; M. Brian Fennerty; John G. Hunter; David E. Fleischer; Virender K. Sharma; Robert H. Hawes; Brenda J. Hoffman; Richard I. Rothstein; Stuart R. Gordon; Hiroshi Mashimo; Kenneth J. Chang; V. Raman Muthusamy; Steven A. Edmundowicz; Stuart J. Spechler; Ali A. Siddiqui; Rhonda F. Souza; Anthony Infantolino; Gary W. Falk; Michael B. Kimmey; Ryan D. Madanick; Amitabh Chak; Charles J. Lightdale

2009-01-01

189

[Electrosmog, cellular phones, sunbeds etc. -- adverse health effects from radiation? Health aspects of non-ionizing radiation].  

PubMed

This review supplies a survey of the three physical influences, i. e. UV radiation, high-frequency electromagnetic fields of radio telephone systems and other wireless radio applications as well as low-frequency fields of electric power supply. The exposure to UV radiation must be considered to be by far the highest health risk. The annual rate of about 2000 deaths from skin cancer in Germany, mainly caused by extensive exposure to solar UV radiation, demands protective measures. Teaching reasonable behaviour is the supreme issue. Recommended protective measures in the order of their effectiveness are protection by adaptation of behaviour, by clothes, sun hats and sunglasses as well as by sun creams. Children are the most important target group. With regard to UV tanning appliances it is recommended not to use artificial UV radiation for cosmetic purposes because of the related health risks. For the assessment of health impairments caused by exposure to electromagnetic fields, direct field reactions due to induced electric body currents, reactions on the surface of the body or heating effects should be separated from indirect field reactions (e. g. electric shocks and burns) due to contact currents or interference with electronic body aids and implants. Risk assessment has led to recommendations of threshold values which-in agreement with international research results-exclude all impairments of health caused by direct field reactions scientifically proven to date. Contrary to public concerns, which are mostly related to base transmitters of radio telephone systems, exposure due to handheld radio telephones (cellular phones) should rather be considered from the viewpoint of precautionary health protection, since it is more likely that their use can lead to high exposure of the user. Due to the protective measures provided so far and observance of the threshold values based on scientific results, exposures do not lead to health impairments-not even in children. Because of the introduction of new technologies more portable devices are to be expected that may be operated near the body. This will further increase the exposure of people to high-frequency electromagnetic fields. PMID:15650908

Bernhardt, J H

2005-01-01

190

A finite element model for radiofrequency ablation of the myocardium.  

PubMed

A finite element model was developed to simulate the temperature distributions produced by radiofrequency catheter ablation. This model incorporated blood, myocardium and torso tissues. The Laplace equation was solved to determine the steady-state electric field. The heat generation in the tissues was then computed from the power density distribution and the bioheat equation was solved to determine the time-varying temperature distribution, taking into account the convective energy exchange at the blood-myocardium and torso-air interfaces. This model was used to predict the lesion depth and to evaluate the effects of electrode location, changes of the electrical and thermal conductivities, and the electrode radius on the thermally induced damage to the myocardium. Temperature distributions induced by radiofrequency ablation were found to be: i) not very sensitive to the reference electrode location, ii) more sensitive to electrical conductivity changes than to thermal conductivity changes, and iii) larger electrodes allow a current distribution at higher level of power with reducing the chance of impedance rise. PMID:7959803

Shahidi, A V; Savard, P

1994-10-01

191

Adiabatic radio-frequency potentials for the coherent manipulation of matter waves  

SciTech Connect

Adiabatic dressed state potentials are created when magnetic substates of trapped atoms are coupled by a radio-frequency field. We discuss their theoretical foundations and point out fundamental advantages over potentials purely based on static fields. The enhanced flexibility enables one to implement numerous configurations, including double wells, Mach-Zehnder, and Sagnac interferometers which even allows for internal state-dependent atom manipulation. These can be realized using simple and highly integrated wire geometries on atom chips.

Lesanovsky, I.; Hofferberth, S.; Schmiedmayer, J. [Physikalisches Institut, Universitaet Heidelberg, D-69120 Heidelberg (Germany); Schumm, T. [Physikalisches Institut, Universitaet Heidelberg, D-69120 Heidelberg (Germany); Laboratoire Charles Fabry de l'Institut d'Optique, UMR 8105 du CNRS, F-91403 Orsay (France); Andersson, L. M. [Physikalisches Institut, Universitaet Heidelberg, D-69120 Heidelberg (Germany); Department of Microelectronics and Information Technology, The Royal Institute of Technology, KTH, Electrum 229, SE-164 40, Kista (Sweden); Krueger, P. [Physikalisches Institut, Universitaet Heidelberg, D-69120 Heidelberg (Germany); Laboratoire Kastler Brossel, 24 Rue Lhomond, 75005 Paris (France)

2006-03-15

192

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

2012-12-01

193

Radio-frequency point-contact electrometer  

NASA Astrophysics Data System (ADS)

We fabricate and characterize a radio-frequency semiconductor point-contact (rf-PC) electrometer analogous to radio-frequency single-electron transistors (rf-SETs) [see Schoelkopf et al., Science 280, 1238 (1998)]. The point contact is formed by surface Schottky gates in a two-dimensional electron gas in an AlGaAs/GaAs heterostructure. In the present setup, the PC is operating as a simple voltage-controlled resistor rather than a quantum point contact and demonstrates a charge sensitivity of about 2×10-1e/Hz at a bandwidth of 30 kHz without the use of a cryogenic rf preamplifier. Since the impedance of a typical point-contact device is much lower than the impedance of the typical SET, a semiconductor-based rf-PC, equipped with practical cryogenic rf preamplifiers, could realize an ultrafast and ultrasensitive electrometer.

Qin, Hua; Williams, David A.

2006-05-01

194

Radiofrequency tonsillotomy in Sweden 2009-2012.  

PubMed

The Swedish National Registry for Tonsil Surgery has been operational since 1997. All ENT clinics in Sweden are encouraged to submit data for all patients scheduled for tonsil surgery. Preoperatively, age, gender and indication are recorded. Postoperatively, method (tonsillectomy or tonsillotomy), technique, and perioperative complications are recorded. Postoperative bleedings, pain, infections, and symptom relief are assessed through questionnaires. An earlier report from this registry showed that tonsillotomy had become more common than tonsillectomy in children with tonsil-related upper airway obstruction. The aim of this study was to categorize which instruments were used for tonsillotomy in Sweden and to compare their outcome and complication rate. All children 2-18 years, reported to the registry from March 2009 until September 2012, who underwent tonsillotomy on the indication upper airway obstruction, were included in the study. 1,676 patients were identified. In 1,602 cases (96 %), a radiofrequency instrument was used. The postoperative bleeding rate was low (1.2 %) and the degree of symptom relief was high (95.1 %). Three different radiofrequency instruments (ArthroCare Coblation(®), Ellman Surgitron(®), and Sutter CURIS(®)) were used in 96 % of the patients. There were no significant differences in the number of postoperative bleedings, postoperative infections or symptom relief between the instruments. The only difference found was in the number of days on analgesics, where more days were registered after use of Coblation(®). In Sweden, radiofrequency tonsillotomy is the dominant surgical technique used for tonsil hypertrophy causing upper airway obstruction in children. There are no significant differences in outcome between the different radiofrequency instruments except for number of days on analgesics after surgery. PMID:24366615

Sunnergren, Ola; Hemlin, Claes; Ericsson, Elisabeth; Hessén-Söderman, Anne-Charlotte; Hultcrantz, Elisabeth; Odhagen, Erik; Stalfors, Joacim

2014-06-01

195

Radiofrequency catheter ablation in recurrent ventricular tachycardia.  

PubMed

Catheter ablation by radiofrequency energy was carried out in 10 patients with one type of recurrent monomorphic sustained ventricular tachycardia resistant to medical antiarrhythmic management. Electrophysiological studies before ablation included activation and pace-mapping. In all patients, the origin of the tachycardia was localized in the left ventricle: in the septum in six, at the posterolateral wall in three and anterobasal in one. The earliest onset of endocardial activation preceding the QRS complex during ventricular tachycardia ranged between -45 and -90 ms. Transcatheter ablation was performed with a bipolar or quadripolar catheter using a radiofrequency generator (HAT 100, Osypka). No complications occurred during the ablation procedure. Thereafter, in all patients, the clinical tachycardia was no longer inducible by programmed stimulation. During a follow-up period of 22 to 32 months including eight patients, the tachycardia recurred in two; one of these patients subsequently died suddenly. A third patient had one episode of a new type of sustained ventricular tachycardia some hours after catheter ablation. In the remaining patients, there was no recurrence of symptomatic tachycardia under maintenance of the antiarrhythmic management which, prior to ablation had been ineffective. Thus, our preliminary results suggest that radiofrequency catheter ablation might be beneficial for these high risk patients. PMID:1778189

Gonska, B D; Brune, S; Bethge, K P; Kreuzer, H

1991-12-01

196

Radiofrequency ablation and breast cancer: a review  

PubMed Central

Background Radiofrequency ablation (RFA) use in breast cancer is a developing area of research. There have been a number of published studies over the last decade, which explores the feasibility of minimally invasive techniques in breast cancer treatment. In this review, we will discuss the most recent data on radiofrequency ablation and examine the current methods, outcomes, complications, and limitations of RFA in breast cancer therapy. Methods Pub Med search for English Language articles on RFA in breast cancer. Results More than 25 studies were reviewed and we searched for number of tumors, average size, electrode used, if they successfully ablated the tumor, when the tumor was then resected and if the patients experienced any complication from the ablation. Conclusions Radiofrequency ablation is an emerging minimally invasive therapy in small, localized breast cancer. Currently, no clinical trials have been published to directly compare RFA to the current standard of surgical resection. Ultimately, RFA will need clinical trials to evaluate oncologic outcomes involving long interval follow-up to determine survival, local control and disease progression before it becomes a reasonable alternative to surgical resection.

Nguyen, Tiffany; Hattery, Eleanor

2014-01-01

197

Radiofrequency Ablation of Pulmonary Neoplasm Complicated by Pulmonary Hemorrhage  

PubMed Central

Pulmonary hemorrhage is a potentially serious complication of radiofrequency ablation of pulmonary neoplasms that may occur with or without hemoptysis. Several factors influence the development of parenchymal hemorrhage, including tumor size, tumor location, and procedural technique. As radiofrequency ablation has become more common, the prompt diagnosis and appropriate treatment of hemorrhage is vital. The authors report a case of radiofrequency ablation of a solitary pulmonary metastasis complicated by pulmonary hemorrhage and hemoptysis.

Dillon, P.; Sato, Kent T.

2011-01-01

198

The Importance of Radiofrequency Safety into Occupational Safety Coursework  

NSDL National Science Digital Library

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

2010-07-29

199

Plasma-beam traps and radiofrequency quadrupole beam coolers.  

PubMed

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

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

2014-02-01

200

Summary of Information on the Effects of Ionizing and Non-ionizing Radiation on Cytochrome P450 and Other Drug Metabolizing Enzymes and Transporters  

PubMed Central

The present paper is an update of data on the effects of ionizing radiation (?-rays, X-rays, high energy UV, fast neutron) caused by environmental pollution or clinical treatments and the effects of non-ionizing radiation (low energy UV) on the expression and/or activity of drug metabolism (e.g., cytochrome P450,, glutathione transferase), enzymes involved in oxidative stress (e.g., peroxidases, catalase,, aconitase, superoxide dismutase), and transporters. The data are presented in tabular form (Tables 1–3) and are a continuation of previously published summaries on the effects of drugs and other chemicals on cytochrome P450 enzymes (Rendic, S.; Di Carlo, F. Drug Metab. Rev., 1997, 29 (1–2), 413–580, Rendic, S. Drug Metab. Rev., 2002, 34 (1–2), 83–448) and of the data on the effects of diseases and environmental factors on the expression and/or activity of human cytochrome P450 enzymes and transporters (Guengerich, F.P.; Rendic, S. Curr. Drug Metab., 2010, 11(1), 1–3, Rendic, S.; Guengerich, F.P. Curr. Drug Metab., 2010, 11 (1), 4–84). The collective information is as presented by the cited author(s) in cases where several references are cited the latest published information is included. Remarks and conclusions suggesting clinically important impacts are highlighted, followed by discussion of the major findings. The searchable database is available as an Excel file (for information about file availability contact the corresponding author).

Rendic, Slobodan; Guengerich, F. Peter

2014-01-01

201

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

202

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

203

Collisional, magnetic, and nonlinear skin effect in radio-frequency plasmas  

NASA Astrophysics Data System (ADS)

The penetration of radio-frequency energy into cylindrical devices is relevant to the production of uniform plasmas for etching and deposition processes in the production of semiconductor circuits. The so-called ``anomalous skin effect'' has been invoked to explain irregularities not predicted by classical electromagnetic theory. These expectations are summarized for the collisionality regimes of interest, and new results are given for nonkinetic effects caused by small direct current magnetic fields and the ponderomotive force.

Chen, Francis F.

2001-06-01

204

Cryocooled wideband digital channelizing radio-frequency receiver based on low-pass ADC  

Microsoft Academic Search

We have demonstrated a digital receiver performing direct digitization of radio-frequency signals over a wide frequency range from kilohertz to gigahertz. The complete system, consisting of a cryopackaged superconductor all-digital receiver (ADR) chip followed by room-temperature interface electronics and a field programmable gate array (FPGA) based post-processing module, has been developed. The ADR chip comprises a low-pass analog-to-digital converter (ADC)

Igor V. Vernik; Dmitri E. Kirichenko; Vladimir V. Dotsenko; Robert Miller; Robert J. Webber; Pavel Shevchenko; Andrei Talalaevskii; Deepnarayan Gupta; Oleg A. Mukhanov

2007-01-01

205

Radiofrequency ablation followed by resection of malignant liver tumors  

Microsoft Academic Search

BACKGROUND: Radiofrequency ablation (RFA) has recently been used to treat liver tumors, but few clinical reports have described the pathological characteristics of radiofrequency ablation in human specimens. This study delineates the gross pathologic and histochemical changes induced by RFA in benign and malignant human liver tissue and confirms the tumor necrosis described in early clinical reports.METHODS:Ten patients with metastatic tumors

Charles H Scudamore; Shung I Lee; Emma J Patterson; Andrzej K Buczkowski; Laura V July; Stephen W Chung; Anne R Buckley; Stephen G. F Ho; David A Owen

1999-01-01

206

Thermal-electrical modeling for epicardial atrial radiofrequency ablation  

Microsoft Academic Search

Epicardial radiofrequency ablation is increasingly being used for intraoperative treatment of atrial fibrillation. However, the effect of different parameters on the lesion characteristics has not been sufficiently characterized. We used a finite element model to calculate the temperature distribution in the atrial tissue under different conditions during a constant voltage radiofrequency ablation. Our simulation results show that although in the

Enrique J. Berjano; Fernando Hornero

2004-01-01

207

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

208

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. PMID:24019215

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

2013-11-01

209

Radiofrequency/microwave protection guides.  

PubMed

Limits for exposure to electromagnetic fields at RF and microwave frequencies have, at times, been subject to criticism and controversy. In many cases the controversy results from a lack of absolute proof that some nominal levels of exposure are safe, from a misunderstanding of how to apply the limits, and from a lack of understanding (by critics) of the rationale upon which the limits were developed and of the consensus process required for approval. Exposure limits, based on rather simple models, were developed during the early 1950s and have been used extensively without revision for almost three decades (and still are by various organizations including the U.S. Department of Labor). During the past decade, however, these limits have been modified extensively to reflect both the increase in knowledge of bioeffects associated with exposure to electromagnetic energy and the advances in dosimetry and, also, to overcome obvious shortcomings in the earlier exposure guides. This paper will review the exposure criteria developed during the past decade by the American National Standards Institute and the National Council on Radiation Protection and Measurements, with particular emphasis on the underlying rationale. PMID:2061050

Petersen, R C

1991-07-01

210

Summary of information on the effects of ionizing and non-ionizing radiation on cytochrome P450 and other drug metabolizing enzymes and transporters.  

PubMed

The present paper is an update of data on the effects of ionizing radiation (?-rays, X-rays, high energy UV, fast neutron) caused by environmental pollution or clinical treatments and the effects of non-ionizing radiation (low energy UV) on the expression and/or activity of drug metabolism (e.g., cytochrome P450 (CYP), glutathione transferase (GST)), enzymes involved in oxidative stress (e.g., peroxidases, catalase (CAT), aconitase (ACO), superoxide dismutase (SOD)), and transporters. The data are presented in tabular form (Tables 1-3) and are a continuation of previously published summaries on the effects of drugs and other chemicals on cytochrome P450 enzymes (Rendic, S.; Di Carlo, F. Drug Metab. Rev., 1997, 29 (1-2), 413-580, Rendic, S. Drug Metab. Rev., 2002, 34 (1-2), 83- 448) and of the data on the effects of diseases and environmental factors on the expression and/or activity of human cytochrome P450 enzymes and transporters (Guengerich, F.P.; Rendic, S. Curr. Drug Metab., 2010, 11(1), 1-3, Rendic, S.; Guengerich, F.P. Curr. Drug Metab., 2010, 11 (1), 4-84). The collective information is as presented by the cited author(s) in cases where several references are cited the latest published information is included. Remarks and conclusions suggesting clinically important impacts are highlighted, followed by discussion of the major findings. The searchable database is available as an Excel file (for information about file availability contact the corresponding author). PMID:22571481

Rendic, Slobodan; Guengerich, F Peter

2012-07-01

211

Symptomatic diaphragmatic hernia after pulmonary radiofrequency ablation.  

PubMed

Radiofrequency ablation (RF) is a relatively safe and reliable technique for the treatment of pulmonary metastases that has seen rapidly expanding use. Lesions situated near the diaphragm are difficult to treat by RF due to the risk of thermal injury to the diaphragm. Diaphragmatic perforation with progressive development of a diaphragmatic hernia is a rare but serious complication. Treatment is surgical. We present the first case reported in the literature of intestinal obstruction in a left diaphragmatic hernia that developed following RF treatment of a pulmonary metastasis. PMID:23541285

Schwartz, A; Desolneux, G; Desjardin, M; Evrard, S; Bechade, D

2013-04-01

212

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

213

Investigation of radiofrequency plasma sources for space travel  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

214

Radio-frequency quadrupole vane-tip geometries  

SciTech Connect

Radio-frequency quadrupole (RFQ) linacs are becoming widely accepted in the accelerator community. They have the remarkable capability of simultaneously bunching low-energy ion beams and accelerating them to energies at which conventional accelerators can be used, accomplishing this with high-transmission efficiencies and low-emittance growths. The electric fields, used for radial focusing, bunching, and accelerating, are determined by the geometry of the vane tips. The choice of the best vane-tip geometry depends on considerations such as the peak surface electric field, per cent of higher multipole components, and ease of machining. We review the vane-tip geometry based on the ideal two-term potential function and briefly describe a method for calculating the electric field components in an RFQ cell with arbitrary vane-tip geometry. We describe five basic geometries and use the prototype RFQ design for the Fusion Materials Irradiation Test (FMIT) accelerator as an example to compare the characteristics of the various geometries.

Crandall, K.R.; Mills, R.S.; Wangler, T.P.

1983-01-01

215

Operating a radio-frequency plasma source on water vapor  

SciTech Connect

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{sub i}{approx_equal}n{sub e}, where n{sub i} is the positive ion density. But in the electronegative water plasma, quasineutrality requires n{sub i+}=n{sub i-}+n{sub 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.

Nguyen, Sonca V. T.; Gallimore, Alec D. [Plasmadynamics and Electric Propulsion Laboratory, University of Michigan, Ann Arbor, Michigan 48108 (United States); Foster, John E. [Plasma Science and Technology Laboratory, University of Michigan, Ann Arbor, Michigan 48108 (United States)

2009-08-15

216

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

PubMed Central

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

2014-01-01

217

Impact of monopolar radiofrequency energy on subchondral bone viability.  

