Rapid radiofrequency field mapping in vivo using single-shot STEAM MRI.
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Rapid radiofrequency field mapping in vivo using single-shot STEAM MRI. / Helms, Gunther; Finsterbusch, Jürgen; Weiskopf, Nikolaus; Dechent, Peter.
in: MAGN RESON MED, Jahrgang 60, Nr. 3, 3, 2008, S. 739-743.Publikationen: SCORING: Beitrag in Fachzeitschrift/Zeitung › SCORING: Zeitschriftenaufsatz › Forschung › Begutachtung
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TY - JOUR
T1 - Rapid radiofrequency field mapping in vivo using single-shot STEAM MRI.
AU - Helms, Gunther
AU - Finsterbusch, Jürgen
AU - Weiskopf, Nikolaus
AU - Dechent, Peter
PY - 2008
Y1 - 2008
N2 - 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 degrees and 100 degrees instead of 90 degrees , 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 T(2)-weighted STEAM images. Flip angles between 75% and 125% of the nominal value were measured in line with other methods.
AB - 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 degrees and 100 degrees instead of 90 degrees , 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 T(2)-weighted STEAM images. Flip angles between 75% and 125% of the nominal value were measured in line with other methods.
M3 - SCORING: Zeitschriftenaufsatz
VL - 60
SP - 739
EP - 743
JO - MAGN RESON MED
JF - MAGN RESON MED
SN - 0740-3194
IS - 3
M1 - 3
ER -