Accelerated spin-echo functional MRI using multisection excitation by simultaneous spin-echo interleaving (MESSI)...

Area of Science:

• Neuroimaging
• Magnetic Resonance Imaging

Background:

• Spin-echo functional MRI (SE-fMRI) offers superior spatial specificity compared to gradient-echo fMRI.
• Acquiring high spatiotemporal resolution SE-fMRI with extensive slice coverage is challenging due to long repetition times required for Blood Oxygenation Level-Dependent (BOLD) contrast.

Purpose of the Study:

• To develop an advanced acquisition technique that enhances slice coverage for SE-fMRI while maintaining high spatiotemporal resolution.

Main Methods:

• Developed a novel acquisition scheme named multisection excitation by simultaneous spin-echo interleaving (MESSI) combined with complex-encoded generalized slice dithered enhanced resolution (cgSlider).
• MESSI utilizes dead time during long echo periods to interleave excitation and readout of two slices, achieving 2x slice acceleration.
• cgSlider encodes and decodes adjacent slices simultaneously using phase constraints, further accelerated with simultaneous multislice (SMS) imaging.
• The combined cgSlider-MESSI-SMS approach achieved 1.5-mm isotropic whole-brain SE-fMRI with 1.5s temporal resolution at 3T.

Main Results:

• The cgSlider-MESSI-SMS technique provides a 4-fold increase in slice coverage compared to conventional SE-SMS at equivalent repetition times, with similar temporal signal-to-noise ratios.
• fMRI activation patterns observed with cgSlider-MESSI-SMS were consistent with conventional SE-SMS for sensory stimulation and breath-hold tasks.
• An overall 32x encoding acceleration was achieved by combining in-plane acceleration, multi-band (MB), cgSlider, and MESSI techniques.

Conclusions:

• High-quality, high-resolution whole-brain SE-fMRI can be acquired with significantly reduced repetition times using the cgSlider-MESSI-SMS method.
• This technique is highly beneficial for studies demanding high spatiotemporal resolution and comprehensive whole-brain coverage in SE-fMRI.