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

Helms, Gunther LU ; 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)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Magnetic Resonance in Medicine
volume
60
issue
3
pages
739 - 743
publisher
Wiley Online Library
external identifiers
  • scopus:51449114690
ISSN
1522-2594
DOI
10.1002/mrm.21676
language
English
LU publication?
yes
id
c5c44b21-0fdc-42b5-9234-e76767139dd3 (old id 8773639)
alternative location
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3077516/
date added to LUP
2016-02-27 00:55:25
date last changed
2017-11-19 03:25:29
@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    = {Wiley Online Library},
  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},
  volume       = {60},
  year         = {2008},
}