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Keywords:

  • fat saturation;
  • pulse design;
  • spectral-spatial pulse;
  • parallel excitation;
  • B0 inhomogeneity;
  • B1 inhomogeneity

Purpose

The conventional spectrally selective fat saturation pulse may perform poorly with inhomogeneous amplitude of static (polarizing) field (B0) and/or amplitude of (excitation) radiofrequency field (B1) fields. We propose a four dimensional spectral-spatial fat saturation pulse that is more robust to inline image inhomogeneity and also shorter than the conventional fat saturation pulse.

Theory

The proposed pulse is tailored for local B0 inhomogeneity, which avoids the need of a sharp transition band in the spectral domain, so it improves both performance and pulse length. Furthermore, it can also compensate for B1 inhomogeneity. The pulse is designed sequentially by small-tip-angle approximation design and an automatic rescaling procedure.

Methods

The proposed method is compared to the conventional fat saturation in phantom experiments and in vivo knee imaging at 3 T for both single-channel and parallel excitation versions.

Results

Compared to the conventional method, the proposed method produces superior fat suppression in the presence of B0 and B1 inhomogeneity and reduces pulse length by up to half of the standard length.

Conclusion

The proposed four dimensional spectral-spatial fat saturation suppresses fat more robustly with shorter pulse length than the conventional fat saturation in the presence of B0 and B1 inhomogeneity. Magn Reson Med 72:1637–1647, 2014. © 2013 Wiley Periodicals, Inc.