NDLI: Spin dephasing under nonlinear gradients: Implications for imaging and field mapping

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Spin dephasing under nonlinear gradients: Implications for imaging and field mapping

Content Provider	Scilit
Author	Galiana, Gigi Stockmann, Jason P. Tam, Leo Constable, R. Todd
Copyright Year	2011
Description	Journal: Magnetic Resonance in Medicine This work examines the prototypical MR echo that would be expected for a voxel of spins evolving in a strong nonlinear field, specifically focusing on the quadratic z(2) - ½(x(2) + y(2) ) field. Dephasing under nonlinear gradients is increasingly relevant given the growing interest in nonlinear imaging, and here, we report several notable differences from the linear case. Most notably, in addition to signal loss, intravoxel dephasing under gradients creating a wide and asymmetric frequency distribution across the voxel can cause skewed and nonlinear phase evolution. After presenting the qualitative and analytical origins of this difference, we experimentally demonstrate that neglecting these dynamics can lead to significant errors in sequences that assume phase evolution is proportional to voxel frequency, such as those used for field mapping. Finally, simplifying approximations to the signal equations are presented, which not only provide more intuitive forms of the exact expression but also result in simple rules to predict key features of the nonlinear evolution.
Related Links	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3289760/pdf
Ending Page	1126
Page Count	7
Starting Page	1120
e-ISSN	15222594
DOI	10.1002/mrm.23085
Journal	Magnetic Resonance in Medicine
Issue Number	4
Volume Number	67
Language	English
Publisher	Wiley-Blackwell
Publisher Date	2011-07-14
Access Restriction	Open
Subject Keyword	Journal: Magnetic Resonance in Medicine Radiology, Nuclear Medicine and Imaging Nonlinear Imaging Parallel Imaging Gradient Echo Gradient Dephasing Field Mapping Nonlinear Gradients Image Distortion
Content Type	Text
Resource Type	Article

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Spin Dephasing Under Nonlinear Gradients: Implications for Imaging and Field Mapping

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