Global ETD Search

61	Compact Helical Antenna for Smart Implant Applications Karnaushenko, Dmitriy D. 19 October 2017 (has links) Medical devices have made a big step forward in the past decades. One of the most noticeable medical events of the twenties century was the development of long-lasting, wireless electronic implants such as identification tags, pacemakers and neuronal stimulators. These devices were only made possible after the development of small scale radio frequency electronics. Small radio electronic circuits provided a way to operate in both transmission and reception mode allowing an implant to communicate with an external world from inside a living organism. Bidirectional communication is a vital feature that has been increasingly implemented in similar systems to continuously record biological parameters, to remotely configure the implant, or to wirelessly stimulate internal organs. Further miniaturisation of implantable devices to make the operation of the device more comfortable for the patient requires rethinking of the whole radio system concept making it both power efficient and of high performance. Nowadays, high data throughput, large bandwidth, and long term operation requires new radio systems to operate at UHF (ultra-high frequency) bands as this is the most suitable for implantable applications. For instance, the MICS (Medical Implant Communication System) band was introduced for the communication with implantable devices. However, this band could only enable communication at low data rates. This was acceptable for the transmission of telemetry data such as heart beat rate, respiratory and temperature with sub Mbps rates. Novel developments such as neuronal and prosthetic implants require significantly higher data rates more than 10 Mbps that can be achieved with large bandwidth communicating systems operating at higher frequencies in a GHz range. Higher operating frequency would also resolve a strong issue of MICS devices, namely the scale of implants defined by dimensions of antennas used at this band. Operation at 2.4 GHz ISM band was recognized to be the most adequate as it has a moderate absorption in the human body providing a compromise between an antenna/implant scale and a total power efficiency of the communicating system. This thesis addresses a key challenge of implantable radio communicating systems namely an efficient and small scale antenna design which allows a high yield fabrication in a microelectronic fashion. It was demonstrated that a helical antenna design allows the designer to precisely tune the operating frequency, input impedance, and bandwidth by changing the geometry of a self-assembled 3D structure defined by an initial 2D planar layout. Novel stimuli responsive materials were synthesized, and the rolled-up technology was explored for fabrication of 5.5-mm-long helical antenna arrays operating in ISM bands at 5.8 and 2.4 GHz. Characterization and various applications of the fabricated antennas are successfully demonstrated in the thesis. info:eu-repo/classification/ddc/620 ddc:620
62	Wireless Signals and Male Fertility Mouradi, Rand 24 October 2011 (has links) No description available. Biomedical Engineering Biomedical Research Electrical Engineering Electromagnetics Electromagnetism Engineering Health Public Health Radiation Wireless signals effects cellular phones mobile phones RF signals and male infertility brain tumors electromegnitic fields Dosimetry FDTD specific absorption rate (SAR) RF radiation cell phones and ROS wireless signals and human health.
63	Detailing radio frequency controlled hyperthermia and its application in ultrahigh field magnetic resonance Winter, Lukas 06 August 2014 (has links) Die vorliegende Arbeit untersucht die grundsätzliche Machbarkeit, Radiofrequenzimpulse (RF) der Ultrahochfeld (UHF) Magnetresonanztomographie (MRT) (B0≥7.0T) für therapeutische Verfahren wie die RF Hyperthermie oder die lokalisierte Freigabe von Wirkstoffträgern und Markern zu nutzen. Im Rahmen der Arbeit wurde ein 8-Kanal Sened/Empfangsapplikator entwickelt, der bei einer Protonenfrequenz von 298MHz operiert. Mit diesem weltweit ersten System konnte in der Arbeit experimentell bewiesen werden, dass die entwickelte Hardware sowohl zielgerichtete lokalisierte RF Erwärmung als auch MR Bildgebung und MR Thermometrie (MRTh) realisiert. Mit den zusätzlichen Freiheitsgraden (Phase, Amplitude) eines mehrkanaligen Sendesystems konnte aufgezeigt werden, dass der Ort der thermischen Dosierung gezielt verändert bzw. festgelegt werden kann. In realitätsnahen Temperatursimulationen mit numerischen Modellen des Menschen, wird in der Arbeit aufgezeigt, dass mittels des entwickelten Hybridaufbaus eine kontrollierte und lokalisierte thermische Dosierung im Zentrum des menschlichen Kopfes erzeugt werden kann. Nach der erfolgreichen Durchführung dieser Machbarkeitsstudie wurden in theoretischen Überlegungen, numerischen Simulationen und in ersten grundlegenden experimentellen Versuchen die elektromagnetischen Gegebenheiten von MRT und lokal induzierter RF Hyperthermie für Frequenzen größer als 298MHz untersucht. In einem Frequenzbereich bis zu 1.44GHz konnte der Energiefokus mit Hilfe spezialisierter RF Antennenkonfigurationen entscheidend