Digital Cross-Term Pre-Emphasis for Higher-Order Dynamic Shimming

Signe Johanna Vannesjo¹, Benjamin E. Dietrich¹, Matteo Pavan¹, Christoph Barmet¹, ², Klaas P. Pruessmann¹

Dynamic shimming holds promise to improve B0 homogeneity for a range of applications, however requires fast updating of the shim fields. Eddy currents limit the shim settling times and also produce strong cross-term field components. Here we show the feasibility of digital cross-term pre-emphasis applied to the input shim waveforms. The pre-emphasis is calculated based on shim impulse response functions (SIRFs) measured with a dynamic field camera. It is shown that settling times can be shortened and cross-term responses much reduced with this approach. The digital pre-emphasis allows for full flexibility in shaping the response, within hardware limitations.