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Author: Joseph Vincent Rispoli
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The growing availability of high-field magnetic resonance (MR) scanners has reignited interest in the in vivo investigation of metabolics in the body. In particular, multinuclear MR spectroscopy (MRS) data reveal physiological details inaccessible to typical proton (1H) scans. Carbon-13 (13C) MRS studies draw considerable appeal owing to the enhanced chemical shift range of metabolites that may be interrogated to elucidate disease metabolism and progression. To achieve the theoretical signal-to-noise (SNR) gains at high B0 fields, however, J-coupling from 1H-13C chemical bonds must be mitigated by transmitting radiofrequency (RF) proton-decoupling pulses. This irradiated RF power is substantial and intensifies with increased decoupling bandwidth as well as B0 field strength. The preferred 13C MRS experiment, applying broadband proton decoupling, thus presents considerable challenges at 7 T. Localized tissue heating is a paramount concern for all high-field studies, with strict Specific Absorption Rate (SAR) limits in place to ensure patient safety. Transmit coils must operate within these power guidelines without sacrificing image and spectral quality. Consequently, RF coils transmitting proton-decoupling pulses must be expressly designed for power efficiency as well as B1 field homogeneity. This dissertation presents innovations in high-field RF coil development that collectively improved the homogeneity, efficiency, and safety of high field 13C MRS. A review of electromagnetic (EM) theory guided a full-wave modeling study of coplanar shielding geometries to delineate design parameters for coil transmit efficiency. Next, a novel RF coil technique for achieving B1 homogeneity, dubbed forced current excitation (FCE), was examined and a coplanar-shielded FCE coil was implemented for proton decoupling of the breast at 7 T. To perform a series of simulation studies gauging SAR in the prone breast, software was developed to fuse a suite of anatomically-derived heterogeneous breast phantoms, spanning the standard four tissue density classifications, with existing whole-body voxel models. The effects of tissue density on SAR were presented and guidance for simulating the worst-case scenario was outlined. Finally, for improving capabilities of multinuclear coils during proton coil transmit, a high-power trap circuit was designed and tested, ultimately enabling isolation of 13C coil elements during broadband proton decoupling pulses. Together, this work advanced the hardware capabilities of high-field multinuclear spectroscopy with immediate applicability for performing broadband proton-decoupled 13C MRS in the breast at 7 T. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155400
Author: Joseph Vincent Rispoli
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The growing availability of high-field magnetic resonance (MR) scanners has reignited interest in the in vivo investigation of metabolics in the body. In particular, multinuclear MR spectroscopy (MRS) data reveal physiological details inaccessible to typical proton (1H) scans. Carbon-13 (13C) MRS studies draw considerable appeal owing to the enhanced chemical shift range of metabolites that may be interrogated to elucidate disease metabolism and progression. To achieve the theoretical signal-to-noise (SNR) gains at high B0 fields, however, J-coupling from 1H-13C chemical bonds must be mitigated by transmitting radiofrequency (RF) proton-decoupling pulses. This irradiated RF power is substantial and intensifies with increased decoupling bandwidth as well as B0 field strength. The preferred 13C MRS experiment, applying broadband proton decoupling, thus presents considerable challenges at 7 T. Localized tissue heating is a paramount concern for all high-field studies, with strict Specific Absorption Rate (SAR) limits in place to ensure patient safety. Transmit coils must operate within these power guidelines without sacrificing image and spectral quality. Consequently, RF coils transmitting proton-decoupling pulses must be expressly designed for power efficiency as well as B1 field homogeneity. This dissertation presents innovations in high-field RF coil development that collectively improved the homogeneity, efficiency, and safety of high field 13C MRS. A review of electromagnetic (EM) theory guided a full-wave modeling study of coplanar shielding