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Single‐shot 3D GRASE with cylindrical k ‐space trajectories
Author(s) -
Ramanna S.,
Feinberg D.A.
Publication year - 2008
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.21735
Subject(s) - artifact (error) , trajectory , imaging phantom , pulse sequence , cartesian coordinate system , signal (programming language) , distortion (music) , noise (video) , pulse (music) , physics , nuclear magnetic resonance , computer science , scanner , computer vision , artificial intelligence , mathematics , image (mathematics) , optics , geometry , amplifier , cmos , astronomy , detector , programming language , optoelectronics
Development of GRASE (gradient‐ and spin‐echo) pulse sequences for single‐shot 3D imaging has been motivated by physiologic studies of the brain. The duration of echo‐planar imaging (EPI) subsequences between RF refocusing pulses in the GRASE sequence is determinant of image distortions and susceptibility artifacts. To reduce these artifacts the regular Cartesian trajectory is modified to a circular trajectory in 2D and a cylindrical trajectory in 3D for reduced echo train time. Incorporation of “fly‐back” trajectories lengthened the time of the subsequences and proportionally increased susceptibility artifact but the unipolar readout gradients eliminate all ghost artifacts. The modified cylindrical trajectory reduced susceptibility artifact and distortion artifact while raising the signal‐to‐noise ratio in both phantom and human brain images. Magn Reson Med 60:976–980, 2008. © 2008 Wiley‐Liss, Inc.