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Master's Dissertation
DOI
10.11606/D.76.2004.tde-28042004-184322
Document
Author
Full name
Fernando Fernandes Paiva
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2004
Supervisor
Committee
Tannus, Alberto (President)
Rabbani, Said Rahnamaye
Schneider, Jose Fabian
Title in Portuguese
"Metodologia de imagens de NMR que utiliza um único pulso adiabático de inversão."
Keywords in Portuguese
Pulsos Adiabáticos
Ressonância Magnética Nuclear
Abstract in Portuguese
Baseado em uma seqüência já conhecida de Multislice Spin Echo convencional, implementamos uma seqüência do tipo Modified Driven Equilibrium Fourier Transform (MDEFT) adiabática multislice em um sistema de 2T e um de microimagens (9.4T). Essa metodologia utiliza, como pulso de inversão, um pulso de RF com modulação em amplitude e freqüência, conhecido por pulso adiabático. Dessa forma, os tempos de inversão são iguais para todos os planos selecionados, resultando num contraste por T1 uniformemente distribuído ao longo dos mesmos. O uso de um único e longo pulso adiabático de inversão tem, ainda, a vantagem de utilizar uma potência de pico menor para operar da mesma forma que um grupo de m pulsos convencionais. Utilizamos pulsos cujas modulações correspondentes de fase e freqüência foram calculadas com base nas condições de “Offset Independent Adiabaticity” (OIA) e a real eficiência dos mesmos foi avaliada através de simulações e experimentalmente. Para realização dos testes da metodologia desenvolvemos e caracterizamos dois “phantoms”, cujas imagens demonstram a aplicabilidade da metodologia nos dois sistemas utilizados.
Title in English
"NMR imaging methodology using a single adiabatic inversion pulse."
Keywords in English
Adiabatic Pulses
Nuclear Magnetic Resonance
Abstract in English
Based on the conventional Multislice Spin Echo pulse sequence, we implemented an adiabatic multislice Modified Driven Equilibrium Fourier Transform (MDEFT) pulse sequence on a 2T and a 9.4T microimaging system. This methodology uses, as inversion pulse, an amplitude and frequency modulated RF pulse, known as adiabatic pulse. In that way, the inversion times are the same for all slices, resulting in an evenly distributed T1 contrast. A single and long adiabatic inversion pulse has in addition the advantage of using a reduced peak power to perform in the same way as the group of m conventional pulses. We used pulses whose corresponding phase and frequency modulations were based on Offset Independent Adiabaticity and their real efficiency were evaluated both through simulations and experimentally. To test the methodology, we developed and characterized two phantoms, whose images demonstrate the applicability of the methodology in the two mentioned systems.
 
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Dissertfernando.pdf (2.93 Mbytes)
Publishing Date
2004-08-16
 
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