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J Magn Reson Imaging. 2006 Sep;24(3):683-9.

EPI image reconstruction with correction of distortion and signal losses.

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  • 1Brain Information Group, National Institute of Information and Communications Technology, Kobe, Hyougo, Japan. lgx@po.nict.go.jp

Abstract

PURPOSE:

To derive and implement a method for correcting geometric distortions and recovering magnetic resonance imaging (MRI) signal losses caused by susceptibility-induced magnetic field gradients (SFGs) in regions with large static field inhomogeneities in echo-planar imaging (EPI).

MATERIALS AND METHODS:

Factors to account for field inhomogeneities and SFGs were added in a traditional EPI equation that was a simple Fourier transform (FT) for expressing the actual k-space data of an EPI scan. The inverse calculation of this "distorted EPI" equation was used as a kernel to correct geometric distortions and reductions in intensity during reconstruction. A step-by-step EPI reconstruction method was developed to prevent complicated phase unwrapping problems. Some EPI images of phantom and human brains were reconstructed from standard EPI k-spaces.

RESULTS:

All images were reconstructed using the proposed multistep method. Geometric distortions were corrected and SFG-induced MRI signal losses were recovered.

CONCLUSION:

Results suggest that applying our method for reconstructing EPI images to reduce distortions and MRI signal losses is feasible.

[PubMed - indexed for MEDLINE]
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