Leveraging multi-echo EPI to enhance BOLD sensitivity in task-based olfactory fMRI.

Area of Science:

• Neuroimaging
• Magnetic Resonance Imaging
• Olfactory Neuroscience

Background:

• Blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is crucial for neuroscience research.
• Acquiring BOLD fMRI in human olfactory regions is challenging due to magnetic field distortions near sinuses and respiratory artifacts.
• Conventional gradient echo-echo planar imaging (GE-EPI) is susceptible to these artifacts, limiting olfactory fMRI studies.

Purpose of the Study:

• To develop and validate a multi-echo EPI (ME-EPI) acquisition protocol for task-based fMRI in human olfactory regions.
• To compare the performance of ME-EPI against conventional single-echo EPI (1E-EPI) in terms of BOLD signal sensitivity and artifact reduction.
• To provide evidence supporting the use of ME-EPI for improved olfactory fMRI.

Main Methods:

• Developed a novel ME-EPI acquisition protocol tailored for olfactory fMRI.
• Acquired fMRI data using both ME-EPI and 1E-EPI sequences.
• Applied signal processing techniques, including a T2*-weighted echo combination and Multi-Echo Independent Components Analysis (ME-ICA) for denoising.

Main Results:

• Demonstrated significantly improved BOLD signal sensitivity with ME-EPI compared to 1E-EPI.
• Observed enhanced BOLD signal changes through T2*-weighted echo combination in ME-EPI.
• Showcased a reduction in non-BOLD artifacts using the ME-ICA denoising method with ME-EPI data.

Conclusions:

• ME-EPI offers superior BOLD signal sensitivity for task-based fMRI in challenging high-susceptibility regions like the human olfactory system.
• The combination of ME-EPI acquisition and ME-ICA denoising effectively mitigates artifacts common in olfactory fMRI.
• This study strongly advocates for the adoption of ME-EPI protocols in future fMRI research involving olfactory tasks and other brain regions prone to susceptibility artifacts.