Optimization of pseudo-continuous arterial spin labeling at 7T with parallel transmission B1 shimming

Kai Wang; Samantha J. Ma; Xingfeng Shao; Chenyang Zhao; Qinyang Shou; Lirong Yan; Danny J.J. Wang

doi:10.1002/mrm.28988

Optimization of pseudo-continuous arterial spin labeling at 7T with parallel transmission B1 shimming

Kai Wang, Samantha J. Ma, Xingfeng Shao, Chenyang Zhao, Qinyang Shou, Lirong Yan, Danny J.J. Wang^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

2 Scopus citations

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 B₁ ((Formula presented.)) shimming. Methods: pCASL parameters were optimized based on (Formula presented.) field distributions at 7 T with simulation. To increase labeling efficiency, the (Formula presented.) amplitude at inflowing arteries was increased with parallel RF transmission (Formula presented.) 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 (Formula presented.) 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 (Formula presented.) 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, (Formula presented.)) achieved robust perfusion measurement in the presence of (Formula presented.) inhomogeneities. Both indv-shim and univ-shim significantly increased (Formula presented.) 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.

Original language	English (US)
Pages (from-to)	249-262
Number of pages	14
Journal	Magnetic resonance in medicine
Volume	87
Issue number	1
DOIs	https://doi.org/10.1002/mrm.28988
State	Published - Jan 2022
Externally published	Yes

Keywords

B1+ shimming
arterial spin labeling
parallel RF transmission
perfusion
ultrahigh field
universal pulse

ASJC Scopus subject areas

Radiology Nuclear Medicine and imaging

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10.1002/mrm.28988

Cite this

@article{796362a9c06e44b09df5053422e997ca,

title = "Optimization of pseudo-continuous arterial spin labeling at 7T with parallel transmission B1 shimming",

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 B1 ((Formula presented.)) shimming. Methods: pCASL parameters were optimized based on (Formula presented.) field distributions at 7 T with simulation. To increase labeling efficiency, the (Formula presented.) amplitude at inflowing arteries was increased with parallel RF transmission (Formula presented.) 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 (Formula presented.) 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 (Formula presented.) 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, (Formula presented.)) achieved robust perfusion measurement in the presence of (Formula presented.) inhomogeneities. Both indv-shim and univ-shim significantly increased (Formula presented.) 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.",

keywords = "B1+ shimming, arterial spin labeling, parallel RF transmission, perfusion, ultrahigh field, universal pulse",

author = "Kai Wang and Ma, {Samantha J.} and Xingfeng Shao and Chenyang Zhao and Qinyang Shou and Lirong Yan and Wang, {Danny J.J.}",

note = "Funding Information: National Institutes of Health; Grand/Award Nos. UH3-NS100614, S10-OD025312, R01-NS114382, R01-EB028297, R01-EB032169 and R01-NS118019 Publisher Copyright: {\textcopyright} 2021 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine",

year = "2022",

month = jan,

doi = "10.1002/mrm.28988",

language = "English (US)",

volume = "87",

pages = "249--262",

journal = "Magnetic Resonance in Medicine",

issn = "0740-3194",

publisher = "John Wiley and Sons Inc.",

number = "1",

}

TY - JOUR

T1 - Optimization of pseudo-continuous arterial spin labeling at 7T with parallel transmission B1 shimming

AU - Wang, Kai

AU - Ma, Samantha J.

AU - Shao, Xingfeng

AU - Zhao, Chenyang

AU - Shou, Qinyang

AU - Yan, Lirong

AU - Wang, Danny J.J.

N1 - Funding Information: National Institutes of Health; Grand/Award Nos. UH3-NS100614, S10-OD025312, R01-NS114382, R01-EB028297, R01-EB032169 and R01-NS118019 Publisher Copyright: © 2021 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine

PY - 2022/1

Y1 - 2022/1

N2 - Purpose: To optimize pseudo-continuous arterial spin labeling (pCASL) for 7 T, and to further improve the labeling efficiency with parallel RF transmission transmit B1 ((Formula presented.)) shimming. Methods: pCASL parameters were optimized based on (Formula presented.) field distributions at 7 T with simulation. To increase labeling efficiency, the (Formula presented.) amplitude at inflowing arteries was increased with parallel RF transmission (Formula presented.) 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 (Formula presented.) 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 (Formula presented.) 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, (Formula presented.)) achieved robust perfusion measurement in the presence of (Formula presented.) inhomogeneities. Both indv-shim and univ-shim significantly increased (Formula presented.) 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.

AB - Purpose: To optimize pseudo-continuous arterial spin labeling (pCASL) for 7 T, and to further improve the labeling efficiency with parallel RF transmission transmit B1 ((Formula presented.)) shimming. Methods: pCASL parameters were optimized based on (Formula presented.) field distributions at 7 T with simulation. To increase labeling efficiency, the (Formula presented.) amplitude at inflowing arteries was increased with parallel RF transmission (Formula presented.) 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 (Formula presented.) 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 (Formula presented.) 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, (Formula presented.)) achieved robust perfusion measurement in the presence of (Formula presented.) inhomogeneities. Both indv-shim and univ-shim significantly increased (Formula presented.) 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.

KW - B1+ shimming

KW - arterial spin labeling

KW - parallel RF transmission

KW - perfusion

KW - ultrahigh field

KW - universal pulse

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Optimization of pseudo-continuous arterial spin labeling at 7T with parallel transmission B1 shimming

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