Dynamic per slice Shimming for Simultaneous Brain and Spinal Cord fMRI

Simultaneous brain and spinal cord functional MRI is emerging as a new tool in study of the central nervous system, but is challenging. Poor B0 homogeneity and small size of spinal cord are principal obstacles to this nascent technology. We extend a dynamic shimming approach, first posed by Finsterbusch for brain/spinal cord, by shimming per slice.

We shim dynamically by optimization of linear gradients and frequency offset for each and every slice in order to minimize off-resonance for both brain and spinal cord. Simultaneous acquisition of brain and spinal cord fMRI is achieved with high spatial resolution in spine by means of echo-planar RF pulse for reduced FOV. Brain slice acquisition is full FOV.

T2*-weighted images of brain and spinal cord are acquired with high clarity and minimal observable image artifacts. fMRI experiments reveal task consistent activation in motor cortices, cerebellum, and C6-T1 spinal segments.

Consistent activation in both brain and spinal cord is observed at individual levels, not only group level. High quality functional results are obtained for a motor task. Because reduced FOV excitation is applicable to any spinal cord section, future continuation of these methods holds great portent.