EPI distortion correction for concurrent human brain stimulation and imaging at 3T

Area of Science:

• Neuroimaging
• Brain Network Mapping
• Magnetic Resonance Imaging

Background:

• Concurrent transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) enable causal investigation of human brain networks.
• Introducing TMS coils into MRI scanners can cause magnetic field inhomogeneities and spatial distortions, limiting data utility.
• Existing methods struggle to mitigate TMS-induced artifacts in fMRI.

Purpose of the Study:

• To evaluate the effectiveness of point spread function corrected echo planar imaging (PSF-EPI) in correcting TMS coil-induced artifacts at 3 Tesla.
• To compare image quality and distortion reduction with and without PSF correction in phantom and human brain scans.
• To assess the temporal dynamics of artifacts during TMS delivery and validate PSF-EPI in concurrent TMS-fMRI experiments.

Main Methods:

• Point spread function corrected echo planar imaging (PSF-EPI) sequence implemented at 3 Tesla.
• Quantitative comparison of coil-induced distortion artifacts in EPI scans with and without PSF correction.
• Phantom and human brain scans, including resting-state fMRI and TMS-fMRI with motor tasks.
• Characterization of temporal artifact profiles relative to TMS pulse timing.

Main Results:

• PSF-EPI significantly improved signal-to-noise ratio and reduced spatial distortions caused by TMS coils.
• High image quality was maintained when TMS pulses preceded radiofrequency excitation by at least 50 ms.
• PSF-EPI was successfully validated in human brain scans, demonstrating its utility for concurrent TMS-fMRI.

Conclusions:

• PSF-EPI offers a viable solution for mitigating TMS coil-related artifacts in concurrent TMS-fMRI.
• This technique enables high-quality resting-state fMRI data acquisition within the same session as TMS-fMRI.
• PSF-EPI enhances the potential for detailed interrogation of human brain network architecture using multimodal neuroimaging.