The effect of concomitant fields in fast spin echo acquisition on asymmetric MRI gradient systems

Shengzhen Tao, Paul T. Weavers, Joshua D Trazasko, John III Huston, Yunhong Shu, Erin M. Gray, Thomas K.F. Foo, Matthew A Bernstein

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

Purpose: To investigate the effect of the asymmetric gradient concomitant fields (CF) with zeroth and first-order spatial dependence on fast/turbo spin-echo acquisitions, and to demonstrate the effectiveness of their real-time compensation. Methods: After briefly reviewing the CF produced by asymmetric gradients, the effects of the additional zeroth and first-order CFs on these systems are investigated using extended-phase graph simulations. Phantom and in vivo experiments are performed to corroborate the simulation. Experiments are performed before and after the real-time compensations using frequency tracking and gradient pre-emphasis to demonstrate their effectiveness in correcting the additional CFs. The interaction between the CFs and prescan-based correction to compensate for eddy currents is also investigated. Results: It is demonstrated that, unlike the second-order CFs on conventional gradients, the additional zeroth/first-order CFs on asymmetric gradients cause substantial signal loss and dark banding in fast spin-echo acquisitions within a typical brain-scan field of view. They can confound the prescan correction for eddy currents and degrade image quality. Performing real-time compensation successfully eliminates the artifacts. Conclusions: We demonstrate that the zeroth/first-order CFs specific to asymmetric gradients can cause substantial artifacts, including signal loss and dark bands for brain imaging. These effects can be corrected using real-time compensation.

Original languageEnglish (US)
JournalMagnetic Resonance in Medicine
DOIs
StateAccepted/In press - 2017

Keywords

  • Asymmetric gradient
  • Concomitant field
  • EPG
  • Extended phase graph
  • Fast spin echo
  • FSE
  • TSE
  • Turbo spin echo

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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