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.