Concomitant field terms for asymmetric gradient coils: Consequences for diffusion, flow, and echo‐planar imaging
- 25 June 2008
- journal article
- Published by Wiley in Magnetic Resonance in Medicine
- Vol. 60 (1), 128-134
- https://doi.org/10.1002/mrm.21615
Abstract
As a consequence of the Maxwell equations, linear field gradients are accompanied by additional spatially dependent field components. A description of the Maxwell field terms is presented which explicitly takes into account the asymmetry of the gradient coil. It is shown both theoretically and experimentally that, in contrast to symmetric coils, an asymmetric coil generates concomitant field terms of zeroth and first order in space. Artifacts induced by concomitant fields can be much more pronounced for asymmetric coil designs than for symmetric ones. For the strong gradient amplitudes available on modern MR systems the effect of these concomitant magnetic fields on the evolution of magnetization has to be taken into consideration in a variety of NMR acquisition techniques. The formalism is used experimentally to compensate for artifacts observed in three different imaging methods: an image shift in standard echo planar imaging (EPI), an echo shift in diffusion‐weighted EPI, and a phase shift in a flow quantification technique based on phase contrast images. Magn Reson Med 60:128–134, 2008.Keywords
This publication has 7 references indexed in Scilit:
- Concomitant gradient field effects in balanced steady‐state free precessionMagnetic Resonance in Medicine, 2007
- Hardware considerations for functional magnetic resonance imagingConcepts in Magnetic Resonance, 2003
- Correction of concomitant magnetic field‐induced image artifacts in nonaxial echo‐planar imagingMagnetic Resonance in Medicine, 2002
- Concomitant gradient field effects in spiral scansMagnetic Resonance in Medicine, 1999
- Artifacts induced by concomitant magnetic field in fast spin‐echo imagingMagnetic Resonance in Medicine, 1998
- Concomitant magnetic‐field‐induced artifacts in axial echo planar imagingMagnetic Resonance in Medicine, 1998
- Concomitant gradient terms in phase contrast MR: Analysis and correctionMagnetic Resonance in Medicine, 1998