Real-time fMRI using multi-band echo-volumar imaging with millimeter spatial resolution and sub-second temporal...

Area of Science:

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

Background:

• Echo-volumar imaging (EVI) offers advantages in sampling efficiency and multi-echo acquisition for fMRI.
• Accelerating EVI is crucial for achieving high spatial-temporal resolution in task-based and resting-state fMRI.

Purpose of the Study:

• To develop and characterize undersampled echo-volumar imaging (EVI) using multi-band/simultaneous multi-slab encoding and multi-shot slab-segmentation.
• To evaluate the feasibility of compressed sensing (CS) and NORDIC denoising for further acceleration and improved sensitivity in fMRI.

Main Methods:

• Developed multi-band echo-volumar imaging (MB-EVI) with CAIPI shifting, GRAPPA acceleration, kZ-segmentation, and partial Fourier acquisitions.
• Performed task-based and resting-state fMRI at 3T across various voxel sizes (1-3mm), repetition times (118-650ms), and slab numbers (up to 12).
• Compared MB-EVI with multi-slab EVI (MS-EVI) and multi-band EPI (MB-EPI).

Main Results:

• MB-EVI demonstrated comparable image quality and temporal SNR to MS-EVI at 2-3mm resolution.
• Achieved high sensitivity for mapping task-based activation and resting-state connectivity, enabling high-frequency connectivity mapping (>0.3 Hz) at 3mm isotropic resolution (TR: 163ms).
• Task-based activation detection at 1mm isotropic resolution was feasible in under 1.5 minutes; CS showed minimal impact on image quality, and NORDIC denoising significantly enhanced sensitivity.

Conclusions:

• Combining MS-EVI with multi-band encoding allows high acceleration factors, optimizing spatial-temporal resolution and coverage.
• The hybrid MB-EVI approach offers high BOLD sensitivity and online reconstruction compatibility for real-time, high spatial-temporal resolution fMRI.