Block-interleaved segmented echo-planar imaging for improved activity detection in submillimeter high-resolution...

Area of Science:

• Neuroimaging
• Magnetic Resonance Imaging
• Functional Magnetic Resonance Imaging

Background:

• Submillimeter high-resolution functional MRI (fMRI) enables mesoscale investigation of neuronal activity.
• Single-shot echo planar imaging (EPI) with parallel imaging (e.g., GRAPPA) reduces temporal signal-to-noise ratio (tSNR), hindering detection of task-evoked activity.
• Conventional multishot EPI (msEPI) improves tSNR but sacrifices temporal resolution, limiting its use for short-duration stimuli.

Purpose of the Study:

• To introduce a novel multishot EPI-based fMRI acquisition and reconstruction method, block-interleaved segmented EPI (BISEPI).
• To overcome the limitations of existing EPI techniques in achieving high temporal resolution and high tSNR simultaneously for submillimeter fMRI.
• To enable noninvasive investigation of neuronal activities at the mesoscale level with improved sensitivity and motion robustness.

Main Methods:

• BISEPI utilizes block design paradigm timing during acquisition and reconstruction to preserve temporal resolution and tSNR.
• A k-space-based motion correction method is integrated to address head motion artifacts.
• The technique was evaluated in human studies using various stimulus paradigms and resolutions (0.7-mm and 0.4-mm isotropic).

Main Results:

• BISEPI reduced g-factor penalties associated with GRAPPA acceleration.
• The method achieved high tSNR, enhanced motion robustness, and improved sensitivity to blood oxygen level-dependent (BOLD) signal responses.
• Detection of BOLD signal responses was demonstrated at submillimeter spatial resolutions.

Conclusions:

• BISEPI effectively addresses limitations of conventional msEPI and GRAPPA-accelerated EPI.
• The method enables the detection of BOLD signal responses at submillimeter spatial resolution (0.7-mm and 0.4-mm isotropic).
• BISEPI is suitable for fMRI paradigms involving short-duration, low-power stimuli at 0.7-mm resolution and standard-power stimuli at 0.4-mm resolution.