2D Pulses using spatially dependent frequency sweeping

Albert Jang, Naoharu Kobayashi, Steen Moeller, J. T Vaughan, Jianyi Zhang, Michael Garwood

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Purpose: To introduce a method of designing two-dimensional (2D) frequency-modulated pulses that produce phase coherence in a spatiotemporal manner. Uniquely, this class of pulses provides the ability to compensate for field inhomogeneity using a spatiotemporally dependent trajectory of maximum coherence in a single-shot. Theory and Methods: A pulse design method based on a k-space description is developed. Bloch simulations and phantom experiments are used to demonstrate sequential spatiotemporal phase coherence and compensation for B+ 0 and B0 inhomogeneity. Results: In the presence of modulated gradients, the 2D frequency-modulated pulses were shown to excite a cylinder in a selective manner. With a surface coil transmitter, compensation of the effect of B+ 0 inhomogeneity was experimentally verified, in agreement with simulation results. In addition, simulations were used to demonstrate partial compensation for B0 inhomogeneity. Conclusion: The 2D frequency-modulated pulses are a new class of pulses that generate phase coherence sequentially along a spatial trajectory determined by gradient- and frequency-modulated functions. By exploiting their spatiotemporal nature, 2D frequency-modulated pulses can compensate for spatial variation of the radiofrequency field in a single-shot excitation. Preliminary results shown suggest extensions might also be used to compensate for static field inhomogeneity. Magn Reson Med 76:1364–1374, 2016.

Original languageEnglish (US)
Pages (from-to)1364-1374
Number of pages11
JournalMagnetic resonance in medicine
Volume76
Issue number5
DOIs
StatePublished - Nov 1 2016

Keywords

  • MRI
  • chirp
  • frequency-modulated pulse
  • hyperbolic secant
  • magnetic field inhomogeneity
  • spatiotemporal encoding

Cite this

2D Pulses using spatially dependent frequency sweeping. / Jang, Albert; Kobayashi, Naoharu; Moeller, Steen; Vaughan, J. T; Zhang, Jianyi; Garwood, Michael.

In: Magnetic resonance in medicine, Vol. 76, No. 5, 01.11.2016, p. 1364-1374.

Research output: Contribution to journalArticle

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