High-resolution motion- and phase-corrected functional MRI at 7 T using shuttered multishot echo-planar imaging.

Area of Science:

• Magnetic Resonance Imaging
• Neuroimaging
• Biomedical Engineering

Background:

• High-resolution multishot echo-planar imaging (EPI) is crucial for functional MRI (fMRI).
• Conventional multishot EPI is sensitive to in-plane motion and inter-shot phase variations, limiting image quality.
• Reducing these artifacts is essential for accurate fMRI studies.

Purpose of the Study:

• To develop and evaluate a novel multishot EPI technique using 2D radiofrequency pulses (shuttered EPI) at 7T.
• To reduce sensitivity to in-plane motion and between-shot phase variations in high-resolution fMRI.
• To improve image quality and artifact reduction compared to conventional multishot EPI.

Main Methods:

• Incorporation of 2D radiofrequency pulses (shutters) in a multishot EPI sequence at 7T.
• Selective excitation of in-plane bands that moved between shots to cover the entire slice.
• Implementation of phase- and motion-corrected reconstruction.
• Evaluation of image quality, temporal stability (tSNR), and fMRI activation using instructed motion and visual stimulation.

Main Results:

• Shuttered EPI demonstrated lower ghosting and improved image quality metrics with motion correction.
• Phase correction enhanced temporal SNR (tSNR) in both conventional and shuttered EPI.
• Shuttered EPI, with phase correction, avoided intermittent ghosting seen in conventional multishot EPI.
• Phase correction increased activation strength but caused spurious activation in conventional multishot EPI, an effect not observed in shuttered EPI.

Conclusions:

• Shuttered EPI is a viable technique for multishot segmented EPI acquisitions.
• It offers reduced sensitivity to motion artifacts, enabling high-resolution fMRI.
• This method enhances image quality and reliability for functional neuroimaging studies.