An Actively Decoupled Dual Transceiver Coil System for Continuous ASL at 7 T.
7 T arterial spin labeling (ASL) faces major challenges including the increased specific absorption rate (SAR) and increased B0and B1inhomogeneity. This work describes the design and implementation of a dual-coil system that allows for continuous ASL (CASL) at 7 T. This system consisted of an actively detunable eight-channel transceiver head coil, and a three-channel transceiver labeling coil. Four experiments were performed in 5 healthy subjects: (i) to demonstrate that active detuning during ASL labeling reduces magnetization transfer; (ii) to measure the B1profile at the labeling plane; (iii) to quantify B0off-resonance at the labeling plane; and (iv) to collectin vivoCASL data. The magnetization transfer ratio in the head coil was reduced to 0.0 ± 0.2% by active detuning during labeling. The measured B1profiles in all 5 subjects were sufficient to satisfy the flow-driven adiabatic inversion necessary for CASL, however the actual labeling efficiency was significantly impacted by B0off-resonance at the labeling plane. The measured CASL percent signal change in gray matter (0.94% ± 0.10%) corresponds with the low labeling efficiency predicted by the B0off-resonance. This work demonstrates progress in the technical implementation of 7 T CASL, and reinforces the need for improved B0homogeneity at the labeling plane.
Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA; Center for Functional Neuroimaging, University of Pennsylvania, Philadelphia, PA, USA; Department of Clinical Neurosciences, University of Calgary, Calgary, AB, Canada.
Randall B
RB
Stafford
Neuroscience Research Institute, Gachon University, Incheon, Korea; Department of Electrical and Computer Engineering, Seoul National University, Seoul, Korea; Department of Electrical Engineering, University of Minnesota, Minneapolis, MN, USA.
Myung-Kyun
MK
Woo
Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA; Center for Functional Neuroimaging, University of Pennsylvania, Philadelphia, PA, USA; Imaging Institute, Cleveland Clinic, Cleveland, OH, USA.
Se-Hong
SH
Oh
Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA; Center for Functional Neuroimaging, University of Pennsylvania, Philadelphia, PA, USA; Department of Neurology, University of Pennsylvania, Philadelphia, PA, USA.
Sudipto
S
Dolui
Siemens Medical Solutions USA, Inc., Siemens Healthcare, New York, NY, USA.
Tiejun
T
Zhao
Neuroscience Research Institute, Gachon University, Incheon, Korea.
Young-Bo
YB
Kim
Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA; Center for Functional Neuroimaging, University of Pennsylvania, Philadelphia, PA, USA; Department of Neurology, University of Pennsylvania, Philadelphia, PA, USA.
John A
JA
Detre
Neuroscience Research Institute, Gachon University, Incheon, Korea; Advanced Institutes of Convergence Technology, Seoul National University, Seoul, Korea.
Zang-Hee
ZH
Cho
Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA; Center for Functional Neuroimaging, University of Pennsylvania, Philadelphia, PA, USA; Department of Electrical and Computer Engineering, Seoul National University, Seoul, Korea.
Jongho
J
Lee
7 T; B0-mapping; B1-mapping; arterial spin labeling; labeling coils; magnetic resonance imaging; specific absorption rate
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