Journal Article Research Support, N.I.H., Extramural Ppublish 14 citations
PubMed: 34427341 DOI: 10.1002/mrm.28988
Optimization of pseudo-continuous arterial spin labeling at 7T with parallel transmission B1 shimming.
Magn Reson Med 87(1):249-262
Authors: Kai Wang, Samantha J Ma, Xingfeng Shao, Chenyang Zhao, Qinyang Shou, Lirong Yan, Danny J J Wang
Affiliations
- Laboratory of FMRI Technology, USC Mark & Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
- Siemens Medical Solutions USA, Los Angeles, California, USA.
- Laboratory of FMRI Technology, USC Mark & Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine, University of Southern California, Los Angeles, California, USA. Department of Neurology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
- Department of Neurology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
Abstract
PURPOSE
To optimize pseudo-continuous arterial spin labeling (pCASL) for 7 T, and to further improve the labeling efficiency with parallel RF transmission transmit B ( ) shimming.
METHODS
pCASL parameters were optimized based on field distributions at 7 T with simulation. To increase labeling efficiency, the amplitude at inflowing arteries was increased with parallel RF transmission shimming. The "indv-shim" with shimming weights calculated for each individual subject, and the "univ-shim" with universal weights calculated on a group of 12 subjects, were compared with circular polarized (CP) shim. The optimized pCASL sequences with three shimming modes (indv-shim, univ-shim, and CP-shim) were evaluated in 6 subjects who underwent two repeated scans 24 hours apart, along with a pulsed ASL sequence. Quantitative metrics including mean amplitude, perfusion, and intraclass correlation coefficient were calculated. The optimized 7T pCASL was compared with standard 3T pCASL on 5 subjects, using spatial SNR and temporal SNR.
RESULTS
The optimal pCASL parameter set (RF duration/gap = 300/250 us, ) achieved robust perfusion measurement in the presence of inhomogeneities. Both indv-shim and univ-shim significantly increased amplitude compared with CP-shim in simulation and in vivo experiment (P < .01). Compared with CP-shim, perfusion signal was increased by 9.5% with indv-shim (P < .05) and by 5.3% with univ-shim (P = .35). All three pCASL sequences achieved fair to good repeatability (intraclass correlation coefficient ≥ 0.5). Compared with 3T pCASL, the optimized 7T pCASL achieved 78.3% higher spatial SNR and 200% higher temporal SNR.
CONCLUSION
The optimized pCASL achieved robust perfusion imaging at 7 T, while both indv-shim and univ-shim further increased labeling efficiency.
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- Whole-Cerebrum distortion-free three-dimensional pseudo-Continuous Arterial Spin Labeling at 7T. medRxiv, 2023
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