Flip Angle and SAR Maps Induced by a Head Displacement in Parallel Transmission and with Cartesian Feedback

Nicolas Boulant¹, Martijn Cloos¹, Alexis Amadon¹, Guillaume Ferrand², Michel Luong², Christopher Wiggins¹, Denis Le Bihan¹, David Ian Hoult³

Despite the considerable variations one can observe in peak local SAR among all possible driving configurations of a Tx-array, the question of how robust both SAR and flip angle distributions are with respect to small perturbations remains. A head displacement for instance not only changes the solutions of Maxwells equations but also the tuning of the coils. Now Cartesian feedback has been proposed as a solution to the latter problem. We therefore present the results of simulations showing the effects of small rotations of the head upon the flip angle and SAR with and without Cartesian feedback being applied.