Relevant bibliographies by topics / Phased array coils

Academic literature on the topic 'Phased array coils'

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Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "Phased array coils"

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Ying, Leslie, and Zhi-Pei Liang. "Parallel MRI Using Phased Array Coils." IEEE Signal Processing Magazine 27, no. 4 (July 2010): 90–98. http://dx.doi.org/10.1109/msp.2010.936731.

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Gareis, Daniel, Tobias Wichmann, Titus Lanz, Gerd Melkus, Michael Horn, and Peter M. Jakob. "Mouse MRI using phased-array coils." NMR in Biomedicine 20, no. 3 (2007): 326–34. http://dx.doi.org/10.1002/nbm.1156.

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Monroe, James W., Petra Schmalbrock, and Dimitrios G. Spigos. "Phased Array Coils for Upper Extremity MRA." Magnetic Resonance in Medicine 33, no. 2 (February 1995): 224–29. http://dx.doi.org/10.1002/mrm.1910330212.

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De Marchi, Daniele, Alessandra Flori, Nicola Martini, and Giulio Giovannetti. "Artifacts by Misalignment of Cardiac Magnetic Resonance Phased-array Coil Elements: From Simulation to In vivo Test." Current Medical Imaging Formerly Current Medical Imaging Reviews 15, no. 3 (February 25, 2019): 301–7. http://dx.doi.org/10.2174/1573405613666171024150250.

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Background: Cardiac magnetic resonance evaluations generally require a radiofrequency coil setup comprising a transmit whole-body coil and a receive coil. In particular, radiofrequency phased-array coils are employed to pick up the signals emitted by the nuclei with high signal-tonoise ratio and a large region of sensitivity. Methods: Literature discussed different technical issues on how to minimize interactions between array elements and how to combine data from such elements to yield optimum Signal-to-Noise Ratio images. However, image quality strongly depends upon the correct coil position over the heart and of one array coil portion with respect to the other. Results: In particular, simple errors in coil positioning could cause artifacts carrying to an inaccurate interpretation of cardiac magnetic resonance images. Conclusion: This paper describes the effect of array elements misalignment, starting from coil simulation to cardiac magnetic resonance acquisitions with a 1.5 T scanner. </P><P> Phased-array coil simulation was performed using the magnetostatic approach; moreover, phantom and in vivo experiments with a commercial 8-elements cardiac phased-array receiver coil permitted to estimate signal-to-noise ratio and B1 mapping for aligned and shifted coil.
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Hricak, H., S. White, D. Vigneron, J. Kurhanewicz, A. Kosco, D. Levin, J. Weiss, P. Narayan, and P. R. Carroll. "Carcinoma of the prostate gland: MR imaging with pelvic phased-array coils versus integrated endorectal--pelvic phased-array coils." Radiology 193, no. 3 (December 1994): 703–9. http://dx.doi.org/10.1148/radiology.193.3.7972810.

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Hatabu, Hiroto, Warren B. Gefter, John Listerud, Eric A. Hoffman, Leon Axel, Joseph C. McGowan, Harold I. Palevsky, Cecil E. Hayes, Junji Konishi, and Herbert Y. Kressel. "Pulmonary MR Angiography Utilizing Phased-Array Surface Coils." Journal of Computer Assisted Tomography 16, no. 3 (May 1992): 410–17. http://dx.doi.org/10.1097/00004728-199205000-00012.

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Damen, Frederick C., and Kejia Cai. "B1− non-uniformity correction of phased-array coils without measuring coil sensitivity." Magnetic Resonance Imaging 51 (September 2018): 20–28. http://dx.doi.org/10.1016/j.mri.2018.04.009.

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Sun, Qi, Min-jun Dong, Xiao-feng Tao, Meng-da Jiang, and Chi Yang. "Selection and application of coils in temporomandibular joint MRI." Dentomaxillofacial Radiology 49, no. 3 (March 2020): 20190002. http://dx.doi.org/10.1259/dmfr.20190002.

