Real‐time correction of respiration‐induced distortions in the human spinal cord using a 24‐channel shim array

Purpose To reduce respiration‐induced magnetic field distortions and the attendant image artifacts in echo‐planar imaging (EPI) of the human spinal cord. Methods Using a custom‐designed 24‐channel shim array, shim updates were issued in real time based on a concurrently monitored respiratory trace and a pair of gradient echo (GRE) field maps acquired during an initial training phase. Proof‐of‐concept application in GRE–EPI was conducted in 6 subjects. Results Over the thoracic spinal cord, real‐time shimming reduced respiration‐induced distortions in the EPI by 48.2% ± 12.2% and increased the mean temporal signal‐to‐noise ratio by 15.7% ± 7.9%. Conclusion Real‐time shim adjustment substantially reduces spatiotemporal B 0 field variation, opening the door to more robust imaging and spectroscopy investigations of the spinal cord. Magn Reson Med 80:935–946, 2018. © 2018 International Society for Magnetic Resonance in Medicine.