Reducing the duration of broadband excitation pulses using optimal control with limited RF amplitude.
J Magn Reson
; 167(1): 68-74, 2004 Mar.
Article
em En
| MEDLINE
| ID: mdl-14987600
ABSTRACT
Combining optimal control theory with a new RF limiting step produces pulses with significantly reduced duration and improved performance for a given maximum RF amplitude compared to previous broadband excitation by optimized pulses (BEBOP). The resulting pulses tolerate variations in RF homogeneity relevant for standard high-resolution NMR probes. Design criteria were transformation of Iz-->Ix over resonance offsets of +/-20kHz and RF variability of +/-5%, with a pulse length of 500 micros and peak RF amplitude equal to 17.5 kHz. Simulations transform Iz to greater than 0.995 Ix, with phase deviations of the final magnetization less than 2 degrees, over ranges of resonance offset and RF variability that exceed the design targets. Experimental performance of the pulse is in excellent agreement with the simulations. Performance tradeoffs for yet shorter pulses or pulses with decreased digitization are also investigated.
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Base de dados:
MEDLINE
Assunto principal:
Ondas de Rádio
/
Algoritmos
/
Processamento de Sinais Assistido por Computador
/
Espectroscopia de Ressonância Magnética
/
Óxido de Deutério
/
Retroalimentação
Tipo de estudo:
Evaluation_studies
Idioma:
En
Revista:
J Magn Reson
Assunto da revista:
DIAGNOSTICO POR IMAGEM
Ano de publicação:
2004
Tipo de documento:
Article
País de afiliação:
Estados Unidos