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Objective: To compare and evaluate the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) values between a 15-channel phased array head coil and 6-channel dS Flex M surface coil in the MRI of temporomandibular joint. Methods: 300 patients were randomly assigned to two groups: 150 patients were examined by using a 15-channel phased array head coil and the other 150 patients were scanned by using a 6-channel dS Flex M surface coil. All of the data were set in the same 6 regions of interest including the temporal lobe, condyle neck, lateral pterygoid muscle, parotid gland, the adipose area and an area of the background noise）. SNR and CNR values were measured respectively. Results: The numerical variation law of SNR and CNR values measured in regionsof interest of each group was similar, although different coils were used. There were statistically significant differences of SNR values in all of the oblique sagittal (OSag) proton density-weighted imaging, the part of OSag T 2 weighted image (T 2WI) except for SNR4 and SNR5. and oblique coronal (OCor) T 2WI sequence except for SNR2. On the contrary, SNR4 and SNR5 values in the OCor T 2WI and SNR5 values in OSag T 2WI sequences by using the surface coil were higher than those by using the head coil. There were no statistically significant intergroup differences of CNR values in OSag proton density-weighted imaging sequence except CNR1 and in OSag T 2WI sequence except CNR5. But, statistically significant differences of all the values in the OCor T 2WI sequence except for CNR1 were observed. Conclusion: Both the phased array head coil and dS Flex M surface coil can be used for temporomandibular joint MRI.
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Fütterer, Jurgen J., Marc R. Engelbrecht, Gerrit J. Jager, Robert P. Hartman, Bernard F. King, Christina A. Hulsbergen-Van de Kaa, J. Alfred Witjes, and Jelle O. Barentsz. "Prostate cancer: comparison of local staging accuracy of pelvic phased-array coil alone versus integrated endorectal–pelvic phased-array coils." European Radiology 17, no. 4 (October 6, 2006): 1055–65. http://dx.doi.org/10.1007/s00330-006-0418-8.

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Beck, Michael J., Dennis L. Parker, and J. Rock Hadley. "Capacitive versus Overlap Decoupling of Adjacent Radio Frequency Phased Array Coil Elements: An Imaging Robustness Comparison When Sample Load Varies for 3 Tesla MRI." Concepts in Magnetic Resonance Part B, Magnetic Resonance Engineering 2020 (December 15, 2020): 1–14. http://dx.doi.org/10.1155/2020/8828047.

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Phased array (PA) receive coils are built such that coil elements approximate independent antenna behavior. One method of achieving this goal is to use an available decoupling method to decouple adjacent coil elements. The purpose of this work was to compare the relative performance of two decoupling methods as a function of variation in sample load. Two PA receive coils with 5 channels (5-ch) each, equal outer dimensions, and formed on 12 cm diameter cylindrical phantoms of conductivities 0.3, 0.6, and 0.9 S/m were evaluated for relative signal-to-noise ratio (SNR) and parallel imaging performance. They were only tuned and matched to the 0.6 S/m phantom. Simulated and measured axial, sagittal, and coronal 5-ch PA coil SNR ratios were compared by dividing the overlap by the capacitive decoupled coil SNR results. Issues related to the selection of capacitor values for the two decoupling methods were evaluated by taking the ratio of the match and tune capacitors for large and small 2 channel (2-ch) PA coils. The SNR ratios showed that the SNR of the two decoupling methods were very similar. The inverse geometry-factor maps showed similar but better overall parallel imaging performance for the capacitive decoupled method. The quotients for the 2-ch PA coils’ maximum and minimum capacitor value ratios are 3.28 and 1.38 for the large and 3.28 and 2.22 for the small PA. The results of this paper demonstrate that as the sample load varies, the capacitive and overlap decoupling methods are very similar in relative SNR and this similarity continues for parallel imaging performance. Although, for the 5-ch coils studied, the capacitive decoupling method has a slight SNR and parallel imaging advantage and it was noted that the capacitive decoupled coil is more likely to encounter unbuildable PA coil configurations.
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Dissertations / Theses on the topic "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.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.
Includes 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.
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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/.

