Teses / dissertações sobre o tema "Radiofrequency"

Radiofrequency ablation (RFA) is an established treatment option for patients with inoperable liver tumours and is now being investigated for the treatment of lung and other solid tumours. The aim of this thesis was to investigate the use RFA to decrease blood loss during liver resection, for the treatment of the liver resection edge and to investigate the safety and efficacy of brain RFA. Blood loss is an important factor affecting both the morbidity and mortality following liver resection. The use of a novel in line RF probe to ablate the transection plane prior to liver resection resulted in decreased blood loss with easier resection. This has potential in the treatment of liver tumors in cirrhotic livers and also in other vascular organs. The other important prognostic factor affecting long-term survival in patients undergoing liver resection for liver tumors is the surgical margins. Positive margins which cannot be treated with repeat resection may be treated with cryotherapy. The use of a novel probe to ablate the resection edge with RFA was found to be equally effective as cryotherapy and superior to argon beam coagulation or diathermy in an ex-vivo model. The radiofrequency ablation of the brain was found to be safe with no hemorrhage or damage to the surrounding brain parenchyma. There was no rise in intra-cranial pressure in the animals treated with RFA. The brain RFA was found to be effective and has potential for the treatment of brain tumours. Dispersive pad site burns was a significant problem in patients treated with radiofrequency ablation for lung and liver tumours occurring in 5% of patients. Pad tissue temperature of 45oC was found to be the threshold temperature above which burns occurred. Monitoring of pad-tissue temperatures with thermocouples and application of ice packs in addition to increasing the number of pads may help decrease this complication.

The overall aim of this thesis is to increase our knowledge of relevant exposure parameters when discussing possible health implication from exposure to radiofrequency electromagnetic fields (RF), especially effects that might occur at non-thermal levels.

In this thesis an effort is made to broaden the exposure assessment and to take the exposure time into account and combine it with the Specific Absorption Rate (SAR) and the field parameters (electric and magnetic field strength) to approach a dose concept.

In the first part of the thesis self-reported subjective symptoms among mobile phone users were studied. As a basis for this an epidemiological study among mobile phone users was completed with the main hypothesis that users of the digital transmission system GSM experience more symptoms than users of the older analogue NMT transmission system.

The hypothesis was falsified, but an interesting side finding was that people with longer calling time per day experienced more symptoms than people with shorter calling time per day. The time-aspect (long duration phone call etc.) was also found to be relevant for the occurrence of symptoms in association with mobile phone use as well as duration of symptoms. The new suggested dosimetric quantity Specific Absorption per Day (SAD), in which both calling time per day as well as the measured SAR1g are included showed a stronger association to the prevalence of some of the symptoms, such as dizziness, discomfort and warmth behind the ear compared to both CT and SAR1g alone.

In the second part whole body exposure conditions were considered. Methods to measure the induced current were examined in an experimental study, where different techniques were compared in different grounding conditions. The results were used in a study of operators of RF plastic sealers (RF operators) where the health status as well as the exposure were studied. The results showed that RF operators are a highly exposed group, which was confirmed by the fact that 16 out of 46 measured work places exceeded the ICNIRP guidelines. Headaches were found to be associated with the mean value of the time integrated E-field during a weld (E-weld) and the warmth sensations in the hands (warm hands) with the time integrated E-field exposure during one day (E-day).

The general findings in this thesis indicated that time should be included in the exposure assessment when studying non-thermal effects such as subjective symptoms in connection with RF exposure. The thesis proposes two different methods for doing this, namely timeintegrated exposure [V/m x t and A/m x t] and dose [J/kg].

The basic form of conventional electronic and acoustooptic radiofrequency spectrum analysers is described. The advantages and disadvantages of the various systems are discussed with particular reference to radar signal processing in a hostile environment. Acoustooptic interaction is described using electromagnetic wave theory and also in terms of particle dynamics. A discussion of the various factors which effect Bragg-cell performance is presented, together with experimental results from the characterisation of acoustooptic cells. Coherent light detection is described when used in conjunction with a Bragg-cell spectrum analyser. Using this approach the dynamic range of the device may be dramatically increased. A novel approach is described which uses optical fibres in the Fourier transform plane and fusion spliced couplers to combine the signal and local oscillator beams. Experimental results are presented using single-mode fibres. Improvements in diffraction efficiency, reduced material intermodulation and increased frequency resolution are possible in an acoustooptic spectrum analyser if a Bragg-cell with a long transducer is used. However this leads to reduced instantaneous bandwidth in a conventional configuration. Two new approaches are described which allow a long transducer to be used without loss of bandwidth. An analysis of Bragg-cell diffraction within active and passive resonant optical cavities shows the diffraction efficiency per watt of a Bragg-cell may be increased by orders of magnitude by placing it within a passive cavity. Various cavity configurations are analysed and experimental results are given. A temporal analysis of light diffracted from radiofrequency pulses within an acoustooptic Bragg-cell is presented. Experimental evidence backs up the theory, which shows a possible means of eliminating the "Rabbit's Ears" phenomenon. Conventional acoustooptic Bragg cells have bandwidths limited by the acoustic losses in the crystals used for the cells and impedance matching of the transducer to the driver and crystal. Commercial cells are available with bandwidths of several gigahertz. Many applications require significantly larger bandwidths than are offered by conventional Bragg cells. We describe a new kind of diffraction cell with a potential bandwidth in excess of fifty gigahertz. The theory of operation and an example design are presented. A novel ultra-high data rate optical communication link is described. This makes use of the temporal distribution produced by light diffracted from radiofrequency pulses within a Bragg-cell. Also a covert, free-space link is described. A two channel system is demonstrated using acoustooptic cells.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1998.
Includes bibliographical references (leaves 58-65).
Radiofrequency energy loss has been investigated for a resonant NMR surface coil between 20 MHz and 400 MHz. High-field NMR (> 64 MHz) is used increasingly for human imaging and spectroscopy to achieve improved SNR and spectral resolution. RF losses in coils designed using conventional lumped-element principles, however, often limit the practicality of high-field imaging. New design principles are required for the construction of efficient high-field RF coils. The RF energy losses investigated include RF coil losses and losses to a phantom load. These were studied using single-loop, resonant surface coils. Coil Q values, both unloaded and loaded, were measured and used to determine the coil radiation resistance, load resistance, B, field magnitude, and SNR. Radiation resistance is shown to increase like RR ~ f04. It is widely believed that load losses dominate all other losses in biomedical NMR. This study indicates that limiting radiation losses may improve loaded coil SNR at high frequencies. To this end, one may decrease the coil electrical length and/or apply transmission line principles in the construction of RF coils. Decreasing the coil electrical wavelength may be accomplished by decreasing the coil dimensions. Transmission line principles, which have been demonstrated for volume coils, improve performance by minimizing the coil radiation resistance.
by Mark D. Skubis.
S.M.