weiter verkleinert werden, sodass Temperaturkegeldurchmesser von wenigen Millimetern erreicht wurden. Gleichzeitig konnte gezeigt werden, dass die vorgestellten Konzepte ausreichende Signalstärke der zirkular polarisierten Spinanregungsfelder bei akzeptabler oberflächlicher Energieabsorption erzeugen, um eine potentielle Machbarkeit von in vivo MRT bei B0=33.8T oder in vivo Elektronenspinresonanz (ESR) im L-Band zu demonstrieren. / The presented work details the basic feasibility of using radiofrequency (RF) fields generated by ultrahigh field (UHF) magnetic resonance (MR) (B0≥7.0T) systems for therapeutic applications such as RF hyperthermia and targeted drug delivery. A truly hybrid 8-channel transmit/receive applicator operating at the 7.0T proton MR frequency of 298MHz has been developed. Experimental verification conducted in this work demonstrated that the hybrid applicator supports targeted RF heating, MR imaging and MR thermometry (MRTh). The approach offers extra degrees of freedom (RF phase, RF amplitude) that afford deliberate changes in the location and thermal dose of targeted RF induced heating. High spatial and temporal MR temperature mapping can be achieved due to intrinsic signal-to-noise ratio (SNR) gain of UHF MR together with the enhanced parallel imaging performance inherent to the multi-channel receive architecture used. Temperature simulations in human voxel models revealed that the proposed hybrid setup is capable to deposit a controlled and localized RF induced thermal dose in the center of the human brain. After demonstrating basic feasibility, theoretical considerations and proof-of-principle experiments were conducted for RF frequencies of up to 1.44GHz to explore electrodynamic constraints for MRI and targeted RF heating applications for a frequency range larger than 298MHz. For this frequency regime a significant reduction in the effective area of energy absorption was observed when using dedicated RF antenna arrays proposed and developed in this work. Based upon this initial experience it is safe to conclude that the presented concepts generate sufficient signal strength for the circular polarized spin excitation fields with acceptable specific absorption rate (SAR) on the surface, to render in vivo MRI at B0=33.8T or in vivo electron paramagnetic resonance (EPR) at L-Band feasible. Bildgebung MRT NMR Tomographie Magnetresonanz Hochfrequenz Antennen Hyperthermie Elektronenspinresonanz mehrkanalige HF Anregung Kernspinresonanz Thermometrie Elektromagnetische Simulationen Thermische Simulationen EPR ESR SAR spezifische Absorptionsrate MR Spulen Phantome neurologische Bildgebung kardiovaskuläre Bildgebung Dipolantennen MRI nuclear magnetic resonance imaging neuroimaging NMR Magnetic resonance tomography antennas radiofrequency Hyperthermia Ultrahigh field MR thermometry electromagnetic simulations multichannel transmission electron paramagnetic resonance EPR ESR SAR specific absorption rate RF coils phantoms cardiovascular imaging thermal simulations dipole antennas 570 Biowissenschaften, Biologie 32 Biologie WC 2600 ddc:570
64	Injectable formulations forming an implant in situ as vehicle of silica microparticles embedding superparamagnetic iron oxide nanoparticles for the local, magnetically mediated hyperthermia treatment of solid tumors Le Renard, Pol-Edern 06 September 2011 (has links) (PDF) Cette thèse présente les travaux de développement de formulations injectables capables de se solidifier in situ, formant ainsi un implant piégeant des microparticules magnétiques en vue du traitement de tumeurs par induction magnétique d'une hyperthermie locale modérée. Nous exposons tout d'abord le contexte physique, biologique et clinique de l'hyperthermie comme traitement anticancéreux, particulièrement des modalités électromagnétiques. Les performances in vitro et in vivo des matériaux et formulations sont alors présentées. L'objet du chapitre suivant est la caractérisation des propriétés physicochimiques, magnétiques, et chauffantes, dans un champ magnétique alternatif (115 kHz, 9 - 12 mT), des microparticules de silice renfermant des nanoparticules d'oxyde de fer superparamagnétiques (SPIONs) et de deux de leurs formulations: un hydrogel d'alginate de sodium et un organogel de poly(éthylène-co-alcool vinylique) dans le diméthylsulfoxide. Finalement, nous présentons le potentiel thérapeutique de 20 minutes d'hyperthermie locale induite après injection de l'organogel superparamagnétique dans un modèle murin sous-cutané de tumeurs nécrosantes de colocarcinome humain. hyperthermie hyperthermie locale induction magnétique champs magnétiques alternatifs implants injectables solidification in situ implant in-situ hydrogels alginate poloxamer chitosan organogel cellulose acétate poly(éthylène-co-alcool vinylique) PMMA diméthylsulfoxide HELA microparticules de silice microparticules nano-composite SPION tumeurs solides injection intratumorale colocarcinome cancer adjuvant thérapie adjuvante chauffage par pertes relaxation de Néel relaxation de Brown SQUID specific absorption rate specific loss power ceramiques liposomes réponse immunitaire chaperonnes moléculaires heat shock protein cibles moleculaires de l'hyperthermie

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