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Experimentos de Imagens por Ressonância Magnética (IRM) em pequenos animais, assim como em humanos, exigem um conjunto especifico de bobinas de Radiofrequência (RF) para maximizar ambos a homogeneidade de campo durante a transmissão e a Relação Sinal Ruído (RSR) durante a recepção. As geometrias mais comuns de bobinas transmissoras utilizadas em sistemas de humanos são as bobinas tipo gaiola ou Birdcage Coil. Dentre as geometrias de bobinas receptoras, o conceito de bobina tipo Phased Array é amplamente utilizado em aplicações que necessitam de alta RSR em uma grande região de interesse, além de permitirem obter imagens com metodologias de aquisição paralela. Este trabalho descreve o desenvolvimento de um conjunto de bobinas transmissoras e receptoras especificamente projetadas para a aquisição de imagens do cérebro de ratos para o estudo do hipocampo. As geometrias de bobinas transmissoras estudadas foram dois Birdcages com 8 e 16 condutores e a geometria proposta por nós chamada Double Crossed Saddle (DCS Coil). Para a recepção desenvolvemos uma bobina de superfície com dois loops e um Phased Array com dois canais de recepção. Os resultados confirmam que dentre as bobinas transmissoras desenvolvidas a geometria do tipo Birdcage com 16 condutores é a mais homogênea, produzindo campos de RF com alta uniformidade em regiões de interesse de até 80% do diâmetro interno das bobinas. No entanto, o elevado número de capacitores em sua estrutura faz com que a geometria DCS coil, devido à sua simplicidade e reduzido número de capacitores, represente uma alternativa em experimentos onde as condições de carga da amostra possam variar. Dentre as geometrias de receptoras estudadas a bobina de superfície obteve maior desempenho em termos de RSR em comparação com o Phased Array de 2 canais. A comparação dos resultados utilizando bobinas específicas para a transmissão e recepção com uma bobina volumétrica operando como transmissora e receptora simultaneamente comprova a superioridade em termo de RSR dos sistemas que utilizam bobinas dedicadas, sendo confirmados através de imagens in vivo do cérebro de ratos, possibilitando aquisições com mesma resolução e RSR em um tempo reduzido de experimento.
Magnetic 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.
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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.

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Le projet Iseult-Inumac mené au sein d'un consortium franco-allemand vise à développer les techniques associées à l'imagerie par résonance magnétique à ultra haut champ, notamment à travers la construction d'un imageur à 11,7 teslas. La résolution accrue du nouvel imageur devrait apporter une meilleure compréhension du système nerveux et de ses dysfonctionnements pour aboutir à un dépistage plus précoce des pathologies telles que la maladie d'Alzheimer, les accidents vasculaires cérébraux ou les tumeurs.La principale difficulté technique du projet, en dehors de la construction de l'aimant statique, réside dans la capacité d'émettre une onde électromagnétique d'amplitude uniforme dans tout le cerveau du patient : problème de l'inhomogénéité de B1 (ou radiofréquence). Une solution proposée consiste à utiliser une antenne réseau à transmission parallèle et des séquences d'excitation IRM spécifiques dites de compensation.Cette thèse se concentre sur la conception des antennes réseaux à transmission parallèle pour l'IRM à 7 et 11,7 T. Un prototype à 8 canaux indépendants utilisant une technologie innovante de résonateurs linéaires est présentée pour l'IRM 7 T. Il a été conçu par la simulation numérique. Un protocole de validation a été développé pour la caractérisation et l'analyse des performances des antennes réseaux. Le succès de cette validation a permis de développer par la simulation une nouvelle antenne à 12 canaux et une stratégie de pilotage innovante permettant de n'utiliser que 8 chaînes de pilotage au lieu de 12. Enfin, la même méthodologie a été appliquée pour concevoir et prédire les performances d'une antenne réseau à 11,7 T.
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Consalter, 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/.

