Optimization and validation of multi-echo, multi-contrast SAGE acquisition in fMRI.

Area of Science:

• Neuroimaging
• Magnetic Resonance Imaging (MRI)

Background:

• Functional MRI (fMRI) is crucial for neuroscience research.
• Existing methods can suffer from signal dropout and limited spatial specificity.

Purpose of the Study:

• To optimize and validate a combined spin- and gradient-echo (SAGE) acquisition for multi-contrast, multi-echo fMRI.
• To enhance sensitivity, spatial specificity, and reduce signal dropout in fMRI.

Main Methods:

• Acquired SAGE-fMRI data across 12 protocols with varying acceleration factors and five echoes.
• Optimized protocol using multiband and SENSE factors, assessed temporal SNR (tSNR).
• Implemented in working memory and vision tasks, analyzed using various echo combinations and relaxation times (T2* and T2).

Main Results:

• Optimized SAGE-fMRI protocol achieved adequate spatiotemporal resolution with minimal artifacts.
• SAGE-fMRI demonstrated higher BOLD contrast-to-noise ratio (CNR) and tSNR compared to single-echo fMRI.
• Activation extent varied by analysis method, with T2*-weighting showing the largest extent in a working memory task.

Conclusions:

• SAGE-fMRI combines benefits of gradient-echo and spin-echo acquisitions for improved spatial localization and sensitivity.
• The method offers substantial advantages for more accurate fMRI analysis by enhancing CNR and tSNR.
• SAGE-fMRI provides two valuable contrasts for comprehensive brain activity assessment.