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Eddy current nulled constrained optimization of isotropic diffusion encoding gradient waveforms.

Grant Yang1,2, Jennifer A McNab2

  • 1Department of Electrical Engineering, Stanford University, Stanford, California.

Magnetic Resonance in Medicine
|October 29, 2018
PubMed
Summary
This summary is machine-generated.

This study introduces a new method for designing isotropic diffusion encoding waveforms that intrinsically correct for eddy currents, reducing image distortions in MRI scans. This technique enhances microstructural information acquisition without compromising image quality.

Keywords:
MRIMaxwell termsconcomitant fieldseddy current nullingisotropic diffusion encodingmicrostructureq-space trajectory imaging

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Area of Science:

  • Magnetic Resonance Imaging (MRI)
  • Diffusion Tensor Imaging (DTI)
  • Biomedical Engineering

Background:

  • Isotropic diffusion encoding offers enhanced microstructural information beyond conventional linear methods.
  • Gradient-intensive isotropic diffusion waveforms often induce significant eddy currents, leading to MRI image distortions.
  • Effective mitigation of eddy currents is crucial for accurate diffusion MRI.

Purpose of the Study:

  • To develop and present a novel method for designing isotropic diffusion encoding waveforms.
  • To achieve intrinsic eddy current nulling within the designed waveforms.
  • To reduce image distortions caused by eddy currents in diffusion MRI.

Main Methods:

  • Utilized a constrained optimization algorithm to design eddy current nulled gradient waveforms for a 3T GE Premier MRI system.
  • Investigated various eddy current null times and sequence timings to assess achievable b-values.
  • Incorporated concomitant field compensation and tested distortion reduction in phantoms and the human brain.

Main Results:

  • Demonstrated the feasibility of isotropic diffusion encoding with intrinsic correction for eddy current distortion and concomitant field signal bias.
  • The optimization algorithm successfully generated gradient waveforms with specified eddy current null times.
  • Observed a reduction in eddy current-induced image distortions in both phantom and in vivo human brain imaging.

Conclusions:

  • The proposed framework enables the design of isotropic diffusion-encoding sequences.
  • This method effectively reduces image distortions in diffusion MRI.
  • Facilitates improved microstructural information acquisition with higher image fidelity.