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Fast rotary nonlinear spatial acquisition (FRONSAC) imaging.

Haifeng Wang1, Leo K Tam1, R Todd Constable1,2,3

  • 1Department of Diagnostic Radiology, Yale University, New Haven, Connecticut, USA.

Magnetic Resonance in Medicine
|May 8, 2015
PubMed
Summary
This summary is machine-generated.

Adding a rotating nonlinear spatial encoding magnetic field (SEMs) significantly enhances image quality for undersampled MRI trajectories like EPI, Spiral, and Rosette. This FRONSAC (Fast ROtary Nonlinear Spatial ACquisition) method improves spatial encoding efficiency and image reconstruction.

Keywords:
EPIRosetteSpiralaccelerated imagingnonlinear gradientsparallel imagingsingle echo imaging

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Area of Science:

  • Magnetic Resonance Imaging (MRI)
  • Biomedical Engineering
  • Signal Processing

Background:

  • Nonlinear spatial encoding magnetic fields (SEMs) are explored for efficient image reconstruction with fewer echoes.
  • Previous research investigated single-shot trajectories within nonlinear SEMs.
  • Optimization of nonlinear SEM schemes for improved spatial encoding and image quality remains an active area of research.

Purpose of the Study:

  • To enhance the encoding efficiency of standard linear gradient trajectories in MRI.
  • To improve the image quality of highly undersampled single-shot trajectories using nonlinear SEMs.
  • To introduce and evaluate a novel technique called FRONSAC (Fast ROtary Nonlinear Spatial ACquisition) imaging.

Main Methods:

  • Implemented FRONSAC imaging by adding a rapidly rotating nonlinear SEM to standard linear gradient trajectories.
  • Utilized simulations incorporating noise and dephasing effects to assess the impact of FRONSAC gradients.
  • Investigated the additional k-space sampling provided by the nonlinear gradient.
  • Studied optimal amplitude and frequency for the FRONSAC field and its role in readout sampling.
  • Performed dynamic field mapping to confirm the feasibility of proposed gradient waveforms.

Main Results:

  • Simulations demonstrated that adding FRONSAC gradients significantly improves image quality for undersampled trajectories like EPI, Spiral, and Rosette.
  • The enhanced performance was attributed to the additional k-space sampling enabled by the nonlinear gradient.
  • Optimal parameters for the FRONSAC field amplitude and frequency were identified.
  • Feasibility of the gradient waveforms was confirmed through dynamic field mapping.

Conclusions:

  • The addition of a rotating nonlinear SEM field, termed FRONSAC, substantially enhances images reconstructed from highly undersampled k-space trajectories.
  • This method offers a straightforward yet effective approach to improve spatial encoding efficiency and image quality in accelerated MRI techniques.
  • FRONSAC imaging presents a promising strategy for advancing fast MRI acquisition methods.