geometries to delineate design parameters for coil transmit efficiency. Next, a novel RF coil technique for achieving B1 homogeneity, dubbed forced current excitation (FCE), was examined and a coplanar-shielded FCE coil was implemented for proton decoupling of the breast at 7 T. To perform a series of simulation studies gauging SAR in the prone breast, software was developed to fuse a suite of anatomically-derived heterogeneous breast phantoms, spanning the standard four tissue density classifications, with existing whole-body voxel models. The effects of tissue density on SAR were presented and guidance for simulating the worst-case scenario was outlined. Finally, for improving capabilities of multinuclear coils during proton coil transmit, a high-power trap circuit was designed and tested, ultimately enabling isolation of 13C coil elements during broadband proton decoupling pulses. Together, this work advanced the hardware capabilities of high-field multinuclear spectroscopy with immediate applicability for performing broadband proton-decoupled 13C MRS in the breast at 7 T. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155400
Author: Andrew G Webb
Publisher: Royal Society of Chemistry
ISBN: 1782623876
Category : Science
Languages : en
Pages : 402
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Book Description
Magnetic resonance systems are used in almost every academic and industrial chemistry, physics and biochemistry department, as well as being one of the most important imaging modalities in clinical radiology. The design of such systems has become increasingly sophisticated over the years. Static magnetic fields increase continuously, large-scale arrays of receive elements are now ubiquitous in clinical MRI, cryogenic technology has become commonplace in high resolution NMR and is expanding rapidly in preclinical MRI, specialized high strength magnetic field gradients have been designed for studying the human connectome, and the commercial advent of ultra-high field human imaging has required new types of RF coils and static shim coils together with extensive electromagnetic simulations to ensure patient safety. This book covers the hardware and engineering that constitutes a magnetic resonance system, whether that be a high-resolution liquid or solid state system for NMR spectroscopy, a preclinical system for imaging animals or a clinical system used for human imaging. Written by a team of experts in the field, this book provides a comprehensive and instructional look at all aspects of current magnetic resonance technology, as well as outlooks for future developments.
Author: Bernat Palau Tomás
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
[ANGLÈS] This work describes the study of coil for Magnetic Resonance Imaging (MRI) application. Concretely, the principal objective is the design of a birdcage coil (RF coil) to use in a 7 Tesla scanner. More strength field has a better SNR and increased chemical shift effects, improving spectral fat suppression and spectroscopy. Moreover, a better SNR increases the spatial resolution or reduces the imaging time. For this reason, it is interesting research with high fields. The birdcage coil achieves circular polarization and generates a high homogeneous radio frequency magnetic field under many conditions. In this project is designed a Birdcage coil for a 7T to obtain images from small animals (like a mouse). It opens the door to design and construct a Birdcage coil for a 7T to obtain human brain images. In this project thesis, for obtain the design, a study is carried out firstly using the computer program BirdcageBuilder. Secondly, the results obtained with this simulator are introduced to the CST Microwave Studio, creating a 3D model and generating a simulation. In this step, finally the parameters are readjusted to obtain our desired Larmor frequency (298,2MHz) for a correct operation in 7T. These simulations demonstrate the theoretical results from our design and it shows the designed antenna behaviour.
Author: Pierre-Marie Robitaille
Publisher: Springer Science & Business Media
ISBN: 0387496483
Category : Medical
Languages : en
Pages : 487
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Book Description
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.
Author: Navin Khaneja
Publisher:
ISBN: 1838804196
Category :
Languages : en
Pages : 147
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Book Description
Author: Shaileshkumar B. Raval, Ph.D.
