Pseudo-MRI Engine for MRI-Free Electromagnetic Source Imaging.

Area of Science:

• Neuroimaging
• Biophysics
• Medical Engineering

Background:

• Structural MRIs are vital for MEG/EEG source imaging, defining models and constraining source spaces.
• Individual MRIs are not always available or of sufficient quality, leading to less accurate generic templates or spherical models.
• Deviations in model geometry from true head structure limit forward solution accuracy in MEG/EEG.

Purpose of the Study:

• To implement an easy-to-use tool, the pseudo-MRI engine, for generating subject-specific head models.
• To utilize head-shape digitization from MEG/EEG measurements for warping an MRI template to fit an individual's head.
• To validate the accuracy of pseudo-MRIs for MEG/EEG source imaging.

Main Methods:

• The pseudo-MRI engine preprocesses digitization points (outlier removal, densification).
• It employs the thin-plate-spline method to warp a template MRI and its segmented surfaces to the individual head shape.
• Validation involved comparing segmented head/cortical surfaces and brain regions between real and pseudo-MRIs, and testing MEG source reconstruction accuracy.

Main Results:

• The pseudo-MRI approach demonstrated comparable source localization accuracy to using individual MRIs.
• Geometric comparisons of head surfaces and brain regions showed good agreement between real and pseudo-MRIs.
• MEG source reconstruction accuracy with pseudo-MRIs was similar to that obtained with real MRIs.

Conclusions:

• The pseudo-MRI engine provides a viable alternative to individual MRI scans in MEG/EEG source imaging.
• This tool is suitable for applications not requiring subcentimeter spatial accuracy.
• Pseudo-MRIs enhance the accessibility and applicability of MEG/EEG source imaging when individual MRIs are lacking.