Analysis and compensation of eddy currents in balanced SSFP

Oliver Bieri*, M. Markl, K. Scheffler

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

117 Scopus citations

Abstract

Balanced steady-state free precession (SSFP) completely compensates for all gradients within each repetition time (TR), and is thus very sensitive to any magnetic field imperfection that disturbs the perfectly balanced acquisition scheme. It is demonstrated that balanced SSFP is especially sensitive to changing eddy currents that are induced by stepwise changing phase-encoding (PE) gradients. In contrast to the linear k-space trajectory, which has small variations between consecutive encoding steps, other encoding schemes (e.g., centric, random, or segmented orderings) exhibit significant jumps in k-space between adjacent PE steps, and consequently induce rapidly changing eddy currents. The resulting disturbances induce significant image artifacts, such that compensation strategies are essential when nonlinear PE schemes are applied. Although direct annihilation of the induced eddy currents by additional, opposing magnetic fields has been investigated, it is limited by uncertainty regarding the time evolution of induced eddy currents. A generic (and thus system-unrelated) compensation strategy is proposed that consists of "pairing" of consecutive PE steps. Another approach is based on partial dephasing along the slice direction that annihilates eddy-current-induced signal oscillations. Both pairing of the PE steps and "through-slice equilibration" are easy to implement and allow the use of arbitrary k-space trajectories for balanced SSFP.

Original languageEnglish (US)
Pages (from-to)129-137
Number of pages9
JournalMagnetic resonance in medicine
Volume54
Issue number1
DOIs
StatePublished - Jul 2005

Keywords

  • Balanced SSFP
  • Compensation
  • Eddy currents
  • TrueFISP
  • View ordering

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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