Дисертації з теми "Phased array coils"
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Stark, Joseph C. (Joseph Charles) 1980. "Wireless power transmission utilizing a phased array of Tesla coils." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/18036.
Повний текст джерелаIncludes bibliographical references (p. 245-247).
This thesis discusses the theory and design of coupled resonant systems and how they can be linked in a phased array for the wireless transmission of electrical power. A detailed derivation of their operational theory is presented with a strong emphasis on the current and voltage waveforms produced. Formulas are presented relating the features of the waveforms to specific parameters of the system. They provide a theoretical basis for the design of the TeslaE coil systems. Unloaded and loaded operating efficiency is considered from both a power and energy perspective with emphasis on maximizing the two quantities. With these design formulas, a working set of two distinct coupled resonant systems were locked in frequency and controllable in phase to produce a phased array capable of wireless power transmission. The operational details and practical design considerations are presented and explained. The measured output waveforms were found to closely agree with the predicted models.
by Joseph C. Stark, III.
M.Eng.
Papoti, Daniel. "Desenvolvimento de bobinas de RF transmissoras e receptoras do tipo phased arrays para experimentos de imagens por ressonância magnética em ratos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-25052011-162055/.
Повний текст джерелаMagnetic Resonance Imaging (MRI) experiments on small animals, as well as in human, require a specific RF coil set in order to maximize the Radiofrequency (RF) field homogeneity during transmission and Signal-to-Noise Ratio (SNR) during reception. The most common geometries of RF transmitter coil used in human systems are the well known Birdcage resonators. Among the receiver coils geometry the concept of NMR Phased Arrays or multi channel coils is widely employed in applications that need a high SNR in a large region of interest (ROI), further allowing parallel imaging acquisition methodologies. The work reported here describes the development of a transmit-only and receive-only RF coil set actively detuned specifically designed to MRI acquisition of rats brain for purposes of neuroscience studies. The transmitter geometries developed were two Birdcages with 8 and 16 rungs and our proposed geometry named Double Crossed Saddle (DCS). For reception we developed one common surface coil made of two turn loops and a 2-channel Phased Array, both actively detuned during reception. The results have confirmed that the 16 rungs Birdcage are superior among other transmit coils in producing homogeneous RF field inside a ROI of 80% of coil´s inner diameter. However, the simplicity and reduced number of capacitors makes the DCS coil a good choice in experiments with different samples and load conditions. Among the receive coils developed, the surface coil showed a better SNR in comparison with the 2-channel Phased array, which has the advantage of producing a large area with high SNR. The SNR of both surface coil and 2-channel array was compared with a transceiver Saddle Crossed coil, available at our lab, specific designed to obtain rat brain images. These results have corroborated that transmit-only and receive-only RF coils have best performance than transceiver volume coils for obtain MRI images of rats brain, allowing image acquisition with same resolution and reduced scan time.
Ferrand, Guillaume. "Antennes reseaux pour la transmission parallele en irm a ultra haut champ : conception, réalisation et stratégie de pilotage." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00647901.
Повний текст джерелаConsalter, Daniel Martelozo. "Implementação de aquisição paralelas de imagens utilizando bobinas de RF tipo phased array e sampled array." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-14092017-154855/.
Повний текст джерелаParallel techniques and dedicated hardware has been developed since the 1980s to reduce acquisition time on Magnetic Resonance Imaging (MRI) scanners. A phased array is a receiver only mode device concept, which uses multiple channels (coils) with their own detection circuits to simultaneously acquire MRI or localized spectroscopic signals. An example of parallel imaging technique that uses phased array coils is Sensitivy Enconding (SENSE). Sampled array is the name proposed in this work for a method in which each channel of a multichannel coil is responsible to acquire independently the signal from its sample so that each sample signal is addressed to its specific channel. In this work, we describe the development of a four-channel phased array coil for rat head anatomy using flexible printed circuit board (PCB), to operate on a 2T pre-clinical MRI scanner to validate the construction method and usage of flexible PCB as a receiver coil. We also developed a four-channel sample array coil to simultaneously perform the imaging of four seeds at the same scan, to validate the proposed method to improve image quality at the same time accelerating multiple seed imaging for agriculture studies. The results show that phased array PCB coil as compared to a regular wire winding coil provide good signal-to-noise ratio (SNR) imaging with more adequate geometry to the anatomy by being flexible. In addition, the coil manufacturing process is facilitated since the entire coil is constructed as a PCB prototype. The sample array imaging showed as a promising method for multiple sample increasing SNR and time to do experiments.
