Minimizing susceptibility-induced BOLD sensitivity loss in multi-band accelerated fMRI using point spread function...

Area of Science:

• Neuroimaging
• Magnetic Resonance Imaging
• Functional Magnetic Resonance Imaging

Background:

• Echo-planar imaging (EPI) in fMRI suffers from signal loss and geometric distortion, particularly in brain regions with high magnetic susceptibility.
• Reverse-gradient fMRI (RG-fMRI) with point-spread-function (PSF) mapping offers a method to correct these distortions and minimize signal loss.

Purpose of the Study:

• To optimize the RG-fMRI imaging protocol for improved temporal and spatial resolution.
• To investigate the application of reverse Fourier acquisition to further enhance RG-fMRI performance.
• To demonstrate the improved reliability of RG-fMRI in high susceptibility brain regions.

Main Methods:

• Multi-band imaging was adapted to RG-fMRI to boost temporal and spatial resolution.
• A theoretical relationship between echo shift and geometric distortion was derived and validated using PSF mapping.
• RG-fMRI protocols were examined on conventional and compact 3 T scanners, followed by high-resolution breath-holding RG-fMRI on nine subjects.
• Reverse Fourier acquisition was applied and assessed via simulation.

Main Results:

• Multi-band RG-fMRI achieved feasible temporal and spatial resolution for whole-brain imaging.
• PSF mapping effectively estimated signal dropout and aided RG-fMRI improvement.
• Breath-holding RG-fMRI showed enhanced reliability in high susceptibility areas.
• Reverse partial Fourier acquisition improved resolution without significant signal or spatial degradation.

Conclusions:

• Optimized RG-fMRI protocols, including multi-band imaging and reverse Fourier acquisition, significantly improve fMRI reliability.
• These advancements enable more reliable investigation of functional mechanisms in challenging brain regions affected by susceptibility-induced signal loss.