PubMed

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

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

2010-05-01

218

Optimizing bipolar radiofrequency ablation treatment by means of pulsed currents.  

PubMed

Given the high mortality rate, liver cancer is considered to be a difficult cancer to treat. Consequently, alternative strategies are being developed such as radiofrequency ablation (RFA). RFA applies radiofrequent currents leading to local heating of the tumoral tissue. Accurate numerical modeling contributes to a better knowledge of the physical phenomena and allows optimizations. In this work, the bipolar radiofrequency ablation technique is explored followed by an optimization by means of pulsed currents. Numerical results clearly show the larger ablation zones due to the pulsed currents. Hence, pulsed bipolar RFA increases the efficacy and has the potential to be incorporated in clinical practice. PMID:24110545

Soetaert, Frederik; Crevecoeur, Guillaume; Dupre, Luc

2013-01-01

219

Radiofrequency ablation of symptomatic but benign ventricular arrhythmias.  

PubMed

Two cases are presented where ablation of severely symptomatic ventricular arrhythmias not responding to medical therapy was accomplished with radiofrequency current application. After a routine programmed stimulation protocol, a quadripolar ablation catheter with a 4-mm tip was advanced percutaneously into the left ventricle in one case and into the right ventricle in the second case; and after precise pace mapping, the arrhythmogenic focus was successfully ablated using radiofrequency current. The postablation ambulatory recording revealed virtual eradication of ventricular ectopy in both cases. In conclusion, in severely symptomatic cases of "benign" ventricular arrhythmias, radiofrequency ablation offers an effective therapeutic alternative. PMID:1382275

Gursoy, S; Brugada, J; Souza, O; Steurer, G; Andries, E; Brugada, P

1992-05-01

220

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

PubMed Central

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

Michaelson, S. M.

1982-01-01

221

Axial force imparted by a conical radiofrequency magneto-plasma thruster  

SciTech Connect

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

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

2012-03-12

222

Axial force imparted by a conical radiofrequency magneto-plasma thruster  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

223

Thermal compression and molding of atherosclerotic vascular tissue with use of radiofrequency energy: implications for radiofrequency balloon angioplasty  

SciTech Connect

The combined delivery of pressure and thermal energy may effectively remodel intraluminal atherosclerotic plaque and fuse intimal tears. To test these hypotheses with use of a non-laser thermal energy source, radiofrequency energy was delivered to postmortem human atherosclerotic vessels from a metal hot-tip catheter, block-mounted bipolar electrodes and from a prototype radiofrequency balloon catheter. Sixty-two radiofrequency doses delivered from a metal electrode tip produced dose-dependent ablation of atherosclerotic plaque, ranging from clean and shallow craters with histologic evidence of thermal compression at doses less than 40 J to tissue charring and vaporization at higher (greater than 80 J) doses. Lesion dimensions ranged between 3.14 and 3.79 mm in diameter and 0.20 and 0.47 mm in depth. Tissue perforation was not observed. To test the potential for radiofrequency fusion of intimal tears, 5 atm of pressure and 200 J radiofrequency energy were delivered from block-mounted bipolar electrodes to 48 segments of human atherosclerotic aorta, which had been manually separated into intima-media and media-adventitial layers. Significantly stronger tissue fusion resulted (28.5 +/- 3.3 g) with radiofrequency compared with that with pressure alone (4.8 +/- 0.26 g; p less than 0.0001). A prototype radiofrequency balloon catheter was used to deliver 3 atm of balloon pressure with or without 200 J radiofrequency energy to 20 postmortem human atherosclerotic arterial segments. In 10 of 10 radiofrequency-treated vessels, thermal molding of both normal and atherosclerotic vessel wall segments resulted with increased luminal diameter and histologic evidence of medial myocyte damage.

Lee, B.I.; Becker, G.J.; Waller, B.F.; Barry, K.J.; Connolly, R.J.; Kaplan, J.; Shapiro, A.R.; Nardella, P.C.

1989-04-01

224

Electromagnetic limits to radiofrequency (RF) neuronal telemetry  

NASA Astrophysics Data System (ADS)

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

Diaz, R. E.; Sebastian, T.

2013-12-01

225

Electromagnetic limits to radiofrequency (RF) neuronal telemetry  

PubMed Central

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

Diaz, R. E.; Sebastian, T.

2013-01-01

226

Radiofrequency Ablation Therapy for Solid Tumors  

SciTech Connect

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

Kam, Anthony (NIH) [NIH

2002-12-04

227

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

228

[Radiofrequency ablation effectively treats chronic radiation proctitis].  

PubMed

Chronic radiation proctitis can develop after radiation therapy of pelvic malignancies. Symptoms include haematochezia, diarrhoea, tenesmus, urgency, faecal incontinence, and rectal pain. Various therapies have been attempted with argon plasma coagulation (APC) currently being the treatment of choice, but complications such as ulceration and stricture are commonly encountered. There are limited data suggesting that radiofrequency ablation (RFA) may be an effective alternative to APC, in particular in transfusion-dependent patients. Here we report two cases of chronic radiation proctitis, one of whom was transfusion-dependent, who were safely and successfully treated with focal RFA. Haematochezia decreased significantly the day subsequent to treatment, and transfusion independence was achieved after a single session. Three to four sessions were required to eradicate the neovascular lesions. Post-therapeutic rectal re-epithelialisation occurred, and no bleeding was encountered during up to nine months of follow-up. PMID:24022204

Huegle, U; Müller-Gerbes, D; Dormann, A J

2013-09-01

229

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

230

Radio-frequency low-coherence interferometry.  

PubMed

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

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

2014-06-15

231

Auditory response to pulsed radiofrequency energy.  

PubMed

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

Elder, J A; Chou, C K

2003-01-01

232

Subcellular Responses to Narrowband and Wideband Radiofrequency Radiation.  

National Technical Information Service (NTIS)

The interest in subcellular effects of radiofrequency radiation has led to the establishment of a Multidisciplinary University Research Initiative (MURI) with scientists from six academic institutions (Old Dominion University, Eastern Virginia Medical Sch...

C. C. Tseng K. H. Schoenbach

2008-01-01

233

Pain Relief Through an Antinociceptive Effect After Radiofrequency Application  

Microsoft Academic Search

Background: Many patients with chronic tendinosis have experienced early pain relief after application of bipolar radiofrequency treatment. Pathologic nerve ingrowth or nerve irritation in the tendon has been considered as a possible cause of the pain experienced with tendinosis.Hypothesis: Bipolar radiofrequency treatment will ablate nerve fibers, resulting in pain relief.Study Design: Controlled laboratory study.Methods: Eighteen Sprague-Dawley rats were used in

Norimasa Takahashi; James P. Tasto; Mark Ritter; Nobuyasu Ochiai; Seiji Ohtori; Hideshige Moriya; David Amiel

2007-01-01

234

Image-guided radiofrequency ablation of renal cell carcinoma  

Microsoft Academic Search

The incidence of renal cell carcinoma is rising with the increased number of incidental detection of small tumours. During\\u000a the past few years, percutaneous imaging-guided radiofrequency ablation has evolved as a minimally invasive treatment of small\\u000a unresectable renal tumours offering reduced patient morbidity and overall health care costs. In radiofrequency ablation, thermal\\u000a energy is deposited into a targeted tumour by

Andreas Boss; Stephan Clasen; Markus Kuczyk; Fritz Schick; Philippe L. Pereira

2007-01-01

235

Percutaneous computed tomography-guided radiofrequency ablation of osteoid osteomas  

Microsoft Academic Search

Twenty-one consecutive patients with osteoid osteoma treated with computed tomography-guided radiofrequency ablation, after\\u000a failed conservative treatment, were retrospectively reviewed. The diagnosis was based on typical clinical and imaging features.\\u000a Radiofrequency ablation of osteoid osteomas was undertaken by heating the tip of the electrode to 90°C for three sessions\\u000a of 2 min each. Follow-up evaluation included clinical examination and questionnaire, and radiographic

Christos K. Kyriakopoulos; Andreas F. Mavrogenis; John Pappas; Panayiotis J. Papagelopoulos

2007-01-01

236

Radiofrequency transmission line for bioluminescent Vibrio sp. irradiation  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

237

Radiofrequency ablation: an alternative treatment method of renal cell carcinoma.  

PubMed

Renal Cell Carcinoma (RCC) is a common renal parenchymal malignancy. Although complete or partial nephrectomy is still the gold standard of management, a lot of minimally invasive techniques are currently emerging into the field of treatment. Recently, image-guided radiofrequency (RF) ablation has received increasing attention and been proposed as an alternation to more invasive procedures such as partial or radical nephrectomy. For the RCC patients who are not amenable to surgery or have a single kidney, RF ablation is another feasible option of management. We present a 71-year-old patient who had right nephrectomy for RCC 10 years prior to admission, and hypertension and arrhythmia under regular treatment. He was noted to have two masses in the left kidney and right adrenal gland, respectively, on follow-up computed tomography images. Percutaneous biopsies of the left renal and right adrenal masses were proven to be renal cell carcinoma. After a right adrenalectomy was performed, this patient underwent two treatment sessions of percutaneous RF ablation to avoid a nephrectomy which would lead her on dialysis. Successful treatment was impressed after 1 year of follow-up. We report this case to emphasize the potential role of percutaneous RF ablation on the treatment of RCC. PMID:15553610

Lui, Kar-Wai; Gervais, Debra A; Mueller, Peter R

2004-08-01

238

Laser ablation loading of a radiofrequency ion trap  

NASA Astrophysics Data System (ADS)

The production of ions via laser ablation for the loading of radiofrequency (RF) ion traps is investigated using a nitrogen laser with a maximum pulse energy of 0.17 mJ and a peak intensity of about 250 MW/cm2. A time-of-flight mass spectrometer is used to measure the ion yield and the distribution of the charge states. Singly charged ions of elements that are presently considered for the use in optical clocks or quantum logic applications could be produced from metallic samples at a rate of the order of magnitude 105 ions per pulse. A linear Paul trap was loaded with Th+ ions produced by laser ablation. An overall ion production and trapping efficiency of 10-7 to 10-6 was attained. For ions injected individually, a dependence of the capture probability on the phase of the RF field has been predicted. In the experiment this was not observed, presumably because of collective effects within the ablation plume.

Zimmermann, K.; Okhapkin, M. V.; Herrera-Sancho, O. A.; Peik, E.

2012-06-01

239

Endovascular Radiofrequency Ablation for Varicose Veins  

PubMed Central

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

2011-01-01

240

Pulsed Radiofrequency Treatment for Trigeminal Neuralgia  

PubMed Central

Background: Pulsed radiofrequency (PRF) treatment is defined as the delivery of short pulses of radiofrequency via a needle tip, which does not result in an actual thermal lesions. There are mixed views regarding the use of PRF for trigeminal neuralgia (TN). In our opinion, one of the main reasons for the contrasting views is the insufficient PRF dose employed in previous studies. In a recent study on the effects of PRF on resiniferatoxin-induced neuropathic pain in an animal model, the anti-allodynic effects of PRF were significantly greater when the PRF exposure duration was increased from 2 to 6 minutes. Objectives: The primary objective of this retrospective study is to report the results for 36 consecutive patients who underwent PRF treatment for TN, for 6 minutes at 45 V at a pulsed frequency of 4 Hz and a pulse width of 10 ms. Patients and Methods: For the study, we obtained procedural records of 36 consecutive patients. Their current state of pain was evaluated over a telephonic survey and the post-procedural data at 2, 6, and 12 months were retrieved thereafter from the patient records. The main outcome measure was excellent pain relief (more than 80%), which was assessed at 2, 6, and 12 months. Results: The percentages of patients who showed excellent pain relief (> 80% pain relief) at 2, 6, and 12 months were 73.5% (25/34), 61.8% (21/34), and 55.9% (19/34), respectively. The percentages of patients showing satisfactory pain relief (50–80% pain relief) at 2, 6, and 12 months were 14.7% (5/34), 17.6% (6/34), and 17.6% (6/34), respectively, and those of patients showing less than satisfactory pain relief (< 50% pain relief) at 2, 6, and 12 months were 11.8% (4/34), 20.6% (7/34), and 23.5% (8/34), respectively. No complications were reported, and none of the patients required hospitalization. Conclusions: PRF of the trigeminal ganglion should be further evaluated as an alternative treatment method for TN.

Chua, Nicholas Hai Liang; Halim, Willy; Beems, Tjemme; Vissers, Kris CP

2012-01-01

241

Percutaneous radiofrequency ablation of a small renal mass complicated by appendiceal perforation.  

PubMed

Percutaneous radiofrequency ablation (RFA) has gained wide acceptance as nephron-sparing therapy for small renal masses in select patients. Generally, it is a safe procedure with minor morbidity and acceptable short-term oncologic outcome. However, as a result of the close proximity of vital structures, such as the bowel, ureter, and large vessels, to the ablative field, complications regarding these structures may occur. This is the first article describing appendiceal perforation as a complication of computed tomography-guided RFA despite hydrodissection. When performing this innovative and promising procedure one should be aware of the possibility of particular minor and even major complications. PMID:22011782

Boone, Judith; Bex, Axel; Prevoo, Warner

2012-06-01

242

Directional Radio-Frequency Identification Tag Reader  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

243

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

244

Non-conventional methods in radiofrequency spectroscopy  

NASA Astrophysics Data System (ADS)

The experiments in the radiofrequency spectroscopy of simple molecules often require non-conventional approaches to solve the problems encountered for the extension towards high frequency. We review the application of the photoacoustic and of the Stark-sweep methods to the measurement of collision line broadening in the millimeter wave region. These two techniques are combined in a third class of experiments aimed to accurate measurement of vibrational frequencies in the near infrared. In each case the motivations for an unusual approach are discussed and the advantages as well as the difficulties of the new methods are presented. Les expériences de spectroscopie radiofréquence de molécules simples demandent souvent des approches non conventionnelles pour résoudre les problèmes rencontrés lors de l'extension vers les hautes fréquences. Nous passons en revue l'application des méthodes photoacoustiques et de balayage Stark à la mesure des élargissements de raie par collisions dans la zone des ondes millimétriques. Ces deux techniques sont combinées dans une troisième classe d'expériences visant à mesurer avec précision les fréquences de vibration dans l'infrarouge proche. Dans chaque cas, les motivations d'une approche inhabituelle sont discutées, et les avantages aussi bien que les difficultés des nouvelles méthodes sont présentés.

Minguzzi, P.; di Lieto, A.; Tonelli, M.

245

Radiofrequency Ablation of Intrahepatic Cholangiocarcinoma: Preliminary Experience  

SciTech Connect

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

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

2010-08-15

246

Current oncologic applications of radiofrequency ablation therapies  

PubMed Central

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.

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

2013-01-01

247

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

248

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

249

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

250

Radiofrequency Ablation for Treatment of Atrial Fibrillation  

PubMed Central

Introduction Atrial Fibrillation (AF) is the most common cardiac arrhythmia which represents a major public health problem. The main purpose of this research is to evaluate the Radiofrequency (RF) ablation effects in the patients with chronic AF scheduled for cardiac surgery because of different heart diseases. Methods The descriptive and prospective study was conducted on 60 patients with AF scheduled for surgery along with RF ablation. The data were collected by questionnaire and included: patients' age, sex, NYHA class, operation type, past medical history, type and cause of valvular heart disease, preoperative ECG (electrocardiogram), duration of surgery, clamping time, cardiopulmonary bypass, and RF ablation time. RF ablation was followed by the main operation. The follow up examination, ECG, and echocardiography were performed 3 and 6 months after operation. Results The mean age of patients was 48±10 years (18-71 years). Forty one patients had permanent AF and 19 had the persistent AF. The left ventricular ejection fraction was 48.27±9.75 percent before operation, and reached to 56.27±7.87 percent after the surgery (P<0.001). The mean NYHA class before the surgery was 2.83±0.68 which decreased to 1.34±0.46 6 months after the surgery with RF ablation (P<0.001). One patient (1.6%) died after surgery. Complete relief and freedom from AF recurrence was observed in 70% of patients in the mean follow up in 7 months after the surgery. The sinus rhythm with efficient atrial contraction was established in 100% of discharged patients. Conclusion RF ablation is an effective procedure to cure atrial fibrillation in patients undergoing cardiac surgeries.

Safaei, Nasser; Montazerghaem, Hossein; Azarfarin, Rasoul; Alizadehasl, Azin; Alikhah, Hossein

2011-01-01

251

Saline-Linked Surface Radiofrequency Ablation  

PubMed Central

Summary Background Data: Saline-linked surface radiofrequency (RF) ablation is a new technique for applying RF energy to surfaces. The surface is cooled, which prevents charring and results in deeper coagulation. However, subsurface heating may lead to steam formation and a form of tissue disruption called steam popping. We determined parameters that predict steam popping and depth of tissue destruction under nonpopping conditions. A commercially available saline-linked surface RF cautery device (Floating Ball 3.0, TissueLink, Inc.) was used. Methods: One hundred eighty circular lesions were created varying in lesion diameter, duration, power, and inflow occlusion. Variables affecting popping were determined. Then factors influencing lesion depth were studied at fixed nonpopping diameter/power combinations (1 cm/10W, 2 cm/15W, 4 cm/60W). Tissue viability was determined in selected samples by staining of tissue NADH. Results: The probability of steam popping was directly related to power level and inflow occlusion, and indirectly related to lesion diameter. Depth of injury under safe nonpopping conditions was directly related to power, lesion size, and inflow occlusion. Maximum depth in excess of 20 mm was achieved using a 4 cm diameter at 60W with inflow occlusion. Microscopy of NADH-stained tissues showed a complete cell killing in the macroscopically visible coagulated area. Conclusions: Steam popping can be avoided by selecting power level/lesion diameter combinations. Tissue destruction to 20 mm can be safely achieved with short periods of inflow occlusion. The device has promise as a treatment of superficial tumors and close resection margins.

Topp, Stefan A.; McClurken, Michael; Lipson, David; Upadhya, Gundumi A.; Ritter, Jon H.; Linehan, David; Strasberg, Steven M.

2004-01-01

252

Photoacoustic characterization of radiofrequency ablation lesions  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

253

Radiofrequency amplifier based on a dc superconducting quantum interference device  

DOEpatents

A low noise radiofrequency amplifier (10), using a dc SQUID (superconducting quantum interference device) as the input amplifying element. The dc SQUID (11) and an input coil (12) are maintained at superconductivity temperatures in a superconducting shield (13), with the input coil (12) inductively coupled to the superconducting ring (17) of the dc SQUID (11). A radiofrequency signal from outside the shield (13) is applied to the input coil (12), and an amplified radiofrequency signal is developed across the dc SQUID ring (17) and transmitted to exteriorly of the shield (13). A power gain of 19.5.+-.0.5 dB has been achieved with a noise temperature of 1.0.+-.0.4 K. at a frequency of 100 MHz.

Hilbert, Claude (Berkeley, CA); Martinis, John M. (Berkeley, CA); Clarke, John (Berkeley, CA)

1986-01-01

254

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

255

Influence of Radiofrequency Surgery on Architecture of the Palatine Tonsils  

PubMed Central

Radiofrequency surgery is a widely used modern technique for submucosal volume reduction of the tonsils. So far there is very limited information on morphologic changes in the human tonsils after radiofrequency surgery. We performed histopathological study of tonsillectomy specimens after previous bipolar radiofrequency induced thermotherapy (RFITT). A total of 83 patients underwent bipolar RFITT for hypertrophy of palatine tonsils. Tonsil volume reduction was measured by 3D ultrasonography. Five patients subsequently underwent tonsillectomy. Profound histopathological examination was performed to determine the effect of RFITT on tonsillar architecture. All tonsillectomy specimens showed the intact epithelium, intact germinal centers, normal vascularization, and no evidence of increased fibrosis. No microscopic morphological changes in tonsillectomy specimens after bipolar RFITT were observed. RFITT is an effective submucosal volume reduction procedure for treatment of hypertrophic palatine tonsils with no destructive effect on microscopic tonsillar architecture and hence most probably no functional adverse effect.

