Fast slice-selective radio-frequency excitation pulses for mitigating B+1 inhomogeneity in the human brain at 7 Tesla.
Magn Reson Med
; 59(6): 1355-64, 2008 Jun.
Article
em En
| MEDLINE
| ID: mdl-18506800
ABSTRACT
A novel radio-frequency (RF) pulse design algorithm is presented that generates fast slice-selective excitation pulses that mitigate B+1 inhomogeneity present in the human brain at high field. The method is provided an estimate of the B+1 field in an axial slice of the brain and then optimizes the placement of sinc-like "spokes" in kz via an L1-norm penalty on candidate (kx, ky) locations; an RF pulse and gradients are then designed based on these weighted points. Mitigation pulses are designed and demonstrated at 7T in a head-shaped water phantom and the brain; in each case, the pulses mitigate a significantly nonuniform transmit profile and produce nearly uniform flip angles across the field of excitation (FOX). The main contribution of this work, the sparsity-enforced spoke placement and pulse design algorithm, is derived for conventional single-channel excitation systems and applied in the brain at 7T, but readily extends to lower field systems, nonbrain applications, and multichannel parallel excitation arrays.
Texto completo:
1
Coleções:
01-internacional
Temas:
Agentes_cancerigenos
Base de dados:
MEDLINE
Assunto principal:
Algoritmos
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Processamento de Imagem Assistida por Computador
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Mapeamento Encefálico
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Imageamento por Ressonância Magnética
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Aumento da Imagem
Limite:
Humans
Idioma:
En
Revista:
Magn Reson Med
Assunto da revista:
DIAGNOSTICO POR IMAGEM
Ano de publicação:
2008
Tipo de documento:
Article
País de afiliação:
Estados Unidos