Cartesian Feedback Control For Mri Transmitter Array Systems

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Cartesian Feedback Control For Mri Transmitter Array Systems

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Author : Marta Gaia Zanchi
language : en
Publisher: Stanford University
Release Date : 2010

Cartesian Feedback Control For Mri Transmitter Array Systems written by Marta Gaia Zanchi and has been published by Stanford University this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.

Accurate control of the radio-frequency (RF) electromagnetic fields in Magnetic Resonance Imaging (MRI) is necessary to ensure patient safety and provide high-quality diagnostic capabilities. Precise control is however becoming increasingly difficult to achieve, given the recent trends toward high fields and transmitter array systems. At high fields, imaging is performed in a frequency regime where the wavelength is on the order of, or smaller than, the dimensions of the human body. This leads to prominent wave behavior, non-uniform field patterns, and increased power deposition. Multi-element transmitter array systems with independent phase and amplitude control of their elements support methods that can mitigate these problems. However, in turn, they demand high fidelity RF reproduction and may lead to undesired electromagnetic interactions between elements of the arrays and with interventional devices. Frequency-offset Cartesian feedback can be used to address all of these issues. In combination with the use of polyphase error amplifiers (to implement a low-IF control bandwidth), Cartesian feedback can be used with MRI power amplifiers and transmit coils to increase the fidelity of RF reproduction, without the in-bandwidth DC-offsets and quadrature mismatches that may lead to imaging artifacts such as bright spots and ghosting. In addition, the control system, which includes autotuning circuitry for stability and vector multipliers circuitry for feedback manipulation, can be used to tune the series output impedance of these amplifiers, thereby reducing the likelihood of interactions between elements of transmit array systems. Furthermore, a miniaturized variation of the control system (called Active Cable Trap) can be used on guidewires to suppress undesired currents elicited by coupling with the RF fields of the transmit coils. In an era of rapid progress in high field MRI for clinical applications, the frequency offset Cartesian feedback method and system thus promises to address many of the challenges faced by designers of multi-element transmitter array systems.

Issues In Electronic Circuits Devices And Materials 2011 Edition

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Author :
language : en
Publisher: ScholarlyEditions
Release Date : 2012-01-09

Issues In Electronic Circuits Devices And Materials 2011 Edition written by and has been published by ScholarlyEditions this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-01-09 with Technology & Engineering categories.

Issues in Electronic Circuits, Devices, and Materials: 2011 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Electronic Circuits, Devices, and Materials. The editors have built Issues in Electronic Circuits, Devices, and Materials: 2011 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Electronic Circuits, Devices, and Materials in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Electronic Circuits, Devices, and Materials: 2011 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.

Neural Metabolism In Vivo

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Author : In-Young Choi
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-03-14

Neural Metabolism In Vivo written by In-Young Choi and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-03-14 with Medical categories.

From the preface: “Neural Metabolism In Vivo aims to provide a comprehensive overview of neurobiology by presenting the basic principles of up-to-date and cutting-edge technology, as well as their application in assessing the functional, morphological and metabolic aspects of the brain. Investigation of neural activity of the living brain via neurovascular coupling using multimodal imaging techniques extended our understanding of fundamental neurophysiological mechanisms, regulation of cerebral blood flow in connection to neural activity and the interplay between neurons, astrocytes and blood vessels. Constant delivery of glucose and oxygen for energy metabolism is vital for brain function, and the physiological basis of neural activity can be assessed through measurements of cerebral blood flow and consumption of glucose and oxygen.... This book presents the complex physiological and neurochemical processes of neural metabolism and function in response to various physiological conditions and pharmacological stimulations. Neurochemical detection technologies and quantitative aspects of monitoring cerebral energy substrates and other metabolites in the living brain are described under the “Cerebral metabolism of antioxidants, osmolytes and others in vivo” section. Altogether, the advent of new in vivo tools has transformed neuroscience and neurobiology research, and demands interdisciplinary approaches as each technology could only approximate a very small fraction of the true complexity of the underlying biological processes. However, translational values of the emerging in vivo methods to the application of preclinical to clinical studies cannot be emphasized enough. Thus, it is our hope that advances in our understanding of biochemical, molecular, functional and physiological processes of the brain could eventually help people with neurological problems, which are still dominated by the unknowns.” -- In-Young Choi and Rolf Gruetter

Novel Mri Technologies For Structural And Functional Imaging Of Tissues With Ultra Short T Values

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Author : Oezen, Ali Caglar
language : en
Publisher: KIT Scientific Publishing
Release Date : 2017-06-30

Novel Mri Technologies For Structural And Functional Imaging Of Tissues With Ultra Short T Values written by Oezen, Ali Caglar and has been published by KIT Scientific Publishing this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-06-30 with Diagnosis categories.

Conventional MRI has several limitations such as long scan durations, motion artifacts, very loud acoustic noise, signal loss due to short relaxation times, and RF induced heating of electrically conducting objects. The goals of this work are to evaluate and improve the state-of-the-art methods for MRI of tissue with short T?, to prove the feasibility of in vivo Concurrent Excitation and Acquisition, and to introduce simultaneous electroglottography measurement during functional lung MRI.

Rf Current Source Drive And Decoupling Technique For Parallel Transmit Arrays In Magnetic Resonance Imaging

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Author : Won-Je Lee
language : en
Publisher:
Release Date : 2008

Rf Current Source Drive And Decoupling Technique For Parallel Transmit Arrays In Magnetic Resonance Imaging written by Won-Je Lee and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.

Electrical Electronics Abstracts

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Author :
language : en
Publisher:
Release Date : 1997

Electrical Electronics Abstracts written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1997 with Electrical engineering categories.

Science Abstracts

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Author :
language : en
Publisher:
Release Date : 1993

Science Abstracts written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with Electrical engineering categories.

Dissertation Abstracts International

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Author :
language : en
Publisher:
Release Date : 1986

Dissertation Abstracts International written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1986 with Dissertations, Academic categories.

The Engineering Index Annual

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Author :
language : en
Publisher:
Release Date : 1992

The Engineering Index Annual written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1992 with Engineering categories.

Since its creation in 1884, Engineering Index has covered virtually every major engineering innovation from around the world. It serves as the historical record of virtually every major engineering innovation of the 20th century. Recent content is a vital resource for current awareness, new production information, technological forecasting and competitive intelligence. The world?s most comprehensive interdisciplinary engineering database, Engineering Index contains over 10.7 million records. Each year, over 500,000 new abstracts are added from over 5,000 scholarly journals, trade magazines, and conference proceedings. Coverage spans over 175 engineering disciplines from over 80 countries. Updated weekly.

International Aerospace Abstracts

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Author :
language : en
Publisher:
Release Date : 1999

International Aerospace Abstracts written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with Aeronautics categories.