Gotshal, Shmuel. "High frequency transmit-receive phased array coil for head and neck MR neuroimaging at 3 Tesla." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000688.
Повний текст джерелаXie, Yuedong. "Modelling techniques and novel configurations for meander-line-coil electromagnetic acoustic transducers (EMATs)." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/modelling-techniques-and-novel-configurations-for-meanderlinecoil-electromagnetic-acoustic-transducers-emats(78777548-e2c6-468f-9a4b-12daaa29b53c).html.
Повний текст джерелаKriegl, Roberta. "A flexible coil array for high resolution magnetic resonance imaging at 7 Tesla." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112425/document.
Повний текст джерелаMagnetic resonance imaging (MRI), among other imaging techniques, has become a major backbone of modern medical diagnostics. MRI enables the non-invasive combined, identification of anatomical structures, functional and chemical properties, especially in soft tissues. Nonetheless, applications requiring very high spatial and/or temporal resolution are often limited by the available signal-to-noise ratio (SNR) in MR experiments. Since first clinical applications, image quality in MRI has been constantly improved by applying one or several of the following strategies: increasing the static magnetic field strength, improvement of the radiofrequency (RF) detection system, development of specialized acquisition sequences and optimization of image reconstruction techniques. This work is concerned with the development of highly sensitive RF detection systems for biomedical ultra-high field MRI. In particular, auto-resonant RF coils based on transmission line technology are investigated. These resonators may be fabricated on flexible substrate which enables form-fitting of the RF detector to the target anatomy, leading to a significant SNR gain. The main objective of this work is the development of a flexible RF coil array for high-resolution MRI on a human whole-body 7 T MR scanner. With coil arrays, the intrinsically high SNR of small surface coils may be exploited for an extended field of view. Further, parallel imaging techniques are accessible with RF array technology, allowing acceleration of the image acquisition. Secondly, in this PhD project a novel design for transmission line resonators is developed, that brings an additional degree of freedom in geometric design and enables the fabrication of large multi-turn resonators for high field MR applications. This thesis describes the development, successful implementation and evaluation of novel, mechanically flexible RF devices by analytical and 3D electromagnetic simulations, in bench measurements and in MRI experiments
Sewonu, Anou. "Développements méthodologiques et techniques pour le contrôle qualité en imagerie par résonance magnétique." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0002/document.
Повний текст джерелаMagnetic Resonance Imaging (MRI) is increasingly being used in clinical routine and is frequently associated with different imaging modalities in multisite studies. Besides, MRI is becoming more complex with a growing use of phased-array coils. Hence there is a rising eagerness for quality assurance and quality control (QC). Indeed, monitoring MR systems is required in order to prevent from diagnostic errors which may be induced by drifts in the instrumentation. The ever first studies about MRI QC issue established the basis for designing test-objects and metrics which are required for monitoring the scanners. These works also resulted in two approaches for performing the testings : the first one is multi-object oriented and the second one is single-object oriented. The research conducted for this thesis are motivated by two objectives : the first one holds about designing a methodology for performing periodic monitoring of MR scanners. The procedure is required to be practical, shortly-timed, statistically robust, and system-independent. It was designed following the single-object approach promoted by the American College of Radiology. In order to fit the procedure with its specifications, all of its aspects were assessed. The resulting 10-minute weekly QC procedure was successfully tested on several MR facilities. The second goal of these works is about specifically assessing the performance of phased-array coils. Using these coils, two parameters were considered as being essential for image quality considerations, namely the sensitivity profiles and the noise covariance matrix. For monitoring these parameters, two metrics were designed in a way that they could be integrated within the weekly QC procedure. Besides, an alternative method was proposed for computing noise covariance matrices. As a matter of prospects, these doctoral works sought clinical applications which may take advantage of the techniques and methodology elaborated for QC purposes. There are interesting insights about using QC techniques in support of targeted clinical MR applications
Bhatia, Sahil. "Geometrically Decoupled Phased Array Coils for Mouse Imaging." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-05-797.
