Quantitative and functional pulsed arterial spin labeling in the human brain at 9.4 T.
OBJECTIVE
The feasibility of multislice pulsed arterial spin labeling (PASL) of the human brain at 9.4 T was investigated. To demonstrate the potential of arterial spin labeling (ASL) at this field strength, quantitative, functional, and high-resolution (1.05 × 1.05 × 2 mm(3)) ASL experiments were performed.


METHODS
PASL was implemented using a numerically optimized adiabatic inversion pulse and presaturation scheme. Quantitative measurements were performed at 3 T and 9.4 T and evaluated on a voxel-by-voxel basis. In a functional experiment, activation maps obtained with a conventional blood-oxygen-level-dependent (BOLD)-weighted sequence were compared with a functional ASL (fASL) measurement.


RESULTS
Quantitative measurements revealed a 23% lower perfusion in gray matter and 17% lower perfusion in white matter at 9.4 T compared with 3 T. Furthermore almost identical transit delays and bolus durations were found at both field strengths whereas the calculated voxel volume corrected signal-to-noise ratio was 1.9 times higher at 9.4 T. This result was confirmed by the high-resolution experiment. The functional experiment yielded comparable activation maps for the fASL and BOLD measurements.


CONCLUSIONS
Although PASL at ultrahigh field strengths is limited by high specific absorption rate, functional and quantitative perfusion-weighted images showing a high degree of detail can be obtained.
Max Planck Institute for Biological Cybernetics, High-Field Magnetic Resonance Center, Tübingen, Germany.|Graduate Training Center of Neuronal Sciences, International Max Planck Research School, University of Tübingen, Tübingen, Germany.
Jonas
J
Bause
Max Planck Institute for Biological Cybernetics, High-Field Magnetic Resonance Center, Tübingen, Germany.|Department of Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany.
Philipp
P
Ehses
Max Planck Institute for Biological Cybernetics, High-Field Magnetic Resonance Center, Tübingen, Germany.|Department of Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany.
Christian
C
Mirkes
Max Planck Institute for Biological Cybernetics, High-Field Magnetic Resonance Center, Tübingen, Germany.
G
G
Shajan
Max Planck Institute for Biological Cybernetics, High-Field Magnetic Resonance Center, Tübingen, Germany.|Department of Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany.
Klaus
K
Scheffler
Max Planck Institute for Biological Cybernetics, High-Field Magnetic Resonance Center, Tübingen, Germany.
Rolf
http://orcid.org/0000-0002-6137-9590
R
Pohmann
D000328:Adult; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D059906:Neuroimaging / Q000379:methods*; D019047:Phantoms, Imaging; D012815:Signal Processing, Computer-Assisted; D013113:Spin Labels
D013113:Spin Labels
9.4 T; ASL; fMRI; perfusion; quantification; ultrahigh field