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PSF mapping‐based correction of eddy‐current‐induced distortions in diffusion‐weighted echo‐planar imaging
Author(s) -
In MyungHo,
Posnansky Oleg,
Speck Oliver
Publication year - 2016
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.25746
Subject(s) - echo planar imaging , eddy current , nuclear magnetic resonance , planar , physics , diffusion , echo (communications protocol) , computer science , magnetic resonance imaging , medicine , radiology , computer graphics (images) , quantum mechanics , thermodynamics , computer network
Purpose To accurately correct diffusion‐encoding direction‐dependent eddy‐current‐induced geometric distortions in diffusion‐weighted echo‐planar imaging (DW‐EPI) and to minimize the calibration time at 7 Tesla (T). Methods A point spread function (PSF) mapping based eddy‐current calibration method is newly presented to determine eddy‐current‐induced geometric distortions even including nonlinear eddy‐current effects within the readout acquisition window. To evaluate the temporal stability of eddy‐current maps, calibration was performed four times within 3 months. Furthermore, spatial variations of measured eddy‐current maps versus their linear superposition were investigated to enable correction in DW‐EPIs with arbitrary diffusion directions without direct calibration. For comparison, an image‐based eddy‐current correction method was additionally applied. Finally, this method was combined with a PSF‐based susceptibility‐induced distortion correction approach proposed previously to correct both susceptibility and eddy‐current‐induced distortions in DW‐EPIs. Results Very fast eddy‐current calibration in a three‐dimensional volume is possible with the proposed method. The measured eddy‐current maps are very stable over time and very similar maps can be obtained by linear superposition of principal‐axes eddy‐current maps. High resolution in vivo brain results demonstrate that the proposed method allows more efficient eddy‐current correction than the image‐based method. Conclusion The combination of both PSF‐based approaches allows distortion‐free images, which permit reliable analysis in diffusion tensor imaging applications at 7T. Magn Reson Med 75:2055–2063, 2016. © 2015 Wiley Periodicals, Inc.