Nonlinear phase correction of navigated multi-coil diffusion images

TY - JOUR

T1 - Nonlinear phase correction of navigated multi-coil diffusion images

AU - Atkinson, David

AU - Counsell, Serena

AU - Hajnal, Joseph V.

AU - Batchelor, Philip G.

AU - Hill, Derek L. G.

AU - Larkman, David J.

PY - 2006/11

Y1 - 2006/11

N2 - 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 singleshot 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.

AB - 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 singleshot 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.

U2 - 10.1002/mrm.21046

DO - 10.1002/mrm.21046

M3 - Article

SN - 1522-2594

VL - 56

SP - 1135

EP - 1139

JO - Magnetic Resonance in Medicine

JF - Magnetic Resonance in Medicine

IS - 5

ER -