[EN] The processing of radiofrequency signals using photonics means is a discipline that appeared almost at the same time as the laser and the optical fibre. Photonics offers the capability of managing broadband radiofrequency (RF) signals thanks to its low transmission attenuation, a variety of linear and non-linear phenomena and, recently, the potential to implement integrated photonic subsystems. These features open the door for the implementation of multiple functionalities including optical transportation, up and down frequency conversion, optical RF filtering, signal multiplexing, de-multiplexing, routing and switching, optical sampling, tone generation, delay control, beamforming and photonic generation of digital modulations, and even a combination of several of these functionalities. This thesis is focused on the application of vector processing in the optical domain to radiofrequency signals in two fields of application: optical beamforming, and photonic vector modulation and demodulation of digital quadrature amplitude modulations. The photonic vector control enables to adjust the amplitude and phase of the radiofrequency signals in the optical domain, which is the fundamental processing that is required in different applications such as beamforming networks for direct radiating array (DRA) antennas and multilevel quadrature modulation. The work described in this thesis include different techniques for implementing a photonic version of beamforming networks for direct radiating arrays (DRA) known as optical beamforming networks (OBFN), with the objectives of providing a precise control in terrestrial applications of broadband signals at very high frequencies above 40 GHz in communication antennas, optimizing the size and mass when compared with the electrical counterparts in space application, and presenting new photonic-based OBFN functionalities. Thus, two families of OBFNs are studied: fibre-based true time delay architectures and integrated networks. The first allow the control of broadband signals using dispersive optical fibres with wavelength division multiplexing techniques and advanced functionalities such as direction of arrival estimation in receiving architectures. In the second, passive OBFNs based on monolithically-integrated Optical Butler Matrices are studied, including an ultra-compact solution using optical heterodyne techniques in silicon-on-insulator (SOI) material, and an alternative implementing a homodyne counterpart in germanium doped silica material. In this thesis, the application of photonic vector processing to the generation of quadrature digital modulations has also been investigated. Multilevel modulations are based on encoding digital information in discrete states of phase and amplitude of an electrical signal to enhance spectral efficiency, as for instance, in quadrature modulation. The signal process required for generating and demodulating this kind of signals involves vector processing (phase and amplitude control) and frequency conversion. Unlike the common electronic or digital implementation, in this thesis, different photonic based signal processing techniques are studied to produce digital modulation (photonic vector modulation, PVM) and demodulation (PVdM). These techniques are of particular interest in the case of broadband signals where the data rate required to be managed is in the order of gigabit per second, for applications like wireless backhauling of metro optical networks (known as fibre-to-the-air). The techniques described use optical dispersion in optical fibres, wavelength division multiplexing and photonic up/down conversion. Additionally, an optical heterodyne solution implemented monolithically in a photonic integrated circuit (PIC) is also described.
[ES] El procesamiento de señales de radiofrecuencia (RF) utilizando medios fotónicos es una disciplina que apareció casi al mismo tiempo que el láser y la fibra óptica. La fotónica ofrece la capacidad de manipular señales de radiofrecuencia de banda ancha, una baja atenuación, procesados basados en una amplia variedad de fenómenos lineales y no lineales y, recientemente, el potencial para implementar subsistemas fotónicos integrados. Estas características ofrecen un gran potencial para la implementación de múltiples funcionalidades incluyendo transporte óptico, conversión de frecuencia, filtrado óptico de RF, multiplexación y demultiplexación de señales, encaminamiento y conmutación, muestreo óptico, generación de tonos, líneas de retardo, conformación de haz en agrupaciones de antenas o generación fotónica de modulaciones digitales, e incluso una combinación de varias de estas funcionalidades. Esta tesis se centra en la aplicación del procesamiento vectorial en el dominio óptico de señales de radiofrecuencia en dos campos de aplicación: la conformación óptica de haces y la modulación y demodulación vectorial fotónica de señales digitales en cuadratura. El control fotónico vectorial permite manipular la amplitud y fase de las señales de radiofrecuencia en el dominio óptico, que es el procesamiento fundamental que se requiere en diferentes aplicaciones tales como las redes de conformación de haces para agrupaciones de antenas y en la modulación en cuadratura. El trabajo descrito en esta tesis incluye diferentes técnicas para implementar una versión fotónica de las redes de conformación de haces de en agrupaciones de antenas, conocidas como redes ópticas de conformación de haces (OBFN). Se estudian dos familias de redes: arquitecturas de retardo en fibra óptica y arquitecturas integradas. Las primeras permiten el control de señales de banda ancha utilizando fibras ópticas dispersivas con técnicas de multiplexado por división de longitud de onda y funcionalidades avanzadas tales como la estimación del ángulo de llegada de la señal en la antena receptora. En la segunda, se estudian redes de conformación pasivas basadas en Matrices de Butler ópticas integradas, incluyendo una solución ultra-compacta utilizando técnicas ópticas heterodinas en silicio sobre aislante (SOI), y una alternativa homodina en sílice dopado con germanio. En esta tesis, también se han investigado técnicas de procesado vectorial fotónico para la generación de modulaciones digitales en cuadratura. Las modulaciones multinivel codifican la información digital en estados discretos de fase y amplitud de una señal eléctrica para aumentar su eficiencia espectral, como por ejemplo la modulación en cuadratura. El procesado necesario para generar y demodular este tipo de señales implica el procesamiento vectorial (control de amplitud y fase) y la conversión de frecuencia. A diferencia de la implementación electrónica o digital convencional, en esta tesis se estudian diferentes técnicas de procesado fotónico tanto para la generación de modulaciones digitales (modulación vectorial fotónica, PVM) como para su demodulación (PVdM). Esto es de particular interés en el caso de señales de banda ancha, donde la velocidad de datos requerida es del orden de gigabits por segundo, para aplicaciones como backhaul inalámbrico de redes ópticas metropolitanas (conocida como fibra hasta el aire). Las técnicas descritas se basan en explotar la dispersión cromática de la fibra óptica, la multiplexación por división de longitud de onda y la conversión en frecuencia. Además, se presenta una solución heterodina implementada monolíticamente en un circuito integrado fotónico (PIC).
[CAT] El processament de senyals de radiofreqüència (RF) utilitzant mitjans fotònics és una disciplina que va aparèixer gairebé al mateix temps que el làser i la fibra òptica. La fotònica ofereix la capacitat de manipular senyals de radiofreqüència de banda ampla, una baixa atenuació, processats basats en una àmplia varietat de fenòmens lineals i no lineals i, recentment, el potencial per implementar subsistemes fotònics integrats. Aquestes característiques ofereixen un gran potencial per a la implementació de múltiples funcionalitats incloent transport òptic, conversió de freqüència, filtrat òptic de RF, multiplexació i demultiplexació de senyals, encaminament i commutació, mostreig òptic, generació de tons, línies de retard, conformació de feix en agrupacions d'antenes i la generació fotònica de modulacions digitals, i fins i tot una combinació de diverses d'aquestes funcionalitats. Aquesta tesi es centra en l'aplicació del processament vectorial en el domini òptic de senyals de radiofreqüència en dos camps d'aplicació: la conformació òptica de feixos i la modulació i demodulació vectorial fotònica de senyals digitals en quadratura. El control fotònic vectorial permet manipular l'amplitud i la fase dels senyals de radiofreqüència en el domini òptic, que és el processament fonamental que es requereix en diferents aplicacions com ara les xarxes de conformació de feixos per agrupacions d'antenes i en modulació multinivell. El treball descrit en aquesta tesi inclou diferents tècniques per implementar una versió fotònica de les xarxes de conformació de feixos en agrupacions d'antenes, conegudes com a xarxes òptiques de conformació de feixos (OBFN), amb els objectius de proporcionar un control precís en aplicacions terrestres de senyals de banda ampla a freqüències molt altes per sobre de 40 GHz en antenes de comunicacions, optimitzant la mida i el pes quan es compara amb els homòlegs elèctrics en aplicacions espacials, i la presentació de noves funcionalitats fotòniques per agrupacions d'antenes. Per tant, s'estudien dues famílies de OBFNs: arquitectures de retard en fibra òptica i arquitectures integrades. Les primeres permeten el control de senyals de banda ampla utilitzant fibres òptiques dispersives amb tècniques de multiplexació per divisió en longitud d'ona i funcionalitats avançades com ara l'estimació de l'angle d'arribada del senyal a l'antena receptora. A la segona, s'estudien xarxes de conformació passives basades en Matrius de Butler òptiques en fotònica integrada, incloent una solució ultra-compacta utilitzant tècniques òptiques heterodinas en silici sobre aïllant (SOI), i una alternativa homodina en sílice dopat amb germani. D'altra banda, també s'ha investigat en aquesta tesi tècniques de processament vectorial fotònic per a la generació de modulacions digitals en quadratura. Les modulacions multinivell codifiquen la informació digital en estats discrets de fase i amplitud d'un senyal elèctric per augmentar la seva eficiència espectral, com ara la modulació en quadratura. El processat necessari per generar i desmodular aquest tipus de senyals implica el processament vectorial (control d'amplitud i fase) i la conversió de freqüència. A diferència de la implementació electrònica o digital convencional, en aquesta tesi s'estudien diferents tècniques de processament fotònic tant per a la generació de modulacions digitals (modulació vectorial fotònica, PVM) com per la seva demodulació (PVdM). Això és de particular interès en el cas de senyals de banda ampla, on la velocitat de dades requerida és de l'ordre de gigabits per segon, per a aplicacions com backhaul sense fils de xarxes òptiques metropolitanes (coneguda com fibra fins l'aire). Les tècniques descrites es basen en explotar la dispersió cromàtica de la fibra òptica, la multiplexació per divisió en longitud d'ona i la conversió en freqüència. A més, es prese
Piqueras Ruipérez, MÁ. (2016). Photonic Vector Processing Techniques for Radiofrequency Signals [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/63264
TESIS