Plzak, Jan; Macokova, Pavla; Zabrodsky, Michal; Kastner, Jan; Lastuvka, Petr; Astl, Jaromir

2014-01-01

256

Radiofrequency amplifier based on a dc superconducting quantum interference device  

DOEpatents

A low noise radiofrequency amplifer, using a dc SQUID (superconducting quantum interference device) as the input amplifying element. The dc SQUID and an input coil are maintained at superconductivity temperatures in a superconducting shield, with the input coil inductively coupled to the superconducting ring of the dc SQUID. A radiofrequency signal from outside the shield is applied to the input coil, and an amplified radiofrequency signal is developed across the dc SQUID ring and transmitted to exteriorly of the shield. A power gain of 19.5 +- 0.5 dB has been achieved with a noise temperature of 1.0 +- 0.4 K at a frequency of 100 MHz.

Hilbert, C.; Martinis, J.M.; Clarke, J.

1984-04-27

257

Successful Management of Atrio-Esophageal Fistula after Cardiac Radiofrequency Catheter Ablation  

PubMed Central

An increase in cardiac radiofrequency catheter ablation for treating refractory atrial fibrillation has resulted in an increased prevalence of complications. Among numerous complications of radiofrequency catheter ablation, atrio-esophageal fistula, although rare, is known to have fatal results. We report a case of successful management of an atrio-esophageal fistula as a complication of cardiac radiofrequency catheter ablation.

Shim, Hun Bo; Kim, Chilsung; Kim, Hong-Kwan

2013-01-01

258

Development of a novel loosely wound helical coil for interstitial radiofrequency thermal therapy.  

PubMed

We have developed a novel, radiofrequency thermal therapy device designed to improve local control of large solid tumours using heat in the range 55-90 degrees C. The device is a solenoid or helical coil designed to be loosely wound inside a tumour and excited with radiofrequency energy. Typically, we associate a uniform axially directed magnetic field with a solenoid coil, which when time varying, results in an electric field inside the coil, which lies mainly in the circumferential direction. In addition to this magnetically induced electric field, there exists a less familiar axially directed electric field inside the coil. Previous investigators have demonstrated the presence of this secondary axial electric field both experimentally and theoretically. Our design exploits the size and uniformity of these electric fields, for heating and coagulating a large tissue volume with a single applicator. The loosely wound solenoid is constructed from Nitinol, an electrically conductive shape memory alloy that permits the minimally invasive percutaneous insertion of the coil through a single cannulating delivery needle. To demonstrate the potential of this device and to determine the optimal frequency of operation, phantom tissue models and finite-element calculation models using COMSOL 3.2 were used to characterize frequency- and geometry-dependent trends in absorption rate density (ARD), which is proportional to electric field intensity. Radial and axial ARD profiles were measured, calculated and evaluated to determine the frequency and geometry best suited for producing large, homogenous coagulation volumes. Based on the trade-off between radial and axial uniformities of the ARD profiles, a 2 cm diameter coil with a 4 cm length and 1 cm pitch, operated at 27.12 MHz, produced the optimal heating pattern, as determined using tissue-mimicking phantom models. PMID:16861784

McCann, Claire; Sherar, Michael D

2006-08-01

259

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

260

Thermal protection with 5% dextrose solution blanket during radiofrequency ablation.  

PubMed

A serious complication for any thermal radiofrequency ablation is thermal injury to adjacent structures, particularly the bowel, which can result in additional major surgery or death. Several methods using air, gas, fluid, or thermometry to protect adjacent structures from thermal injury have been reported. In the cases presented in this report, 5% dextrose water (D5W) was instilled to prevent injury to the bowel and diaphragm during radiofrequency ablation. Creating an Insulating envelope or moving organs with D5W might reduce risk for complications such as bowel perforation. PMID:16802079

Chen, Enn Alexandria; Neeman, Ziv; Lee, Fred T; Kam, Anthony; Wood, Brad

2006-01-01

261

Optical serial coherent analyzer of radio-frequency (OSCAR).  

PubMed

Optical serial coherent analyzer of radio-frequency is a novel scheme that enables fast-scanning microwave signal measurements in a large bandwidth. The measurements are performed based on serial channelization realized by using a fast scanning laser source as the local oscillator to down-convert the to-be-measured radio-frequency (RF) signals. Optical coherent detection effectively removes interferences induced by RF's self-beating and guarantees the accuracy of measurements. In the experimental demonstration, instantaneous multi-frequency measurements and vector information acquisition of RF signals can be achieved by this scheme within 2.8 ?s over 14 GHz bandwidth. PMID:24921552

Li, Ruiyue; Chen, Hongwei; Lei, Cheng; Yu, Ying; Chen, Minghua; Yang, Sigang; Xie, Shizhong

2014-06-01

262

Biological indicators in response to radiofrequency/microwave exposure.  

PubMed

Over the years, due to rapid technological progress, radiation from man-made sources exceeded that of natural origin. There is a general concern regarding a growing number of appliances that use radiofrequency/ microwave (RF/MW) radiation with particular emphasis on mobile communication systems. Since nonthermal biological effects and mechanisms of RF/MW radiation are still uncertain, laboratory studies on animal models, tissues, cells, and cell free system are of extraordinary importance in bioelectromagnetic research. We believe that such investigations play a supporting role in public risk assessment. Cellular systems with the potential for a clear response to RF/MW exposures should be used in those studies. It is known that organism is a complex electrochemical system where processes of oxidation and reduction regularly occur. One of the plausible mechanisms is connected with generation of reactive oxygen species (ROS). Depending on concentration, ROS can have both beneficial and deleterious effects. Positive effects are connected with cell signalling, defence against infectious agents, and proliferative cell ability. On the other hand, excessive production, which overloads antioxidant defence mechanism, leads to cellular damage with serious potential for disease development. ROS concentration increase within the cell caused by RF/MW radiation seems to be a biologically relevant hypothesis to give clear insight into the RF/MW action at non-thermal level of radiation. In order to better understand the exact mechanism of action and its consequences, further research is needed in the field. We would like to present current knowledge on possible biological mechanisms of RF/MW actions. PMID:23152390

Marjanovi?, Ana Marija; Pavi?i?, Ivan; Troši?, Ivan?ica

2012-09-01

263

A novel global model for radio-frequency driven plasmas at atmospheric pressure  

NASA Astrophysics Data System (ADS)

Over the last years microplasma research gained a lot of attention both from an experimental and theoretical perspective. One particular type of microplasma sources that shows a variety of interesting physics and applications are the so called plasma jets. Besides the more elaborated fluid or hybrid approaches the so called global models offer the ability to explore averaged species densities and energies while remaining computationally efficient. This contribution investigates a coplanar radio-frequency driven plasma jet by means of a novel global model. The model takes into account the strong modulation of the electric field in time and space both in the sheath and bulk region. By means of a consistent scale analysis we find an analytical expression for the electric field. We compare our obtained electric field to results from PIC simulations and present the general concept for this novel global model of the microplasma jet.

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

2012-10-01

264

RF system description for the ground test accelerator radio-frequency quadrupole  

NASA Astrophysics Data System (ADS)

This paper describes the RF system being used to provide RF power and to control the cavity field used for the ground test accelerator (GTA) radio-frequency quadrupole (RFQ). The RF system consists of a low-level RF (LLRF) control system that uses a tetrode as a high-power amplifier (HPA) as part of its plant to deliver up to 300 kW of peak power to the RFQ at a 2 percent duty factor. The LLRF control system implements in-phase and quadrature (I&Q) control to maintain the cavity field within tolerances of 0.5 percent in amplitude and 0.5 degrees in phase in the presence of beam-induced instabilities. This paper describes the identified components and presents measured performance data. The user interface with the systems is described, and cavity field measurements are included.

Regan, A. H.; Brittain, D.; Rees, D. E.; Ziomek, D.

1992-08-01

265

Rf system description for the ground test accelerator radio-frequency quadrupole  

SciTech Connect

This paper describes the RF system being used to provide RF power and to control the cavity field used for the ground test accelerator (GTA) radio-frequency quadrupole (RFQ). The RF system consists of a low-level RF (LLRF) control system that uses a tetrode as a high-power amplifier (HPA) as part of its plant to deliver up to 300 kW of peak power to the RFQ at a 2% duty factor. The LLRF control system implements in-phase and quadrature (I&Q) control to maintain the cavity field within tolerances of 0.5% in amplitude and 0.5{degrees} in phase in the presence of beam-induced instabilities. This paper describes the identified components and presents measured performance data. The user interface with the systems is described, and cavity field measurements are included.

Regan, A.H.; Brittain, D.; Rees, D.E.; Ziomek, D.

1992-09-01

266

Rf system description for the ground test accelerator radio-frequency quadrupole  

SciTech Connect

This paper describes the RF system being used to provide RF power and to control the cavity field used for the ground test accelerator (GTA) radio-frequency quadrupole (RFQ). The RF system consists of a low-level RF (LLRF) control system that uses a tetrode as a high-power amplifier (HPA) as part of its plant to deliver up to 300 kW of peak power to the RFQ at a 2% duty factor. The LLRF control system implements in-phase and quadrature (I Q) control to maintain the cavity field within tolerances of 0.5% in amplitude and 0.5{degrees} in phase in the presence of beam-induced instabilities. This paper describes the identified components and presents measured performance data. The user interface with the systems is described, and cavity field measurements are included.

Regan, A.H.; Brittain, D.; Rees, D.E.; Ziomek, D.

1992-01-01

267

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

NASA Astrophysics Data System (ADS)

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

Mistoco, Valerie F. M.

268

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]. 1 figure.

Cha, C.Y.

1993-09-21

269

Radiofrequency coblation for the treatment of laryngotracheal papillomas  

Microsoft Academic Search

Objectives: Recurrent respiratory papillomatosis can affect the larynx and trachea. Lesions have conventionally been treated with laser ablation with or without antiviral injection. When the distal airway is involved, laser risks increase and lesions are more difficult to treat using the laser bronchoscope. Distal seeding via the laser flume is also a major risk. Radiofrequency coblation has been successfully used

Simon Carney; Alkis Psaltis

2004-01-01

270

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

271

Transvenous radiofrequency catheter ablation of atrioventricular accessory pathways.  

PubMed

Transvenous delivery of radiofrequency energy is an attractive new technique in nonsurgical treatment of cardiac arrhythmias. We used radiofrequency catheter ablation in two patients with tachycardias complicating the Wolff-Parkinson-White syndrome. The first patient was a 28-year-old male who had suffered cardiac arrest from rapid preexcited atrial fibrillation (shortest RR interval of 180 ms) due to a left anterolateral free wall accessory pathway. The accessory pathway was mapped by means of positioning a 7F quadripolar catheter with a 4 mm tip to obtain the shortest atrial to ventricular timing during preexcited sinus rhythm. Unmodulated radiofrequency energy (750 KHz) was applied unipolarly between the distal pole of the catheter against an indifferent plate at the back. Using an applied energy of 30W, this resulted in the disappearance of both anterograde and retrograde conduction. The second patient was a 26-year-old man with concealed left posterolateral pathway. This was ablated at the site which corresponded to the shortest ventriculatrial timing during sustained atrioventricular reciprocating tachycardia. There was no complication from this procedure and both patients were discharged on the fourth day after the procedure and returned to work soon afterwards. Radiofrequency ablation is a safe and effective means for the treatment of paroxysmal supraventricular tachycardias. PMID:1598608

Lau, C P; Tai, Y T

1992-02-01

272

Palliation of Painful Perineal Metastasis Treated with Radiofrequency Thermal Ablation  

SciTech Connect

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.

Thanos, L., E-mail: loutharad@yahoo.com; Mylona, S.; Kalioras, V.; Pomoni, M.; Batakis, N. [Red-Cross Hospital of Athens, Radiology Department, 'Korgialeneio-Benakeio' (Greece)

2005-04-15

273

Pulsed Radiofrequency Ablation Under Ultrasound Guidance for Huge Neuroma  

PubMed Central

Amputation neuroma can cause very serious, intractable pain. Many treatment modalities are suggested for painful neuroma. Pharmacologic treatment shows a limited effect on eliminating the pain, and surgical treatment has a high recurrence rate. We applied pulsed radiofrequency treatment at the neuroma stalk under ultrasonography guidance. The long-term outcome was very successful, prompting us to report this case.

Jung, Il; Lee, Chang Hee; Kim, Se Hun; Kim, Jin Sun; Yoo, Byoung Woo

2014-01-01

274

High-resolution laser-radiofrequency double resonance molecular spectroscopy  

NASA Astrophysics Data System (ADS)

A primary difficulty in obtaining radiofrequency spectra is that the size of the quantum is usually much smaller than kT, so that upper and lower states of a transition have practically equal populations and any resulting absorption must be weak; absorption and stimulated emission rates will be very similar. This difficulty is circumvented by using a laser to depopulate one of the states, while a further gain is obtained by detecting a laser quantum (nu much greater than kT/h) following absorption of a radiofrequency quantum (nu much less than kT/h). A carbon dioxide laser is used to saturate vibration-rotation transitions in the 10 micrometer region and, by using an expanded laser beam of diameter 35 mm and an interaction length of some 10 m, radiofrequency spectra are obtained at linewidths below 20 kHz. This approaches the limit implied by the transit time for a molecule traversing the laser beam, and contrasts strongly with earlier work using a radiofrequency cell within the laser cavity. A rate-equation model of the experiment is explored. The new resolution and precision available are applied to hyperfine transitions in the ground and nu(sub 6) = 1 states of CH3I. It is shown that, although current hamiltonians represent most of the hyperfine structure well, a new term to represent vibration-nuclear magnetic coupling must be introduced. Finally, a new interpretation is put on the hyperfine spectrum of CH3Cl.

Gray, A. J.; Butcher, R. J.

1994-06-01

275

Radio-frequency controllable quantum interference in Mössbauer spectroscopy  

Microsoft Academic Search

The role of quantum interference (QI) in spectra of the resonant Mssbauer scattering is investigated. As a mechanism ensuring\\u000a the QI conditions, the radio-frequency (RF) mixing of the spin sublevels of the excited nuclear state is considered. It is\\u000a shown that QI leads to a significant intensity redistribution of the elastic and Raman scattering.

E. K. Sadykov; V. V. Arinin; G. I. Petrov; A. V. Pyataev; F. G. Vagizov; O. A. Kocharovskaya

2006-01-01

276

Radio-frequency controllable quantum interference in Mössbauer spectroscopy  

Microsoft Academic Search

The role of quantum interference (QI) in spectra of the resonant Mossbauer scattering is investigated. As a mechanism ensuring the QI conditions, the radio-frequency (RF) mixing of the spin sublevels of the excited nuclear state is considered. It is shown that QI leads to a significant intensity redistribution of the elastic and Raman scattering.

E. K. Sadykov; V. V. Arinin; G. I. Petrov; A. V. Pyataev; F. G. Vagizov; O. A. Kocharovskaya

2007-01-01

277

77 FR 43535 - Grantee Codes for Certified Radiofrequency Equipment  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION 47 CFR Part 2 [FCC 12-60] Grantee Codes for Certified Radiofrequency Equipment...the rules to remove the restriction that grantee codes must consist of only three characters...permit the Commission to issue longer grantee codes, thus greatly increasing the...

2012-07-25

278

The physiologic effect of the pneumoperitoneum on radiofrequency ablation  

Microsoft Academic Search

Background: Radiofrequency ablation (RFA) is gaining widespread acceptance as a safe and effective method for liver tumor ablation. Complete tumor ablation is essential for the success of the procedure. Multiple modalities have been explored in an effort to increase the size of the lesion created by RFA. The purpose of this study was to determine the physiologic effects of the

M. K. Smith; D. Mutter; L. E. Forbes; S. Mulier; J. Marescaux

2004-01-01

279

PET guidance for liver radiofrequency ablation: an evaluation  

Microsoft Academic Search

Radiofrequency ablation (RFA) is emerging as the primary mode of treatment of unresectable malignant liver tumors. With current intraoperative imaging modalities, quick, precise, and complete localization of lesions remains a challenge for liver RFA. Fusion of intraoperative CT and preoperative PET images, which relies on PET and CT registration, can produce a new image with complementary metabolic and anatomic data

Peng Lei; Omkar Dandekar; Faaiza Mahmoud; David Widlus; Patrick Malloy; Raj Shekhar

2007-01-01

280

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

281

Experimental development and theoretical studies of radio-frequency absorbers  

Microsoft Academic Search

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

J. L. L. M. Massa

1991-01-01

282

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...

283

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

284

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

285

Intraoperative radiofrequency maze ablation for atrial fibrillation: the Berlin modification  

Microsoft Academic Search

Background. The Cox-maze procedure combined with an operation for organic heart disease is highly successful in the elimination of chronic atrial fibrillation. However, it prolongs significantly the aortic cross-clamp and operating time. In this study, a simplified left atrial maze procedure, which is a short procedure performed using a surgical radiofrequency ablation probe, is added to elective open heart procedures

Miralem Pasic; Peter Bergs; Peter Müller; Michael Hofmann; Onnen Grauhan; Hermann Kuppe; Roland Hetzer

2001-01-01

286

Radio-frequency Ablation in the Treatment of Hepatic Malignancies  

Microsoft Academic Search

Tumour ablation using radio-frequency energy is attracting increasing attention as an effective minimally invasive ablative technique in the treatment of primary and secondary hepatic tumours. It has been shown to be safe and relatively well tolerated by patients, with few major complications and minimal patient discomfort, and is increasingly being used as an alternative to surgery in patients with unresectable

Richard HG; Lo FRCR

2004-01-01

287

Nonablative facelift in Indian skin with superpulsed radiofrequency  

PubMed Central

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

Sharad, Jaishree

2011-01-01

288

Multisource, Phase-controlled Radiofrequency for Treatment of Skin Laxity  

PubMed Central

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

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

2011-01-01

289

Modular System Concept For Soil Heating Using Radio-Frequency Energy  

NASA Astrophysics Data System (ADS)

Soil is one of the most important natural resources and its exploitation, preservation and regeneration are huge challenges for modern industrial society. For this reason it is essential to have innovative, efficient, cost-effective and reliable technologies for the decontamination and soil remediation. These technologies should be flexibly applicable for a wide spectrum of contaminants. Beside other biological, physical and chemical methods, research on thermally-supported soil remediation methods has increased over the last years. Due to a controlled heating of soil, the mobility of pollutants, their water solubility and their vapor pressures can be enhanced. To support biodegradation of pollutants, the maximum activity of most microorganisms can be realized by moderate heating independent of ambient temperature and seasonal conditions. A new technological approach for direct heating of large volumes of contaminated soil using radio-frequency (RF) energy is described. This method can be used to thermally enhance a variety of remediation techniques such as biodegradation and soil vapor extraction. The technical basis, a container-based modular and mobile radio-frequency platform is presented and the benefits of this platform working under harsh field conditions are demonstrated. Additionally, aspects of electromagnetic compatibility, system reliability and safety are discussed.

Holzer, Frank; Lippik, Dirk; Heimbold, Tilo; Roland, Ulf; Kopinke, Frank-Dieter; Schenk, Joachim

2010-06-01

290

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

291

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

2013-03-01

292

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

293

Radio-frequency coupling of a Bose-Einstein condensate in a TOP trap  

NASA Astrophysics Data System (ADS)

A radio-frequency (RF) transition is used to convert a pure F = 2,mF = 2 87Rb Bose-Einstein condensate confined in a TOP trap into a mixture of F = 2,mF = 2 and F = 2,mF = 1 states. We show that the nature of this coupling process is strongly influenced by the presence of the time-varying field of the TOP trap, and complicated by the presence of multiple Zeeman substates. In particular, the effective Rabi frequency associated with the applied RF field is not constant across the spatial extent of the cloud leading to a complex geometry for atom-laser output coupling and `averaging out' of Rabi oscillations. Further, a time-varying detuning can give rise to complex spatial structures.

