Dynamic field mapping and distortion correction using single-shot blip-rewound EPI and joint multi-echo...

Area of Science:

• Magnetic Resonance Imaging
• Image Reconstruction
• Neuroimaging

Background:

• Echo-planar imaging (EPI) is crucial for rapid fMRI acquisition.
• Distortions in EPI are a significant challenge, often addressed by static magnetic field mapping.
• Dynamic B0 mapping can potentially improve EPI data quality.

Purpose of the Study:

• To develop a novel method for dynamic B0 mapping and distortion correction in EPI.
• To enable simultaneous B0 mapping and image acquisition within a single readout.
• To assess the method's performance in phantom and in vivo scenarios, including during subject motion.

Main Methods:

• A blip-rewound EPI trajectory was employed to acquire multiple interleaved 2D EPI images with a short echo time (TE) difference.
• Joint multi-echo reconstruction exploited shared information between EPI images for improved reconstruction.
• Dynamic B0 maps were calculated from the phase of reconstructed images for distortion correction.

Main Results:

• The proposed method achieved dynamic B0 mapping at matched resolution with a significantly shorter TR compared to conventional multi-echo EPI.
• Reconstructed magnitude images were comparable to conventional single-shot EPI.
• In vivo B0 mapping was more accurate than conventional multi-echo EPI, avoiding phase wrapping issues.
• Dynamic B0 mapping improved EPI time series temporal stability during motion compared to static field mapping.

Conclusions:

• The developed method enables accurate dynamic B0 mapping for robust EPI distortion correction.
• The technique preserves spatial and temporal resolution without compromise.
• This approach offers a significant advancement for improving EPI data quality and reliability.