The acute effects of radiofrequency electromagnetic fields (RF EMF) on human cognitive performance were investigated. Cognitive tasks were identified from RF EMF cognitive research; tests used most extensively were psychomotor performance, attention, working and episodic memory tasks. Review of published imaging research enabled selection of a battery of cognitive tasks for use in the experimental studies. Effects of practice and the test-retest reliabilities on the tests were evaluated and the relationship between the tests within the battery and measures of ability and personality investigated. Three studies were conducted to identify whether RF EMF produced by occupational communication systems had reliable effects on cognitive performance and self-reports of mood, anxiety and workload. Double-blind repeated measures design was used to investigate the following fields in comparison to sham; a high frequency (HF) 29MHz continuous wave (CW) signal, a very high frequency (VHF) 75MHz CW field, an Ultra High Frequency (UHF) modulated 448MHz field, a UHF 1206MHz CW signal and a TETRA 388MHz field pulse modulated at 17.6Hz. The first study demonstrated no significant effects of the VHF signal on performance when compared to sham. The HF signal appeared to reduce response time to two of the cognitive tasks and affect error rate on one of them. Investigation of the two UHF signals showed no reliable differences between conditions on the cognitive measures. The third study showed reliable differences between TETRA exposure and sham conditions on two of the tasks. Overall the results indicate that RF EMF signals at the frequencies and power levels used in these studies are well tolerated in healthy subjects. In general, the signals do not appear to have reliable and robust effects on human cognitive performance. However, there may be subtle transitory effects of RF EMF that are not well understood at the present time.

In this thesis, the probes were modelled and constructed at the SPMMRC. All measurements were performed on a 7T Philips scanner. The coils have been successfully evaluated. The dipole, loops, strip line and wrist probes for imaging the pelvis, knee and wrist were tested for clinical use at 7T. Two elements wrist coil can pick up signals from the whole region of interest. The advantage is more uniformity of field of view and better sensitivity. The in vivo MRI images acquired in the wrist showed the two elements provided the good quality images for the human wrist. The second study is microstrip line probe. The current flows over the flat-strip were computed, it showed that a significant increase of current close to the edges. This result agrees with theory. We did not use the strip line coil to image a human body, because the coil generated a high SAR/B1 +2 level in the region of interest. The third study was of a coil of two square loops. One way of achieving decoupling is to use the overlapping technique to decouple the coils in the simulation. It produced high signal-to-noise ratio and provides a large field of view. Finally, the dipole has been developed for in vivo MRI applications. We presented a novel model for determining the length of the PECs required for tuning the dipole at 298 MHz. The efficiency, field of view and homogeneity were improved by adding the flat strip, two strips and array strips dipole. The SAR/B1 +2 generated by the dipoles was much less than produced by the loop coil and strip line coil in the pelvis. The dipoles showed the desired improvement in SNR and homogenous coverage. Coverage goes much further into the pelvis and knee as well.

Radiofrequency (RF) heating of composite magnetic materials enables direct and efficient transfer of energy to the sites of catalytic reactions within a chemical reactor. The materials consist of an RF heated magnetic component and a catalytic component. The two components can be optimised separately according to the demands of the application. This approach was applied to continuous direct amide formation from amines and carboxylic acids under flow conditions, a reaction of great interest and potential to the pharmaceutical industry. The RF heat generation of NiFe2 04-TiO2 magnetic materials were optimised. Catalyst screening showed sulfated commercial P 25 Ti02 to give good catalytic activity in the reaction of 4-phenylbutyric acid with aniline in xylene. The composite material was prepared mechanochemically from a mixture of the optimised magnetic and catalytic components. A continuous RF heated reactor was developed, consisting of a 6 mm diameter insulated micro packed-bed reactor placed within an RF induction coil. The reactor was operated at 7 bar and up to 200°C for up to 10 hours. The sulfated composite achieved t he highest activity of up to 50% conversion in a single pass and the least deactivation. Temperature profiles obtained from the analytical solutions were combined with a catalyst kinetic model to form a reactor model, which was validated by the experimental results. The concentration profiles obtained from the reactor model gave an insight into the mechanism of the observed process intensification - the temperature rise along the RF heated reactor axis helped to offset the reduction in the reaction rate as a result of depletion of the reactants. This novel type of process is therefore most suited to reactions with high reaction rate orders and it would therefore be of great interest to investigate other processes where this effect could be demonstrated.

