High-resolution gradient-recalled echo imaging at 9.4T using 16-channel parallel transmit simultaneous multislice spokes excitations with slice-by-slice flip angle homogenization.
Magn Reson Med
; 78(3): 1050-1058, 2017 09.
Article
en En
| MEDLINE
| ID: mdl-27774641
ABSTRACT
PURPOSE:
In order to fully benefit from the improved signal-to-noise and contrast-to-noise ratios at 9.4T, the challenges of B1+ inhomogeneity and the long acquisition time of high-resolution 2D gradient-recalled echo (GRE) imaging were addressed. THEORY ANDMETHODS:
Flip angle homogenized excitations were achieved by parallel transmission (pTx) of 3-spoke pulses, designed by magnitude least-squares optimization in a slice-by-slice fashion; the acquisition time reduction was achieved by simultaneous multislice (SMS) pulses. The slice-specific spokes complex radiofrequency scaling factors were applied to sinc waveforms on a per-channel basis and combined with the other pulses in an SMS slice group to form the final SMS-pTX pulse. Optimal spokes locations were derived from simulations.RESULTS:
Flip angle maps from presaturation TurboFLASH showed improvement of flip angle homogenization with 3-spoke pulses over CP-mode excitation (normalized root-mean-square error [NRMSE] 0.357) as well as comparable excitation homogeneity across the single-band (NRMSE 0.119), SMS-2 (NRMSE 0.137), and SMS-3 (NRMSE 0.132) 3-spoke pulses. The application of the 3-spoke SMS-3 pulses in a 48-slice GRE protocol, which has an in-plane resolution of 0.28 × 0.28 mm, resulted in a 50% reduction of scan duration (total acquisition time 652 min including reference scans).CONCLUSION:
Time-efficient flip angle homogenized high-resolution GRE imaging at 9.4T was accomplished by using slice-specific SMS-pTx spokes excitations. Magn Reson Med 781050-1058, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.Palabras clave
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Procesamiento de Imagen Asistido por Computador
/
Imagen por Resonancia Magnética
Límite:
Adult
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Humans
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Male
Idioma:
En
Revista:
Magn Reson Med
Asunto de la revista:
DIAGNOSTICO POR IMAGEM
Año:
2017
Tipo del documento:
Article
País de afiliación:
Países Bajos