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Improving T -weighted imaging at high field through the use of k -points

Eggenschwiler, Florent
Marques, José P.
Published in Magnetic Resonance in Medicine. 2014, vol. 71, no. 4, p. 1478-1488
Abstract PURPOSE: At high magnetic field strengths (B0 >/= 3 T), the shorter radiofrequency wavelength produces an inhomogeneous distribution of the transmit magnetic field. This can lead to variable contrast across the brain which is particularly pronounced in T2 -weighted imaging that requires multiple radiofrequency pulses. To obtain T2 -weighted images with uniform contrast throughout the whole brain at 7 T, short (2-3 ms) 3D tailored radiofrequency pulses (kT -points) were integrated into a 3D variable flip angle turbo spin echo sequence. METHODS: The excitation and refocusing "hard" pulses of a variable flip angle turbo spin echo sequence were replaced with kT -point pulses. Spatially resolved extended phase graph simulations and in vivo acquisitions at 7 T, utilizing both single channel and parallel-transmit systems, were used to test different kT -point configurations. RESULTS: Simulations indicated that an extended optimized k-space trajectory ensured a more homogeneous signal throughout images. In vivo experiments showed that high quality T2 -weighted brain images with uniform signal and contrast were obtained at 7 T by using the proposed methodology. CONCLUSION: This work demonstrates that T2 -weighted images devoid of artifacts resulting from B1 + inhomogeneity can be obtained at high field through the optimization of extended kT -point pulses. Magn
PMID: 23788025
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EGGENSCHWILER, Florent et al. Improving T -weighted imaging at high field through the use of k -points. In: Magnetic Resonance in Medicine, 2014, vol. 71, n° 4, p. 1478-1488. https://archive-ouverte.unige.ch/unige:45060

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Deposited on : 2015-01-13

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