Electrophysical agents (EPA) are a fundamental element of therapy practice and are vital for the treatment of a variety of conditions. Many of these agents employ some form of electromagnetic fields (EMF), in which radiofrequency (RF) is a major component. The therapeutic effects of RF are mainly linked to their effects on pain relief and potential effects on tissue repair. Although RF across various frequency ranges has been in use, reviews have shown that the frequency ranges currently used in therapy practice have narrowed to within 30 kHz-30,000 kHz (30 MHz). The most commonly used and hence the most commonly researched are shortwave therapies (SWT) that operate at 27.12 MHz, which is presently used predominantly in its pulsed form (PSWT). In addition to SWT, devices employing significantly lower RF ranges have also been used widely despite their lack of evidence. Capacitive Resistive Monopolar Radiofrequency (CRMRF) that operates at 448 kHz is one such RF. This programme of research was designed to investigate the physiological and clinical efficacy of CRMRF delivered using the 'Indiba Activ 902' device. The project also evaluated the scope and evidence for RF-based EPAs in therapy, through a comprehensive review of literature. A total of 120 relevant clinical studies on either acute (30 studies) or chronic (90 studies) conditions were reviewed. Notable evidence was identified for chronic OA knee and acute postoperative pain and wound healing. Some evidence also exists for chronic low back pain and healing of chronic wounds. Only eight studies reported devices that employed RF outside the shortwave frequency band. In a randomised crossover laboratory study on asymptomatic adults, the effects of contrasting doses of CRMRF on skin temperature (SKT), skin blood flow (SBF), nerve conduction velocity (NCV), deep blood flow and the extensibility of tissues were examined against a placebo dose and a control condition with no treatment. The study further compared CRMRF results with that of PSWT. The results showed that high (moderately thermal) and low (sub/minimally thermal) doses of CRMRF significantly enhanced and sustained SKT (p < 0.001), while only the high dose meaningfully increased SBF (p < 0.001). High dose PSWT increased SKT marginally (p < 0.001) but did not sustain it. Further, the high and low dose CRMRF significantly enhanced blood flow volume at depth (p=0.003), while PSWT failed to show any significant impact. None of the treatments significantly affected deep blood flow velocity, tissue extensibility or NCV. These results were reproduced on a cohort of patients affected by OA knee in a randomised controlled trial (RCT), and the effects appeared more pronounced in the patients than in the asymptomatic people. More importantly, the RCT showed that a four-week high dose CRMRF treatment (eight sessions) produced statistically and clinically significant gains in pain and function associated with OA knee in the short to medium term (p < 0.001), which was also significantly more pronounced than the gains produced by a placebo, or standard care (p=0.001for pain; p=0.031 for function). The findings of this study were considered promising. It is therefore suggested that CRMRF-based treatment can potentially be used as an adjunct to current therapeutic methods to enhance the clinical outcomes. However, further studies are needed to substantiate this, and the current results will provide credible baseline data for future research.

Orientador: Antonio José Maria Cataneo
Resumo: Introdução: A hiperidrose primária (HP) é um distúrbio caracterizado pela sudorese excessiva, levando a uma piora na qualidade de vida de seus portadores. Objetivo: Determinar a efetividade da radiofrequência (RF) no tratamento da HP. Método: Revisão sistemática de ensaios clínicos randomizados, estudos controlados e estudos observacionais em indivíduos portadores de HP, nos quais foram realizados o tratamento por RF comparado com qualquer outra modalidade de tratamento ou em que foram comparados os resultados antes e após a intervenção no tratamento isolado por RF. Os desfechos avaliados foram: grau de intensidade da hiperidrose, qualidade de vida, sudorese compensatória e recorrência dos sintomas. Resultados: Foram selecionados dez estudos, oito deles (204 participantes) empregando somente a RF (74 microagulhamentos e 130 ablações) e dois (65 participantes) comparando a RF com a simpatectomia videotoracoscópica. Houve redução da intensidade da HP no subgrupo que aplicou microagulhamento (3 estudos, 74 participantes, diferença média -1,24, IC 95% -1,44 a -1,03, I2=50%). Em um estudo em que se realizou ablação simpática por RF (36 participantes) houve maior redução da intensidade da HP do que nos três estudos em que se realizou microagulhamento (-2,56, IC 95% -2,76 a -2,36 versus -1,24, IC 95% -1,44 a -1,03). Houve melhora na qualidade de vida após ablação simpática (2 estudos, diferença média -15,92, IC 95% -17,61 a -14,24, I²= 23%). No microagulhamento também houve melhora ... (Resumo completo, clicar acesso eletrônico abaixo)
Doutor

Le traitement des arythmies cardiaques par ablation radiofréquence est une procédure thérapeutique permettant de restaurer un rythme normal par destruction thermique des tissus arythmogènes. A l'heure actuelle, l'intervention est réalisée sans imagerie temps réel permettant de visualiser la lésion pendant l'ablation. La thermométrie IRM permet de mesurer la température du tissu en chaque pixel et d'estimer directement l'étendue de la lésion via le calcul de la dose thermique cumulée. Si cette technique est déjà établie pour guider l'ablation de tumeurs dans différents organes, elle reste difficile à mettre en œuvre sur le cœur, notamment à cause des mouvements de respiration et de contraction myocardique. Dans le cadre de cette thèse, une méthode de thermométrie cardiaque a été implémentée pour réaliser une cartographie temps réel de la température du myocarde en condition de respiration libre. Plusieurs séquences IRM rapides ont été développées pour permettre l'acquisition d'environ 5 coupes par battement cardiaque avec une taille de voxel de 1.6X1.6X3 mm3. Plusieurs solutions de réduction des mouvements hors plan de coupe ont été évaluées : positionnement des coupes dans le sens principal du déplacement, suivi dynamique de la position des coupes en fonction de l'état respiratoire (navigateur, mesure de la position du cathéter). Le mouvement résiduel et les artéfacts de susceptibilité associés sont corrigés par des algorithmes temps réels pour permettre une précision de la thermométrie IRM à ±2°C sur les ventricules. Ce protocole a été utilisé avec succès pour le suivi d'ablations radiofréquences chez la brebis (N=3), permettant une corrélation (R=0.87) entre la dose thermique et la taille réelle des lésions induites. Les résultats sont très prometteurs quant à la pertinence de cette mesure pour une estimation en ligne de l'étendue de la lésion pendant l'ablation. Ces méthodes permettent d'envisager une évaluation clinique à court terme
Radiofrequency ablation is a therapeutic procedure for the treatment of cardiac arrhythmia by inducing a local necrosis of the arrhythmogenic tissue. This intervention is currently performed without online imaging of the lesion formation during radiofrequency delivery. MR thermometry provides a monitoring of temperature in the targeted tissue in each pixel and an immediate estimation of lesion via the calculation of the thermal dose. If this technique is well established for the guidance of tumor ablation in various organs, it remains challenging in the heart due to motion (breathing and myocardial contraction). In this work, a cardiac MR thermometry method was developed to perform a real-time temperature mapping of the heart under free-breathing conditions. Several MR pulse sequences were designed to ensure the acquisition of up to 5 slices per heartbeat with a voxel size of 1.6X1.6X3 mm3. Different solutions of minimization of out-of-plane motion were evaluated: alignment of the slices in the main direction of displacement, dynamic update of slice position depending on the respiratory state (echo-navigator, measure of the catheter position). Residual in-plane motion and associated susceptibility artifacts were corrected by real-time algorithms to allow a precision of MR thermometry of ±2°C in ventricles. This protocol was successfully used for the monitoring of radiofrequency ablation in sheep (N=3), allowing a correlation (R=87) between thermal dose maps and sizes of created lesions. These results are promising regarding the relevance of this measure for an inline estimation of the lesion extent during ablation

