Download or read book Optimizing Radio Frequency Coil Performance for Parallel Magnetic Resonance Imaging at Ultra High Field written by Gillian Haemer and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Coil Array Optimization and Wireless Transceiver Design for MRI written by Juan Wei and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Coil Array Optimization and Wireless Transceiver Design for MRI" by Juan, Wei, 魏娟, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled Coil Array Optimization and Wireless Transceiver Design for MRI submitted by Wei Juan for the degree of Doctor of Philosophy at The University of Hong Kong in February 2007 In recent years, parallel imaging has revolutionized the field of fast MRI. Array coils with independent receivers and the use of the additional spatial encoding enable parallel imaging techniques much more efficiently. Recently, due to the cost reduction of RF receivers, the number of array channels has risen to 96. This thesis presents the author's investigations into the optimization of RF coil array for ultra high field MRI and the design of a wireless RF transceiver for MRI signal transmission. On the optimization of RF coil array, the author emphasizes the parallel imaging performance which is closely related to the uniqueness of each element sensitivity pattern. For such applications, the design process begins by choosing the number, shape and arrangement of the elements. Then the electromagnetic field modeling is applied to predict sensitivity patterns and the noise covariance matrix to calculate parameters such as G-factor and SNR dedicated to the evaluation of parallel imaging performance. However, the mutual coupling of coil array causes the shift of the resonant frequency of the elements and degrades their sensitivity. There are some decoupling techniques, such as the "geometric," "preamplifier" and "reactive" methods, but they make the coil array design much more complicated. An investigation into the intrinsic coupling characteristics of array elements is also presented in this thesis to provide a simple guidance to minimize the mutual coupling for array design. In recent years, there has been a trend to dramatically increase the number of receive channels of coil array to shorten imaging time without sacrificing much of their SNR. However, with many elements, the cable crosstalk and RF burn become the serious problem. Wireless transmission is a promising alternative to coaxial cables for the MRI coil array to avoid this problem. Although wireless links have been widely used in the field of telecommunications, some special critical issues for MRI are highly imposed in order to maintain the image quality. In this thesis, the wireless transmission system based on IEEE 802.11b standard is implemented. With this new technique the MR images of both phantom and human head are successfully obtained from XinaoMDT 0.3T MRI system (Langfang, China). In summary, the author optimizes the different RF coil arrays based on the simulations and bench tests to present guidelines for future coil array design. The implementation of digital wireless transmission and the MR images obtained have demonstrated the potential of wireless multi-channel transmission for MRI array. DOI: 10.5353/th_b3858302 Subjects: Imaging systems Signal detection Magnetic resonance imaging

Download or read book Ultra High Field Magnetic Resonance Imaging written by Pierre-Marie Robitaille and published by Springer Science & Business Media. This book was released on 2007-12-31 with total page 487 pages. Available in PDF, EPUB and Kindle. Book excerpt: The foundation for understanding the function and dynamics of biological systems is not only knowledge of their structure, but the new methodologies and applications used to determine that structure. This volume in Biological Magnetic Resonance emphasizes the methods that involve Ultra High Field Magnetic Resonance Imaging. It will interest researchers working in the field of imaging.

Download or read book Microstrip Radio Frequency Coil and Array Design for Magnetic Resonance Imaging written by Bing Wu and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Microstrip Radio-frequency Coil and Array Design for Magnetic Resonance Imaging" by Bing, Wu, 吳冰, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled Microstrip Radio-frequency Coil and Array Design for Magnetic Resonance Imaging submitted by Wu Bing For the degree of Doctor of Philosophy at The University of Hong Kong in September 2006 In the past five years, microstrip RF coils have been developed and widely applied for MR applications at high magnetic fields. In contrast to conventional surface coils, the microstrip coil uses the microstrip transmission line which in its simplest form consists of a thin strip conductor and a ground plane separated by a low-loss dielectric substrate. The semi-open, unbalanced structure microstrip generates a unique B field distribution mainly on one side of the coil where a sample is located. This results in several unique features: reduced losses, higher Q- factor, reduced coupling among multiple microstrip coils. In addition, the microstrip RF coil's unbalanced nature obviates the need of a matching balun. This dissertation presents the author's investigates in microstrip RF coil and array designs at the fields higher than 1.5 Tesla. Firstly, a novel tunable loop microstrip (TLM) RF coil based on the ring resonant circuit has been presented. SNR comparison between the TLM coil and conventional surface coil has been performed at various magnetic field strengths from 1.5 Tesla to 11.1 Tesla. Our study has demonstrated that utilization of the TLM coil can substantially reduce radiation loss and deliver better SNR performance than a conventional coil at ultra high fields. Results also indicate a trend to superior performance of the TLM coil as the field increases. Secondly, several current decoupling techniques have been utilized to the TLM planar array, which consists of two identical TLM coils elements. Simulation, bench test and MRI experiments have been carried out to provide a quantitative analysis of those decoupling schemes. Thirdly, the commonly used capacitive decoupling method for microstrip arrays has been analyzed. It appears that the decoupling capacitance is usually quite small at ultra-high fields and difficult to finely tune. A capacitively decoupled TLM array has been proposed, fabricated and tested at 7 Tesla. Using the TLM array, the capacitive decoupling method can be easily applied with reasonable decoupling capacitance. Bench test and MRI experiments at 7 Tesla show that excellent isolations (-37 dB) between the adjacent elements can be achieved and this TLM array is appropriate for SENSE imaging. Lastly, a new inductive decoupling approach for microstrip arrays has been presented at fields higher than 7 Tesla. In contrast to the capacitive decoupling methods, the decoupling inductance is independent of the resonant frequency, making this method much easier to be implemented. An inductively decoupled eight- channel microstrip array has been implemented and tested at 9.4 Tesla. This decoupling approach should enable more elements to be packed into microstrip arrays for the purpose of parallel imaging at ultrahigh fields. Number of words: 425 Signature: DOI: 10.5353/th_b3704672 Subjects: Magnetic resonance imaging

