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Rapid radiofrequency field mapping in vivo using single-shot STEAM MRI

Helms, Gunther LU orcid ; Finsterbusch, Jurgen ; Weiskopf, Nikolaus and Dechent, Peter (2008) In Magnetic Resonance in Medicine 60(3). p.739-743
Abstract
Higher field strengths entail less homogeneous RF fields. This may influence quantitative MRI and MRS. A method for rapidly mapping the RF field in the human head with minimal distortion was developed on the basis of a single-shot stimulated echo acquisition mode (STEAM) sequence. The flip angle of the second RF pulse in the STEAM preparation was set to 60° and 100° instead of 90°, inducing a flip angle-dependent signal change. A quadratic approximation of this trigonometric signal dependence together with a calibration accounting for slice excitation-related bias allowed for directly determining the RF field from the two measurements only. RF maps down to the level of the medulla could be obtained in less than 1 min and registered to... (More)
Higher field strengths entail less homogeneous RF fields. This may influence quantitative MRI and MRS. A method for rapidly mapping the RF field in the human head with minimal distortion was developed on the basis of a single-shot stimulated echo acquisition mode (STEAM) sequence. The flip angle of the second RF pulse in the STEAM preparation was set to 60° and 100° instead of 90°, inducing a flip angle-dependent signal change. A quadratic approximation of this trigonometric signal dependence together with a calibration accounting for slice excitation-related bias allowed for directly determining the RF field from the two measurements only. RF maps down to the level of the medulla could be obtained in less than 1 min and registered to anatomical volumes by means of the T2-weighted STEAM

images. Flip angles between 75% and 125% of the nominal value were measured in line with other methods. (Less)
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author
; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Magnetic Resonance in Medicine
volume
60
issue
3
pages
739 - 743
publisher
John Wiley & Sons Inc.
external identifiers
  • scopus:51449114690
ISSN
1522-2594
DOI
10.1002/mrm.21676
language
English
LU publication?
yes
additional info
3
id
c5c44b21-0fdc-42b5-9234-e76767139dd3 (old id 8773639)
alternative location
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3077516/
date added to LUP
2016-04-01 11:36:10
date last changed
2022-01-26 07:26:22
@article{c5c44b21-0fdc-42b5-9234-e76767139dd3,
  abstract     = {{Higher field strengths entail less homogeneous RF fields. This may influence quantitative MRI and MRS. A method for rapidly mapping the RF field in the human head with minimal distortion was developed on the basis of a single-shot stimulated echo acquisition mode (STEAM) sequence. The flip angle of the second RF pulse in the STEAM preparation was set to 60° and 100° instead of 90°, inducing a flip angle-dependent signal change. A quadratic approximation of this trigonometric signal dependence together with a calibration accounting for slice excitation-related bias allowed for directly determining the RF field from the two measurements only. RF maps down to the level of the medulla could be obtained in less than 1 min and registered to anatomical volumes by means of the T2-weighted STEAM<br/><br>
images. Flip angles between 75% and 125% of the nominal value were measured in line with other methods.}},
  author       = {{Helms, Gunther and Finsterbusch, Jurgen and Weiskopf, Nikolaus and Dechent, Peter}},
  issn         = {{1522-2594}},
  language     = {{eng}},
  number       = {{3}},
  pages        = {{739--743}},
  publisher    = {{John Wiley & Sons Inc.}},
  series       = {{Magnetic Resonance in Medicine}},
  title        = {{Rapid radiofrequency field mapping in vivo using single-shot STEAM MRI}},
  url          = {{http://dx.doi.org/10.1002/mrm.21676}},
  doi          = {{10.1002/mrm.21676}},
  volume       = {{60}},
  year         = {{2008}},
}