The invention and development of Radiofrequency Endometrial Ablation (RaFEA) has been, by turns, exciting, frustrating and anxiety - provoking. Although one of the major motives for developing an alternative means of effective endometrial ablation to the hysteroscopically directed modalities was to improve safety, it seems that in using RaFEA, one set of potential dangers may have been exchanged for another set. Whilst the potentially fatal risks of uterine penetration and fluid toxicity are not encountered with RaFEA, the charging of the patient with an electric field for the duration of therapy brings its own risks, requiring very special precautions of their own (see section 2 - safety). At the time of writing, the future role of the technique is still being decided. It may be that the technique requires such specialist monitoring that it is unsuitable for general use, and may be restricted to one or two specialist centres for the treatment of certain patients who cannot be treated easily any other way. What is certain is that safety is of paramount importance, and the adequate training of those concerned and a basic knowledge of RF physics are both essential to safe practice. Practiced safely, the technique is highly successful, and has proved of considerable benefit to hundreds of patients. However, there have been a number of serious complications in other centres, each of which has been analysed in very great detail. These are considered in section 2 - safety.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.
Includes bibliographical references (p. 67-70).
Parallel MRI techniques allow acceleration of MR imaging beyond traditional speed limits. In parallel MRI, arrays of radiofrequency (RF) detector coil arrays are used to perform some degree of spatial encoding which complements traditional encoding using magnetic field gradients. As the acceleration factor increases, coil design becomes critical to the overall image quality. The quality of a design is commonly judged on how it compares with other coil configurations. A procedure to evaluate the absolute performance of RF coil arrays is proposed. Electromagnetic calculations to compute the ultimate intrinsic signal-to-noise ratio (SNR) available for any physically realizable coil array are shown, and coil performance maps are generated based on the ratio of experimentally measured SNR to this ultimate intrinsic SNR.
by Riccardo Lattanzi.
S.M.

Liver cancer is a major cause of death worldwide and the impact that it has is set to increase in the coming decades. More than half a million cases are diagnosed each year and it is likely many more sufferers are dying unidentified in parts of the world with poor healthcare. Survival rates for untreated cases after diagnosis are low with few patients living beyond one year. A key cause for low survival rates being that the standard treatment is surgical resection; fewer than one quarter of patients are suitable for invasive surgery and five year survival rates rarely exceeds 66 %. RadioFrequency Ablation (RFA) is a minimally invasive technique which utilises the electrically resistive property of tissue to deposit heat energy locally in the vicinity of the tips of an RFA needle. Heat is transferred away through the tissue by conduction, convection of large blood vessels, and bulk flow of blood in smaller vessels. Liver cells, both cancerous and benign, when exposed to the resultant abnormally high temperatures die considerably more rapidly than in cases of natural hyperthermia. It is thus the radiotherapist’s objective to place the RFA needle in a position that maximises destruction of tumour cells, but minimises the collateral damage of surrounding healthy cells. The learning curve of this nontrivial task is reflected unfavourably in the statistics that relate patient survival rate to clinician experience. In this thesis two mathematical models are presented that could be combined into a ‘global’ model of the effects of RFA. To predict cell death in these conditions under RFA, the O’NeillModel is presented in which cells are accounted for by one of three states: alive, vulnerable, and dead. A mechanistic interpretation of the O’Neill Model is attained through comparison to a model from the literature. A known, but little investigated occurrence of tissue swelling in the annular region peripheral to the ablation volume is modelled in a novel way through equations from the literature that track ion transport across the cell membrane; the O’Neill Model for cell death is also incorporated into this model of oedema.

Particle accelerators are a leading tool for frontier science. Pushing that frontier further demands more machines with higher performance, and more of a very expensive technology: superconducting radio-frequency (SRF) acceleration. From a materials perspective this means reducing residual surface resistance or raising the operating temperature (currently ~2 K) of SRF cavities. Both are pursued by materials modification: nitrogen doping/infusion in the first instance and coating with Nb3Sn in the second. Materials characterization is key to achieving understanding and directing RandD. However, very little has been done. This present work aims to fill the knowledge gap and to provide needed, validated tools to the accelerator science community. In this connection, SIMS, XPS and EBSD have proven especially valuable and represent the majority of discussion in this dissertation.
Doctor of Philosophy
Particle accelerators are a powerful tool that helps us expand our knowledge of science and how the universe works. Pushing that knowledge further requires us to use more and more powerful particle accelerators. Particle accelerators are based on a very expensive technology: superconducting radio-frequency (SRF) cavities. These cavities are hollow tubes made from niobium and shaped in such a way as to cause electromagnetic waves to form. These waves are what are used to accelerate particles. The energy input and loss of energy as heat are massive resulting in millions of dollars a year in electric bills at particle accelerator facilities. In order to build bigger and more powerful particle accelerates they most be more efficient or they become prohibitively expensive. In this dissertation I look at several next generation materials used in building particle accelerators. In particular I describe and go into detail about how to characterize these materials. In other words, how we determine the materials properties and how those properties affect the performance.

