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Abstract #0669

Full 3rd Order Real-Time Shim Feedback for Field Stabilization and Its Application in Brain MRI at 7T

Yolanda Duerst1, Bertram J. Wilm2, Benjamin E. Dietrich3, David Otto Brunner3, Christoph Barmet3, 4, Thomas Schmid2, Signe Johanna Vannesjo2, Klaas P. Pruessmann2

1Institute for Biomedical Engineering, University of Zurich and ETH Zurich , Zurich, Switzerland; 2Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland; 3Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland; 4Skope Magnetic Resonance Technologies, Zurich, Switzerland

Spatio-temporal field fluctuations caused by hardware imperfections or physiological motion can lead to signal loss through increased T2* decay or off-resonant RF pulses and severely degrade image quality. We present a first implementation of a concurrent real-time feedback system correcting for full 3rd order spherical harmonics field changes. A proportional-integral controller was used to address gradient and shim coils of a whole-body scanner to actively compensate field fluctuations. The control loop achieved robust field stabilization of breathing induced field perturbations and significantly enhanced image quality of a commonly used T2*-weighted gradient-echo scan which otherwise strongly suffers from breathing artifacts.