Andreas Bungert1,2, Christopher Chambers1,
John Evans1
1Cubric, School of
Psychology, Cardiff University, Cardiff, United Kingdom; 2Magnetic
Resonance Centre, School of Physics & Astronomy, University of
Nottingham, Nottingham, Nottinghamshire, United Kingdom
In concurrent TMS/fMRI, susceptiblity effects of the mostly diamagnetic TMS-coil cause field inhomogneities and image artefacts. We demonstrate that these artefacts can be reduced using stainless steel attached to the TMS coil for passive shimming. An MR-compatible figure-of-8 TMS coil was used and the steel was distributed on the back of the coil, approximately along the wire. Field maps of the effects of the coil with and without the shim on B0 were acquired. Also the artefacts in EP-images were studied in a phantom and a human. The shim reduced field inhomogeneities by 50-70% and improved the EP-images significantly.