Las técnicas ablativas basadas en energía por radiofrecuencia (RF) se emplean con el fin de lograr un calentamiento seguro y localizado en el tejido biológico. En los últimos años ha habido un rápido crecimiento en el número de nuevos procedimientos médicos que hacen uso de dichas técnicas, lo cual ha ido acompañado de la aparición de nuevos diseños de electrodos y protocolos de aplicación de energía. Sin embargo, existen todavía muchas incógnitas sobre el verdadero comportamiento electro-térmico de los aplicadores de energía, así como de la interacción energía-tejido en aplicaciones concretas. El principal propósito de esta Tesis Doctoral es adquirir un mejor conocimiento de los fenómenos eléctricos y térmicos involucrados en los procesos de calentamiento de tejidos biológicos mediante corrientes de RF. Esto permitirá, por un lado, mejorar la eficacia y seguridad de las técnicas actualmente empleadas en la clínica en campos tan diferentes como la cirugía cardiaca, oncológica o dermatológica; y por otro, sugerir mejoras tecnológicas para el diseño de nuevos aplicadores. La Tesis Doctoral combina dos metodologías ampliamente utilizadas en el campo de la Ingeniería Biomédica, como son el modelado computacional (matemático) y la experimentación (ex vivo e in vivo). En cuanto al área cardiaca, la investigación se ha centrado, por una parte, en mejorar la ablación intraoperatoria de la fibrilación auricular por aproximación epicárdica, es decir, susceptible de ser realizada de forma mínimamente invasiva. Para ello, se ha estudiado mediante modelos matemáticos un sistema de medida de la impedancia epicárdica como método de valoración de la cantidad de grasa previo a la ablación. Por otra parte, se ha estudiado cómo mejorar la ablación de la pared ventricular por aproximación endocárdica-endocárdica (septo interventricular) y endocárdica-epicárdica (pared libre del ventrículo). Con este objetivo, se han comparado mediante modelado por computador la eficacia de los modos de ablación bipolar y unipolar en términos de la transmuralidad de la lesión en la pared ventricular. En lo que respecta al área de cirugía oncológica, la investigación se ha centrado en la resección hepática asistida por RF. Las técnicas de calentamiento por RF deberían ser capaces de minimizar el sangrado intraoperatorio y sellar vasos y ductos mediante la creación de una necrosis coagulativa por calentamiento. Si este calentamiento se produce en las cercanías de grandes vasos, existe un problema potencial de daño a la pared de dicho vaso. En este sentido, se ha evaluado con modelos matemáticos y experimentación in vivo si el efecto del flujo de sangre dentro de un gran vaso es capaz de proteger térmicamente su pared cuando se realiza una resección asistida por RF en sus cercanías. Además, se ha realizado un estudio computacional y experimental ex vivo e in vivo del comportamiento electro-térmico de aplicadores de RF bipolares internamente refrigerados, puesto que representan una opción más segura frente a los monopolares en la medida en que las corrientes de RF fluyen casi exclusivamente por el tejido biológico situado entre ambos electrodos. Respecto al área dermatológica, la investigación se ha centrado en mejorar el tratamiento de enfermedades o desórdenes del tejido subcutáneo (tales como lipomatosis, lipedema, enfermedad de Madelung y celulitis) mediante el estudio teórico de la dosimetría correcta en cada caso. Para ello, se han evaluado los efectos eléctricos, térmicos y termo-elásticos de dos estructuras diferentes de tejido subcutáneo durante el calentamiento por RF, y se ha cuantificado el daño térmico producido en ambas estructuras tras dicho calentamiento
González Suárez, A. (2014). Computational Models and Experimentation for Radiofrequency-based Ablative Techniques [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/36502
TESIS

The continuously growing throughput in wireless applications severely impacts the architecture and design of modern transceivers. One of the most challenging aspects is the design of the power amplifier (PA). Indeed, this block dominantly determines the overall transceiver power efficiency and therefore battery life-time. On the other hand, PA linearity is a key feature that limits the maximum allowed data rate. The goal of this thesis is to investigate and design novel smart architectures circumventing the stringent linearity/efficiency trade-off for third generation cellular and data transmission standards. A demonstrator has been developed on silicon (0.25µm BiCMOS ST Microelectronics technology), and has allowed validating the efficiency/linearity improvement principle
Abstract

Significant concern has been expressed regarding the potential link between various health problems (eg cancer) and exposure to radiofrequency (RF) electromagnetic energy (EME). In particular mobile phone base stations, commonly referred to as radio base stations (RBS) have attracted public attention. With the number of these RBS increasing around the world, questions have been raised about the fields generated by these types of equipment. In particular the public and the industry are interested in the strengths of these fields and how they compare to the regulatory standards of various countries. There are two approaches that can be used to determine the field strengths generated by the RF EME transmitting installations. They can be physically measured using expensive and sophisticated equipment, requiring a significant level of technical knowledge, or alternatively, they can be modelled theoretically using complex simulations. Due to the number of installations that already exist, and the rate at which their numbers are increasing, the physical measurement of these sites may be considered impractical and expensive. Therefore, simulation of the RF EME fields from these installations is often the preferred option. In Australia, the industry code C564:2011 – Mobile Phone Base Station Deployment (CA 2011) ‐ requires that site RF EME assessments for Mobile Phone Radiocommunications Infrastructure must be completed in accordance with the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) prediction methodology Technical Report – Radio Frequency EME Exposure Levels – Prediction Methodologies (Bangay 2002). The purpose of the assessments is to provide affected persons in the community with a reliable, objective and near worst case, line‐of‐sight estimate of the maximum levels of RF EME likely to be emitted by the proposed or upgraded mobile phone base station installation, for full‐power operation without producing a gross over‐estimate (CA 2011). The aim of this study is to test, using actual field measurements, whether the assumptions made in the ARPANSA prediction methodology result in achieving the stated purpose of the assessments as explained above. This study compares the calculated RF EME levels by a number of commercial software packages, for a number of service providers and technology types (i.e. WCDMA850, GSM900 and 1800 and UMTS2100), at a number of locations, to the measured levels for those same locations. As part of the measurement component of this study the applicability of a number of spatial averaging assessment techniques will also be considered. In particular the 3, 6 and 9 point spatial averaging techniques recommended in the IEC assessment standard and a 7 point spatial averaging technique, recommended by the Australian Radiation Protection Agency (ARPANSA) are compared and evaluated. The main findings of this study are: 1. Overall, the ARPANSA prediction methodology does achieve its stated purpose. 2. The largest overestimation of the RF EME levels by simulation was 20.92 dB (124 times). Whilst, this appears to be quite large the largest simulated level was 624 times below the general public limit. 3. The use of a single measurement point to determine RF EME levels for a given location could result in an under estimation of the levels beyond the ±3 dB uncertainity of the measurements (‐8.18 dB). If completing measurements to confirm compliance to the regulatory limits it would be better to use the 9 pt averaging technique when the 1pt measured level is greater than 30% of the applicable limit. 4. Comparisons between the measurement and simulation results revealed that they do not always closely align with each other. However, in all cases where this occurred, the simulated levels did not under estimate the measured levels by more than 0.82 dB beyond the combined uncertainty of the measurements and simulations.

Thesis (M.S. in Electrical Engineering and Electrical Engineer) Naval Postgraduate School, June 1997.
Thesis advisors, Randy L. Borchardt, Rudlof Panholzer. Includes bibliographical references (p. 99). Also available online.

As MRI systems have increased in static magnetic field strength, the radiofrequency (RF) fields that are used for magnetisation excitation and signal reception have become significantly less uniform. This can lead to image artifacts and errors when performing quantitative MRI. A further complication arises if the RF fields vary substantially in time. In the first part of this investigation temporal variations caused by respiration were explored on a 3T scanner. It was found that fractional changes in transmit field amplitude between inhalation and expiration ranged from 1% to 14% in the region of the liver in a small group of normal subjects. This observation motivated the development of a pulse sequence and reconstruction method to allow dynamic observation of the transmit field throughout the respiratory cycle. However, the proposed method was unsuccessful due to the inherently time-consuming nature of transmit field mapping sequences. This prompted the development of a novel data reconstruction method to allow the acceleration of transmit field mapping sequences. The proposed technique posed the RF field reconstruction as a nonlinear least-squares optimisation problem, exploiting the fact that the fields vary smoothly. It was shown that this approach was superior to standard reconstruction approaches. The final component of this thesis presents a unified approach to RF field calibration. The proposed method uses all measured data to estimate both transmit and receive sensitivities, whilst simultaneously insisting that they are smooth functions of space. The resulting maps are robust to both noise and imperfections in regions of low signal.