Повний текст джерелаHsu, Cheng-yun, and 許正昀. "Investigation on Absolute Quantification of in Vivo Proton MR Spectroscopy with Phased Array Coils." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/74cm44.
Повний текст джерела國立中山大學
資訊工程學系研究所
96
LCModel has been widely used for MR spectroscopy analysis. LCMgui, which is the built-in user interface of LCModel, based on Linux system, provides the functionality to convert MRS data of various formats to match the format of LCModel raw file, except for GE MRSI data which can be analyzed by LCModel only with GE Sage/IDL software. Hence, the first part of this work was to develop a multi-platform tool with LCModel to support all GE data, including GE MRSI data and phased array data. With this tool, users can analyze MRS data with LCModel on their familiar environment such as Windows, and Linux. The MR spectroscopy experiments with phased array coils provide optimized SNR which lead to more accurate absolute quantification by some sophisticate combination algorithms of phased array coils. Thus, the second part of this work was to propose an algorithm of combining data obtained from phased array coils by doing phase correction and calculation of weighting factor. In addition, the comparison of the accuracy between using quadrature coil and phased array coils with different combination algorithms was investigated in order to demonstrate the efficiency of using phased array coils and the combination program.
Liu, Ju-feng, and 劉儒峯. "The quantitative comparison of doing eddy current correction before and after combination for 1H MRS using phased array coils with LCModel." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/51708548015730107734.
Повний текст джерела國立中山大學
資訊工程學系研究所
98
Phased array coils are composed of several surface coils receiving individual element signals simultaneously. Each individual surface coil provides the equivalent of the coil diameter range, and higher SNR. Therefore, combining these non-interactive phased array coils, can achieve a wide range of scan areas, uniform sensitivity and better SNR. Therefore our experiment was performed with two different coils of quadrature coil and phased array coil. Phased array MRS data were compared using various combination approaches. Data acquired by quadrature coil was regarded as a standard to verify the reliability and accuracy of metabolite concentration. The aim of our study is to do eddy current correction before and after the combination of each element coil data with LCModel analysis for quantitative comparison of metabolite concentrations. Our result shows that doing eddy current correction for each phased array coil before signal combination can achieve higher reliability and accuracy of SNR and quantitative concentrations of MR spectra in vivo.
Βλάχος, Φώτιος. "Σχεδίαση, ανάπτυξη και κλινική εφαρμογή πηνίων φασικής συνάφειας για απεικόνιση και φασματοσκοπία μαγνητικού συντονισμού". Thesis, 2008. http://nemertes.lis.upatras.gr/jspui/handle/10889/1398.
Повний текст джерелаThe doctoral thesis refers to the use of receiver coils during MR imaging experiments. We simulated a 4-channel phased array system of orthogonal elements with reduced size compare to the conventional coils in order to improve the signal-to-noise ratio in prostate MR imaging. That system was then designed and developed using particular decoupling, tuning, matching and switching techniques. The final design was tested clinically on a 1.5T MRI system using phantoms at first and then an average sized human pelvic region. The results were compared to those extracted from a conventional flex 4-channel cardiac coil, while the in vivo images showed considerable improvement in contrast when we used more localized field of views.
