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Master's Dissertation
DOI
https://doi.org/10.11606/D.54.1986.tde-03062015-105553
Document
Author
Full name
Nicolau Beckmann
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1986
Supervisor
Title in Portuguese
Geração de imagens por ressonância magnética nuclear
Keywords in Portuguese
Não disponível
Abstract in Portuguese
Neste trabalho são abordadas duas técnicas de geração de imagens por ressonância magnética nuclear, a retroprojeção e o método da transformada direta. Estas técnicas baseiam-se na aquisição de sinais de RMN cujas fases e componentes de freqüência são espacialmente codificadas por aplicação de gradientes de campo magnético. A construção de bobinas de gradiente é discutida no caso particular de uma geometria apropriada para um ímã com peças polares e "gap" de ar. Analisa-se também a obtenção de contraste pelos tempos de relaxação T1 e T2 em imagens reconstruídas a partir de sinais gerados empregando seqüências como a de spin-eco, inversão-recuperação e eco estimulado. Sob forma de apêndice, apresenta-se o formalismo matemático que fornece uma solução matricial para as equações de BLOCH, permitindo a determinação da evolução de um sinal em presença de gradientes de campo e pulsos de radiofreqüência, e da dependência de sua magnitude com os tempos de relaxação da amostra.
Title in English
Not available
Keywords in English
Not available
Abstract in English
This work treats two techniquesfor the generation of images by nuclear magnetic resonance, the method of the direct transform. These techniques are based on the acquisition of NMR signals whose phases and frequency components gradients. The construction of gradient coils is discussed for the particular geometry appropriate for a magnet with pole caps and air gap. It contains also an analysis of the obtention of contrast by the relaxation times T1 and T2 in images reconstructed from signals generated employing sequences such as spin-echo, inversion-recovery and stimulated echo. In form of an appendix, a mathematical formalism is presented, that furnishes a matrix solution for the BLOCH equations, allowing the determination of the evolution of a signal in presence of gradients and radiofrequency pulses, and the dependence of its magnitude with relaxation times of the sample.
 
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NicolauBeckmannM.pdf (8.60 Mbytes)
Publishing Date
2015-06-12
 
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