Martin, J. L.; McKenzie, C. R.; Thomas, N. R.; Warrington, D. M.; Wilson, A. C.

2000-10-01

294

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

295

Pulsed radiofrequency treatment for idiopathic trigeminal neuralgia: a retrospective analysis of the causes for ineffective pain relief.  

PubMed

We retrospectively analyzed the reasons for ineffective pain relief in patients with idiopathic trigeminal neuralgia (TN) who had undergone pulsed radiofrequency (PRF) treatment guided by computed tomography scan. We found that intraoperative PRF output voltage and electrical field intensity was significantly higher (p?field intensity) may therefore, provide better pain relief in patients with TN. PMID:23322665

Luo, F; Meng, L; Wang, T; Yu, X; Shen, Y; Ji, N

2013-09-01

296

78 FR 25916 - Authorization of Radiofrequency Equipment  

Federal Register 2010, 2011, 2012, 2013

...with the accreditation of electromagnetic compatibility (EMC...rod antennas for electric field measurements below 30...with the accreditation of electromagnetic compatibility (EMC...with the accreditation of electromagnetic compatibility...

2013-05-03

297

Extremely-low-frequency (elf) communications program: non-ionizing electromagnetic radiation literature evaluation and assessment; 1977-1986 literature review. Final report  

SciTech Connect

Chapter I of this report presents brief summaries for nine different and probably most-important issue areas associated with the ELF electric- and magnetic-field bioeffects. These general issue areas are: Physical Hazards Including Electric Shocks and Effects on Electronic Medical Devices, Therapuetical Effects, In Vitro Cellular Studies Including Membrane and Extracellular Interactions, In Vivo Physiological Studies Including Neural and Neuroendocrinological Effects, Metabolism, Growth, and Development, Reproductive Effects, Cancer Risk, Behavioral Effects, and Ecological Effects. The overall conclusion at the end of Chapter I integrates all of the summaries into one compact statement on the status of current scientific knowledge of possible effects on living systems exposed to ELF electric and magnetic fields. A detailed description of the developed ELF bioeffects libraries, including data-base computer-file features and operation, is presented in Chapter II. Chapter III presents details on the review, evaluation, and assessment procedures. Chapter IV presents a more thorough discussion of the evaluated and assessed literature used in preparation of the summary in Chapter I. The review is confined to the same categories and order as those outlined in Chapter I.

Not Available

1986-11-01

298

A radio-frequency sheath model for complex waveforms  

NASA Astrophysics Data System (ADS)

Plasma sheaths driven by radio-frequency voltages occur in contexts ranging from plasma processing to magnetically confined fusion experiments. An analytical understanding of such sheaths is therefore important, both intrinsically and as an element in more elaborate theoretical structures. Radio-frequency sheaths are commonly excited by highly anharmonic waveforms, but no analytical model exists for this general case. We present a mathematically simple sheath model that is in good agreement with earlier models for single frequency excitation, yet can be solved for arbitrary excitation waveforms. As examples, we discuss dual-frequency and pulse-like waveforms. The model employs the ansatz that the time-averaged electron density is a constant fraction of the ion density. In the cases we discuss, the error introduced by this approximation is small, and in general it can be quantified through an internal consistency condition of the model. This simple and accurate model is likely to have wide application.

Turner, M. M.; Chabert, P.

2014-04-01

299

A review of current concepts in radiofrequency chondroplasty.  

PubMed

Radiofrequency (RF) chondroplasty is a promising treatment of chondral defects. The purpose of this study is to summarize current literature reporting the use of radiofrequency energy as an alternative treatment to mechanical shaving in chondroplasty. This review depicts the basic understanding of RF energy in ablating cartilage while exploring the basic science, laboratory evidence and clinical effectiveness of this form of chondroplasty. Laboratory studies have indicated that RF energy decreases inflammatory markers in the cartilage as well as providing optimal results with smoothing of chondral clefts. There have been concerns of chondrolysis due to heat damage of chondrocytes; however, this is unsubstantiated in clinical studies. These clinical trials have highlighted that RF energy is a safe and efficacious method of chondroplasty when compared to the mechanical shaving technique. PMID:23551491

Horton, Damien; Anderson, Suzanne; Hope, Nigel G

2014-06-01

300

Radiofrequency Thermal Ablation in Painful Myeloma of the Clavicle  

PubMed Central

A 57-year-old male patient had myeloma. He had severe pain in the left clavicle that did not respond to radiotherapy; therefore, it was treated with radiofrequency thermal ablation (RFTA). Under fluoroscopic guidance, two RF needles at a distance of 1.5 cm from each other were inserted into the mass and conventional radiofrequency (90? and 60 seconds) at two different depths (1 cm apart) was applied. Then, 2 ml of 0.5% ropivacaine along with triamcinolone 40 mg was injected in each needle. The visual analogue pain score (VAS from 0 to 10) was decreased from 8 to 0. In the next 3 months of follow-up, the patient was very satisfied with the procedure and the mass gradually became smaller. There were no complications. This study shows that RFTA could be a useful method for pain management in painful osteolytic myeloma lesions in the clavicle.

Imani, Farnad; Vakily, Masoud

2014-01-01

301

A Surgical Device for Radiofrequency Ablation of Large Liver Tumours  

PubMed Central

Radiofrequency ablation has become an accepted treatment option of patients with primary and metastatic liver tumours. We propose an ablation electrode array consisting of 4–8 blade shaped electrodes arrangend in a circular geometry for the treatment of large liver tumours. We developed a 3D code based on the finite difference method to evaluate the effect of diFferent numbers of electrodes (4, 6 and 8) and electrode distance on lesion size. The configuration with six electrodes can ablate a volume of 70 × 70 × 40 mm3 in approximately 5 minutes, with tissue temperature above 50 °C throughout the treatment volume. We then performed an experimental study in polyacrylamide gel in order to validate the theoretical results. The average temperature error between the simulation and the experiment was 3.8% at the center of the electrode array. This study shows that the proposed device potencially allows more rapid treatment of large tumours compared to current radiofrequency ablation devices.

dos Santos, I; Correia, D; Soares, A J M; Goes, J A; da Rocha, A F; Schutt, D; Haemmerich, D

2013-01-01

302

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

303

Radio-frequency ablation of renal cell carcinoma  

Microsoft Academic Search

Purpose: To report the authors' early experience with radio-frequency (RF) ablation of renal cell carcinoma.Materials and Methods: Twenty-four percutaneous RF ablation treatments for nine tumors were performed in eight patients with renal cell carcinoma. Indications included coexistent morbidity, previous surgery, or solitary kidney in patients with a life expectancy shorter than 10 years. Smaller (?3-cm) peripheral lesions (n = 3)

DA Gervais; FJ McGovern; BJ Wood; SN Goldberg; WS McDougal; PR Mueller

2002-01-01

304

Thermal Protection with 5% Dextrose Solution Blanket During Radiofrequency Ablation  

Microsoft Academic Search

A serious complication for any thermal radiofrequency ablation is thermal injury to adjacent structures, particularly the\\u000a bowel, which can result in additional major surgery or death. Several methods using air, gas, fluid, or thermometry to protect\\u000a adjacent structures from thermal injury have been reported. In the cases presented in this report, 5% dextrose water (D5W)\\u000a was instilled to prevent injury

Enn Alexandria Chen; Ziv Neeman; Fred T. Lee; Anthony Kam; Brad Wood

2006-01-01

305

Effects of multipolar electrode radiofrequency energy delivery on ventricular endocardium.  

PubMed

This study examined the effects of radiofrequency energy applied in a bipolar fashion with single as compared with multiple sequential applications at the canine endocardium. In this closed-chest model, radiofrequency energy (750 kHz) was delivered between two adjacent poles of an electrode catheter. Single applications were performed at distinct sites in the left (n = 30) and right ventricles (n = 29) of 13 normal dogs. A multiple sequential technique, which enlarges the ablated endocardial surface, was applied in the left (n = 13) and right ventricles (n = 4) of seven normal dogs and six dogs with remote myocardial infarction. Single applications (199 +/- 200 joules) resulted in lesions with a volume of 0.12 +/- 0.06 cm3 (range 0.03 to 0.31 cm3) and an endocardial surface area of 0.29 +/- 0.15 cm2 (range 0.06 to 0.63 cm2). Changes at the catheter/tissue interface led to a rise in impedance, restricting further enlargement of the necrosis. Sequential delivery of radiofrequency energy between poles 1 and 2, 2 and 3, and 3 and 4 of a quadripolar electrode catheter repeated 9 to 11 times in slightly different positions allowed a cumulative energy of 6571 +/- 3857 joules to be applied to the endocardium, resulting in a lesion volume of 0.84 +/- 0.38 cm3, with an endocardial lesion surface area of 3.7 +/- 1.2 cm2 (range 2.9 to 5.1 cm2). Histologically, all radiofrequency lesions were restricted to the endocardium/subendocardium with a small border zone of injury. Aggressive stimulation techniques did not induce ventricular tachycardia in any of the dogs before and 19 +/- 11.4 days after multiple sequential ablations.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2309603

Oeff, M; Langberg, J J; Franklin, J O; Chin, M C; Sharkey, H; Finkbeiner, W; Herre, J M; Scheinman, M M

1990-03-01

306

Computer simulations of ions in radio-frequency traps  

NASA Technical Reports Server (NTRS)

The motion of ions in a trapped-ion frequency standard affects the stability of the standard. In order to study the motion and structures of large ion clouds in a radio-frequency (RF) trap, a computer simulation of the system that incorporates the effect of thermal excitation of the ions was developed. Results are presented from the simulation for cloud sizes up to 512 ions, emphasizing cloud structures in the low-temperature regime.

Williams, A.; Prestage, J. D.; Maleki, L.; Djomehri, J.; Harabetian, E.

1990-01-01

307

Pulsed radiofrequency application in treatment of chronic zygapophyseal joint pain  

Microsoft Academic Search

BACKGROUND CONTEXT: Chronic zygapophyseal joint arthropathy is a cause of back and neck pain. One proposed method of treating facet joint pathology is ablation of medial branches and dorsal rami with pulsed radiofrequency (RF) waves.PURPOSE: Assessment of efficacy of pulsed RF application for treatment of chronic zygapophyseal joint pain.STUDY DESIGN\\/SETTING: Retrospective study of 114 patients at a pain management clinic.PATIENT

Georgi Mikeladze; Ramon Espinal; Robert Finnegan; James Routon; Dan Martin

2003-01-01

308

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

309

Right hemi-diaphragm paralysis following cardiac radiofrequency ablation.  

PubMed

Diaphragm paralysis may occur after traumatic phrenic nerve injury. Here we report three patients in whom right hemi-diaphragmatic paralysis developed after cardiac radiofrequency ablation. We hypothesise that local focused thermal energy at the time of the ablation may have caused direct neuronal damage by axonal coagulation necrosis. The prognosis for this type of injury may be reasonably good; two of the three patients fully recovered diaphragm function by 1 year. PMID:16488125

Swallow, E B; Dayer, M J; Oldfield, W L; Moxham, J; Polkey, M I

2006-09-01

310

A tunable EBG absorber for radio-frequency power imaging  

Microsoft Academic Search

Absorption characteristics of a tunable electromagnetic band-gap (EBG) absorber are analyzed, which is designed to capture 2d radio-frequency (RF) power distributions incident on the absorber surface. The EBG absorber has lumped resistors interconnecting the mushroom-type surface patches to absorb the incident RF power at the resonance frequency where the EBG structure exhibits a high-impedance feature. The absorbed RF power distribution

Satoshi Yagitani; Keigo Katsuda; Ryo Tanaka; Masayuki Nojima; Yoshiyuki Yoshimura; Hirokazu Sugiura

2011-01-01

311

Arthroscopic Gluteal Muscle Contracture Release With Radiofrequency Energy  

PubMed Central

Gluteal muscle contracture is common after repeated intramuscular injections and sometimes is sufficiently debilitating to require open surgery. We asked whether arthroscopic release of gluteal muscle contracture using radiofrequency energy would decrease complications with clinically acceptable results. We retrospectively reviewed 108 patients with bilateral gluteal muscle contractures (57 males, 51 females; mean age, 23.7 years). We used inferior, anterosuperior, and posterosuperior portals. With the patient lying laterally, we developed and enlarged a potential space between the gluteal muscle group and the subcutaneous fat using blunt dissection. Under arthroscopic guidance through the inferior portal, we débrided and removed fatty tissue overlying the contractile band of the gluteal muscle group using a motorized shaver introduced through the superior portal. Radiofrequency then was introduced through the superior portal to gradually excise the contracted bands from superior to inferior. Finally, hemostasis was ensured using radiofrequency. Patients were followed a minimum of 7 months (mean, 17.4 months; range, 7–42 months). At last followup, the adduction and flexion ranges of the hip were 45.3° ± 8.7° and 110.2° ± 11.9°, compared with 10.4° ± 7.2° and 44.8° ± 14.1° before surgery. No hip abductor contracture recurred and no patient had residual hip pain or gluteal muscle wasting. We found gluteal muscle contracture could be released effectively with radiofrequency energy. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. Electronic supplementary material The online version of this article (doi:10.1007/s11999-008-0595-7) contains supplementary material, which is available to authorized users.

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

2008-01-01

312

Measurement and modelling of a radiofrequency micro-thruster  

Microsoft Academic Search

A capacitively coupled radiofrequency (rf) (13.56 MHz) cylindrical argon micro-discharge expanding into a larger glass tube is studied by performing optical and electrical measurements over a pressure range 0.3–5 Torr and a rf power range 5–40 W. Measurements of the axial and radial plasma density profiles at the Paschen minimum near 1.5 Torr are used to develop a global model

C Charles; R W Boswell

2012-01-01

313

Effects of Radiofrequency Energy on Human Articular CartilageAn Analysis of 5 Systems  

Microsoft Academic Search

Background: Previous radiofrequency work has not rigidly controlled energy application to the articular cartilage, giving uncertain results published to date.Hypothesis: At minimal settings, radiofrequency probes cause cell death in measurable areas when applied to human articular cartilage.Study Design: Controlled laboratory study.Methods: Simulating operating room conditions, 5 commercially available radiofrequency probes were attached to a customized jig to standardize a minimal

Sean Caffey; Edward McPherson; Brian Moore; Thomas Hedman; C. Thomas Vangsness

2005-01-01

314

First report of transradial renal denervation with the dedicated radiofrequency Iberis™ catheter.  

PubMed

We describe the first use of transradial access renal denervation in a patient with resistant hypertension using a dedicated radiofrequency catheter (Iberis™; Terumo Medical Corporation, Tokyo, Japan). The system includes a generator and a 4 Fr single-use radiofrequency (RF) device which has to be introduced via a 6 Fr guiding catheter. Radiofrequency energy is delivered at the tip of the catheter. The system was CE approved in March 2013. PMID:24161437

Honton, Benjamin; Pathak, Atul; Sauguet, Antoine; Fajadet, Jean

2014-04-01

315

The Optical Detection of Radiofrequency Resonance  

Microsoft Academic Search

Calculations are made of the frequency, intensity, and polarization of the light emitted by an atom in a 2P-2S transition in a weak magnetic field having an oscillating component. Near resonance, or when the frequency of the oscillating component approaches the Larmor frequency of one of the two states involved in the radiation process, all of the quantities calculated are

F. Bitter

1949-01-01

316

Degradation of carbon nanotubes by electron bombardment in radio-frequency glow discharge afterglows  

NASA Astrophysics Data System (ADS)

A capacitively coupled radio-frequency afterglow is used to isolate the role of electron bombardment in the degradation process of muti-walled carbon nanotubes (MWNTs). MWNTs grown on a metal substrate act as a nanostructured anode that accelerate and focus electron bombardment, facilitated by the field enhancement effect. Tip-localized MWNT degradation has been observed in scanning electron microscope images showing the progression of the MWNT degradation process. This finding is confirmed by Raman spectra. GC-MS measurements indicate that the major products of MWNT degradation are short unsaturated hydrocarbons, identified as both propyne and 1,3-butadiyne vapours. This finding is corroborated by time-resolved optical emission spectroscopy during plasma oxidation of the degradation products. Analysis of the kinetics of plasma oxidation confirm that MWNT degradation produces species consistent with thermal evaporation, such as short carbon chains, C3-C4, but not monatomic or diatomic species, C1 and C2.

Vandsburger, Leron; Coulombe, Sylvain; Meunier, Jean-Luc

2013-12-01

317

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

PubMed

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

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

2014-02-01

318

Radio-Frequency Silicon-on-Insulator Modeling Considering the Neutral-Body Effect  

NASA Astrophysics Data System (ADS)

This paper presents small-signal modeling for state-of-the-art radio-frequency (RF) silicon-on-insulator (SOI) metal-oxide-semiconductor field effect transistors (MOSFETs). Especially, we have incorporated the neutral-body effect in our RF SOI model. This effect is significant in both RF extrinsic and intrinsic modeling stages. In addition, we have developed a physically-accurate parameter extraction method based on our analytical expressions. Our modeling results agree well with the measured data and can capture the frequency dependences of both output conductance and capacitance in the GHz frequency region. The anomalous S22 and S21 behaviors as well as the output conductance rising effect observed in our measurements can be predicted and described using the proposed model.

Wang, Sheng-Chun; Su, Pin; Chen, Kun-Ming; Lin, Chien-Ting; Liang, Victor; Huang, Guo-Wei

2008-04-01

319

The effect of radiofrequency hyperthermia on the Ca755 murine adenocarcinoma.  

PubMed

Radiofrequency (RF) was used to induce hyperthermia in the Ca755 murine adenocarcinoma. Thermal kinetic studies revealed a selective heating of tumors over normal tissues during RF, which occurred in larger but not smaller tumors. Small tumors required a significantly greater RF output than did larger neoplasms for heating to the tumoricidal range of 42 C. Rates of tumor growth were not changed after single RF treatments at 42 C, but tumors receiving three applications of RF were significantly smaller than a control group at 28 days tumor age. RF may be of value in the treatment of large neoplasms by using multiple applications; however, microscopic mitoses may not be affected directly without simultaneously damaging normal tissues in the RF field. PMID:7427906

Slotman, G J; Milazzo, J; Jain, K; Swaminathan, A P; Rush, B F

1980-11-01

320

Assessment of radiofrequency radiation within the vicinity of some GSM base stations in Ghana.  

PubMed

A radiofrequency (RF) electromagnetic radiation safety survey had been carried out at public access points in 46 towns with 76 Global Systems for Mobile communication cell sites in two major cities in Ghana. The objective was to determine the levels of RF field in residential areas, schools and market places, and compare the measured results with the guidelines set by the International Commission of Non-Ionising Radiation (ICNIRP). Measurements were made with log-periodic antenna coupled with spectrum analyzer. The results varied from 0.85 to 1.07 mW m(-2) and 0.78 to 1.19 mW m(-2) for the transmission frequencies of 900 and 1800 MHz, respectively. The result generally shows a compliance with the ICNIRP limit of 0.024 % but was 108 times higher than a similar survey carried out in Ghana 2 y ago. PMID:22262818

Deatanyah, P; Amoako, J K; Fletcher, J J; Asiedu, G O; Adjei, D N; Dwapanyin, G O; Amoatey, E A

2012-08-01

321

Improved fluid simulations of radio-frequency plasmas using energy dependent ion mobilities  

SciTech Connect

Symmetric and asymmetric capacitively coupled radio-frequency plasmas in oxygen at 40 Pa, 300 V voltage amplitude and a discharge gap of 40 mm are investigated by means of one-dimensional numerical semi-kinetic fluid modeling on the basis of a simplified reaction scheme including the dominant positive and negative ions, background gas, and electrons. An improved treatment, by accounting for the dependence of ion mobilities on E/N, is compared to the standard approach, based on using zero-field mobility values only. The charged particle dynamics as a result of direct electron impact ionization of oxygen, secondary electron release from the electrodes, the spatial distribution of all involved particles as well as impact of geometry and model modification on ion energies is analyzed and compared to independent simulations and experiments.

