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  Numerical and experimental evaluation of RF shimming in the human brain at 9.4 T using a dual-row transmit array

Hoffmann, J., Shajan, G., Scheffler, K., & Pohmann, R. (2014). Numerical and experimental evaluation of RF shimming in the human brain at 9.4 T using a dual-row transmit array. Magnetic Resonance Materials in Physics, Biology and Medicine, 27(5), 373-386. doi:10.1007/s10334-013-0419-y.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-001A-12BA-A Version Permalink: http://hdl.handle.net/21.11116/0000-0001-1E2F-B
Genre: Journal Article

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Hoffmann, J1, 2, Author              
Shajan, G1, 2, Author              
Scheffler, K1, 2, Author              
Pohmann, R1, 2, Author              
Affiliations:
1Department High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497796              
2Max Planck Institute for Biological Cybernetics, Max Planck Society, Spemannstrasse 38, 72076 Tübingen, DE, ou_1497794              

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 Abstract: Objective To provide a numerical and experimental investigation of the static RF shimming capabilities in the human brain at 9.4 T using a dual-row transmit array. Materials and methods A detailed numerical model of an existing 16-channel, inductively decoupled dual-row array was constructed using time-domain software together with circuit co-simulation. Experiments were conducted on a 9.4 T scanner. Investigation of RF shimming focused on B1 + homogeneity, efficiency and local specific absorption rate (SAR) when applied to large brain volumes and on a slice-by-slice basis. Results Numerical results were consistent with experiments regarding component values, S-parameters and B1 + pattern, though the B1 + field was about 25 weaker in measurements than simulations. Global shim settings were able to prevent B1 + field voids across the entire brain but the capability to simultaneously reduce inhomogeneities was limited. On a slice-by-slice basis, B1 + standard deviations of below 10 without field dropouts could be achieved in axial, sagittal and coronal orientations across the brain, even with phase-only shimming, but decreased B1 + efficiency and SAR limitations must be considered. Conclusion Dual-row transmit arrays facilitate flexible 3D RF management across the entire brain at 9.4 T in order to trade off B1 + homogeneity against power-efficiency and local SAR.

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 Dates: 2013-112014-10
 Publication Status: Published in print
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 Identifiers: DOI: 10.1007/s10334-013-0419-y
BibTex Citekey: HoffmannSSP2013_3
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Title: Magnetic Resonance Materials in Physics, Biology and Medicine
Source Genre: Journal
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Pages: - Volume / Issue: 27 (5) Sequence Number: - Start / End Page: 373 - 386 Identifier: -