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Doubling the resolution of echo‐planar brain imaging by acquisition of two k‐space lines per gradient reversal using TRAIL
Author(s) -
Priest Andrew N.,
De Vita Enrico,
Ordidge Roger J.
Publication year - 2008
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.1155
Subject(s) - ghosting , k space , echo planar imaging , physics , nuclear magnetic resonance , slew rate , amplitude , resolution (logic) , planar , flip angle , nyquist–shannon sampling theorem , temporal resolution , computer science , optics , fourier transform , magnetic resonance imaging , artificial intelligence , computer vision , medicine , computer graphics (images) , quantum mechanics , voltage , radiology
Abstract Single‐shot echo‐planar imaging (EPI) is an important method for MRI of the brain. A method has been developed to double the resolution of EPI in the phase‐encode direction, without requiring increases in the maximum gradient amplitude or slew rate. The new approach is based on an EPI implementation of the TRAIL (two reduced acquisitions interleaved) method, in which two images, acquired in rapid succession, are spatially interleaved. In addition, two lines of k‐space are acquired for each reversal of the readout gradient. Two full‐length readouts are needed, therefore power deposition is increased and the total acquisition time is doubled compared with conventional EPI. However, the individual readouts do not increase in length, so there is no increase in image blurring, and distortion is halved as a result of the closer temporal spacing of the acquired k‐space lines. A correction method is also presented to remove additional potential Nyquist ghosting. The new method is demonstrated in vivo at 4.7 T and could in principle be combined with existing approaches for increasing resolution, such as partial Fourier or parallel imaging. Copyright © 2007 John Wiley & Sons, Ltd.