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

PurposeTo reduce respiration-induced magnetic field distortions and the attendant image artifacts in echo-planar imaging (EPI) of the human spinal cord. MethodsUsing 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. ResultsOver 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%. ConclusionReal-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. (c) 2018 International Society for Magnetic Resonance in Medicine.