In a pilot study, radiofrequency backscatter data was collected in the paravertebral (PV) spaces of 4 healthy individuals. Using the associated gray scale ultrasound and Doppler data as guidance, regions-of-interest (ROIs) were chosen inside vessel in the PV space and outside vessel.. ROI sizes of 1.0 mm, 1.5 mm, and 2.0 mm square were examined for auto-regressive (AR) orders of 10, 20, 30, and 40 and bandwidths of 3dB, 6dB, 20dB. Spectral estimations were performed for each ROI size, AR order, and bandwidth over the A-lines of the ultrasound radiofrequency (RF) data. The spectra were averaged and normalized using data collected from a tissue phantom (Siemens S3000 with a 9L4 probe, Siemens Medical Solutions USA, Inc., Malvern, PA). Eight spectral parameters—Y-intercept, slope, and mid-band fit of the regression line, maximum dB of the spectra, frequency at maximum dB, minimum dB of the spectra, frequency at minimum dB, and integrated backscatter were calculated for each spectral estimate and used create ensembles of bagged tree classifiers. An AR order of 10, bandwidth of 6 dB, and an ROI size of 1.0 mm resulted in the minimum out-of-bag error. An additional random forest, using these chosen values, was created from 70% of the data and evaluated independently with the remaining 30% of data. The random forest achieved a predictive accuracy of 92% and Youden’s Index of 0.85. These results suggest that spectral analysis of ultrasound RF backscatter has the potential to identify intercostal blood vessels.

Using the associated gray scale ultrasound and Doppler data as guidance, regions-of-interest (ROIs) were chosen to represent five tissue types found in and around the PV space—rib, pleura, superior costotransverse ligament, intercostal vessel (artery or vein), and the PV space away from the vessel. An ROI size of 2.0 mm, bandwidth of 20 dB, and AR order 10 had the lowest out-of-bag OOB error at 0.315, and averaged across all tissue types, an accuracy of 89.15%, sensitivity of 0.70, specificity of 0.93, and Youden’s Index (YI) of 0.62. These results show that the identification of the five tissues types in radiofrequency backscatter from intercostal ultrasound is feasible.

Another ROI type was added, rib, along with 2-D spectral parameters, real and complex cepstral peaks were added to the data set. All 5 frames of ultrasound data were used to grow the database by a factor of 5. Ensembles of bagged trees created using ROIs of size 2.0 mm, bandwidths of 20 dB, and AR order of 10 were found to have the lowest OOB error at 0.123. After retraining the classifier for data with an ROI size of 2.0 mm, bandwidth 20, AR order 10, and 200 trees, for the 30% test data, accuracy was found to be an average of 95.90% across all tissue types, average sensitivity was found to be 0.85 across all tissue types, average specificity was found to be 0.98 across all tissue types, and average YI across all tissue types was found to be 0.83.

Introduction The majority of primary and secondary liver tumours are inoperable. „In situ‟ thermal destruction techniques such as radiofrequency, microwave ablation and cryotherapy have been employed to treat these inoperable tumours. Despite recent advances in these technologies, large and peri-vascular tumours still suffer from a relatively high recurrence rate post ablation. This is thought to be due to the loss of thermal energy to surrounding vasculature, known as the heat sink effect. The aim of this project was to investigate the effect of surrounding vasculature on ablation morphology and success and compare the three most popular ablation modalities. Methods Standard sized ablations were created in rat liver at various distances from the hilum with all three methods. At various time points, tissue samples were retrieved and underwent histological (H&E) and immuno-cytochemical (Hsp70 and Caspase 3) staining in order to assess lesion evolution and the effects of surrounding vasculature on ablation completeness. Results All rats survived. The greatest amount of activity was seen in the transition zone. H&E and immuno-cytochemical analyses of lesion evolution discovered previously unreported cellular changes, particularly in the transition zone. Cryotherapy ablation seemed to be the most irregular and unpredictable of the three. Radiofrequency ablation was uniform but showed evidence of extra-lesional apoptosis and perivascular cell survival in addition to Hsp 70 activity in the transition zone that was affected by surrounding vasculature. Microwave ablation seemed to be influenced least by surrounding vasculature and formed the most uniform lesion with very little extra-lesional collateral damage. Conclusion The success of ablation is dependent upon the adjacent blood vessels and microwave ablation seemed to form the most predictable burn and be least affected by surrounding vasculature compared to radiofrequency. Cryotherapy should not be used as first line treatment to treat unresectable liver tumours. In addition the exact role of HSP 70 on the fate of cells in the transition zone, and the subsequent final ablation size and morphology is yet to be determined. Larger ablations in larger animal models may help answer some of these questions.

This doctoral thesis raises the idea that 3D printing can change the paradigm of radio- frequency electronics, which has been traditionally developed mainly conceiving planar topologies. A review on additive manufacturing and the different existing technologies is reported. To focus on the concerning topic, several applications of 3D-printed electronics in the RF field are collected to elaborate the State-of-the-Art. The main objectives of this project is to develop a 3D manufacturing technology for RF electronics passive components and circuits and to generate innovative research about the possibilities of AM in this area. Once the context is exposed, the manufacturing process for 3D-printed electronics developed within the frame of this project is described and characterized. This technology consists of three different steps. First of all, the 3D model of the prototype is designed using a CAD environment with electromagnetic simulation features, hence size parameters are adjusted to fit the specifications. Hereon, the 3D polymer substrate is printed by using either stereolithography or material jetting techniques. Stereolithography is found to be a cheaper AM technology while material jetting offers a better printing resolution and softer surface endings. Finally the object is partially metallized to obtain the conductive layer of the component or circuit using an electrolytic process, such as electroless plating or electroplating. The characterization includes the electromagnetic specifications of the dielectric substrates (i.e. the dielectric constant and the loss tangent) and the quality of the metallization (i.e. the resistivity and the layer thickness). The results of the plating resitivity are found to be competitive compared to the SoA. In order to demonstrate the possibilities of the developed technology, several devices are designed and tested. The key factor of these prototypes is that they would be very difficult, costly or impossible to manufacture using conventional technologies. As a preliminary demonstration, a hello-world circuit to turn on a LED proves that almost any kind of shape can be plated, including vias; both through hole and SMD components can be soldered and that mechanical stress such as USB plugging is resisted by the metal layer. In addition, a study on conical inductors is carried out showing the advantages of these components for broadband applications with compact devices. They offer a larger bandwidth cylindrical solenoids and are more compact than planar coils. As an application example, they are used in the manufacturing of 3D passive filters. The prototypes present agreement with simulations and the ideal response. Slight discrepancies are caused by the manufacturing tolerances. Moreover, 3D filters are also designed as one single-printed part, a new technique for 3D discrete component integration. That permits to reduce the number of components to assembly so that it does not increase with the order of the filter. These single 3D-printed prototypes present improvement in performance and compactness as well. In addition to the lumped circuits, a whole chapter is dedicated to distributed-element devices. A study on helical-microstrip transmission lines is carried out showing an important enhancement for line segment miniaturization. Hereon, they are implemented on the design of impedance transformers, which also benefit from bandwidth broadening. Another proposed device is the hybrid branch-line coupler, which, besides the implementation of helical lines, it has been designed conceiving a capacitively loaded folded structure. This coupler gives very interesting results in compactness improvement, without significant reduction of the bandwidth. The prototypes have been compared to the conventional topology as well as to other designs found within the SoA. Finally, helical-microstrip coupled-line couplers have also been designed, fabricated and studied. They offer a good enhancement in terms of compactness though it goes in slight detriment of the coupling factor due to the manufacturing tolerances.
Aquesta tesi doctoral proposa la idea que la impressió 3D pot canviar el paradigma de l’electrònica de radiofreqüència. S’hi anomenen i expliquen les tecnologies de manufactura additiva existents. Per centrar-se en el principal tema d’interès, s’exposa un compendi d’aplicacions d’electrònica impresa en 3D en el camp de la RF amb el qual s’ha confeccionat l’estat de la qüestió. Un cop exposat el context, el procés de manufactura per a electrònica impresa en 3D que s’ha desenvolupat en el marc d’aquest projecte és descrit i caracteritzat. Aquesta tecnologia consisteix en la impressió en 3D d’un substrat de polímer utilitzant tècniques basades, o bé en estereolitografia, o bé en material jetting. Posteriorment, el component o circuit es metal·litza parcialment mitjançant un procés electrolític ja sigui electroless plating o electroplating. La caracterització inclou les especificacions electromagnètiques del substrat dielèctric i la qualitat de metal·lització, que s’han resultat ser competitives relació amb l’estat de la qüestió. Amb l’objectiu de demostrar les possibilitats de la tecnologia desenvolupada, s’han dissenyat i testejat dispositius electrònics de RF, concebent-los en l’espai tridimensional. El punt clau és que els dispositius dissenyats serien molt difícils, costosos o directament impossibles de fabricar usant tecnologies convencionals. A remarcar, s’ha dut a terme un estudi sobre inductors cònics, mostrant els avantatges d’aquests components per a aplicacions de banda ampla amb dispositius compactes. Aquests inductors shan fet servir per a la fabricació de filtres passius en 3D. A més, a més, s’han dissenyat filtres 3D per ser impresos en una sola part, una tècnica nova que per produir circuits 3D amb components discrets integrats. A part dels circuits d’elements discrets, s’ha dedicat un capítol sencer als dispositius d’elements distribuïts. S’ha dut a terme un estudi sobre línies de transmissió microstrip helicoidals, les quals aporten una millora important de miniaturització dels segments de línia. Partint d’aquí, aquestes línies s’han implementat en el disseny de transformadors d’impedància, que també milloren en termes d’ample de banda, acobladors híbrids de tipus branch-line i acobladors basats en línies acoblades. Aquests dispositius han resultat tenir millores importants de compacitat respecte els dissenys convencionals fabricats en estructures planars.

