Susceptibility-induced distortion that varies due to motion: Correction in diffusion MR without acquiring additional...

Area of Science:

• Magnetic Resonance Imaging
• Diffusion Tensor Imaging

Background:

• Susceptibility-induced off-resonance fields cause distortions in echo planar imaging (EPI), particularly in the phase-encode (PE) direction.
• These distortions are critical to correct for diffusion studies using EPI.
• Existing correction methods assume a static magnetic field, which is inaccurate when subjects move and rotate, leading to residual distortions.

Purpose of the Study:

• To present a novel post-processing method for estimating and correcting susceptibility-induced field changes during diffusion imaging experiments.
• To address the limitations of static field correction methods that fail to account for subject motion and rotation.

Main Methods:

• A post-processing method is introduced to estimate field changes dynamically during an experiment.
• The method requires only a single measured field and the subject's orientation at the time of acquisition.
• It directly estimates volume-to-volume field changes from diffusion data using a generative model, without special acquisitions.

Main Results:

• The method accurately tracks magnetic field changes resulting from subject motion.
• Validated on simulations and experimental data, demonstrating high accuracy in field tracking.
• Successful correction of diffusion data for adverse effects caused by the changing magnetic field.

Conclusions:

• The developed method effectively corrects for susceptibility-induced distortions in EPI caused by subject motion.
• This approach improves the accuracy of diffusion studies by accounting for dynamic field variations.
• The technique offers a practical solution for mitigating motion-related artifacts in MRI.