Real Time Dynamic Shimming for MR Spectroscopy using 2-Dimensional RF Excitations

Brian Keating¹, Thomas Ernst²

Patient motion can compromise the shim quality in MR spectroscopy. Therefore, we incorporated a dynamic shimming module into the dead time in a standard PRESS sequence. 2-dimensional spatial rf pulses excite 3 columns, parallel to the coordinate axes. Two echoes are read out for each column along the direction of the column axes. One-dimensional field maps are computed for each column. Shim corrections are fed back into the sequence, where they are applied as shim gradients during the following PRESS read out. Phantom and in vivo experiments confirm that dynamic shimming improved spectral quality in the presence of B0 inhomogeneities.