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Técnicas de aquisição paralelas e hardware dedicados vem sendo desenvolvidos desde a década de 1980 para reduzir o tempo de aquisição de imagens via ressonância magnética (IRM). Uma bobina do tipo phased array é um dispositivo do tipo receptor, que usa múltiplas bobinas (canais) cada qual com seu próprio circuito de detecção para adquirir simultaneamente os sinais que formam uma imagem ou espectro via IRM. Exemplos de técnica de imagem paralela que usa bobinas tipo phased array são Sensitivy Enconding (SENSE) e GeneRalized Autocalibrating Partial Parallel Acquisition (GRAPPA). Sampled array é o nome de um método proposto neste trabalho em que cada canal de uma bobina multicanal é responsável por adquirir de forma independente o sinal da sua amostra de modo que cada sinal de amostra é endereçado ao seu canal específico. Neste trabalho, descrevemos o desenvolvimento de uma bobina phased array de quatro canais para anatomia de cabeça de rato usando circuito impresso flexível para operar em um sistema de IRM pré-clínico de 2T com objetivo de validar o método de construção e uso de circuito flexível como bobina de recepção. Também desenvolvemos uma bobina de quatro canais para realizar simultaneamente a imagem de quatro sementes na mesma varredura para validar o método Sampled Array com objetivo de melhorar a qualidade da imagem e simultaneamente acelerar experimentos de múltiplas amostras. Os resultados mostram que a bobina de circuito impresso phased array, em comparação com uma bobina de enrolamento de fio regular, forneceu uma boa relação sinal / ruído (RSR) e possui geometria mais adequada à anatomia por ser flexível. Além disso, o processo de fabricação da bobina seja facilitado desde que toda a bobina é construída como um protótipo de circuito impresso. Os bons resultados da bobina sampled array mostraram o método como promissor para imageamento de múltiplas amostras com aumento de RSR e diminuição de tempo de experimentos em relação ao uso de bobinas de canal único.
Parallel 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.
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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.

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Xie, 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.

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Electromagnetic acoustic transducers (EMATs) are increasingly used in industries due to their attractive features of being non-contact, cost-effective and the fact that a variety of wave modes can be generated, etc. There are two major EMATs coupling mechanisms: the Lorentz force mechanism for conductive materials and the magnetostriction mechanism for ferromagnetic materials; EMATs operated on Lorentz force mechanism are the focus of this study. This work aims to investigate novel efficient modelling techniques for EMATs, in order to gain further knowledge and understanding of EMATs wave pattern, how design parameters affect its wave pattern and based on above propose and optimise novel sensor structures. In this study, two novel modelling methods were proposed: one is the method combining the analytical method for EM simulation and the finite-difference time-domain (FDTD) method for US simulation for studying the Rayleigh waves' properties on the vertical plane of the material; the other one is the method utilizing a wholly analytical model to explore the directivity of surface waves. Both simulations models have been validated experimentally. The wholly analytical model generates the radiation pattern of surface waves, which lays a solid foundation for the optimum design of such sensors. The beam directivity of surface waves was investigated experimentally, and results showed the length of wires has a significant effect on the beam directivity of Rayleigh waves. A novel configuration of EMATs, variable-length meander-line-coil (VLMLC), was proposed and designed. The beam directivity of surface waves generated by such novel EMATs were analytically investigated. Experiments were conducted to validate such novel EMATs models, and results indicated that such EMATs are capable of supressing side lobes, and therefore resulting in a more concentrated surface waves in the desired direction. Further, another two novel configuration of EMATs, the four-directional meander-line-coil (FDMLC) and the six-directional meander-line-coil (SDMLC), were proposed and designed; results showed these EMATs are capable of generating Rayleigh waves in multiple directions and at the same time suppressing side lobes.
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Kriegl, Roberta. "A flexible coil array for high resolution magnetic resonance imaging at 7 Tesla." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112425/document.