Download or read book Radio Frequency Coils for Ultra high Field Magnetic Resonance Imaging written by Shajan Gunamony and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Radio Frequency Coils for Ultra high Field Magnetic Resonance Imaging written by Daniel Lee and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book RF Coil Design for Multi frequency Magnetic Resonance Imaging and Spectroscopy written by Arash Dabirzadeh and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic Resonance Spectroscopy is known as a valuable diagnostic tool for physicians as well as a research tool for biochemists. In addition to hydrogen (which is the most abundant atom with nuclear magnetic resonance capability), other species (such as 31P or 13C) are used as well, to obtain certain information such as metabolite concentrations in neural or muscular tissues. However, this requires nuclear magnetic resonance (NMR) transmitter/receivers (coils) capable of operating at multiple frequencies, while maintaining a good performance at each frequency. The objective of this work is to discuss various design approaches used for second-nuclei RF (radio frequency) coils, and to analyze the performance of a particular design, which includes using inductor-capacitor (LC) trap circuits on a 31P coil. The method can be easily applied to other nuclei. The main advantage of this trapping method is the enabling design of second-nuclei coils that are insertable into standard proton coils, maintaining a near-optimum performance for both nuclei. This capability is particularly applicable as MRI field strengths increase and the use of specialized proton coils becomes more prevalent. A thorough performance analysis shows the benefit of this method over other designs, which usually impose a significant signal-to-noise (SNR) sacrifice on one of the nuclei. A methodology based on a modular coil configuration was implemented, which allowed for optimization of LC trap decoupling as well as performance analysis. The 31P coil was used in conjunction with various standard 1H coil configurations (surface/volume/array), using the trap design to overcome the coupling problem (degraded SNR performance) mentioned above. An analytical model was developed and guidelines on trap design were provided to help optimize sensitivity. The performance was analyzed with respect to the untrapped case, using RF bench measurements as well as data obtained from the NMR scanner. Insertability of this coil design was then verified by using it with general-purpose proton coils available. Phantoms were built to mimic the phosphorus content normally found in biologic tissues in order to verify applicability of this coil for in vivo studies. The contribution of this work lies in the quantification of general design parameters to enable "insertable" second-nuclei coils, in terms of the effects on SNR and resonance frequency of a given proton coil.

Download or read book Radio frequency Coil Design for High Field Magnetic Resonance Imaging written by Gene Bogdanov and published by . This book was released on 2002 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Radio Frequency Probes for Ultra high Field Magnetic Resonance Imaging written by Daniel James Lee and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the design, construction and testing of a dome coil. The dome coil is hemispherical in shape and is intended to be used within a set of hemispherical gradient coils in a seven tesla magnetic resonance imaging magnet. The dome coil has eight independent elements and is designed to be used for parallel transmission and reception. It is shown that the dome coil produces less specific absorption rate than a conventional birdcage coil and is suitable for head imaging. A study of travelling wave magnetic resonance imaging is also presented. In this study two different methods of generating a travelling wave (using a patch antenna and an end-fire helix antenna) are compared, and the power requirements and specific absorption rate of the travelling wave approach are considered. It is concluded that travelling wave magnetic resonance imaging is best performed using a local receive coil and with the travelling wave antenna placed at least 50 cm from the subject. All theory relevant to the design, construction, testing and use of these coils and antennas is also presented.

