Improving T2*-weighted human cortico-spinal acquisitions with a dedicated algorithm for region-wise shimming

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Neuroimaging
• Biophysics

Background:

• Cortico-spinal functional MRI (fMRI) studies brain-spinal cord interactions but requires dynamic shim updates for image quality.
• Existing region-wise shim methods are suboptimal and labor-intensive, combining different shim terms and demanding significant user interaction.

Purpose of the Study:

• To present a dedicated shim algorithm,
• CoSpi
• , for cortico-spinal fMRI.
• To optimize joint shim settings for improved magnetic field homogeneity and image quality in both brain and spinal cord regions simultaneously.
• To reduce user interaction and procedural time for shim optimization.

Main Methods:

• Developed and applied the
• CoSpi
• , algorithm for joint optimization of static second-order and linear/constant shim terms.
• Conducted echo-planar imaging (EPI) and field map measurements on a 3T MRI system using phantoms and healthy volunteers.
• Compared
• CoSpi
• , settings against conventional region-wise and single-volume "gold standard" shim settings.

Main Results:

• CoSpi
• reduced overall field inhomogeneity by 65-75% compared to conventional methods.
• Geometric distortions were reduced by 35-70%, and temporal SNR increased by 10-17%.
• Variation of mean field between slices was reduced by 45-90%, improving fat saturation and reducing ghosting artifacts.

Conclusions:

• The
• CoSpi
• , algorithm significantly enhances magnetic field homogeneity and image quality in cortico-spinal fMRI.
• It simplifies and speeds up the shim procedure, reducing user interaction and errors.
• Improved image quality will enhance the applicability of cortico-spinal fMRI for studying neural pathways and processing.