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L’imagerie par résonance magnétique (IRM) est un outil d’investigation majeur donnant accès de manière non invasive à des nombreuses informations quantitatives et fonctionnelles. La qualité des images obtenues (rapport-signal-sur-bruit, RSB) est cependant limitée dans certaines applications nécessitant des résolutions spatiales et/ou temporelles poussées. Afin d’améliorer la sensibilité de détection des équipements d’IRM, diverses orientations peuvent être suivies telles qu’augmenter l’intensité du champ magnétique des imageurs, améliorer les performances des systèmes de détection radiofréquence (RF), ou encore développer des séquences d’acquisition et des techniques de reconstruction d’images plus efficaces. La thématique globale dans laquelle s’inscrit cette thèse concerne le développement des systèmes de détection RF à haute sensibilité pour l’IRM à haut champ chez l’homme. En particulier, des antennes auto-résonantes basées sur le principe des lignes de transmission sont utilisées parce qu’elles peuvent être réalisée sur substrat souple. Cette adaptabilité géométrique du résonateur permet d’ajuster précisément sa forme aux spécificités morphologiques de la zone anatomique observée, et ainsi d’augmenter le RSB. La première visée technologique de ce projet concerne le développement, de la conception jusqu’à la mise en œuvre dans un appareil 7 T corps entier, d’un système de détection RF flexible à haute sensibilité, utilisant des antennes miniatures associées en réseau. L’utilisation d’un réseau d’antennes miniatures permet d’obtenir des images sur un champ de vue élargi tout en conservant la haute sensibilité inhérente à chaque antenne miniature. De plus, la technologie de l’imagerie parallèle devient accessible, ce qui permet d’accélérer l’acquisition des images. De surcroît, un nouveau schéma de résonateur de ligne transmission avec un degré de liberté supplémentaire est introduit, ce qui permet de réaliser de grands résonateurs multi-tours pour l’IRM à haut champ. Cette thèse décrit le développement, la mise en œuvre et l’évaluation des nouveaux systèmes de détection RF au moyen de simulations analytiques et numériques, et des études expérimentales
Magnetic 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
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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.

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De plus en plus utilisée en routine clinique, l'Imagerie par Résonance Magnétique (IRM) est très fréquemment associée à d'autres modalités d'imagerie médicale dans le cadre d'études multicentriques. Elle est également utilisée à des fins de quantification et sa technologie se complexifie, notamment avec l'utilisation croissante d'antennes en réseau phasé. Ces raisons contribuent à amplifier le besoin d'assurance qualité car il importe de surveiller les performances des appareils cliniques afin de se prémunir d'erreurs de diagnostic que leurs dérives peuvent entrainer. Des travaux, très tôt engagés sur le contrôle qualité (CQ) en IRM, ont posé les bases pour la conception d'objets-test et des mesures physiques nécessaires au suivi. Ces travaux ont aussi permis de dégager deux approches pour les procédures de CQ en IRM, à savoir des approches mono-objet et multi-objet. Les travaux menés poursuivent le premier objectif de développer une méthodologie de suivi périodique des appareils d'IRM qui soit pratique, peu chronophage, statistiquement robuste et compatible avec différents appareils. L'approche mono-objet issue des travaux de l'American College of Radiology a été choisie pour élaborer la procédure. Les travaux ont porté sur les principaux aspects du processus de réalisation des tests. La procédure hebdomadaire résultante, d'une durée de réalisation inférieure à 10 min, a été testée avec succès sur 6 sites disposant d'appareils de différentes gammes. Le deuxième objectif porte sur le contrôle spécifique des antennes en réseau phasé. Ceux-ci sont essentiellement caractérisés par deux paramètres qui ont été identifiés comme déterminants pour la reconstruction et la qualité des images. Il s'agit des profils de sensibilité des antennes et des corrélations en termes de bruit d'acquisition. Deux métriques ont été élaborées pour surveiller ces deux paramètres. Une technique alternative a également été développée pour calculer les covariances de bruit. Enfin, cette thèse propose quelques pistes pour mettre les outils de CQ au service d'applications cliniques ciblées. Les travaux engagés en ce sens ouvrent des perspectives intéressantes pour l'utilisation de techniques de CQ dans le cadre d'applications cliniques ciblées
Magnetic 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
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Bhatia, Sahil. "Geometrically Decoupled Phased Array Coils for Mouse Imaging." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-05-797.