Download or read book Brain and Human Body Modeling written by Sergey Makarov and published by Springer Nature. This book was released on 2019-08-27 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book describes modern applications of computational human modeling with specific emphasis in the areas of neurology and neuroelectromagnetics, depression and cancer treatments, radio-frequency studies and wireless communications. Special consideration is also given to the use of human modeling to the computational assessment of relevant regulatory and safety requirements. Readers working on applications that may expose human subjects to electromagnetic radiation will benefit from this book’s coverage of the latest developments in computational modelling and human phantom development to assess a given technology’s safety and efficacy in a timely manner. Describes construction and application of computational human models including anatomically detailed and subject specific models; Explains new practices in computational human modeling for neuroelectromagnetics, electromagnetic safety, and exposure evaluations; Includes a survey of modern applications for which computational human models are critical; Describes cellular-level interactions between the human body and electromagnetic fields.

Download or read book Metamaterials written by Nader Engheta and published by John Wiley & Sons. This book was released on 2006-06-23 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: Leading experts explore the exotic properties and exciting applications of electromagnetic metamaterials Metamaterials: Physics and Engineering Explorations gives readers a clearly written, richly illustrated introduction to the most recent research developments in the area of electromagnetic metamaterials. It explores the fundamental physics, the designs, and the engineering aspects, and points to a myriad of exciting potential applications. The editors, acknowledged leaders in the field of metamaterials, have invited a group of leading researchers to present both their own findings and the full array of state-of-the-art applications for antennas, waveguides, devices, and components. Following a brief overview of the history of artificial materials, the publication divides its coverage into two major classes of metamaterials. The first half of the publication examines effective media with single (SNG) and double negative (DNG) properties; the second half examines electromagnetic band gap (EBG) structures. The book further divides each of these classes into their three-dimensional (3D volumetric) and two-dimensional (2D planar or surface) realizations. Examples of each type of metamaterial are presented, and their known and anticipated properties are reviewed. Collectively, Metamaterials: Physics and Engineering Explorations presents a review of recent research advances associated with a highly diverse set of electromagnetic metamaterials. Its multifaceted approach offers readers a combination of theoretical, numerical, and experimental perspectives for a better understanding of their behaviors and their potentialapplications in components, devices, and systems. Extensive reference lists provide opportunities to explore individual topics and classes of metamaterials in greater depth. With full-color illustrations throughout to clarify concepts and help visualize actual results, this book provides a dynamic, user-friendly resource for students, engineers, physicists, and other researchers in the areas of electromagnetic materials, microwaves, millimeter waves, and optics. It equips newcomers with a basic understanding of metamaterials and their potential applications. Advanced researchers will benefit from thought-provoking perspectives that will deepen their knowledge and lead them to new areas of investigation.

Download or read book Applications of Parallel Radiofrequency Transmission to Ultra high field Magnetic Resonance Imaging written by Yan Tong and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Parallel Imaging in Clinical MR Applications written by Stefan O. Schönberg and published by Springer Science & Business Media. This book was released on 2007-01-11 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the first in-depth introduction to parallel imaging techniques and, in particular, to the application of parallel imaging in clinical MRI. It will provide readers with a broader understanding of the fundamental principles of parallel imaging and of the advantages and disadvantages of specific MR protocols in clinical applications in all parts of the body at 1.5 and 3 Tesla.

Download or read book Nmr Probeheads For Biophysical And Biomedical Experiments Theoretical Principles And Practical Guidelines 2nd Edition written by Joel Mispelter and published by World Scientific Publishing Company. This book was released on 2015-05-27 with total page 754 pages. Available in PDF, EPUB and Kindle. Book excerpt: NMR Probeheads for Biophysical and Biomedical Experiments 2nd Edition is essential reading for anyone in the field of NMR or MRI, from students to medical or biological scientists performing experiments under certain physical and/or geometrical conditions, unattainable by conventional or available probes. The material guides the reader through the most basic and comprehensive stages in accomplishing a correct probe design, from a very basic oscillating circuit to much more elaborate designs.This new edition has been revised and updated to include a chapter dedicated to RF components, which are commonly used for probes realization and their frequency-dependent characteristics. Another completely revised chapter concerns the multiple coil systems and discusses arrays coils, different decoupling methods, and some principles for interfacing coils with low-noise preamplifiers. The principles of linear circuit analysis are presented in a dedicated chapter. Last but not least, accompanying files containing updated software for probe design have been made available from the publisher's website.

