Multi-shot acquisitions for stimulus-evoked spinal cord BOLD fMRI

Area of Science:

• Neuroimaging
• Functional Magnetic Resonance Imaging (fMRI)
• Spinal Cord Imaging

Background:

• Functional MRI (fMRI) is crucial for understanding brain function by detecting blood oxygenation level dependent (BOLD) signal changes.
• Investigating spinal cord function using fMRI presents unique challenges due to its smaller size and susceptibility to motion artifacts.
• Developing advanced imaging techniques is essential for improving the resolution and reliability of spinal cord fMRI.

Purpose of the Study:

• To assess the feasibility of using 3D multi-shot magnetic resonance imaging (MRI) acquisitions for stimulus-evoked blood oxygenation level dependent (BOLD) functional MRI (fMRI) in the human spinal cord in vivo.
• To compare the performance of a 3D multi-shot fast field echo (FFE) sequence with conventional single-shot echo-planar imaging (EPI) for spinal cord fMRI.
• To evaluate the sensitivity and specificity of these sequences in detecting BOLD signal changes during functional tasks.

Main Methods:

• Two fMRI studies were conducted at 3 Tesla (3T) using healthy volunteers.
• The first study involved a hypercapnic gas challenge, acquiring data with both multi-shot 3D fast field echo (FFE) and single-shot echo-planar imaging (EPI) sequences.
• The second study utilized a 3D multi-shot acquisition during an upper extremity motor task.

Main Results:

• Both 2D-EPI and 3D-FFE sequences demonstrated sensitivity to BOLD signal changes in the cervical spinal cord, with comparable contrast-to-noise ratios in gray matter.
• The 3D-FFE sequence exhibited significantly less signal drop-out and reduced geometric distortions compared to the EPI sequence.
• In the motor task, active voxels were predominantly observed in the ventral gray matter horns ipsilateral to the task and at the spinal level corresponding to finger extensor innervation.

Conclusions:

• 3D multi-shot acquisition sequences, particularly 3D-FFE, are highly suitable for stimulus-evoked BOLD fMRI of the spinal cord.
• These advanced sequences offer improved image quality and reduced artifacts compared to conventional EPI, enhancing the reliability of spinal cord functional imaging.
• The findings support the use of 3D multi-shot fMRI for in vivo investigation of human spinal cord function.