Publisher: Index of Sciences Ltd
ISBN: 1838088849
Category : Science
Languages : en
Pages : 340
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Book Description
Magnetic Resonance Imaging“Magnetic Resonance Imaging” (MRI) is the most widely clinically used diagnostic tool for soft tissue imaging. This advanced technology and its applications are under continuous research and development, ranging from lower fields to ultra-high fields to the highest possible fields for preclinical (animal) and human imaging. Formerly known as Nuclear Magnetic Resonance Imaging (NMR), with the rising demands of clinical diagnosis requirements, it is under constant development and innovation in hospitals for populations around the world because of constant desire to go to higher fields that lead to unique research and clinical applications that aren’t achievable with other commercially and or research technologies. The basics of MRIThe human body is rich in hydrogen, when a human body is subjected to a large magnetic field, many of the free hydrogen nuclei align themselves with the direction of the magnetic field. MRI works on the principle of the directional magnetic field associated with charged particles in motion. MRI is also known as nuclear magnetic resonance imaging, a technique used to create images of parts of the human body based on the resonance of nuclei in motion under the effect of a magnetic field. Overview of the bookThis book’s lucid style makes it an easy read. It is written in a simple and comprehensible way, making it easy to followand readfor a large audience ranging from students to researchers. The areas covered include an overview of the theories and practical aspects of High-Field MRIwith each chapter Introduction, Challenges, Objectives, Methods(Materials), Results, Discussion, FutureWworks,including basic concepts, along with research-oriented and clinical concepts, technologies that are researched and developed, and implemented clinically, and published nationally and internationally recognized conferences, and publications with global awards recognition from ISMRM, TTS, and many other academic and industry organizationsthat are recognized worldwide. In this book, unexplored research theories are described along with a list of products, project developments, and completion of major and unattempted theories, which are considered to be challenging in high-field MRI. These unexplored research theories are further delved into to emerge with practical and translational products, as described in various chapters. These products are deemed to be of potential research and clinical use if implemented in clinical and hospital settings, to help thus could the patients as well as healthy populations to improve the standard of their lives. Advances in extremities and musculoskeletal imaging in patients undergoing transplants, including first-ever(never been implemented)technologies such as Ultra high field upper extremity RF coils, research publications, and intellectual properties have been explored in detail. Another major advancement discussed in this book is the Whole-body MRI RF high density transmit coil and receiver array designs(first evevr application of antenna design), published in national and international journals as intellectual properties. Various other aspects of these 4intellectual properties have been discussed such as instrumentation developed, design procedures, Electromagnetic Simulations (simulated versions), Novel whole head(Brain) MRI RF array, Innovative Visualization Techniques, Neuro and vascular flow imaging, Segmentation methods. Regenerative Imaging, Pre and post-operative (surgical) imaging, clinical implementations, pulse sequence developments and optimizations, imaging resultswith 3D volume Texture and Visualizations, also peer research and references from around the world, plus future works, and more have been entailed. This is a rather different book in terms of depth and detail in which the subject is dealt with in this book. The data is well represented with tables, equations, and nearly three hundred figures. Combining technologies, research, and clinical applications of innovations in the field of MRI, it is one of a kind and a treat for curious minds. The content is mainly focused on whole head imaging, whole-body imaging, and extremity imaging, describing their clinical applications and their implementation for high risk and high demand patient populations, healthy populations for enhanced human anatomical, biological, functional and physiological performances in a detailed manner. The research has been utilized by peers in their studies, research, publications, and learning as part of the research and clinical developments, and implementations. This book presents the author’s original research works and their applications in the real world to offer advanced innovations to the healthcare sector and improve quality and standard of life for the masses around the world and beyond as future goals as there are many aviations,Biomedical Applications and projects are in demand. The author’s research works have been publishedand awarded in various nationalllyand internationallyrecognized journals and presented in numerous conferences as well. The chapters of this book are each one of the many research publications by the author
Author: J. Thomas Vaughan
Publisher: John Wiley & Sons
ISBN: 1118590457
Category : Medical
Languages : en
Pages : 34
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Book Description
The content of this volume has been added to eMagRes (formerly Encyclopedia of Magnetic Resonance) - the ultimate online resource for NMR and MRI. To date there is no single reference aimed at teaching the art of applications guided coil design for use in MRI. This RF Coils for MRI handbook is intended to become this reference. Heretofore, much of the know-how of RF coil design is bottled up in various industry and academic laboratories around the world. Some of this information on coil technologies and applications techniques has been disseminated through the literature, while more of this knowledge has been withheld for competitive or proprietary advantage. Of the published works, the record of technology development is often incomplete and misleading, accurate referencing and attribution assignment being tantamount to admission of patent infringement in the commercial arena. Accordingly, the literature on RF coil design is fragmented and confusing. There are no texts and few courses offered to teach this material. Mastery of the art