Simultaneous correction of ghost and geometric distortion artifacts in EPI using a multiecho reference scan

Area of Science:

• Magnetic Resonance Imaging
• Image Reconstruction
• Medical Physics

Background:

• Echo-planar imaging (EPI) is susceptible to ghosting and geometric distortions due to k-space trajectory imperfections and limited bandwidth.
• These artifacts, including Nyquist ghosts and geometrical distortion, hinder accurate overlay of functional MRI activation maps onto anatomical images.
• Sources of artifact include gradient eddy currents, B0 field inhomogeneity, and chemical shift.

Discussion:

• A novel, computationally efficient technique simultaneously corrects ghosting and geometrical distortion in EPI.
• The method employs a multiecho, gradient-echo reference scan for robust artifact removal.
• The algorithm leverages 2D phase information for superior ghost artifact correction compared to 1D methods.

Key Insights:

• The technique effectively corrects geometrical distortions arising from B0 inhomogeneity, gradient eddy currents, RF pulse frequency offset, and chemical shift.
• Demonstrated effectiveness in both phantom and human brain imaging at 3 Tesla.
• The required reference scan adds minimal time (approx. 2 min for 64x64 matrix, TR 2s).

Outlook:

• Potential for improved accuracy in functional MRI studies by providing cleaner EPI data.
• Facilitates more reliable image registration and overlay with high-resolution anatomical scans.
• Further validation in diverse clinical and research settings is warranted.