Abstract #3567

Comparison of preemphasis based on a broadband filter vs. a standard exponential model for higher-order dynamic shimming

Signe Johanna Vannesjo¹, Yuhang Shi¹, Klaas P Pruessmann², Andrew Dewdney³, Karla L Miller¹, and Stuart Clare¹

¹FMRIB centre, NDCN, University of Oxford, Oxford, United Kingdom, ²Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland, ³Magnetic Resonance, Siemens Healthcare GmbH, Erlangen, Germany

Traditionally, shim preemphasis filters to compensate for eddy current fields have consisted of a sum of exponentially decaying terms. It has recently been proposed to instead implement a non-parametric preemphasis filter based on the shim impulse response function. This can address features that are not captured with the exponential model, such as oscillatory responses. We here compared the two preemphasis approaches for higher-order dynamic shim updating. The non-parametric filter yielded an improved frequency response of the system and about 10 ms faster shim settling, as well as suppression of field oscillations after a shim step.

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