Hybrid B1+-shimming and gradient adaptions for improved pseudo-continuous arterial spin labeling at 7 Tesla
Meixner C, Eisen C, Schmitter S, Müller M, Herrler J, Hensel B, Dörfler A, Uder M, Nagel AM (2021)
Publication Type: Journal article
Publication year: 2021
Journal
DOI: 10.1002/mrm.28982
Abstract
Purpose: To improve pseudo-continuous arterial spin labeling (pcASL) at 7T by exploiting a hybrid homogeneity- and efficiency-optimized (Formula presented.) -shim with adapted gradient strength as well as background suppression. Methods: The following three experiments were performed at 7T, each employing five volunteers: (1) A hybrid (ie, homogeneity-efficiency optimized) (Formula presented.) -shim was introduced and evaluated for variable-rate selective excitation pcASL labeling. Therefore, (Formula presented.) -maps in the V3 segment and time-of-flight images were acquired to identify the feeding arteries. For validation, a gradient-echo sequence was applied in circular polarized (CP) mode and with the hybrid (Formula presented.) -shim. Additionally, the gray matter (temporal) signal-to-noise ratio (tSNR) in pcASL perfusion images was evaluated. (2) Bloch simulations for the pcASL labeling were conducted and validated experimentally, with a focus on the slice-selective gradients. (3) Background suppression was added to the (Formula presented.) -shimmed, gradient-adapted 7T sequence and this was then compared to a matched sequence at 3T. Results: The (Formula presented.) -shim improved the signal within the labeling plane (23.6%) and the SNR/tSNR increased (+11%/+11%) compared to its value in CP mode; however, the increase was not significant. In accordance with the simulations, the adapted gradients increased the tSNR (35%) and SNR (45%) significantly. Background suppression further improved the perfusion images at 7T, and this protocol performed as well as a resolution-matched protocol at 3T. Conclusion: The combination of the proposed hybrid (Formula presented.) -phase-shim with the adapted slice-selective gradients and background suppression shows great potential for improved pcASL labeling under suboptimal (Formula presented.) conditions at 7T.
Authors with CRIS profile
Christian Meixner
Institute of Radiology
Christian Eisen
Institute of Radiology
Max Müller
Institute of Radiology
Jürgen Herrler
Department of Neuroradiology
Bernhard Hensel
Naturwissenschaftliche Fakultät
Arnd Dörfler
Department of Neuroradiology
Michael Uder
Lehrstuhl für Diagnostische Radiologie
Armin Michael Nagel
Professur für metabolische und funktionelle MR-Bildgebung
Involved external institutions
Germany (DE)How to cite
APA:
Meixner, C., Eisen, C., Schmitter, S., Müller, M., Herrler, J., Hensel, B.,... Nagel, A.M. (2021). Hybrid B1+-shimming and gradient adaptions for improved pseudo-continuous arterial spin labeling at 7 Tesla. Magnetic Resonance in Medicine. https://dx.doi.org/10.1002/mrm.28982
MLA:
Meixner, Christian, et al. "Hybrid B1+-shimming and gradient adaptions for improved pseudo-continuous arterial spin labeling at 7 Tesla." Magnetic Resonance in Medicine (2021).
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