Design of calibration-free RF pulses for T 2 $$ {}_2 $$ -weighted single-slab 3D turbo-spin-echo sequences at 7T utilizing parallel transmission.
Magn Reson Med
; 92(5): 2037-2050, 2024 Nov.
Article
en En
| MEDLINE
| ID: mdl-39054786
ABSTRACT
PURPOSE:
T 2 $$ {}_2 $$ -weighted turbo-spin-echo (TSE) sequences are a fundamental technique in brain imaging but suffer from field inhomogeneities at ultra-high fields. Several methods have been proposed to mitigate the problem, but were limited so far to nonselective three-dimensional (3D) measurements, making short acquisitions difficult to achieve when targeting very high resolution images, or needed additional calibration procedures, thus complicating their application.METHODS:
Slab-selective excitation pulses were designed for flexible placement utilizing the concept of k T $$ {}_T $$ -spokes. Phase-coherent refocusing universal pulses were subsequently optimized with the Gradient Ascent Pulse Engineering algorithm and tested in vivo for improved signal homogeneity.RESULTS:
Implemented within a 3D variable flip angle TSE sequence, these pulses led to a signal-to-noise ratio (SNR) improvement ranging from 10% to 30% compared to a two-dimensional (2D) T2w TSE sequence employing B 1 + $$ {\mathrm{B}}_1^{+} $$ -shimmed pulses. B 1 + $$ {\mathrm{B}}_1^{+} $$ field inhomogeneities could be mitigated and artifacts from B 0 $$ {\mathrm{B}}_0 $$ deviations reduced. The concept of universal pulses was successfully applied.CONCLUSION:
We present a pulse design method which provides a set of calibration-free universal pulses (UPs) for slab-selective excitation and phase-coherent refocusing in slab-selective TSE sequences.Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Algoritmos
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Encéfalo
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Imagen por Resonancia Magnética
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Imagenología Tridimensional
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Relación Señal-Ruido
Límite:
Humans
Idioma:
En
Revista:
Magn Reson Med
Asunto de la revista:
DIAGNOSTICO POR IMAGEM
Año:
2024
Tipo del documento:
Article
País de afiliación:
Alemania
Pais de publicación:
Estados Unidos