Dynamic shimming of the spinal cord using a 15-channel AC/DC coil

Motivation: The static magnetic field around the spinal cord has complex and small-scale non-uniformities, making it difficult to shim with low-order spherical harmonics. Goal(s): Assess the impact of slice-wise shimming in the cervico-thoracic spinal cord using a 15-channel AC/DC coil. Approach: Measure the magnetic field and acquire echo-planar images using three different shimming scenarios involving volume-wise 0-2nd order spherical harmonics, volume-wise multi-coil shimming, and slice-wise multi-coil shimming. Results: Multi-coil shimming decreased magnetic field inhomogeneities by 22% compared to 0-2nd order spherical harmonics when used across the whole imaging volume, and by 36% when used on a slice-wise basis. Impact: Advanced shimming (using multi-coils) significantly improves the quality of spinal cord MRI images by mitigating susceptibility artifacts. This leap forward facilitates the clinical adoption of challenging imaging techniques like functional MRI in the spinal cord.