A new EPI-based dynamic field mapping method: Application to retrospective geometrical distortion corrections
J. Magn. Reson. Imaging. 2007-01-01; 26(3): 747-755
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1. J Magn Reson Imaging. 2007 Sep;26(3):747-55.
A new EPI-based dynamic field mapping method: application to retrospective
geometrical distortion corrections.
Lamberton F(1), Delcroix N, Grenier D, Mazoyer B, Joliot M.
(1)Unité Mixte de Recherche (UMR)6194 Centre National de Recherche Scientifique
(CNRS), Commissariat à l’Energie Atomique (CEA), Université de Caen et Paris 5,
PURPOSE: To retrospectively correct for geometrical distortions, a new dynamic
field mapping method suitable for dynamic single-shot gradient-echo type
echo-planar imaging (GRE-EPI) is proposed.
MATERIALS AND METHODS: The method requires a single volume additional acquisition
and allows the extraction of a field map from each phase volume, assuming
invariance across time of the echo time-independent phase component. Performances
of the method are assessed using three sets of experiments: the first tests the
prerequisite and the modeling; the second tests the method with time-dependent
geometrical distortions; and the third presents a comparison with two other
RESULTS: Our results legitimize the modeling procedure and demonstrate that the
dynamic method is less sensitive to noise than the other methods. A theoretical
explanation for this is proposed in the discussion section.
CONCLUSION: Given the minor increase in the acquisition time, this method is well
suited for functional magnetic resonance imaging; prospective direction.
(c) 2007 Wiley-Liss, Inc.
PMID: 17729370 [Indexed for MEDLINE]