and science of RF coil design is perhaps best achieved through the learning that comes with a long career in the field at multiple places of employment...until now. RF Coils for MRI combines the lifetime understanding and expertise of many of the senior designers in the field into a single, practical training manual. It informs the engineer on part numbers and sources of component materials, equipment, engineering services and consulting to enable anyone with electronics bench experience to build, test and interface a coil. The handbook teaches the MR system user how to safely and successfully implement the coil for its intended application. The comprehensive articles also include information required by the scientist or physician to predict respective experiment or clinical performance of a coil for a variety of common applications. It is expected that RF Coils for MRI becomes an important resource for engineers, technicians, scientists, and physicians wanting to safely and successfully buy or build and use MR coils in the clinic or laboratory. Similarly, this guidebook provides teaching material for students, fellows and residents wanting to better understand the theory and operation of RF coils. Many of the articles have been written by the pioneers and developers of coils, arrays and probes, so this is all first hand information! The handbook serves as an expository guide for hands-on radiologists, radiographers, physicians, engineers, medical physicists, technologists, and for anyone with interests in building or selecting and using RF coils to achieve best clinical or experimental results. About EMR Handbooks / eMagRes Handbooks The Encyclopedia of Magnetic Resonance (up to 2012) and eMagRes (from 2013 onward) publish a wide range of online articles on all aspects of magnetic resonance in physics, chemistry, biology and medicine. The existence of this large number of articles, written by experts in various fields, is enabling the publication of a series of EMR Handbooks / eMagRes Handbooks on specific areas of NMR and MRI. The chapters of each of these handbooks will comprise a carefully chosen selection of articles from eMagRes. In consultation with the eMagRes Editorial Board, the EMR Handbooks / eMagRes Handbooks are coherently planned in advance by specially-selected Editors, and new articles are written (together with updates of some already existing articles) to give appropriate complete coverage. The handbooks are intended to be of value and interest to research students, postdoctoral fellows and other researchers learning about the scientific area in question and undertaking relevant experiments, whether in academia or industry. Have the content of this Handbook and the complete content of eMagRes at your fingertips! Visit: www.wileyonlinelibrary.com/ref/eMagRes View other eMagRes publications here
Author:
Publisher:
ISBN:
Category : Magnetic resonance imaging
Languages : en
Pages : 328
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Book Description
Abstract: This research concentrates on two major engineering areas associated with biomedical instrumentation that have recently gained significant academic and industrial interest: the gradient coil design for Magnetic Resonance Imaging (MRI) and the high frequency full-wave field simulations with the Method of Moments (MoM). A new computational approach to the design of gradient coils for magnetic resonance imaging is introduced. The theoretical formulation involves a constrained cost function between the desired field in a particular region of interest in space and the current-carrying coil plane. Based on Biot-Savart's integral equation, an appropriate weight function is introduced in conjunction with linear approximation functions. This permits the transformation of the problem formulation into a linear matrix equation whose solution yields discrete current elements in terms of magnitude and direction within a specified coil plane. These current elements can be synthesized into practical wire configuration by suitably combining the individual wire loops. Numerical predictions and measurements underscore the success of this approach in terms of achieving a highly linear field while maintaining low parasitic fields, low inductance and a sufficient degree of shielding. Experimental results confirm the field predictions of the computational approach. Extending the numerical modeling efforts to dynamic phenomena, a novel MoM formulation permits the computation of electromagnetic fields in conductive surfaces and in three-dimensional biological bodies. The excitation can be provided with current loops, voltage sources, or an incident electromagnetic wave. This method enables us to solve a broad spectrum of problems arising in MRI: full-wave RF coil simulations, eddy currents predictions in the magnet bore, and induced currents in the biological body. Surfaces are represented as triangles and the three-dimensional bodies are subdivided into tetrahedra. This numerical discretization methodology makes the approach very flexible to handle a wide range of practical coil geometries. Specifically, in this thesis the MoM is employed to study the effect of switching gradient coils in the presence of a biological load.
Author: Hristos T. Anastassiu
Publisher: MDPI
ISBN: 3036500642
Category : Technology & Engineering
Languages : en
Pages : 196
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Book Description
Like all branches of physics and engineering, electromagnetics relies on mathematical methods for modeling, simulation, and design procedures in all of its aspects (radiation, propagation, scattering, imaging, etc.). Originally, rigorous analytical techniques were the only machinery available to produce any useful results. In the 1960s and 1970s, emphasis was placed on asymptotic techniques, which produced approximations of the fields for very high frequencies when closed-form solutions were not feasible. Later, when computers demonstrated explosive progress, numerical techniques were utilized to develop approximate results of controllable accuracy for arbitrary geometries. In this Special Issue, the most recent advances in the aforementioned approaches are presented to illustrate the state-of-the-art mathematical techniques in electromagnetics.
Author: Joel Mispelter
Publisher: World Scientific Publishing Company
ISBN: 1783268042
Category : Technology & Engineering
Languages : en
Pages : 754
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Book Description
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.
