Prospective motion correction of 3D echo-planar imaging data for functional MRI using optical tracking.

Area of Science:

• Neuroimaging
• Biomedical Engineering
• Medical Physics

Background:

• Head motion is a significant source of artifacts in functional MRI (fMRI), degrading data quality and limiting the utility of advanced imaging sequences like 3D echo-planar imaging (EPI).
• Existing motion correction methods are often retrospective, applied after data acquisition, which cannot fully compensate for motion-induced signal loss during image acquisition.

Purpose of the Study:

• To evaluate the performance of an optical camera-based prospective motion correction (PMC) system for improving 3D EPI fMRI data quality.
• To assess the impact of PMC on temporal signal-to-noise ratio (tSNR) and task-based activation in the presence of head motion.

Main Methods:

• An optical camera and marker dynamically tracked subject head motion during fMRI scanning.
• PMC utilized real-time motion data to adjust RF excitation and gradient waveforms, realigning the field-of-view to compensate for head movement.
• Experiments involved task-free and task-based fMRI on healthy volunteers using varying resolutions (3.0mm and 1.5mm isotropic) and head movement conditions (none, slow, fast).

Main Results:

• The PMC system did not introduce artifacts in the absence of motion.
• PMC improved tSNR by 30%–40% across all resolution and motion conditions compared to standard acquisition without prospective correction.
• Task-based experiments showed increased activated voxels by 78% and 330% with PMC compared to no PMC under slow motion conditions.

Conclusions:

• The optical camera-based PMC system effectively reduces motion sensitivity in multi-shot 3D EPI sequences.
• PMC is a robust solution to overcome motion-induced artifacts, enhancing the reliability and applicability of 3D EPI fMRI for research.