Spatially Resolved Extended Phase Graphs: Modeling & Design of Multi-Pulse Sequences with Parallel Transmission

Shaihan J. Malik¹, Joseph V. Hajnal¹

RF inhomogeneity correction using parallel transmission usually focuses on optimising RF field uniformity. Although improving field homogeneity generally improves images, most imaging sequences employ rapid successions of RF pulses, making the received signals depend on the combined history of many pulses interspersed with periods of relaxation. Independent modulation of separate pulses provides additional degrees of freedom for manipulation of resulting signal. Using a spatially resolved extended phase graph (SREPG) signal model, RF inputs may be optimised to produce uniform signals from non-uniform fields. Improved image homogeneity with more uniform contrast is demonstrated on 3D TSE brain imaging at 3T.