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  Local excitation universal parallel transmit pulses at 9.4T

Geldschläger, O., Bosch, D., Glaser, S., & Henning, A. (2021). Local excitation universal parallel transmit pulses at 9.4T. Magnetic Resonance in Medicine, 86(5), 2589-2603. doi:10.1002/mrm.28905.

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Geldschläger, O1, 2, Author              
Bosch, D2, 3, Author              
Glaser, S, Author
Henning, A1, 2, Author              
Affiliations:
1Research Group MR Spectroscopy and Ultra-High Field Methodology, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_2528692              
2Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497794              
3Department High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497796              

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 Abstract: Purpose: To demonstrate that the concept of "universal pTx pulses" is applicable to local excitation applications. Methods: A database of B0 / B+1 maps from eight different subjects was acquired at 9.4T. Based on these maps, universal pulses that aim at local excitation of the visual cortex area in the human brain (with a flip angle of 90° or 7°) were calculated. The remaining brain regions should not experience any excitation. The pulses were designed with an extension of the "spatial domain method." A 2D and a 3D target excitation pattern were tested, respectively. The pulse performance was examined on non-database subjects by Bloch simulations and in vivo at 9.4T using a GRE anatomical MRI and a presaturated TurboFLASH B+1 mapping sequence. Results: The calculated universal pulses show excellent performance in simulations and in vivo on subjects that were not contained in the design database. The visual cortex region is excited, while the desired non-excitation areas produce the only minimal signal. In simulations, the pulses with 3D target pattern show a lack of excitation uniformity in the visual cortex region; however, in vivo, this inhomogeneity can be deemed acceptable. A reduced field of view application of the universal pulse design concept was performed successfully. Conclusions: The proposed design approach creates universal local excitation pulses for a flip angle of 7° and 90°, respectively. Providing universal pTx pulses for local excitation applications prospectively abandons the need for time-consuming subject-specific B0 / B+1 mapping and pTx-pulse calculation during the scan session.

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 Dates: 2021-062021-11
 Publication Status: Published in print
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 Identifiers: DOI: 10.1002/mrm.28905
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Title: Magnetic Resonance in Medicine
Source Genre: Journal
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Publ. Info: New York : Wiley-Liss
Pages: - Volume / Issue: 86 (5) Sequence Number: - Start / End Page: 2589 - 2603 Identifier: ISSN: 0740-3194
CoNE: https://pure.mpg.de/cone/journals/resource/954925538149