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Phased array surface coils offer high SNR over a large field of view. Phased array volume coils have high SNR at the surface and centre of the volume. Most array coil designs typically employ a combination of geometrical and additional techniques, such as isolating preamplifiers for element-to-element decoupling. The development of array coils for small animal MRI is of increasing interest. However isolation preamplifiers are expensive and not ubiquitous at the field strengths typically employed for small animal work (4.7T, 9.4T, etc). In addition, isolating preamps complicates the designs of coils for transmit SENSE since they do not decouple during transmitting. Therefore, this thesis reexamines a "tried and true" method for decoupling coil elements. In this work five different coils for mouse imaging at 200MHz are presented: a 16 leg trombone design quadrature birdcage coil and four geometrically decoupled volume phased array coils. The first mouse array coil is a two saddle quadrature coil with a circularly polarized field. The second coil is a four channel transmit/receive volume array coil that is decoupled purely geometrically, without the need for other forms of decoupling. The third array coil is a modified 'open' configuration to facilitate the loading of animals. The fourth coil presented is a 'tunable' decoupling coil, where the geometric decoupling between elements is 'tunable', in order to compensate for different loading conditions of the coil. Tunable decoupling between elements was achieved using two mechanisms, a decoupling paddle for isolation of top to bottom elements, with a variable overlap mechanism for decoupling diagonal elements. Bench measurements demonstrate good decoupling (better than -20dB) of the coil elements and 'tunability' of both mechanisms. Phantom images from all coils are presented.
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Hsu, 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.

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碩士
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.
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Book chapters on the topic "Phased array coils"

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Giovannetti, G., V. Viti, V. Hartwig, F. Frijia, and L. Landini. "Simulations of Magnetic Resonance Phased Array Coils Using FDTD Algorithm." In IFMBE Proceedings, 888–90. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03882-2_237.

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Vemuri, Prashanthi, Eugene G. Kholmovski, Dennis L. Parker, and Brian E. Chapman. "Coil Sensitivity Estimation for Optimal SNR Reconstruction and Intensity Inhomogeneity Correction in Phased Array MR Imaging." In Lecture Notes in Computer Science, 603–14. Berlin, Heidelberg: Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/11505730_50.

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Conference papers on the topic "Phased array coils"

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Morey, Abhay M., Sheetal Bhujade, Tapas Bhuiya, Samruddha Thakur, and Twisha Pandey. "Design and development of phased-array coils for 1.5T MRI scanner." In 2015 International Conference on Technological Advancements in Power and Energy (TAP Energy). IEEE, 2015. http://dx.doi.org/10.1109/tapenergy.2015.7229611.

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Basari, Eko Tjipto Rahardjo, and Fitri Yuli Zulkifli. "Eight-channel phased array RF coils design for 3T parallel MRI system." In 2015 IEEE 4th Asia-Pacific Conference on Antennas and Propagation (APCAP). IEEE, 2015. http://dx.doi.org/10.1109/apcap.2015.7374269.

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Marrufo, O., and A. O. Rodriguez. "Study of optimal separation of two circular phased-array coils via an equivalent circuit." In 2005 27th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE, 2005. http://dx.doi.org/10.1109/iembs.2005.1615411.

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Liang, Dandan, Hon Tat Hui, and Tat Soon Yeo. "Design of phased array coils for increasing the signal-to-noise ratio of magnetic resonance imaging." In 2012 IEEE Antennas and Propagation Society International Symposium and USNC/URSI National Radio Science Meeting. IEEE, 2012. http://dx.doi.org/10.1109/aps.2012.6349160.

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Chen, Zhenmao, Yongbin Zuo, Dongli Zhang, Ying Mao, and Taihui Huang. "Proposal and Demonstration of Strategies for NDT of Conduit Tube of Cable in Conduit Conductors Used in ITER PF Coils." In 18th International Conference on Nuclear Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/icone18-29901.

