Suppressing Respiration Effects when Geometric Distortion Is Corrected Dynamically by Phase Labeling for Additional...

Area of Science:

• Neuroimaging
• Magnetic Resonance Imaging (MRI)
• Functional Magnetic Resonance Imaging (fMRI)

Background:

• Echo planar imaging (EPI) is susceptible to geometric distortions from magnetic field inhomogeneities.
• Head motion during fMRI experiments causes time-varying, or dynamic, geometric distortions.
• Existing correction methods may reduce temporal resolution or fail to address dynamic distortions.

Purpose of the Study:

• To develop and validate a technique to mitigate dynamic geometric distortion in EPI-based fMRI.
• To preserve temporal resolution while correcting for motion-induced geometric distortions.
• To improve the quality and reliability of fMRI data.

Main Methods:

• A combined technique integrating dynamic off-resonance in k-space (DORK) and Phase Labeling for Additional Coordinate Encoding (PLACE) with averaging was proposed.
• This DORK+PLACE+averaging method corrects within-EPI pair magnetic field inhomogeneities.
• The technique was tested using phantom data and fMRI scans from six healthy volunteers.

Main Results:

• Phantom data showed reduced temporal standard deviation of fMRI signal intensities after applying the DORK+PLACE+averaging technique.
• Human fMRI data demonstrated substantial improvements in temporal standard deviation compared to standard processing and static correction.
• Activation maps derived from the corrected fMRI data showed significant enhancement.

Conclusions:

• The combined DORK+PLACE+averaging technique effectively mitigates dynamic geometric distortion in EPI-based fMRI.
• This approach preserves temporal resolution, offering a valuable tool for improving fMRI data quality.
• The technique shows significant utility for enhancing fMRI studies affected by head motion.