Design And Evaluation Of A 2d Tx Rx Rf Coil Array For Cardiovascular Magnetic Resonance Imaging At 7 Tesla
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Design And Evaluation Of A 2d Tx Rx Rf Coil Array For Cardiovascular Magnetic Resonance Imaging At 7 Tesla
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Author : Christof Thalhammer
language : en
Publisher:
Release Date : 2010
Design And Evaluation Of A 2d Tx Rx Rf Coil Array For Cardiovascular Magnetic Resonance Imaging At 7 Tesla written by Christof Thalhammer and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Microstrip Radio Frequency Coil And Array Design For Magnetic Resonance Imaging
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Author : Bing Wu
language : en
Publisher: Open Dissertation Press
Release Date : 2017-01-27
Microstrip Radio Frequency Coil And Array Design For Magnetic Resonance Imaging written by Bing Wu and has been published by Open Dissertation Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-01-27 with categories.
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
Coil Array Optimization And Wireless Transceiver Design For Mri
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Author : Juan Wei
language : en
Publisher: Open Dissertation Press
Release Date : 2017-01-27
Coil Array Optimization And Wireless Transceiver Design For Mri written by Juan Wei and has been published by Open Dissertation Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-01-27 with categories.
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
Development Of Rf Coils And Pulsing Methods For Nmr Mri
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Author : BuSik Park
language : en
Publisher:
Release Date : 2009
Development Of Rf Coils And Pulsing Methods For Nmr Mri written by BuSik Park and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
Radiofrequency magnetic (B1) field inhomogeneity and absorbed power in sample and RF coil have been among the main causes for image degradation in magnetic resonance imaging (MRI) since its inception. The problem becomes more pronounced at high frequencies as wavelengths in tissue become shorter. To address these problems, we present methods for design, implementation, and evaluation of RF coils considering excitation uniformity and/or specific absorption rate (SAR) for high field nuclear magnetic resonance (NMR) and MRI. Specifically, we present 1) the design of a novel radiofrequency (RF) coil for imaging of histological slices of tissue using a 7.0 T MRI system, 2) numerical model of a dielectric resonator for high field MRI, 3) a method to separate conservative and magnetically-induced electric fields from numerical calculations for MR microscopy, 4) a simple method to decrease sample heating using conductive wires, 5) a numerical analysis of conservative and magnetically-induced electric field for low-frequency human imaging, 6) numerical calculation results for the B1 field and SAR evaluation in a 3T neonate head coil, and 7) design of a slice-selective array-optimized composite pulse to improve B1 uniformity and reduce SAR using an 8-channel transmit head array loaded with a head model. The methods and results presented here can provide very useful information for designing RF coils considering excitation uniformity and SAR simultaneously in high field MRI/NMR.
Microstrip Radio Frequency Coil And Array Design For Magnetic Resonance Imaging
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Author : Bing Wu (Ph. D.)
language : en
Publisher:
Release Date : 2006
Microstrip Radio Frequency Coil And Array Design For Magnetic Resonance Imaging written by Bing Wu (Ph. D.) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Magnetic resonance imaging categories.
Rf Coil Design For Multi Frequency Magnetic Resonance Imaging And Spectroscopy
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Author : Arash Dabirzadeh
language : en
Publisher:
Release Date : 2010
Rf Coil Design For Multi Frequency Magnetic Resonance Imaging And Spectroscopy written by Arash Dabirzadeh and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
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.
Radio Frequency Coil Design For Magnetic Resonance Imaging And Spectroscopy
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Author : Paul Joseph Cassidy
language : en
Publisher:
Release Date : 2002
Radio Frequency Coil Design For Magnetic Resonance Imaging And Spectroscopy written by Paul Joseph Cassidy and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with Radiofrequency spectroscopy categories.
Design Of Multi Channel Radio Frequency Front End For 200mhz Parallel Magnetic Resonance Imaging
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Author : Xiaoqun Liu
language : en
Publisher:
Release Date : 2010
Design Of Multi Channel Radio Frequency Front End For 200mhz Parallel Magnetic Resonance Imaging written by Xiaoqun Liu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
The increasing demands for improving magnetic resonance imaging (MRI) quality, especially reducing the imaging time have been driving the channel number of parallel magnetic resonance imaging (Parallel MRI) to increase. When the channel number increases to 64 or even 128, the traditional method of stacking the same number of radio-frequency (RF) receivers with very low level of integration becomes expensive and cumbersome. However, the cost, size, power consumption of the Parallel MRI receivers can be dramatically reduced by designing a whole receiver front-end even multiple receiver front-ends on a single chip using CMOS technology, and multiplexing the output signal of each receiver front-end into one channel so that as much hardware resource can be shared by as many channels as possible, especially the digitizer. The main object of this research is focused on the analysis and design of fully integrated multi-channel RF receiver and multiplexing technology. First, different architectures of RF receiver and different multiplexing method are analyzed. After comparing the advantages and the disadvantages of these architectures, an architecture of receiver front-end which is most suitable for fully on-chip multi-channel design is proposed and a multiplexing method is selected. According to this proposed architecture, a four-channel receiver front-end was designed and fabricated using TSMC 0.18Bm technology on a single chip and methods of testing in the MRI system using parallel planar coil array and phase coil array respectively as target coils were presented. Each channel of the receiver front-end includes an ultra low noise amplifier (LNA), a quadrature image rejection down-converter, a buffer, and a low-pass filter (LPF) which also acts as a variable gain amplifier (VGA). The quadrature image rejection downconverter consists of a quadrature generator, a passive mixer with a transimpedance amplifier which converts the output current signal of the passive mixer into voltage signal while acts as a LPF, and a polyphase filter after the TIA. The receiver has an over NF of 0.935dB, variable gain from about 80dB to 90dB, power consumption of 30.8mW, and chip area of 6mm2. Next, a prototype of 4-channel RF receiver with Time Domain Multiplexing (TDM) on a single printed circuit board (PCB) was designed and bench-tested. Then Parallel MRI experiment was carried out and images were acquired using this prototype. The testing results verify the proposed concepts.
Loop Radiofrequency Coils For Clinical Magnetic Resonance Imaging At 7 Tesla
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Author : Oliver Kraff
language : en
Publisher:
Release Date : 2011
Loop Radiofrequency Coils For Clinical Magnetic Resonance Imaging At 7 Tesla written by Oliver Kraff and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Coil Array Optimization And Wireless Transceiver Design For Magnetic Resonance Imaging
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Author : Juan Wei (Ph. D.)
language : en
Publisher:
Release Date : 2007
Coil Array Optimization And Wireless Transceiver Design For Magnetic Resonance Imaging written by Juan Wei (Ph. D.) and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Imaging systems categories.