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The Poloidal Field (PF) coils, made of superconducting Cable in Conduit Conductor (CICC), are important for keeping plasma inside the vacuum vessel of ITER Tokamak device. To ensure the safety of the PF coil, Non-Destructive Testing (NDT) has to be performed for each conduit tube of CICC, as it is the boundary of liquid Helium and supporting structure of the electromagnetic load. However, the complicated cross section shape of the PF conduit tube causes difficulty in its NDT. Aiming at solving the NDT problem of the PF conduit tube, two approaches are proposed and their validity is demonstrated in this paper. One is a hybrid strategy of the ultrasonic phased array and the eddy current array technology. The other is of the immersed ultrasonic testing method. The experimental results reveal that both approaches are promising for the NDT of ITER conduit tubes though the later one is more efficient.
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Yu Li, Hua Wang, Feng Liu, Bing Keong Li, Guofa Shou, Ewald Weber, and Stuart Crozier. "A comparison study of regularization techniques on the theoretical design of phased array RF coils in MRI." In 2008 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE, 2008. http://dx.doi.org/10.1109/iembs.2008.4649184.

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Martini, N., M. F. Santarelli, M. Milanesi, G. Giovannetti, V. Positano, N. Vanello, and L. Landini. "Signal-to-noise ratio improvement of cardiac magnetic resonance spectroscopy signals acquired by phased array coils: a simulation based approach." In 4th IET International Conference on Advances in Medical, Signal and Information Processing (MEDSIP 2008). IEE, 2008. http://dx.doi.org/10.1049/cp:20080445.

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Nguyen, Vu Huy, and Won-jong Kim. "A Two-Phase Framework for Linear Permanent-Magnet Machines and Multi-Axis Stages With Magnetic Levitation." In ASME 2014 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/dscc2014-5936.

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This paper presents the electromagnetic design and experimental validation of a new framework for linear permanent-magnet (PM) machines with magnetic levitation. In this framework, a single forcer, which can generate two force components in two perpendicular directions, consists of a stationary Halbach magnet array and two Lorentz coils with a phase difference of 90° or 270°. Any number of coil pairs can be attached on the same moving frame to work with a common magnet array or matrix, forming a linear or planar permanent-magnet motor. Key advantages of this framework are simple force calculation, linear force, and a reduced number of coils for force generation and allocation in multi-axis positioners. The proposed framework effectively allows for decoupled dynamics of multi-axis stages, simplifying their linear controller design and real-time implementation. This framework is experimentally verified by a high-precision 6-degree-of-freedom (6-DOF) magnetically–levitated (maglev) stage.
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Burat, Olivier, Marc Piriou, Yann Kernin, Mikael Debroise, Christophe Moreau, Samuel W. Glass, and Olivier Casula. "Inspection of Bottom Mounted Instrumentation (BMI) J-Weld." In ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/pvp2010-26173.

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Reactor Pressure Vessel (RPV) Bottom Mounted Instrumentation (BMI) primary nozzle ultrasonic (UT) inspections have been performed by AREVA for more than 15 years. EPRI demonstrations were performed in 2004 and an RSEM qualification was obtained in 2005, This UT inspection detects and characterizes cracks in the base metal of the penetration and its interface with the weld. A complementary Visual Examination of the weld or an Eddy Current examination may also be performed but these tests are understood to be marginal with a possibility to miss indications or to mistake inclusions or weld voids for in-service cracks and therefore could force an unnecessary repair. Difficulties associated with examination of this area include: • Unpredictable ultrasonic behaviour in the weld material; • Wavy and complex OD weld surface profile; • Restricted accessibility around the weld surface. AREVA’s Non Destructive Examination Technical Center (NETEC), has developed and/or evaluated several techniques to improve surface and volumetric inspection of this weld including: • A TOFD ultrasonic (UT) probe to detect and characterize cracks within the weld metal from the ID surface of the nozzle. • A flexible UT Phased Array probe to accommodate the wavy and complex weld surface, in partnership with CEA, • Reduced surface ET probes and flexible ET multi-coils (in partnership with CEA), for improved surface inspection, • Infrared Photo-Thermal Camera examination of the weld surface. This paper discusses the designs and performances of these specific probes and NDT techniques as applied to the BMI nozzles, J-welds, and other similar components.
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Omar, Abbas. "RF Coils of Magnetic-Resonance Imaging as Phased Arrays." In 2018 IEEE Conference on Antenna Measurements & Applications (CAMA). IEEE, 2018. http://dx.doi.org/10.1109/cama.2018.8530674.

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