Rf coil design for multi-frequency magnetic resonance imaging & spectroscopy

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Title: Rf coil design for multi-frequency magnetic resonance imaging & spectroscopy
Author: Dabirzadeh, Arash
Abstract: 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 .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -3157
Date: 2009-05-15

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Rf coil design for multi-frequency magnetic resonance imaging & spectroscopy. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -3157 .

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