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Nonlinear phase correction of navigated multi‐coil diffusion images
Author(s) -
Atkinson David,
Counsell Serena,
Hajnal Joseph V.,
Batchelor Philip G.,
Hill Derek L.G.,
Larkman David J.
Publication year - 2006
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.21046
Subject(s) - pulsatile flow , computer science , diffusion mri , single shot , diffusion , phase (matter) , electromagnetic coil , artificial intelligence , sensitivity (control systems) , computer vision , nuclear magnetic resonance , physics , optics , magnetic resonance imaging , radiology , medicine , quantum mechanics , cardiology , thermodynamics , electronic engineering , engineering
Cardiac pulsatility causes a nonrigid motion of the brain. In multi‐shot diffusion imaging this leads to spatially varying phase changes that must be corrected. A conjugate gradient based reconstruction is presented that includes phase changes measured using two‐dimensional navigator echoes, coil sensitivity information, navigator‐determined weightings, and data from multiple coils and averages. A multi‐shot echo planar sequence was used to image brain regions where pulsatile motion is not uniform. Reduced susceptibility artifacts were observed compared to a clinical single‐shot sequence. In a higher slice, fiber directions derived from single‐shot data show distortions from anatomical scans by as much as 7 mm compared to less than 2 mm for our multi‐shot reconstructions. The reduced distortions imply that phase encoding can be applied in the shorter left–right direction, enabling time savings through the use of a rectangular field of view. Higher resolution diffusion imaging in the spine permits visualization of a nerve root. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.