Download or read book Novel Radio Frequency Resonators for in Vivo Magnetic Resonance Imaging and Spectroscopy at Very High Magnetic Fields written by Xiaoliang Zhang and published by . This book was released on 2002 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Ultra Low Field Nuclear Magnetic Resonance written by Robert Kraus Jr. and published by Oxford University Press. This book was released on 2014-02-26 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is designed to introduce the reader to the field of NMR/MRI at very low magnetic fields, from milli-Tesla to micro-Tesla, the ultra-low field (ULF) regime. The book is focused on applications to imaging the human brain, and hardware methods primarily based upon pre-polarization methods and SQUID-based detection. The goal of the text is to provide insight and tools for the reader to better understand what applications are best served by ULF NMR/MRI approaches. A discussion of the hardware challenges, such as shielding, operation of SQUID sensors in a dynamic field environment, and pulsed magnetic field generation are presented. One goal of the text is to provide the reader a framework of understanding the approaches to estimation and mitigation of low signal-to-noise and long imaging time, which are the main challenges. Special attention is paid to the combination of MEG and ULF MRI, and the benefits and challenges presented by trying to accomplish both with the same hardware. The book discusses the origin of unique relaxation contrast at ULF, and special considerations for image artifacts and how to correct them (i.e. concomitant gradients, ghost artifacts). A general discussion of MRI, with special consideration to the challenges of imaging at ULF and unique opportunities in pulse sequences, is presented. The book also presents an overview of some of the primary applications of ULF NMR/MRI being pursued.

Download or read book Study of Bi 2223 High Temperature Superconducting Tapes for RF and Gradient Coils in Magnetic Resonance Imaging written by Jing Yuan and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Study of Bi-2223 High Temperature Superconducting Tapes for RF and Gradient Coils in Magnetic Resonance Imaging" by Jing, Yuan, 袁璟, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled Study of Bi-2223 High Temperature Superconducting Tapes for RF and Gradient Coils in Magnetic Resonance Imaging submitted by Yuan Jing for the degree of Doctor of Philosophy at The University of Hong Kong in April 2006 Since the discovery of high temperature superconductor (HTS) by Bednorz and Muller in 1986, there has been a fast development in research and industry. In the domain of MRI, HTS materials are firstly used in RF receive coil to greatly reduce the coil noise and hence improve the signal-to-noise ratio (SNR). Epitaxial thin films such as YBCO are excellent for their good alignment of grains and extremely low surface resistance, so they are well-suited for RF receive coils to significantly increase the image SNR or shorten the scan time. SNR improvements of up to tens of times have been successfully demonstrated for high field micro-imaging or low field imaging, where the sample loss dominates the total loss. However, many intrinsic restrictions and engineering issues associated with HTS thin films limit their large-scale applications and commercialization. Bi-2223 tape is such a flexible and low-cost commercial HTS material that shows promise for use in both passive low-power electronic applications to increase SNR and active high-power electrical applications to reduce power loss. In this thesis, the use of Bi-2223 HTS tapes for RF and gradient coils for MRI is considered. For applications in RF coils, Bi-2223 HTS tape is low cost, easy coil fabrication, convenient tuning and matching, flexibility for large coil size, and potential for use in fabricating various types of RF coils, gives it several advantages over YBCO thin films. In this thesis, a theoretical model for quality factor of a Bi-2223 RF coil is set up to investigate its feasibility for high field applications and predict the SNR improvement. A normal-sized 5cm RF coil made of Bi-2223 tape is designed and applied to phantom imaging at high field of 1.5T for the first time. The results show moderate SNR improvements by a factor of 1.36 and 1.11, over a same-sized copper coil at room temperature and at liquid nitrogen of 77K, respectively. It is predictable that HTS tape coils would show merits on SNR from 0.2T with coil size of 5-inch up to 1.5T with coil size of 2-inch. The SNR performance by Bi-2223 tape coil can be further optimized by well addressing the engineering issues and the material development of the HTS tape itself. In the study of Bi-2223 HTS tapes for MRI gradient coils, AC power loss mechanism of the tape is analyzed theoretically first. The power loss measurement of the Bi-2223 tape is carried out to cover the normal working frequencies of gradient coils from 200Hz to 2KHz, and the results show the great advantage of the tape in much lower power loss than copper, even if the critical current degradation is considered. A prototype HTS gradient coil is designed and fabricated. The gradient field distribution by the prototype is measured and agrees well with the theoretical values. The HTS coil performances are compared with a copper coil in the aspects of resistance, inductance, power loss and continuous gradient rating. The technical issues in designing and fabricating HTS gradient coils are also addressed including resistance, gradient strength, continuous gradient rating, critical current degradation, magnetic anisotropy, cryostat and