Greb, Arthur; Niemi, Kari; O'Connell, Deborah; Gans, Timo [York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom)] [York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom); Ennis, Gerard J.; MacGearailt, Niall [Intel Ireland Ltd., Leixlip (Ireland)] [Intel Ireland Ltd., Leixlip (Ireland)

2013-05-15

322

Self-compensated standing wave probe for characterization of radio-frequency plasmas.  

PubMed

A simple self-compensated Langmuir probe using the character of a standing wave is developed for characterization of radio-frequency (RF) discharge plasmas. This probe is based on a concept that the interference of RF field is eliminated at the node of a standing wave which exists ideally at one-fourth of the RF wavelength (?/4) away from the probe tip in the plasma. The fluctuation of plasma space potential is suppressed as confirmed by comparison with a non-compensated probe and a self-compensated probe using an inductor-capacitor (LC) resonant circuit. The plasma parameters obtained with the standing wave probe are in agreement with those with the LC resonant probe within discrepancy of 15% indicating high reliability of the results. PMID:24985819

Sung, Ta-Lun; Matsumura, Shosaku; Teii, Kungen; Teii, Shinriki

2014-06-01

323

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

324

A digital low-level radio-frequency system R&D for a 1.3 GHz nine-cell cavity  

NASA Astrophysics Data System (ADS)

To test and verify the performance of the digital low-level radio-frequency (LLRF) and tuner system designed by the IHEP RF group, an experimental platform with a retired KEK 1.3 GHz nine-cell cavity is set up. A radio-frequency (RF) field is established successfully in the cavity and the frequency of the cavity is locked by the tuner in ±0.5° (about ±1.2 kHz) at room temperature. The digital LLRF system performs well in a five-hour experiment, and the results show that the system achieves field stability at amplitude <0.1% (peak to peak) and phase <0.1° (peak to peak). This index satisfies the requirements of the International Linear Collider (ILC), and this paper describes this closed-loop experiment of the LLRF system.

Qiu, Feng; Gao, Jie; Lin, Hai-Ying; Liu, Rong; Ma, Xin-Peng; Sha, Peng; Sun, Yi; Wang, Guang-Wei; Wang, Qun-Yao; Xu, Bo

2012-03-01

325

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

PubMed

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

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

2005-10-01

326

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

SciTech Connect

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

Land, V.; Goedheer, W.J.; Akdim, M.R. [FOM Institute for Plasma Physics Rijnhuizen, Association Euratom-Fom, Trilateral Euregional Cluster, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands)

2005-10-01

327

Dielectric supported radio-frequency cavities  

DOEpatents

A device which improves the electrical and thermomechanical performance of an RF cavity, for example, in a disk-loaded accelerating structure. A washer made of polycrystalline diamond is brazed in the middle to a copper disk washer and at the outer edge to the plane wave transformer tank wall, thus dissipating heat from the copper disk to the outer tank wall while at the same time providing strong mechanical support to the metal disk. The washer structure eliminates the longitudinal connecting rods and cooling channels used in the currently available cavities, and as a result minimizes problems such as shunt impedance degradation and field distortion in the plane wave transformer, and mechanical deflection and uneven cooling of the disk assembly.

Yu, David U. L. (Rancho Palos Verdes, CA); Lee, Terry G. (Cupertino, CA)

2000-01-01

328

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

329

Efficient dipolar recoupling in the NMR of rotating solids. A sevenfold symmetric radiofrequency pulse sequence  

Microsoft Academic Search

A new radiofrequency pulse sequence is introduced for the efficient reintroduction of magnetic dipolar couplings in the magic-angle-spinning NMR of solids. The sequence involves seven phase-shifted radiofrequency pulse cycles, timed to span two rotational periods of the sample. Double-quantum coherences are excited with high efficiency in a rotating powder sample of zinc acetate-13C2.

Y. K Lee; N. D Kurur; M Helmle; O. G Johannessen; N. C Nielsen; M. H Levitt

1995-01-01

330

Efficacy of radiofrequency catheter ablation for ventricular tachycardia in healed myocardial infarction  

Microsoft Academic Search

Radiofrequency catheter ablation has been useful in the treatment of ventricular tachycardia (VT) in selected patients with healed myocardial infarction. Previous studies have demonstrated success rates of 60% to 96% for targeted VT morphologies; however, these studies included patients only after they have had successful mapping procedures and have received radiofrequency lesions. All patients referred for VT ablation from July

David J. Callans; Erica Zado; Brian H. Sarter; David Schwartzman; Charles D. Gottlieb; Francis E. Marchlinski

1998-01-01

331

The effect of radiofrequency energy on the length and temperature properties of the glenohumeral joint capsule  

Microsoft Academic Search

The purpose of this in vitro study was to evaluate the effect of radiofrequency energy on the length and temperature properties of the glenohumeral joint capsule in a sheep model. Dissected glenohumeral joint capsules were placed in a 37 degrees C tissue bath and treated with radiofrequency energy at temperature settings of 60 degrees, 65 degrees, 70 degrees, 75 degrees

SL Obrzut; P Hecht; K Hayashi; GS Fanton; G THABITIII

1998-01-01

332

TURP with the New Superpulsed Radiofrequency Energy:Mo re than a Gold Standard  

Microsoft Academic Search

Objective: Superpulsed radiofrequency, a new energy, has been developed and applied in transurethral resection of the prostate (TURP) using a regular cutting loop. The aim of the study was to evaluate the clinical application of superpulsed radiofrequency to reduce bleeding morbidity and to improve patient outcome. The original results of the experimental and clinical study are presented. Methods: From November

Mauro Dimitri

1999-01-01

333

An Increase in Body Temperature During Radiofrequency Ablation of Liver Tumors  

Microsoft Academic Search

Radiofrequency ablation (RFA) therapy using an active needle electrode inserted into liver tumors has been used clinically. To avoid hyperthermia, we investigated the relationship between the total output energy of the applied radiofrequency wave and changes in body tem- perature (BT) in patients receiving RFA. Fifteen pa- tients undergoing RFA of liver tumors with general an- esthesia were enrolled. The

Maiko Sawada; Seiji Watanabe; Hideaki Tsuda; Tatsuhiko Kano

2002-01-01

334

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

335

Precision test apparatus for evaluating the heating pattern of radiofrequency ablation devices  

Microsoft Academic Search

Radiofrequency has established itself as a useful technique for managing cardiac arrhythmias and treating soft tissue tumors. However, despite its pervasive use, many of the biophysical principals needed to fully understand and optimize the radiofrequency ablation technique have not been explored. We have designed a test rig that is useful for studying the heat transfer mechanisms that affect the outcome

I Chang; B Beard

2002-01-01

336

Ionizing and Non-Ionizing Radiation  

MedlinePLUS

... Decay Modes Radiation has a wide range of energies that form the electromagnetic spectrum (illustrated below). The ... ionizing radiation ionizing radiation Radiation that has enough energy to move around atoms in a molecule or ...

337

Nanometer-resolved radio-frequency absorption and heating in biomembrane hydration layers.  

PubMed

Radio-frequency (RF) electromagnetic fields are readily absorbed in biological matter and lead to dielectric heating. To understand how RF radiation interacts with macromolecular structures and possibly influences biological function, a quantitative description of dielectric absorption and heating at nanometer resolution beyond the usual effective medium approach is crucial. We report an exemplary multiscale theoretical study for biomembranes that combines (i) atomistic simulations for the spatially resolved absorption spectrum at a single planar DPPC lipid bilayer immersed in water, (ii) calculation of the electric field distribution in planar and spherical cell models, and (iii) prediction of the nanometer resolved temperature profiles under steady RF radiation. Our atomistic simulations show that the only 2 nm thick lipid hydration layer strongly absorbs in a wide RF range between 10 MHz and 100 GHz. The absorption strength, however, strongly depends on the direction of the incident wave. This requires modeling of the electric field distribution using tensorial dielectric spectral functions. For a spherical cell model, we find a strongly enhanced RF absorption on an equatorial ring, which gives rise to temperature gradients inside a single cell under radiation. Although absolute temperature elevation is small under conditions of typical telecommunication usage, our study points to hitherto neglected temperature gradient effects and allows thermal RF effects to be predicted on an atomistically resolved level. In addition to a refined physiological risk assessment of RF fields, technological applications for controlling temperature profiles in nanodevices are possible. PMID:24779642

Gekle, Stephan; Netz, Roland R

2014-05-01

338

Quantifying Local Stiffness Variations in Radiofrequency Ablations with Dynamic Indentation  

PubMed Central

Elastographic imaging can be used to monitor ablation procedures, however confident and clear determination of the ablation boundary is essential to ensure complete treatment of the pathological target. To investigate the potential for ablation boundary representation on elastographic images, local variations in the viscoelastic properties in radiofrequency ablated regions that were formed in vivo in porcine liver tissue were quantified using dynamic indentation. Spatial stiffness maps were then correlated to stained histology, the gold standard for determination of the ablation periphery or boundary. Regions of interest in eleven radiofrequency ablation samples were indented at 18–24 locations each, including the central zone of complete necrosis and more peripheral transition zones including normal tissue. Storage modulus and rate of stiffening were both greatest in the central ablation zone and decreased with radial distance away from the center. The storage modulus and modulus contrast at the ablation outer transition zone boundary were 3.1 ± 1.0 kPa and 1.6 ± 0.4, respectively, and 36.2 ± 9.1 kPa and 18.3 ± 5.5 at the condensation boundary within the ablation zone. Elastographic imaging modalities were then compared to gross pathology in ex vivo bovine liver tissue. Area estimated from strain, shear wave velocity, and gross pathology images were 470 mm2, 560 mm2, and 574 mm2, respectively, and ablation widths were 19.4 mm, 20.7 mm, and 23.0 mm. This study has provided insights into spatial stiffness distributions within radiofrequency ablations and suggests that low stiffness contrast on the ablation periphery leads to the observed underestimation of ablation extent on elastographic images.

DeWall, Ryan J.; Varghese, Tomy; Brace, Christopher L.

2012-01-01

339

[Submucosal bipolar radiofrequency therapy for treatment of turbinate hypertrophy].  

PubMed

Disturbance of nasal airflow occurs in about 30% of human population. Turbinate hypertrophy is frequently the base of many nasal obturative diseases. The aim of this study was to determine short- term and long term effects of the radiofrequency therapy (RFT) for patients with turbinate hypertrophy. Forty- one patients with inferior turbinate hypertrophy (19 females and 22 males) were enrolled in this study prospectively. The examination included: rhinoscopy, subiective visual analogue scale (VAS) score, in which a patient described his symptoms in points from 0, (always very good nasal airflow) to 10 points (always total obstruction) and anterior rhinomanometry. The clinical assessment was before radiofrequency-turbinectomy and within the days 7 to 25 afther this therapy (follow-up 1) and 12 months later (follow-up 2). RFT was performed in local anesthesia (1% Lidocain) by means of CELON. Rhinoscopy before RFT revealed turbinate hypertrophy, which was decreased in the follow-up examination. Subjective improvement of nasal airflow was felt by 39 patients (95%) at follow-up 1. At follow-up 2 fifteen patients (37%) reported a decreased nasal airflow when compared with the follow-up 1. Rhinomanometric results were better at follow-up 1 for the left side (p = 0,0003), the right side (p = 0,0002) and both sides altogether (p = 0,0001). The improvement continued at follow-up 2 for the left side (p = 0,0004), the right side (p = 0,001) and both sides (p = 0,001) when compared with rhinomanometry before RFT. There were not statistically significant differences between the rhinomanometric results at follow-up 1 and follow-up 2. Bipolar radiofrequency thermal ablation is an effective method for the therapy of turbinate hypertrophy. PMID:17847783

Luczaj, Jaros?aw; Rogowski, Marek

2007-01-01

340

The radio-frequency impedance of individual intrinsic Josephson junctions  

SciTech Connect

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

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

2009-12-21

341

Myoglobinuria After Laparoscopic Radiofrequency Ablation of Liver Tumors  

Microsoft Academic Search

Background  There are scant data in the literature about myoglobinuria after radiofrequency ablation (RFA) of liver tumors. The aim of\\u000a this study is to analyze the incidence and identify the risk factors involved in this complication after RFA.\\u000a \\u000a \\u000a \\u000a \\u000a Patients and Methods  An initial case of myoglobinuria and acute kidney injury (AKI) during laparoscopic liver RFA after 10 years of the liver ablation\\u000a program

John Rodriguez; Gurkan Tellioglu; Allan Siperstein; Eren Berber

2010-01-01

342

A Complicated Postsurgical Echinococcal Cyst Treated with Radiofrequency Ablation  

SciTech Connect

Surgery of hydatid cysts is often complicated with intrabiliary rupture (IBR), which if not recognized may lead to biliary fistula with rather high rates of morbidity and mortality. We report our experience with the application of radiofrequency (RF) ablation for the treatment of an operated hepatic echinococcal cyst which was complicated with biliocystic communication and cysteocutaneous fistula with bile leakage. RF ablation was performed under CT guidance into the remaining cyst through the cutaneous fistula. Since ablation of the cyst and the fistula the patient has been asymptomatic.

Thanos, L., E-mail: Loutharad@yahoo.com; Mylona, S. [Korgialeneio-Benakeio 'Red Cross Hospital of Athens', Department of Radiology (Greece); Brontzakis, P. [Korgialeneio-Benakeio 'Red Cross Hospital of Athens', Department of Surgery (Greece); Ptohis, N. [Korgialeneio-Benakeio 'Red Cross Hospital of Athens', Department of Radiology (Greece); Karaliotas, K. [Korgialeneio-Benakeio 'Red Cross Hospital of Athens', Department of Surgery (Greece)

2008-01-15

343

Successful treatment of multiple hepatocellular adenomas with percutaneous radiofrequency ablation  

PubMed Central

Hepatocellular adenoma (HCA) is one of the important complications of glycogen storage disease type?Ia (GSD-Ia) because it can be transformed into hepatocellular carcinoma. Although surgical resection is a standard treatment of choice for solitary HCA, multiple HCAs in GSD-Ia patients present as therapeutic challenges for curative treatment. Therefore, treatment strategy according to malignant potential is important in management of HCAs in GSD-Ia. The authors present a case of histologically proven multiple HCAs without ?-catenin mutations occurred in a GSD-Ia patient treated successfully with percutaneous radiofrequency ablation as a minimally invasive therapy.

Ahn, Sun Young; Park, Soo Young; Kweon, Young Oh; Tak, Won Young; Bae, Han Ik; Cho, Seung Hyun

2013-01-01

344

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

345

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

346

Successful treatment of multiple hepatocellular adenomas with percutaneous radiofrequency ablation.  

PubMed

Hepatocellular adenoma (HCA) is one of the important complications of glycogen storage disease type Ia (GSD-Ia) because it can be transformed into hepatocellular carcinoma. Although surgical resection is a standard treatment of choice for solitary HCA, multiple HCAs in GSD-Ia patients present as therapeutic challenges for curative treatment. Therefore, treatment strategy according to malignant potential is important in management of HCAs in GSD-Ia. The authors present a case of histologically proven multiple HCAs without ?-catenin mutations occurred in a GSD-Ia patient treated successfully with percutaneous radiofrequency ablation as a minimally invasive therapy. PMID:24259982

Ahn, Sun Young; Park, Soo Young; Kweon, Young Oh; Tak, Won Young; Bae, Han Ik; Cho, Seung Hyun

2013-11-14

347

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

348

Mediastinal fibrosis and radiofrequency radiation exposure: is there an association?  

PubMed

A 45-year-old officer, working for a period of 18 years at a military radar base, presented with progressive exertional dyspnea, dry cough, and hemoptysis. Subsequent evaluation demonstrated a left pulmonary artery occlusion as well as a left upper lobe bronchus stenosis, due to a dense fibrotic mediastinal mass. Histologically, this proved to be idiopathic mediastinal fibrosis (IMF). The development of IMF in a man exposed for a long period to radio-frequency radiation (RFR) is unique in the literature in English. The possible association of radiation exposure with IMF is discussed. PMID:1439233

Papandreou, L; Panagou, P; Bouros, D

1992-01-01

349

Bronchobiliary fistula after radiofrequency thermal ablation of hepatic tumor.  

PubMed

A broad spectrum of complications can occur after radiofrequency (RF) ablation of hepatic tumors, even though it has been accepted as a safe and effective technique for unresectable hepatic tumors. Recently, the rare complication of brochobiliary fistula was encountered after RF ablation in a patient with a metastatic tumor from stomach cancer. It was assumed to have developed from collateral damage to the adjacent diaphragm and lung base as well as biloma formation at the ablation zone. Symptomatic improvement was achieved by conservative management with an external drainage catheter, but the fistula was still persistent on a 2-month follow-up image. PMID:15758140

Kim, Young-Sun; Rhim, Hyunchul; Sung, Jung Hwan; Kim, Sung Kyu; Kim, Yongsoo; Koh, Byung Hee; Cho, On Koo; Kwon, Sung-Joon

2005-03-01

350

Further developments in oxidation of methane traces with radiofrequency discharge  

NASA Technical Reports Server (NTRS)

The radiofrequency discharge, previously shown to oxidize trace levels of methane in oxygen, was studied with contaminated air at 50, 600, and 760 torr. As with oxygen, the concentration of methane traces could be reduced by several orders of magnitude, and no organic reaction products were detected in the effluent; however, substantial concentrations of NOx (0.1-6%) were formed during treatment. The concentration of NOx was decreased by using a large diameter electrode. There is evidence that the process will oxidize N2 and NO as well as organic impurities in oxygen or oxygen/inert gas atmospheres.

Flamm, D. L.; Wydeven, T. J.

1977-01-01

351

Multiplexing of Radio-Frequency Single Electron Transistors  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

352

Bipolar radiofrequency treatment for snoring with mild to moderate sleep apnea: a comparative study between the radiofrequency assisted uvulopalatoplasty technique and the channeling technique  

Microsoft Academic Search

We compared radiofrequency techniques used in the treatment of snoring and obstructive sleep apnea [radiofrequency assisted\\u000a uvulopalatoplasty (RAUP) and channeling] as regard the efficacy and morbidity. A pilot, prospective randomized single blinded\\u000a study was conducted on 40 patients in the ENT Department, Kasr Al-Aini Hospital, Cairo University during the period from April\\u000a to December 2003. Patients were randomized into two groups

Ahmed Bassiouny; Ahmed El Salamawy; Mohamed Abd El-Tawab; Ahmed Atef

2007-01-01

353

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

PubMed

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

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

2006-06-01

354

Percutaneous plasma mediated radiofrequency ablation of spinal osteoid osteomas.  

PubMed

Plasma mediated radiofrequency ablation (pmRFA) may allow for the percutaneous treatment of spinal tumors with a decreased risk of thermal injury to neural structures compared with traditional (radiofrequency or interstitial laser) ablation. However, usage of pmRFA has not been previously reported for a primary bone tumor, including an osteoid osteoma. Three patients with a spinal osteoid osteoma underwent pmRFA. The procedure was performed under computed tomography guidance using the 11 gauge Coblation SpineWand (ArthroCare). One lesion (at T11) was directly abutting the spinal canal. With an average follow-up of 20.7 (range 16-24) months, the mean Visual Analog Scale score for back pain decreased from 8.67 to 0.67 and no patient experienced tumor recurrence. pmRFA of spinal osteoid osteomas is feasible, even when the tumor is abutting the spinal canal. Larger studies with a longer follow-up are needed to further delineate the safety and efficacy of this technique. PMID:21990513

Dasenbrock, Hormuzdiyar H; Gandhi, Dheeraj; Kathuria, Sudhir

2012-05-01

355

Transcatheter radiofrequency ablation in the canine right atrium.  

