Magnetization transfer weighted EPI facilitates cortical depth determination in native fMRI space

Area of Science:

• Neuroimaging
• Human Brain Anatomy
• Functional Magnetic Resonance Imaging (fMRI)

Background:

• Ultra-high field scanners enable sub-millimeter fMRI for probing human brain laminar function.
• Previous methods rely on separate anatomical images, causing geometric distortion and registration issues for laminar analysis.
• Accurate anatomical referencing is crucial for high-resolution functional brain studies.

Purpose of the Study:

• To introduce a novel fMRI acquisition technique incorporating magnetization transfer (MT) for in vivo laminar function analysis.
• To generate an anatomical image directly within the fMRI sequence, eliminating the need for separate anatomical scans.
• To enable distortion-free laminar analysis in the native fMRI space.

Main Methods:

• Incorporation of magnetization transfer (MT) weighted imaging into the fMRI acquisition sequence.
• Utilized small flip angle binomial pulse trains for MT preparation prior to EPI segments.
• Demonstrated feasibility at 7 Tesla (7T) with 0.8 mm isotropic resolution for partial or near-whole brain coverage.

Main Results:

• Achieved tissue contrast comparable to state-of-the-art MP2RAGE anatomical references.
• Successfully demonstrated the method's feasibility at 7T with high spatial resolution.
• The MT-weighted EPI images facilitated automatic cortical surface reconstruction for laminar analysis.

Conclusions:

• The proposed MT-weighted EPI method allows for laminar analysis directly in native fMRI space.
• This approach obviates the need for complex distortion correction and inter-modal registration steps.
• The technique enhances the precision and efficiency of in vivo human brain laminar function studies.