Bellec, Jesse. "A Target Field Based Design of a Phase Gradient Transmit Array for TRASE MRI." 2015. http://hdl.handle.net/1993/30720.
Повний текст джерелаOctober 2015
Sung, Po-Jung, and 宋柏融. "Magnetic Resonance Imaging of Rat’s Brain and Spine Using Curved Four-channel Phased Array Coil." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/61472278079858390347.
Повний текст джерела國立臺灣大學
生醫電子與資訊學研究所
104
Magnetic resonance imaging (MRI) techniques such as anatomical and diffusion tensor imaging (DTI) have been widely applied to investigate the central nervous system (CNS). However, commercial MRI coils could not provide sufficient signal-to-noise ratio (SNR) at the neck due to cervical lordosis (inward curvature), therefore hampering the applications from brain to the spine. The aim of this work was to design and implement a 4-channel curved array coil that provides uniform sensitivity along the CNS, improving studies of the head and spinal column. The 4-channel curved array coil was fabricated on a flexible printed circuit board that could be bent to fit the rat’s contour along the neck while a homemade low input impedance preamplifier eliminates the crosstalk between overlapping coils elements. We evaluated the performance of the coil through anatomical imaging of phantom and rat cervical spine, and finally perform rat cerebrospinal DTI and tractography to show the benefits of a curved array coil. Compared to conventional array coils, the curved array coil offered 1.3- and 1.45-fold SNR gain in phantom and anatomical images of the rat cervical spine respectively. In addition, the contrast-to-noise ratio (CNR) between gray and white matter in spine was alleviated. By combining Wideband MRI technique, the 3D anatomical and high-resolution diffusion weighted images were obtained with a 11-fold acceleration. In reproducibility of DTI, the experimental reproducibility deviation angle acquired by curved array coil was 77% of that by plane array coil. Moreover, the DTI tractography of rat nervous system using the curved array coil was more complete. The 4-channel curved array platform was successfully implemented for rat cerebrospinal MRI. We evaluated its performance by phantom as well as in vivo anatomical imaging and further demonstrated the feasibility of rat cerebrospinal DTI. With improved SNR and CNR, the curved array coil platform could improve or even create new possibilities for biomedical applications in cerebral nervous system.
Lin, Fa-Hsuan, and 林發暄. "Optimization of head phased array coil design in magnetic resonance imaging using method of moment its principles and applications." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/09025167341333010350.
Повний текст джерела國立臺灣大學
電機工程研究所
84
Brain research has utilized lots of the most advanced radiological medicine technologies, such as functional magnetic resonance imaging (fMRI), magnetic resonance angiography (MRA), in-vivo magnetic reso- nance spectroscopy(InVivo MRS) and radiosurgery. While these techno- logies are usually implemented with high SNR, high resolution magnetic resonance imaging (MRI) for optimal performance. Nowadays, clinical brain MR images are often acquired via conventional volume coils, such as saddle, Alderman-Grant or birdcage coil. These coils function as RF pulse transmitters as well as RF signal receivers. Due to anatomical size of brain, volume coils require field-of-view (FOV) no less than 25 cm x 25 cm to avoid aliasing artifact. Such a constraint sets the upper bound of spatial resolution of images from volume coils. Although we can get high resolution images by combing volume saturation and small FOV scanning, images are usually with low SNR due to volume coil characteristics. Phased array coil provides an alternative solution to this dilemma. Several surface coils consist a phased array coil with appropriate over- lapping among one another to cancel mutual interaction. Thus each sur- face coil receives different local region images while maintains image characteristics of high signal-to-noise ratio (SNR) of surface coils. These surface coil images can then be combined to generate an image of large FOV comparable to the volume coil images. The goal of this study is to develop a new RF coil phased array. During initial clinical diagnosis, we can utilize this system to have large FOV/low resolution images without neglecting sparsely distributed mul- tiple lesions. Afterward, we can also use this RF coil array to acquire local high resolution high SNR images for further detailed diagnosis and therapy planning.