PubMed

The feasibility of using radiofrequency energy for potential ablation of atrial tachycardia foci was assessed by performing transcatheter ablation in the right atrium in 11 closed-chest dogs. Single-pulsed radiofrequency (750 kHz) energy was delivered to the right atrium (29-254 J) between the tip electrode of a standard 6 Fr quadripolar catheter and a chest patch electrode. There were no significant arrhythmias or complications noted. Dogs were sacrificed 0-29 days after ablation to assess acute and subacute effects of this technique. Of 47 attempted ablations, 36 well-delineated coagulative lesions were identified. The lesions had a mean dimension of 5.2 +/- 0.57 mm (+/- SE) in length, 3.9 +/- 0.27 mm in width, and 2.6 +/- 0.17 mm in depth. Transmural necrosis was noted in 6 of 36 lesions (17%) without perforation. A thin layer of mural thrombus was found in 5 of 36 lesions (14%). Thus, this technique appears to be feasible and relatively safe for right atrial ablations in a short-term follow-up period. The potential application of this method to ablate right atrial tachycardia foci needs to be further investigated. PMID:10150927

Lee, M A; Huang, S K; Graham, A R; Gorman, G; Bharati, S; Lev, M

1991-01-01

356

Radiofrequency ablation as first-line treatment of varicose veins.  

PubMed

Endovascular radiofrequency ablation is a minimally invasive method to safely treat symptomatic refluxing varicose veins. A retrospective chart review was used to determine patient demographics, disease severity, treatment algorithm, and outcome in patients who underwent radiofrequency ablation of symptomatic refluxing veins that had failed conservative management. Statistical analysis was done using GraphPad Demo Version (San Diego, CA). Two hundred forty-one limbs in 179 patients (average age, 53 years; 73% females, 27% males) were treated. Preprocedure Clinical Etiological Anatomic and Pathologic (CEAP) scores were C2s: 236, C3s: 4, and C5s:1. Procedures were performed in the office using tumescent anesthetic; all patients could ambulate immediately after the procedure. Postprocedure total occlusion (TO) rate was seen in 93 per cent of limbs (223 limbs) at 3 months and 91 per cent of limbs (220 limbs) at 12 months posttreatment. No relationship was found between patients who did not have total occlusion and age, sex, diameter of veins, CEAP scores, preoperative reflux time, and volume of tumescent anesthetic (P > 0.05). The VNUS procedure is an in-office, minimally invasive procedure with a low complication rate and quick recovery. Total occlusion rates are high and there is improvement in disease severity after treatment. PMID:24666862

Avery, John; Kumar, Keshav; Thakur, Vijaya; Thakur, Anjani

2014-03-01

357

Health implications of exposure to radiofrequency/microwave energies  

PubMed Central

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

Michaelson, S M

1982-01-01

358

Understanding Pound-Drever-Hall locking using voltage controlled radio-frequency oscillators: An undergraduate experiment  

NASA Astrophysics Data System (ADS)

We have developed a senior undergraduate experiment that illustrates frequency stabilization techniques using radio-frequency electronics. The primary objective is to frequency stabilize a voltage controlled oscillator to a cavity resonance at 800 MHz using the Pound-Drever-Hall method. This technique is commonly applied to stabilize lasers at optical frequencies. By using only radio-frequency equipment, it is possible to systematically study aspects of the technique more thoroughly, inexpensively, and free from eye hazards. Students also learn about modular radio-frequency electronics and basic feedback control loops. By varying the temperature of the resonator, students can determine the thermal expansion coefficients of copper, aluminum, and super invar.

Liekhus-Schmaltz, C. E.; Martin, J. D. D.

2012-03-01

359

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

SciTech Connect

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

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

1996-11-01

360

Method for in situ characterization of radiofrequency heating in parallel transmit MRI.  

PubMed

In ultra-high-field magnetic resonance imaging, parallel radiofrequency (RF) transmission presents both opportunities and challenges for specific absorption rate management. On one hand, parallel transmission provides flexibility in tailoring electric fields in the body while facilitating magnetization profile control. On the other hand, it increases the complexity of energy deposition as well as possibly exacerbating local specific absorption rate by improper design or delivery of RF pulses. This study shows that the information needed to characterize RF heating in parallel transmission is contained within a local power correlation matrix. Building upon a calibration scheme involving a finite number of magnetic resonance thermometry measurements, this work establishes a way of estimating the local power correlation matrix. Determination of this matrix allows prediction of temperature change for an arbitrary parallel transmit RF pulse. In the case of a three transmit coil MR experiment in a phantom, determination and validation of the power correlation matrix were conducted in less than 200 min with induced temperature changes of <4°C. Further optimization and adaptation are possible, and simulations evaluating potential feasibility for in vivo use are presented. The method allows general characteristics indicative of RF coil/pulse safety determined in situ. PMID:22714806

Alon, Leeor; Deniz, Cem Murat; Brown, Ryan; Sodickson, Daniel K; Zhu, Yudong

2013-05-01

361

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

PubMed

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

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

2014-05-01

362

Effect of the levitating microparticle cloud on radiofrequency argon plasma  

SciTech Connect

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. [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse 1, 85741, Garching (Germany)

2010-06-16

363

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

364

Atrial flutter: arrhythmia circuit and basis for radiofrequency catheter ablation.  

PubMed

The term atrial flutter was introduced 90 years ago for an arrhythmia with a unique electrocardiographic pattern. The development of endocardial mapping techniques in the last decade allowed the detailed characterization of the tachycardia circuit and the identification of the cavotricuspid isthmus as its critical part. This review stresses the position of atrial flutter in the new classification of atrial tachycardias and focuses on its unique electrophysiological characteristics and different variants described in humans. Transcatheter radiofrequency ablation across the cavotricuspid isthmus constitutes a feasible and safe therapy, which prevents flutter recurrences during the long-term follow-up. This paper describes the different techniques that validate bidirectional isthmus block, which is an important endpoint for successful ablation. PMID:12898804

Földesi, Csaba; Pandozi, Claudio; Peichl, Petr; Bulava, Alan; Castro, Antonio; Lamberti, Filippo; Calò, Leonardo; Loricchio, Maria Luisa; Santini, Massimo

2003-06-01

365

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

366

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

367

Treatment of trigeminal neuralgia: role of radiofrequency ablation.  

PubMed

Trigeminal neuralgia (TN) is a neuropathic pain condition affecting the face. It has a significant impact on the quality of life and physical function of patients. Evidence suggests that the likely etiology is vascular compression of the trigeminal nerve leading to focal demyelination and aberrant neural discharge. Secondary causes such as multiple sclerosis or brain tumors can also produce symptomatic TN. Treatment must be individualized to each patient. Carbamazepine remains the drug of choice in the first-line treatment of TN. Minimally invasive interventional pain therapies and surgery are possible options when drug therapy fails. Younger patients may benefit from microvascular decompression. Elderly patients with poor surgical risk may be more suitable for percutaneous trigeminal nerve rhizolysis. The technique of radiofrequency rhizolysis of the trigeminal nerve is described in detail in this review. PMID:21311718

Emril, Dessy R; Ho, Kok-Yuen

2010-01-01

368

Transurethral radiofrequency hot balloon thermal therapy in chronic nonbacterial prostatitis.  

PubMed

There is no universally successful therapy for chronic nonbacterial prostatitis. Successful outcomes of treatment have been independently reported with transurethral heat therapy and balloon dilation. The THERP transurethral "hot balloon" uses balloon dilation of the prostatic urethra and radiofrequency heating of the prostate. Patients with refractory chronic nonbacterial prostatitis were assessed with validated prostatitis-specific symptom indices prior to, 3, and 6 months after 900 seconds of THERP treatment. Although early results appeared promising the long-term results in four patients led to early termination of the study. Although one patient did have improvement at 6 months, no patient reported improvement at 9 months, and the adverse events (urinary retention, retrograde ejaculation, hematuria, urethral stricture, worsening of symptoms) of this treatment in prostatitis patients was significant. This study demonstrated no sustainable efficacy and substantial adverse effects for the use of combination balloon dilation and heat therapy for patients with chronic nonbacterial prostatitis. PMID:9800889

Nickel, J C; Siemens, D R; Johnston, B

1998-09-01

369

Laparoscopic Ultrasound-Guided Radiofrequency Ablation of Uterine Fibroids  

SciTech Connect

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

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

2006-08-15

370

Squamous cell carcinoma after radiofrequency ablation for Barrett's dysplasia  

PubMed Central

Barrett’s oesophagus (BO) is a usually indolent condition that occasionally requires endoscopic therapy. Radiofrequency ablation (RFA) is an effective endoscopic treatment for high grade dysplasia (HGD) and intramucosal cancer in BO. It has a good efficacy, durability and safety profile although complications can occur. Here we describe a case of RFA in a patient with high grade dysplasia. Although the response to treatment was initially very good with the development of neosquamous epithelium, the patient very rapidly developed a squamous cell cancer of the oesophagus confirmed on radiology, histology and immunohistochemistry. Sanger sequencing confirmed that the original HGD and the squamous cell cancer (SCC) were derived from separate clonal origins. The report highlights the fact that SCC of the oesophagus has been noted after endoscopic ablation for BO previously and suggest that ablation of BO may encourage the clonal expansion of cells carrying carcinogenic mutations once a dominant clonal population has been eradicated.

Zeki, Sebastian S; Haidry, Rehan; Justo-Rodriguez, Manuel; Lovat, Laurence B; Wright, Nicholas A; McDonald, Stuart A

2014-01-01

371

Characteristics of Radio-Frequency Circuits Utilizing Ferroelectric Capacitors  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

372

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

373

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

374

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

375

Factors Limiting Complete Tumor Ablation by Radiofrequency Ablation  

SciTech Connect

The purpose of this study was to determine radiological or physical factors to predict the risk of residual mass or local recurrence of primary and secondary hepatic tumors treated by radiofrequency ablation (RFA). Eighty-two patients, with 146 lesions (80 hepatocellular carcinomas, 66 metastases), were treated by RFA. Morphological parameters of the lesions included size, location, number, ultrasound echogenicity, computed tomography density, and magnetic resonance signal intensity were obtained before and after treatment. Parameters of the generator were recorded during radiofrequency application. The recurrence-free group was statistically compared to the recurrence and residual mass groups on all these parameters. Twenty residual masses were detected. Twenty-nine lesions recurred after a mean follow-up of 18 months. Size was a predictive parameter. Patients' sex and age and the echogenicity and density of lesions were significantly different for the recurrence and residual mass groups compared to the recurrence-free group (p < 0.05). The presence of an enhanced ring on the magnetic resonance control was more frequent in the recurrence and residual mass groups. In the group of patients with residual lesions, analysis of physical parameters showed a significant increase (p < 0.05) in the time necessary for the temperature to rise. In conclusion, this study confirms risk factors of recurrence such as the size of the tumor and emphasizes other factors such as a posttreatment enhanced ring and an increase in the time necessary for the rise in temperature. These factors should be taken into consideration when performing RFA and during follow-up.

Paulet, Erwan, E-mail: erwanpaulet@yahoo.fr; Aube, Christophe [University Hospital Angers, Department of Radiology (France); Pessaux, Patrick [University Hospital Angers, Department of Visceral Surgery (France); Lebigot, Jerome [University Hospital Angers, Department of Radiology (France); Lhermitte, Emilie [University Hospital Angers, Department of Visceral Surgery (France); Oberti, Frederic [University Hospital Angers, Department of Hepato-Gastroenterology (France); Ponthieux, Anne [University Hospital Angers, Clinical Research Center (France); Cales, Paul [University Hospital Angers, Department of Hepato-Gastroenterology (France); Ridereau-Zins, Catherine [University Hospital Angers, Department of Radiology (France); Pereira, Philippe L. [Eberhard-Karls University, Department of Diagnostic Radiology (Germany)

2008-01-15

376

Electronics and Electrical Engineering Laboratory Radio-Frequency Technology Division: Programs, Activities, and Accomplishments.  

National Technical Information Service (NTIS)

Contents: Welcome; Mission; Division Function; Our Technical Programs; Radio-Frequency Technology Division Organization; Fundamental Microwave Quantities (Power and Voltage, Scattering Parameters and Impedance, Noise); High-Speed Microelectronics; Wireles...

2001-01-01

377

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...

378

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

379

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

380

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

381

Application of a Finite-Difference Technique to the Human Radiofrequency Dosimetry Problem.  

National Technical Information Service (NTIS)

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. Co...

R. J. Spiegel M. B. E. Fatmi K. S. Kunz

1985-01-01

382

Radio-Frequency Driven Dielectric Heaters for Non-Nuclear Testing in Nuclear Core Development  

NASA Technical Reports Server (NTRS)

Apparatus and methods are provided through which a radiofrequency dielectric heater has a cylindrical form factor, a variable thermal energy deposition through variations in geometry and composition of a dielectric, and/or has a thermally isolated power input.

Sims, William Herbert, III (Inventor); Godfroy, Thomas J. (Inventor); Bitteker, Leo (Inventor)

2006-01-01

383

Multilevel radiofrequency ablation to the soft palate and tongue base: tips and pitfalls.  

PubMed

The objective of the study is to increase awareness and understanding of the techniques and safety measures to minimise complications and improve patient outcomes. Literature review using MedLine and keywords snoring; obstructive sleep apnoea; radiofrequency ablation; electrosurgery; palate; tongue base was conducted. There is no accepted gold standard technique for radiofrequency ablation; to date, there is no published literature regarding common tips and pitfalls in radiofrequency application specifically for superficial applications and second-stage surgery. Surgery for snoring and obstructive sleep apnoea is typically multilevel. Pre-operative patient assessment and selection are critical to ensure good outcomes. Radiofrequency is generally safe and efficacious in this subset of patients. However, as with all surgery, it is operator-dependent. In particular, we emphasise the methodology for second-stage surgery, optimising visualisation and avoiding ulceration/fistulation of the soft palate, which are previously undescribed in the literature. PMID:24337879

Virk, Jagdeep Singh; Nouraei, Reza; Kotecha, Bhik

2014-06-01

384

Radiofrequency Ablation of Breast Cancer: First Report of an Emerging Technology  

Microsoft Academic Search

PATIENTS, MATERIALS, AND METHODS RESULTS COMMENT References Abstract Hypothesis: Radiofrequency (RF) energy applied to breast cancers will result in cancer cell death. Design: Prospective nonrandomized interventional trial. Setting: A university hospital tertiary care center.

Stefanie S. Jeffrey; Robyn L. Birdwell; Debra Ikeda; Bruce L. Daniel; Kent W. Nowels; Stephen M. DVM

1999-01-01

385

Comparison of Power and Temperature-Guided Radiofrequency Modification of the Atrioventricular Node  

Microsoft Academic Search

The purpose of this study was to compare the performance and clinical outcome of radiofrequency ablation of the substrate of atrioventricular (AV) nodal reentrant tachycardia (AVNRT) when guided by power output or temperature monitoring. Two sequential multicenter studies of power-controlled and open-loop, temperature-controlled radiofrequency ablation were analyzed in 171 patients undergoing AV node modification for the treatment of AVNRT. After

Neal G. Kavesh; Mark R. Gosnell; Stephen R. Shorofsky; Michael R. Gold

1997-01-01

386

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

PubMed Central

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

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

2012-01-01

387

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

Microsoft Academic Search

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

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

2010-01-01

388

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

389

Development of an in vivo tumor-mimic model for learning radiofrequency ablation  

Microsoft Academic Search

Radiofrequency ablation requires accurate probe placement using ultrasound guidance. The purpose of this study was to develop\\u000a an in vivo tumor-mimic model for learning open and laparoscopic radiofrequency ablation. Tumor-mimics were created in ex vivo\\u000a porcine livers by injecting a mixture of 3% agarose, 3% cellulose, 7% glycerol, and 0.05% methylene blue, which formed 1 cm\\u000a hyperechoic, discrete lesions on

Daniel J. Scott; William N. Young; Lori M. Watumull; Guy Lindberg; Jason B. Fleming; Robert V. Rege; Ron J. Brawn; Daniel B. Jones

2000-01-01

390

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

391

Culturing of cells as influenced by exposure to AC and DC fields  

NASA Astrophysics Data System (ADS)

This paper is aimed at investigating culturing of living cells as influenced by exposure to AC and DC ionized and non-ionized fields in a point-to-plane gap. A cell suspension including yeast was placed on the ground plane at the gap axis and exposed to AC and DC fields of varying magnitudes. The effect of exposure time, frequency of the AC fields and magnitude of the applied fields on the survival rate of cells was investigated. The survival rate was also investigated as influenced by blowing the ionized field by air.

Abdel-Salam, M.; Nakano, M.; Tanino, M.; Mizuno, A.

2008-12-01

392

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

393

Effects of Cell Phone Radiofrequency Signal Exposure on Brain Glucos Metabolism  

SciTech Connect

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. To evaluate if acute cell phone exposure affects brain glucose metabolism, a marker of brain activity. 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 ({sup 18}F)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 cm{sup 3}) and P < .05 (corrected for multiple comparisons) were considered significant. Brain glucose metabolism computed as absolute metabolism ({micro}mol/100 g per minute) and as normalized metabolism (region/whole brain). 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 {micro}mol/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). 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, N.D.; Wang, G.; Volkow, N.D.; Tomasi, D.; Wang, G.-J.; Vaska, P.; Fowler, J.S.; Telang, F.; Alexoff, D.; Logan, J.; Wong, C.

2011-03-01

394

Workgroup Report: Base Stations and Wireless Networks--Radiofrequency (RF) Exposures and Health Consequences  

PubMed Central

Radiofrequency (RF) waves have long been used for different types of information exchange via the airwaves—wireless Morse code, radio, television, and wireless telephony (i.e., construction and operation of telephones or telephonic systems). Increasingly larger numbers of people rely on mobile telephone technology, and health concerns about the associated RF exposure have been raised, particularly because the mobile phone handset operates in close proximity to the human body, and also because large numbers of base station antennas are required to provide widespread availability of service to large populations. The World Health Organization convened an expert workshop to discuss the current state of cellular-telephone health issues, and this article brings together several of the key points that were addressed. The possibility of RF health effects has been investigated in epidemiology studies of cellular telephone users and workers in RF occupations, in experiments with animals exposed to cell-phone RF, and via biophysical consideration of cell-phone RF electric-field intensity and the effect of RF modulation schemes. As summarized here, these separate avenues of scientific investigation provide little support for adverse health effects arising from RF exposure at levels below current international standards. Moreover, radio and television broadcast waves have exposed populations to RF for > 50 years with little evidence of deleterious health consequences. Despite unavoidable uncertainty, current scientific data are consistent with the conclusion that public exposures to permissible RF levels from mobile telephony and base stations are not likely to adversely affect human health.

Valberg, Peter A.; van Deventer, T. Emilie; Repacholi, Michael H.

2007-01-01

395

Most cancer in firefighters is due to radio-frequency radiation exposure not inhaled carcinogens.  

PubMed

Recent reviews and reports of cancer incidence and mortality in firefighters conclude that they are at an increased risk of a number of cancers. These include leukemia, multiple myeloma, non-Hodgkin's lymphoma, male breast cancer, malignant melanoma, and cancers of the brain, stomach, colon, rectum, prostate, urinary bladder, testes, and thyroid. Firefighters are exposed to a long list of recognized or probable carcinogens in combustion products and the presumed route of exposure to these carcinogens is by inhalation. Curiously, respiratory system cancers and diseases are usually not increased in firefighters as they are in workers exposed to known inhaled carcinogens. The list of cancers with increased risk in firefighters strongly overlaps the list of cancers at increased risk in workers exposed to electromagnetic fields (EMF) and radiofrequency radiation (RFR). Firefighters have increased exposure to RFR in the course of their work, from the mobile two-way radio communications devices which they routinely use while fighting fires, and at times from firehouse and fire vehicle radio transmitters. I suggest that some of the increased cancer risk in firefighters is caused by RFR exposure, and is therefore preventable. The precautionary principle should be applied to reduce the risk of cancer in firefighters, and workman's compensation rules will necessarily need to be modified. PMID:19464814

Milham, S

2009-11-01

396

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

397

Exposure to 1800 MHz radiofrequency radiation impairs neurite outgrowth of embryonic neural stem cells.  