Le refroidissement évaporatif d'un nuage d'atomes de rubidium ultra froids a été étudié dans le cadre d'un piégeage radio-fréquence dans un champ magnétique inhomogène de type Ioffe-Pritchard. Contrairement à la situation rencontrée dans les pièges magnétiques statiques où une transition radio-fréquence à un photon est utilisée pour contrôler la hauteur du piège, nous montrons qu'une transition à plusieurs photons est nécessaire pour contrôler la hauteur d'un piège habillé par un champ radio-fréquence. L'efficacité de l'évaporation n'est pas identique pour toutes les transitions : une transition à deux photons s'est avérée la plus efficace par rapport aux autres. Des résultats préliminaires de refroidissement évaporatif sont discutés. La dégénérescence quantique, qui est le but poursuivi dans le refroidissement évaporatif, n'a pas été atteinte : la très grande anisotropie du piège rendant pratiquement impossible la thermalisation à l'intérieur du piège. La dégénérescence quantique dans un piège radio-fréquence très anisotrope pourrait être satisfaite par la transformation adiabatique vers ce piège à partir d'un condensat de Bose-Einstein produit dans un piège magnétique de type Ioffe-Pritchard. Les expériences qui ont été réalisées dans ce sens ont été négatives : les fréquences latérales du pièges radio-fréquences sont trop basses pour assurer une transformation adiabatique en un temps raisonnable pour l'expérience. La fin de la thèse expose des résultats préliminaires de piégeage d'atomes dans une configuration magnétique quadrupolaire, cette dernière configuration conduisant à des fréquences d'oscillation de piège plus élevées dans les directions latérales
In this thesis, I describe the spectroscopic investigations and preliminary results of evaporative cooling of rubidium atoms done on a magnetic trap dressed with a radiofrequency field. Unlike the case of a static magnetic trap, where a single radiofrequency photon is used to outcouple atoms we have demonstrated that a multiphoton transitions is necessary. This transitions are nearly resonant with the energy spacing of the radiofrequency dressed states. The evaporation efficiency is not the same for all the observed transitions: the transition involving a two photon process is more efficient compared to the others. Preliminary results of evaporative cooling in radiofrequency dressed trap is discussed. The quantum degeneracy is not reached as it is difficult to satisfy the adiabaticity condition in the direction perpendicular to the tightly confined direction in the radiofrequency dressed trap, since the oscillation frequencies are a few Hz in this direction. One way to render the evaporative cooling more efficiently is by increasing the oscillation frequency in this direction. Lastly, we discuss a method to load the atoms into a radiofrequency dressed Quadrupole trap where the oscillation frequency is higher in this direction

Kyoto University (京都大学)
0048
新制・課程博士
博士(人間・環境学)
甲第13165号
人博第372号
新制||人||91(附属図書館)
18||D||173(吉田南総合図書館)
UT51-2007-H438
京都大学大学院人間・環境学研究科相関環境学
(主査)教授 小松 賢志, 助教授 倉橋 和義, 助教授 三浦 智行
学位規則第4条第1項該当

Hypertension is a prevalent condition affecting one third of the adult population worldwide. Medications alone have failed to control the blood pressure (BP) in a large proportion of the hypertensive population. Therefore, renal artery denervation (RAD) was developed for the management of resistant hypertension. However, its efficacy was found to be inconsistent in clinical trials. Delivery of effective ablation that results in sufficient nerve injury is one important criterion for a successful procedure. This thesis focuses on evaluation of various commercially available RAD devices and understanding their unique properties and limitations. Using an in-house built renal artery phantom model, we demonstrated that single electrode Symplicity Flex produced larger lesions, in depth and width compared to multi-electrode EnligHTN when both systems were used under identical experimental conditions, and with optimal vessel wall contact. Clinically, in a small cohort of patients who underwent RAD using either systems, we found no significant difference in office BP reduction between the two systems and both groups had a significant reduction in office BP, which persisted up to 4 years. When the new generation multi-electrode Symplicity Spyral and multi-electrode EnligHTN systems were assessed in the same model, EnligHTN lesions were larger in depth. However, lesion depth of the new generation devices was reduced by 30-40% compared to older generation devices. In a phantom model of branch renal artery, Symplicity Spyral produced lesion that were of similar size and with bigger circumferential coverage compared to main vessel phantom model. No overheating at the electrode-tissue interface occurred during branch ablation. Overall, this thesis broadens our knowledge in the field of RAD with respect to information regarding properties and limitation of different RAD systems and it aids in refining the procedure in order to achieve the best clinical outcome.