Local Dynamic Shimming for Slice-wise Image Acquisition
Hsu J, Glover G
Lucas Center for Imaging, Stanford University School of Medicine
To compensate for field inhomogeneity caused by local structures, we have implemented active, local dynamic shimming in which shim fields are generated by adjustable electric currents and have a smaller scale of spatial variation, comparable to the target region. The shim currents are optimized slice-wise and output in accordance with the slice being scanned. It is found that the dynamic shimming is effective and offers convenience and flexibility in shim coil design. Thepresent study is focused on the brain for fMRI; nevertheless, other areas of problematic geometry may also benefit.