PubMed

A radiofrequency electromagnetic field (RF-EMF) of 1800?MHz is widely used in mobile communications. However, the effects of RF-EMFs on cell biology are unclear. Embryonic neural stem cells (eNSCs) play a critical role in brain development. Thus, detecting the effects of RF-EMF on eNSCs is important for exploring the effects of RF-EMF on brain development. Here, we exposed eNSCs to 1800?MHz RF-EMF at specific absorption rate (SAR) values of 1, 2, and 4?W/kg for 1, 2, and 3 days. We found that 1800?MHz RF-EMF exposure did not influence eNSC apoptosis, proliferation, cell cycle or the mRNA expressions of related genes. RF-EMF exposure also did not alter the ratio of eNSC differentiated neurons and astrocytes. However, neurite outgrowth of eNSC differentiated neurons was inhibited after 4?W/kg RF-EMF exposure for 3 days. Additionally, the mRNA and protein expression of the proneural genes Ngn1 and NeuroD, which are crucial for neurite outgrowth, were decreased after RF-EMF exposure. The expression of their inhibitor Hes1 was upregulated by RF-EMF exposure. These results together suggested that 1800?MHz RF-EMF exposure impairs neurite outgrowth of eNSCs. More attention should be given to the potential adverse effects of RF-EMF exposure on brain development. PMID:24869783

Chen, Chunhai; Ma, Qinlong; Liu, Chuan; Deng, Ping; Zhu, Gang; Zhang, Lei; He, Mindi; Lu, Yonghui; Duan, Weixia; Pei, Liping; Li, Min; Yu, Zhengping; Zhou, Zhou

2014-01-01

398

Bronchopleural fistula after non small cell lung cancer radiofrequency ablation: what it implying to us?  

PubMed Central

Abstract Radiofrequency ablation (RFA) is an alternative method to treat the inoperable NSCLC and there were few serious complications after RFA therapy have been reported. Here, we reported a NSCLC patient endured empyema after treatment by RFA for one month. There was a 20?×?25?×?20 mm mass on the right middle lobe by CT scan before RFA and a huge gas cavity with liquid was found in the right chest cavity after RFA treatment for twenty- eight days. A hole in the right middle lobe was found with large amount of pus in the pleural cavity as well as the bronchopleural fistula (BPF) during the operation. Results from the postoperative pathology showed a multiple small foci differentiated adenocarcinoma, partial bronchiolar-alveolar carcinoma, 0.5 cm away around the hole at the same time. It is difficult to diagnose and treat the rare complication of BPF, while, the larger field of ablation might be helpful to postpone the tumor local progression. Therefore, surgery was a good option for BPF especially when an empyema occurred. Virtual slides The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/8028049341122276.

2013-01-01

399

Exposure to 1800 MHz radiofrequency radiation impairs neurite outgrowth of embryonic neural stem cells  

PubMed Central

A radiofrequency electromagnetic field (RF-EMF) of 1800?MHz is widely used in mobile communications. However, the effects of RF-EMFs on cell biology are unclear. Embryonic neural stem cells (eNSCs) play a critical role in brain development. Thus, detecting the effects of RF-EMF on eNSCs is important for exploring the effects of RF-EMF on brain development. Here, we exposed eNSCs to 1800?MHz RF-EMF at specific absorption rate (SAR) values of 1, 2, and 4?W/kg for 1, 2, and 3 days. We found that 1800?MHz RF-EMF exposure did not influence eNSC apoptosis, proliferation, cell cycle or the mRNA expressions of related genes. RF-EMF exposure also did not alter the ratio of eNSC differentiated neurons and astrocytes. However, neurite outgrowth of eNSC differentiated neurons was inhibited after 4?W/kg RF-EMF exposure for 3 days. Additionally, the mRNA and protein expression of the proneural genes Ngn1 and NeuroD, which are crucial for neurite outgrowth, were decreased after RF-EMF exposure. The expression of their inhibitor Hes1 was upregulated by RF-EMF exposure. These results together suggested that 1800?MHz RF-EMF exposure impairs neurite outgrowth of eNSCs. More attention should be given to the potential adverse effects of RF-EMF exposure on brain development.

Chen, Chunhai; Ma, Qinlong; Liu, Chuan; Deng, Ping; Zhu, Gang; Zhang, Lei; He, Mindi; Lu, Yonghui; Duan, Weixia; Pei, Liping; Li, Min; Yu, Zhengping; Zhou, Zhou

2014-01-01

400

Comparison of a global model to semi-kinetic fluid simulations for atmospheric pressure radio-frequency plasmas  

NASA Astrophysics Data System (ADS)

A global model of a homogeneous plasma bulk oscillating between electron-free radio-frequency (rf) sheaths is developed. Particle and power balance, including ohmic heating loss for bulk-electrons and ions in the sheaths, yield the bulk electron temperature and density. Explicit time dependence of the reduced bulk electric field and correspondingly of the total ionization rate and electron transport coefficients is accounted for. Results for a gas mixture of 0.5 vol% oxygen in helium at atmospheric pressure within a 1 mm discharge gap as a function of the 13.56 MHz rf power density are presented and compared with a semi-kinetic 1D-fluid simulation. The quality of agreement is critically analyzed and correlated with the individual global model assumptions.

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

2013-06-01

401

Radiofrequency catheter ablation of atypical atrial flutter in dogs.  

PubMed

Five dogs were presented to our institution for fatigue caused by an incessant supraventricular tachycardia. In all dogs, an ECG on admission showed a narrow QRS complex tachycardia with a median ventricular cycle length of 220 ms (range 180-360 ms), and a positive atrial depolarization identifiable in the ST segment following the previous QRS complex. There was a 1:1 atrioventricular conduction ratio in all but one dog, which presented with 2:1 atrioventricular block. Electrophysiologic studies identified the underlying arrhythmogenic mechanism as a right atrial macro-reentrant tachycardia with two distinct isthmic areas: right septal (RS) in three dogs and right atrial free wall (RAFW) in two dogs. Linear radiofrequency catheter ablation was performed during tachycardia in all dogs at the identified isthmic area, which acutely blocked the macroreentrant circuit. At 18-month follow-up, 3 dogs (1 with RAFW isthmus and 2 with RS isthmus) showed no recurrence of the arrhythmia on Holter monitoring. One dog with RS isthmus showed recurrence of the supraventricular tachycardia 15 days post-ablation, and 1 dog with RAFW isthmus presented with persistent atrial fibrillation 2 months post-ablation. PMID:24461642

Santilli, Roberto A; Ramera, Lucia; Perego, Manuela; Moretti, Paolo; Spadacini, Giammario

2014-03-01

402

Radio-Frequency Current Drive in DIII-D  

SciTech Connect

Two methods of radio-frequency (rf) current drive that are well suited to controlling and sustaining the current profile in burning plasma experiments have been studied in the DIII-D tokamak. Fast-wave current drive (FWCD) gave centrally peaked current densities that increased linearly with central electron temperature. While high harmonic absorption of the fast waves on energetic beam ions could reduce the available power for current drive, FWCD figures of merit as high as {gamma}{sub FW} = 0.5 x 10{sup 19} A/m{sup 2}.W were still achieved. Electron cyclotron current drive (ECCD) was shown to be localized to the region of power deposition, with a current drive efficiency that decreased as the magnetic well depth increased. The detrimental effect of the magnetic well could be mitigated by raising the electron beta. ECCD figures of merit as high as {gamma}{sub EC} = 0.5 x 10{sup 19} A/m{sup 2}.W were measured for central deposition. The experimental FWCD and ECCD were both extensively tested against theoretical models and were found to be in excellent agreement. Validation of these predictive models of rf current drive aids in scenario development for next-step tokamaks.

Petty, C.C. [General Atomics (United States)

2005-10-15

403

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

404

[Transvesical radiofrequency needle ablation on prostatic benign hyperplasia].  

PubMed

Transurethral needle ablation (TUNA) of the prostate is an effective method of thermal treatment of patients with benign prostatic hyperplasia (BPH). Suprapubic transvesical access was used in order to extend indications for interstitial application of radiofrequency energy. Transvesical needle ablation (TVNA) was performed in 89 patients with BPH under conditions of chronic ischuria or in the presence of a suprapubic cystostoma. A cystoscope with an attachment for fixation and insertion of a needle electrode into prostatic tissue is inserted into the bladder through a newly created or adapted suprapubic access. The position of the needle is monitored by transurethral sonography. The ablation protocol is virtually the same as transurethral. Spontaneous urination normalized in 63 (70.8%) patients within 12 months. I-PSS, Qol, Qmax, RU, and PQmax improved. The prostate volume decreased by 1-.5%. TVNA is more effective than TUNA as a less invasive method which allows interventions under local anesthesia; there are virtually no contraindications to the use of TVNA and in many patients it can be performed in an outpatient setting. PMID:11186320

Arustamov, D L; Mukhtarov, Sh T; Arustamov, L D

2000-01-01

405

Radiofrequency Ablation of Lung Malignancies: Where Do We Stand?  

SciTech Connect

Percutaneous radiofrequency (RF) ablation is a minimally invasive technique used to treat solid tumors. Because of its ability to produce large volumes of coagulation necrosis in a controlled fashion, this technique has gained acceptance as a viable therapeutic option for unresectable liver malignancies. Recently, investigation has been focused on the clinical application of RF ablation in the treatment of lung malignancies. In theory, lung tumors are well suited to RF ablation because the surrounding air in adjacent normal parenchyma provides an insulating effect, thus facilitating energy concentration within the tumor tissue. Experimental studies in rabbits have confirmed that lung RF ablation can be safely and effectively performed via a percutaneous, transthoracic approach, and have prompted the start of clinical investigation. Pilot clinical studies have shown that RF ablation enables successful treatment of relatively small lung malignancies with a high rate of complete response and acceptable morbidity, and have suggested that the technique could represent a viable alternate or complementary treatment method for patients with non-small cell lung cancer or lung metastases of favorable histotypes who are not candidates for surgical resection. This article gives an overview of lung RF ablation, discussing experimental animal findings, rationale for clinical application, technique and methodology, clinical results, and complications.

Lencioni, Riccardo, E-mail: Lencioni@do.med.unipi.it; Crocetti, Laura; Cioni, Roberto [University of Pisa, Division of Diagnostic and Interventional Radiology, Department of Oncology, Transplants, and Advanced Technologies in Medicine (Italy); Mussi, Alfredo [University of Pisa, Division of Thoracic Surgery, Cardiac and Thoracic Department (Italy); Fontanini, Gabriella [University of Pisa, Division of Pathology, Department of Oncology, Transplants, and Advanced Technologies in Medicine (Italy); Ambrogi, Marcello [University of Pisa, Division of Thoracic Surgery, Cardiac and Thoracic Department (Italy); Franchini, Chiara; Cioni, Dania [University of Pisa, Division of Diagnostic and Interventional Radiology, Department of Oncology, Transplants, and Advanced Technologies in Medicine (Italy); Fanucchi, Olivia [University of Pisa, Division of Thoracic Surgery, Cardiac and Thoracic Department (Italy); Gemignani, Raffaello; Baldassarri, Rubia [Cisanello University Hospital, Division of Anesthesiology (Italy); Angeletti, Carlo Alberto [University of Pisa, Division of Thoracic Surgery, Cardiac and Thoracic Department (Italy); Bartolozzi, Carlo [University of Pisa, Division of Diagnostic and Interventional Radiology, Department of Oncology, Transplants, and Advanced Technologies in Medicine (Italy)

2004-11-15

406

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

407

Complications of intraoperative radiofrequency ablation of liver metastases  

PubMed Central

Background Intraoperative radiofrequency ablation (IRFA) of liver metastases can be used to treat patients with complex tumours that are unsuitable for parenchymal resection alone. This systematic review assesses the frequency, patterns and severity of complications associated with this procedure. Methods We carried out a bibliographic search on MEDLINE focused on IRFA for liver metastases, excluding hepatocarcinomas, and on intraoperative use, excluding percutaneous application. Results Thirty papers published between 1999 and 2007 were analysed. They covered a total of 2822 patients and 1755 IRFA procedures. The indications and techniques for IRFA differ from those for percutaneous treatment, as do associated results and complications. Specific complications associated with IRFA, such as liver abscesses, biliary stenoses and vascular thromboses, are directly correlated with the indications and associated procedures. Published results should be interpreted with caution as IRFA can be used alone or combined with parenchymal resection. Conclusions Specific complications related to IRFA are rare, especially for lesions of <35 mm in size located far from a main biliary duct, when additional septic procedures are not used. A lesion-by-lesion approach based on the benefit : risk ratio should therefore be used in the process of making surgical decisions. Combining resection with IRFA leads to higher morbidity, especially in difficult patients with numerous bilateral lesions, but may be necessary to achieve R0 (microscopically negative margins) outcomes.

Razafindratsira, Tsiriniaina; Isambert, Milene; Evrard, Serge

2011-01-01

408

Radiofrequency Ablation for Early-Stage Nonsmall Cell Lung Cancer  

PubMed Central

This review examines studies of radiofrequency ablation (RFA) of nonsmall cell lung cancer (NSCLC) and discusses the role of RFA in treatment of early-stage NSCLC. RFA is usually performed under local anesthesia with computed tomography guidance. RFA-associated mortality, while being rare, can result from pulmonary events. RFA causes pneumothorax in up to 63% of cases, although pneumothorax requiring chest drainage occurs in less than 15% of procedures. Other severe complications are rare. After RFA of stage I NSCLC, 31–42% of patients show local progression. The 1-, 2-, 3-, and 5-year overall survival rates after RFA of stage I NSCLC were 78% to 100%, 53% to 86%, 36% to 88%, and 25% to 61%, respectively. The median survival time ranged from 29 to 67 months. The 1-, 2-, and 3-year cancer-specific survival rates after RFA of stage I NSCLC were 89% to 100%, 92% to 93%, and 59% to 88%, respectively. RFA has a higher local failure rate than sublobar resection and stereotactic body radiation therapy (SBRT). Therefore, RFA may currently be reserved for early-stage NSCLC patients who are unfit for sublobar resection or SBRT. Various technologies are being developed to improve clinical outcomes of RFA for early-stage NSCLC.

Hiraki, Takao; Gobara, Hideo; Iguchi, Toshihiro; Matsui, Yusuke; Kanazawa, Susumu

2014-01-01

409

Feasibility of fast MR-thermometry during cardiac radiofrequency ablation.  

PubMed

Online MR temperature monitoring during radiofrequency (RF) ablation of cardiac arrhythmias may improve the efficacy and safety of the treatment. MR thermometry at 1.5 T using the proton resonance frequency (PRF) method was assessed in 10 healthy volunteers under normal breathing conditions, using a multi-slice, ECG-gated, echo planar imaging (EPI) sequence in combination with slice tracking. Temperature images were post-processed to remove residual motion-related artifacts. Using an MR-compatible steerable catheter and electromagnetic noise filter, RF ablation was performed in the ventricles of two sheep in vivo. The standard deviation of the temperature evolution in time (TSD) was computed. Temperature mapping of the left ventricle was achieved at an update rate of approximately 1 Hz with a mean TSD of 3.6 ± 0.9 °C. TSD measurements at the septum showed a higher precision (2.8 ± 0.9 °C) than at the myocardial regions at the heart-lung and heart-liver interfaces (4.1 ± 0.9 °C). Temperature rose maximally by 9 °C and 16 °C during 5 W and 10 W RF applications, respectively, for 60 s each. Tissue temperature can be monitored at an update rate of approximately 1 Hz in five slices. Typical temperature changes observed during clinical RF application can be monitored with an acceptable level of precision. PMID:22553824

de Senneville, Baudouin Denis; Roujol, Sébastien; Jaïs, Pierre; Moonen, Chrit T W; Herigault, Gwenaël; Quesson, Bruno

2012-04-01

410

Percutaneous radiofrequency ablation of spinal osteoid osteoma under CT guidance.  

PubMed

Objective: Osteoid osteoma (OO) accounts for approximately 10-12% of all benign bone tumours and 3% of all bone tumours. Spinal involvement appears in 10-25% of all cases. The purpose of this study was to evaluate the safety and efficacy of CT-guided radiofrequency (RF) ablation in the treatment of spinal OOs and report our experience. Methods: 13 patients suffering from spinal OO and treated at the authors' institution using CT-guided RF ablation were retrospectively evaluated. The RF probe was introduced through a 11-G Jamshidi® needle, and the lesion was heated at 90?(°)C for 6?min. Results: All procedures were considered technically successful as the correct positioning of the probe was proven by CT. 11 of the 13 patients reported pain relief after RF ablation. In two cases, RF ablation was repeated 1 month after the first procedure. Pain relief was achieved in both cases after the second procedure. No recurrence was reported throughout the follow-up. No complications like skin burn, soft-tissue haematoma, infection, vessel damage or neurological deficit were reported. Conclusion: This study demonstrates that CT-guided percutaneous RF ablation is a safe and effective method for the treatment of spinal OOs. Advances in knowledge: The data of this study support the efficacy and safety of the recently applied CT-guided percutaneous RF ablation technique for the treatment of spinal OOs. PMID:24712322

Morassi, L G; Kokkinis, K; Evangelopoulos, D S; Karargyris, O; Vlachou, I; Kalokairinou, K; Pneumaticos, S G

2014-06-01

411

Value of radiofrequency ablation in the treatment of hepatocellular carcinoma  

PubMed Central

Hepatocellular carcinoma (HCC) is a malignant disease that substantially affects public health worldwide. It is especially prevalent in east Asia and sub-Saharan Africa, where the main etiology is the endemic status of chronic hepatitis B. Effective treatments with curative intent for early HCC include liver transplantation, liver resection (LR), and radiofrequency ablation (RFA). RFA has become the most widely used local thermal ablation method in recent years because of its technical ease, safety, satisfactory local tumor control, and minimally invasive nature. This technique has also emerged as an important treatment strategy for HCC in recent years. RFA, liver transplantation, and hepatectomy can be complementary to one another in the treatment of HCC, and the outcome benefits have been demonstrated by numerous clinical studies. As a pretransplantation bridge therapy, RFA extends the average waiting time without increasing the risk of dropout or death. In contrast to LR, RFA causes almost no intra-abdominal adhesion, thus producing favorable conditions for subsequent liver transplantation. Many studies have demonstrated mutual interactions between RFA and hepatectomy, effectively expanding the operative indications for patients with HCC and enhancing the efficacy of these approaches. However, treated tumor tissue remains within the body after RFA, and residual tumors or satellite nodules can limit the effectiveness of this treatment. Therefore, future research should focus on this issue.

Feng, Kai; Ma, Kuan-Sheng

2014-01-01

412

Disinfection of dairy and animal farm wastewater with radiofrequency power.  

PubMed

Radiofrequency (RF) power was investigated as a new, physical (nonchemical), thermal process to disinfect wastewater from dairy and animal facilities. Samples (n = 38) from 8 dairy, 2 calf, and 3 swine facilities in California were collected over a 3-yr period and characterized for their dielectric properties, chemical composition, and suitability for thermal processing using RF power. To establish efficacy for disinfection, selected samples were inoculated with high levels (10(6) to 10(9) cfu/mL) of bacterial pathogens such as Salmonella sp., Escherichia coli O157:H7, and Mycobacterium avium ssp. paratuberculosis and processed with an RF prototype system. The capabilities of RF power as a method for thermal disinfection of wastewater were demonstrated when bacteria pathogens were completely and rapidly (<1 min) inactivated when temperatures of 60 to 65 degrees C were achieved. Furthermore, RF technology can be used for large-scale, batch or continuous and portable applications, allowing significant improvements in energy-use efficiencies compared with conventional thermal (surface heating) technologies. Therefore, RF power has potential as an alternative to disinfect dairy/animal farm wastewater before recycling. PMID:16230716

Lagunas-Solar, M C; Cullor, J S; Zeng, N X; Truong, T D; Essert, T K; Smith, W L; Piña, C

2005-11-01

413

Radiofrequency thermal ablation of abdominal tumors: lessons learned from complications.  

