On the Feasibility of Single-Shot EPI During Higher-Order Shim Settling

Signe Johanna Vannesj¹, Lars Kasper¹, Matteo Pavan¹, Christoph Barmet¹, Klaas Paul Pruessmann¹

Susceptibility artefacts is a major problem in MRI, becoming more severe with higher field strengths and longer read-out trajectories. Updating the shim settings between acquisition of different slices allows for optimizing the shims to smaller subvolumes, but puts high requirements on the timing characteristics of the shim switching. Here the settling dynamics of the higher order shims were measured using a 3rd order dynamic field camera. Long-living (seconds) eddy currents were found, which had a significant effect on image quality. Based on measured k-space trajectories, it was possible to reconstruct phantom images acquired during eddy current settling.