An actively decoupled dual transceiver coil system for continuous ASL at 7 T

Autor: Tiejun Zhao, Randall B. Stafford, John A. Detre, Jongho Lee, Zang-Hee Cho, Young-Bo Kim, Myung Kyun Woo, Se-Hong Oh, Sudipto Dolui
Rok vydání: 2016
Předmět:
Zdroj: International Journal of Imaging Systems and Technology. 26:106-115
ISSN: 0899-9457
DOI: 10.1002/ima.22165
Popis: 7 T arterial spin labeling (ASL) faces major challenges including the increased specific absorption rate (SAR) and increased B0 and B1 inhomogeneity. 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 B1 profile at the labeling plane; (iii) to quantify B0 off-resonance at the labeling plane; and (iv) to collect in vivo CASL data. The magnetization transfer ratio in the head coil was reduced to 0.0 ± 0.2% by active detuning during labeling. The measured B1 profiles 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 B0 off-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 B0 off-resonance. This work demonstrates progress in the technical implementation of 7 T CASL, and reinforces the need for improved B0 homogeneity at the labeling plane.
Databáze: OpenAIRE
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