PubMed

Radiofrequency (RF) thermal ablation has shown promise as a technique for treating inoperable solid tumors involving the liver, kidney, adrenal gland, and lung. However, like all other imaging-guided interventional procedures, RF ablation involves some element of risk. Varying degrees of complications can be expected, depending on factors such as the organ site and the aggressiveness of the procedure. General complications of RF ablation may be related to either imaging-guided electrode placement (eg, bleeding, infection, tumor seeding, pneumothorax) or thermal therapy (eg, nontarget thermal damage, grounding pad burns). Liver and renal-adrenal ablation may be associated with organ-specific complications. A fundamental understanding of RF ablation principles, along with adequate operator training and experience and familiarity with both thermal ablation and the broad spectrum of postablation complications, are necessary to maximize the safety and efficacy of this procedure. The standard of care for decreasing the morbidity of complications consists of prevention (including careful patient selection), early detection, and prompt, appropriate treatment. PMID:14730035

Rhim, Hyunchul; Dodd, Gerald D; Chintapalli, Kedar N; Wood, Bradford J; Dupuy, Damian E; Hvizda, Julia L; Sewell, Patrick E; Goldberg, S Nahum

2004-01-01

414

Software-assisted post-interventional assessment of radiofrequency ablation  

NASA Astrophysics Data System (ADS)

Radiofrequency ablation (RFA) is becoming a standard procedure for minimally invasive tumor treatment in clinical practice. Due to its common technical procedure, low complication rate, and low cost, RFA has become an alternative to surgical resection in the liver. To evaluate the therapy success of RFA, thorough follow-up imaging is essential. Conventionally, shape, size, and position of tumor and coagulation are visually compared in a side-by-side manner using pre- and post-interventional images. To objectify the verification of the treatment success, a novel software assistant allowing for fast and accurate comparison of tumor and coagulation is proposed. In this work, the clinical value of the proposed assessment software is evaluated. In a retrospective clinical study, 39 cases of hepatic tumor ablation are evaluated using the prototype software and conventional image comparison by four radiologists with different levels of experience. The cases are randomized and evaluated in two sessions to avoid any recall-bias. Self-confidence of correct diagnosis (local recurrence vs. no local recurrence) on a six-point scale is given for each case by the radiologists. Sensitivity, specificity, positive and negative predictive values as well as receiver operating curves are calculated for both methods. It is shown that the software-assisted method allows physicians to correctly identify local tumor recurrence with a higher percentage than the conventional method (sensitivity: 0.6 vs. 0.35), whereas the percentage of correctly identified successful ablations is slightly reduced (specificity: 0.83 vs. 0.89).

Rieder, Christian; Geisler, Benjamin; Bruners, Philipp; Isfort, Peter; Na, Hong-Sik; Mahnken, Andreas H.; Hahn, Horst K.

2014-03-01

415

Analysis of the medium field Q-slope in superconducting cavities made of bulk niobium  

Microsoft Academic Search

The quality factor of superconducting radio-frequency cavities made of high purity, bulk niobium increases with rf field in the medium field range (peak surface magnetic field between 20 and about 100 mT). The causes for this effect are not clear yet. The dependence of the surface resistance on the peak surface magnetic field is typically linear and quadratic. This contribution

Gianluigi Ciovati; J. Halbritter

2005-01-01

416

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

417

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

SciTech Connect

We present detailed experimental and theoretical investigations of hotspots produced by trapped vortex bundles and their effect on the radio-frequency (rf) surface resistance R{sub s} of superconductors at low temperatures. Our measurements of R{sub s}, 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 R{sub s} 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 ?10{sup 6} 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 R{sub s} on the rf field amplitude H{sub p}, 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.

A. Gurevich, G. Ciovati

2013-02-01

418

Self-consistent modeling of radio-frequency plasma generation in stellarators  

SciTech Connect

A self-consistent model of radio-frequency (RF) plasma generation in stellarators in the ion cyclotron frequency range is described. The model includes equations for the particle and energy balance and boundary conditions for Maxwell’s equations. The equation of charged particle balance takes into account the influx of particles due to ionization and their loss via diffusion and convection. The equation of electron energy balance takes into account the RF heating power source, as well as energy losses due to the excitation and electron-impact ionization of gas atoms, energy exchange via Coulomb collisions, and plasma heat conduction. The deposited RF power is calculated by solving the boundary problem for Maxwell’s equations. When describing the dissipation of the energy of the RF field, collisional absorption and Landau damping are taken into account. At each time step, Maxwell’s equations are solved for the current profiles of the plasma density and plasma temperature. The calculations are performed for a cylindrical plasma. The plasma is assumed to be axisymmetric and homogeneous along the plasma column. The system of balance equations is solved using the Crank-Nicholson scheme. Maxwell’s equations are solved in a one-dimensional approximation by using the Fourier transformation along the azimuthal and longitudinal coordinates. Results of simulations of RF plasma generation in the Uragan-2M stellarator by using a frame antenna operating at frequencies lower than the ion cyclotron frequency are presented. The calculations show that the slow wave generated by the antenna is efficiently absorbed at the periphery of the plasma column, due to which only a small fraction of the input power reaches the confinement region. As a result, the temperature on the axis of the plasma column remains low, whereas at the periphery it is substantially higher. This leads to strong absorption of the RF field at the periphery via the Landau mechanism.

Moiseenko, V. E., E-mail: moiseenk@ipp.kharkov.ua; Stadnik, Yu. S., E-mail: stadnikys@kipt.kharkov.ua [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine); Lysoivan, A. I., E-mail: a.lyssoivan@fz-juelich.de [Royal Military Academy, EURATOM-Belgian State Association, Laboratory for Plasma Physics (Belgium); Korovin, V. B. [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine)] [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine)

2013-11-15

419

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

420

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

SciTech Connect

A previous study showed a substantial increase in the colonic temperature of rhesus monkeys (Macaca mulatta) exposed to radiofrequency (RF) fields at a frequency near whole-body resonance and specific absorption rates (SAR) of 2-3 W/kg. The present experiments were conducted to determine the metabolic and vasomotor responses during exposures to similar RF fields. We exposed five adult male rhesus monkeys to 225 MHz radiation (E orientation) in an anechoic chamber. Oxygen consumption and carbon dioxide production were measured before, during, and after RF exposure. Colonic, tail and leg skin temperatures were continuously monitored with RF-nonperturbing probes. The monkeys were irradiated at two carefully-controlled ambient temperatures, either cool (20 degrees C) or thermoneutral (26 degrees C). Power densities ranged from 0 (sham) to 10.0 mW/cm2 with an average whole-body SAR of 0.285 (W/kg)/(mW/cm2). We used two experimental protocols, each of which began with a 120-min pre-exposure equilibration period. One protocol involved repetitive 10-min RF exposures at successively higher power densities with a recovery period between exposures. In the second protocol, a 120-min RF exposure permitted the measurement of steady-state thermoregulatory responses. Metabolic and vasomotor adjustments in the rhesus monkey exposed to 225 MHz occurred during brief or sustained exposures at SARs at or above 1.4 W/kg. The SAR required to produce a given response varied with ambient temperature. Metabolic and vasomotor responses were coordinated effectively to produce a stable deep body temperature. The results show that the thermoregulatory response of the rhesus monkey to an RF exposure at a resonant frequency limits storage of heat in the body. However, substantial increases in colonic temperature were not prevented by such responses, even in a cool environment.

Lotz, W.G.; Saxton, J.L.

1987-01-01

421

Noninvasive Assessment of Tissue Heating During Cardiac Radiofrequency Ablation Using MRI Thermography  

PubMed Central

Background Failure to achieve properly localized, permanent tissue destruction is a common cause of arrhythmia recurrence after cardiac ablation. Current methods of assessing lesion size and location during cardiac radiofrequency ablation are unreliable or not suited for repeated assessment during the procedure. MRI thermography could be used to delineate permanent ablation lesions because tissue heating above 50°C is the cause of permanent tissue destruction during radiofrequency ablation. However, image artifacts caused by cardiac motion, the ablation electrode, and radiofrequency ablation currently pose a challenge to MRI thermography in the heart. In the current study, we sought to demonstrate the feasibility of MRI thermography during cardiac ablation. Methods and Results An MRI-compatible electrophysiology catheter and filtered radiofrequency ablation system was used to perform ablation in the left ventricle of 6 mongrel dogs in a 1.5-T MRI system. Fast gradient-echo imaging was performed before and during radiofrequency ablation, and thermography images were derived from the preheating and postheating images. Lesion extent by thermography was within 20% of the gross pathology lesion. Conclusions MR thermography appears to be a promising technique for monitoring lesion formation and may allow for more accurate placement and titration of ablation, possibly reducing arrhythmia recurrences.

Kolandaivelu, Aravindan; Zviman, Menekhem M.; Castro, Valeria; Lardo, Albert C.; Berger, Ronald D.; Halperin, Henry R.

2010-01-01

422

Radiofrequency catheter ablation of accessory atrioventricular pathways in children and young adults.  

PubMed Central

OBJECTIVE--To assess the efficacy of radiofrequency ablation for reentrant tachyarrhythmias in children and young adults. SETTING--A tertiary cardiac referral centre. PATIENTS AND INTERVENTIONS--Over a 16 month period 22 patients aged less than 20 years (median age 16.5 years) underwent 26 radiofrequency ablation procedures for atrioventricular reentry tachycardia through an accessory pathway. The results of radiofrequency ablation were compared with those in a group of 16 patients (median age 14 years) who had had surgical ablation for atrioventricular reentry tachycardia over a preceding six year period. RESULTS--Ablation of an accessory atrioventricular pathway was accomplished for 18 (76%) of 25 pathways in 16 (73%) of 22 patients. There were no procedure-related complications. Surgery was eventually curative in 15/16 patients (94%). However, three patients required a second open heart surgical procedure because tachyarrhythmia recurred. There were no surgical deaths. Failures for radiofrequency ablation were related to accessory pathway location, and were greater for right free wall and posteroseptal pathways (success rate of 50% and 57% respectively). Recurrence after surgery was also associated with pathways in these locations. CONCLUSIONS--Transcatheter radiofrequency current ablation was safe and achieved a cure with less patient morbidity and improved cost efficiency. It is an attractive alternative to long-term drug therapy or surgery in older children and adolescents. A higher success rate may be expected with increased experience.

Sreeram, N; Smeets, J L; Pulles-Heintzberger, C F; Wellens, H J

1993-01-01

423

Hydrogen production in a radio-frequency plasma source operating on water vapor  

NASA Astrophysics Data System (ADS)

The global energy and climate challenges have motivated development of innovative techniques to satisfy energy demand while minimizing emissions. To this end, hydrogen as an alternative energy carrier in the transportation sector is an attractive option. In addition, there is already a great need for hydrogen gas in several industrial processes such as hydro-cracking of crude oil to produce gasoline and production of ammonia and methanol. The current dominant methods of hydrogen production from fossil fuels are well-developed and have reached relatively high energy efficiencies (up to 85%), but these methods rely on non-renewable natural resources and produce carbon dioxide emissions. This work investigates the feasibility of hydrogen production by dissociating water molecules in a radio-frequency (RF) plasma discharge. In addition to the widespread usage of hydrogen gas, applications of water plasma have permeated in many areas of research, and information on basic behaviors of a water plasma discharge will provide fruitful insights for other researchers. An RF plasma source equipped with a double-helix antenna (m = 1 mode) and an applied axial magnetic field is designed to operate on water vapor. It is shown that water molecules are being dissociated in the discharge. Experimental results show that the rate of hydrogen production increases linearly with RF power in the absence of the applied axial magnetic field. With the magnetic field, the rate of hydrogen production increases from 250 to 500 W, and begins to saturate with RF power. Despite this saturation, it is shown that hydrogen increases with magnetic field strength at a fixed RF power. Further, the rate of hydrogen production increases with water input flow rate up to 100 sccm for a fixed RF power level, and begins to decrease at 125 sccm. This dissertation characterizes the rate of hydrogen production and plasma properties as a function of RF power, applied B-field strength, and water input flow rate. A zero-dimensional kinetics model is used to determine the theoretical energy efficiency.

Nguyen, Son-Ca Viet Thi

424

Characterization of buried glands before and after radiofrequency ablation by using 3-dimensional optical coherence tomography (with videos)  

PubMed Central

Background Radiofrequency ablation (RFA) is an endoscopic technique used to eradicate Barrett’s esophagus (BE). However, such ablation can commonly lead to neosquamous epithelium overlying residual BE glands not visible by conventional endoscopy and may evade detection on random biopsy samples. Objective To demonstrate the capability of endoscopic 3-dimensional optical coherence tomography (3D-OCT) for the identification and characterization of buried glands before and after RFA therapy. Design Cross-sectional study. Setting Single teaching hospital. Patients Twenty-six male and 1 female white patients with BE undergoing RFA treatment. Interventions 3D-OCT was performed at the gastroesophageal junction in 18 patients before attaining complete eradication of intestinal metaplasia (pre–CE-IM group) and in 16 patients after CE-IM (post–CE-IM group). Main Outcome Measurements Prevalence, size, and location of buried glands relative to the squamocolumnar junction. Results 3D-OCT provided an approximately 30 to 60 times larger field of view compared with jumbo and standard biopsy and sufficient imaging depth for detecting buried glands. Based on 3D-OCT results, buried glands were found in 72% of patients (13/18) in the pre–CE-IM group and 63% of patients (10/16) in the post–CE-IM group. The number (mean [standard deviation]) of buried glands per patient in the post–CE-IM group (7.1 [9.3]) was significantly lower compared with the pre–CE-IM group (34.4 [44.6]; P = .02). The buried gland size (P = .69) and distribution (P = .54) were not significantly different before and after CE-IM. Limitations A single-center, cross-sectional study comparing patients at different time points in treatment. Lack of 1-to-1 coregistered histology for all OCT data sets obtained in vivo. Conclusion Buried glands were frequently detected with 3D-OCT near the gastroesophageal junction before and after radiofrequency ablation.

Zhou, Chao; Tsai, Tsung-Han; Lee, Hsiang-Chieh; Kirtane, Tejas; Figueiredo, Marisa; Tao, Yuankai K.; Ahsen, Osman O.; Adler, Desmond C.; Schmitt, Joseph M.; Huang, Qin; Fujimoto, James G.; Mashimo, Hiroshi

2012-01-01

425

Nanoionics-Based Switches for Radio-Frequency Applications  

NASA Technical Reports Server (NTRS)

Nanoionics-based devices have shown promise as alternatives to microelectromechanical systems (MEMS) and semiconductor diode devices for switching radio-frequency (RF) signals in diverse systems. Examples of systems that utilize RF switches include phase shifters for electronically steerable phased-array antennas, multiplexers, cellular telephones and other radio transceivers, and other portable electronic devices. Semiconductor diode switches can operate at low potentials (about 1 to 3 V) and high speeds (switching times of the order of nanoseconds) but are characterized by significant insertion loss, high DC power consumption, low isolation, and generation of third-order harmonics and intermodulation distortion (IMD). MEMS-based switches feature low insertion loss (of the order of 0.2 dB), low DC power consumption (picowatts), high isolation (>30 dB), and low IMD, but contain moving parts, are not highly reliable, and must be operated at high actuation potentials (20 to 60 V) generated and applied by use of complex circuitry. In addition, fabrication of MEMS is complex, involving many processing steps. Nanoionics-based switches offer the superior RF performance and low power consumption of MEMS switches, without need for the high potentials and complex circuitry necessary for operation of MEMS switches. At the same time, nanoionics-based switches offer the high switching speed of semiconductor devices. Also, like semiconductor devices, nanoionics-based switches can be fabricated relatively inexpensively by use of conventional integrated-circuit fabrication techniques. More over, nanoionics-based switches have simple planar structures that can easily be integrated into RF power-distribution circuits.

Nessel, James; Lee, Richard

2010-01-01

426

Radiofrequency ablation during continuous saline infusion can extend ablation margins  

PubMed Central

AIM: To determine whether fluid injection during radiofrequency ablation (RFA) can increase the coagulation area. METHODS: Bovine liver (1-2 kg) was placed on an aluminum tray with a return electrode affixed to the base, and the liver was punctured by an expandable electrode. During RFA, 5% glucose; 50% glucose; or saline fluid was infused continuously at a rate of 1.0 mL/min through the infusion line connected to the infusion port. The area and volume of the thermocoagulated region of bovine liver were determined after RFA. The Joule heat generated was determined from the temporal change in output during the RFA experiment. RESULTS: No liquid infusion was 17.3 ± 1.6 mL, similar to the volume of a 3-cm diameter sphere (14.1 mL). Mean thermocoagulated volume was significantly larger with continuous infusion of saline (29.3 ± 3.3 mL) than with 5% glucose (21.4 ± 2.2 mL), 50% glucose (16.5 ± 0.9 mL) or no liquid infusion (17.3 ± 1.6 mL). The ablated volume for RFA with saline was approximately 1.7-times greater than for RFA with no liquid infusion, representing a significant difference between these two conditions. Total Joule heat generated during RFA was highest with saline, and lowest with 50% glucose. CONCLUSION: RFA with continuous saline infusion achieves a large ablation zone, and may help inhibit local recurrence by obtaining sufficient ablation margins. RFA during continuous saline infusion can extend ablation margins, and may be prevent local recurrence.

Ishikawa, Toru; Kubota, Tomoyuki; Horigome, Ryoko; Kimura, Naruhiro; Honda, Hiroki; Iwanaga, Akito; Seki, Keiichi; Honma, Terasu; Yoshida, Toshiaki

2013-01-01

427

Laparoscopic Radiofrequency Fibroid Ablation: Phase II and Phase III Results  

PubMed Central

Background and Objectives: To review phase II and phase III treatments of symptomatic uterine fibroids (myomas) using laparoscopic radiofrequency volumetric thermal ablation (RFVTA). Methods: We performed a retrospective, multicenter clinical analysis of 206 consecutive cases of ultrasound-guided laparoscopic RFVTA of symptomatic myomas conducted on an outpatient basis under two phase II studies at 2 sites (n = 69) and one phase III study at 11 sites (n = 137). Descriptive and exploratory, general trend, and matched-pair analyses were applied. Results: From baseline to 12 months in the phase II study, the mean transformed symptom severity scores improved from 53.9 to 8.8 (P < .001) (n = 57), health-related quality-of-life scores improved from 48.5 to 92.0 (P < .001) (n = 57), and mean uterine volume decreased from 204.4 cm3 to 151.4 cm3 (P = .008) (n = 58). Patients missed a median of 4 days of work (range, 2–10 days). The rate of possible device-related adverse events was 1.4% (1 of 69). In the phase III study, approximately 98% of patients were assessed at 12 months, and their transformed symptom severity scores, health-related quality-of-life scores, mean decrease in uterine volume, and mean menstrual bleeding reduction were also significant. Patients in phase III missed a median of 5 days of work (range, 1–29 days). The rate of periprocedural device-related adverse events was 3.5% (5 of 137). Despite the enrollment requirement for patients in both phases to have completed childbearing, 4 pregnancies occurred within the first year after treatment. Conclusions: RFVTA does not require any uterine incisions and provides a uterine-sparing procedure with rapid recovery, significant reduction in uterine size, significant reduction or elimination of myoma symptoms, and significant improvement in quality of life.

Pemueller, Rodolfo Robles; Garza Leal, Jose Gerardo; Abbott, Karen R.; Falls, Janice L.; Macer, James

2014-01-01