Coping with Off-Resonance Effects and Gradient Imperfections in Parallel Transmission Experiments

Johannes Thomas Schneider^1,2, Martin Haas², Jrgen Hennig², Sven Junge¹, Wolfgang Ruhm¹, Peter Ullmann¹

For parallel spatially-selective excitation / TransmitSENSE the exact matching of the RF pulses and the gradient waveforms to be played out simultaneously is crucial in order to achieve high spatial accuracy and selectivity. In particular, off-resonance effects and gradient-system imperfections may significantly disturb this interplay resulting in poor spatial definition and artifacts. Therefore, in this study we investigated different methods to determine and compensate for such effects. It is shown that using measured global k-space trajectories, off-resonance maps and local phase evolutions for trajectory pre-calibration and accordingly adapted pulse calculations allow very precise excitation despite of experimental imperfections.