Robust 2D phase correction for echo planar imaging under a tight field-of-view

Area of Science:

• Magnetic Resonance Imaging
• Image Processing

Background:

• Nyquist ghost artifacts are a significant problem in echo planar imaging (EPI).
• These artifacts arise from phase differences between even and odd echo images.
• Current 1D phase correction is limited to the readout axis, necessitating 2D correction for multi-axis phase differences.

Purpose of the Study:

• To address limitations of existing 2D phase correction methods for EPI.
• To investigate and mitigate issues like noise amplification, phase estimation errors, Gibbs ringing, and field-of-view constraints.
• To propose a novel, robust 2D phase correction technique for EPI.

Main Methods:

• Theoretical analysis of noise amplification and phase estimation error effects.
• Study of the trade-off between noise and ghosting artifacts.
• Development of a new 2D phase correction method incorporating improved polynomial fitting and joint homodyne processing.
• Ensuring compatibility with tight field-of-view acquisitions.

Main Results:

• The proposed method effectively eliminates Nyquist ghosts and other artifacts.
• Demonstrated robustness in oblique scans and with significant cross-term eddy currents.
• Successfully addressed issues of noise behavior, phase estimation accuracy, and Gibbs ringing.
• Validated compatibility with tight field-of-view imaging.

Conclusions:

• The novel 2D phase correction method significantly improves EPI image quality.
• It offers a practical solution for artifact reduction in challenging imaging scenarios.
• This technique enhances the reliability and applicability of EPI in various clinical and research settings.