A Simple Low-SAR Technique for Chemical-Shift Selection with High-Field Spin-Echo Imaging

Dimo Ivanov*, Andreas Schaefer, Markus N. Streicher, Robin M. Heidemann, Robert Trampel, Robert Turner

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

23 Citations (Web of Science)

Abstract

We have discovered a simple and highly robust method for removal of chemical shift artifact in spin-echo MR images, which simultaneously decreases the radiofrequency power deposition (specific absorption rate). The method is demonstrated in spin-echo echo-planar imaging brain images acquired at 7 T, with complete suppression of scalp fat signal. When excitation and refocusing pulses are sufficiently different in duration, and thus also different in the amplitude of their slice-select gradients, a spatial mismatch is produced between the fat slices excited and refocused, with no overlap. Because no additional radiofrequency pulse is used to suppress fat, the specific absorption rate is significantly reduced compared with conventional approaches. This enables greater volume coverage per unit time, well suited for functional and diffusion studies using spin-echo echo-planar imaging. Moreover, the method can be generally applied to any sequence involving slice-selective excitation and at least one slice-selective refocusing pulse at high magnetic field strengths. The method is more efficient than gradient reversal methods and more robust against inhomogeneities of the static (polarizing) field (B(0)).
Original languageEnglish
Pages (from-to)319-326
JournalMagnetic Resonance in Medicine
Volume64
Issue number2
DOIs
Publication statusPublished - Aug 2010
Externally publishedYes

Keywords

  • chemical shift
  • spin-echo
  • fat suppression
  • high-field MRI
  • specific absorption rate
  • spin-echo echo-planar imaging
  • fMRI
  • diffusion imaging

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