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Method for spatially interleaving two images to halve EPI readout times: Two reduced acquisitions interleaved (TRAIL)
Author(s) -
Priest Andrew N.,
Carmichael David W.,
De Vita Enrico,
Ordidge Roger J.
Publication year - 2004
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.20085
Subject(s) - pixel , interleaving , computer science , echo planar imaging , multislice , computer vision , artificial intelligence , phase (matter) , image resolution , fourier transform , physics , k space , nuclear magnetic resonance , magnetic resonance imaging , medicine , quantum mechanics , radiology , operating system
Abstract A new MRI method is presented that can generate images using half the normal readout time or, more usefully, half the number of phase‐encode steps, combining two readouts per excitation. However, the corresponding data are interleaved in image space—not in k ‐space, as in many other fast techniques. This gives a resilience to the phase‐related artifacts that can occur in many other techniques due to subject motion. A modified stimulated‐echo experiment is used to create two low‐resolution images from a single sequence. The magnetization that contributes to these images is nonuniformly distributed within each pixel, forming two sinusoidal waves in quadrature, with an oscillation period of exactly two pixels. Since only half of each pixel contributes significant signal, the two images can be interleaved to create a full image with twice as many pixels and double the resolution. When the technique is used in the phase‐encode direction, the effective imaging time is halved, though with two readouts per TR period. When two half‐length echo‐planar readouts are used, the method can also reduce blurring and distortion by halving the effective readout time for echo‐planar imaging (EPI). For even further improvements, the technique can be combined with partial Fourier or parallel imaging. Magn Reson Med 51:1212–1222, 2004. © 2004 Wiley‐Liss, Inc.