SAR sensitivity to phase andSAR sensitivity to phase and amplitude perturbations when utilizing parallel transmission

Introduction: When using parallel transmission at high field, it is well established that high local specific absorption rate (SAR) values can occur [1]. A conservative approach to guarantee patient safety can be provided by using the worst-case scenario to derive the limits to be enforced by the SAR monitor [2]. This approach significantly limits the in-vivo applications of parallel transmission at high field. More advanced solutions have been proposed to allow more power while guaranteeing patient safety [3]. Knowledge of the SAR under different conditions is vital for the design of such less restrictive SAR monitors. In the recent past, studies have investigated the variability in SAR by comparing various pulse designs and design methods [4,5]. However, no reports have been made regarding the behavior of transmit-SENSE [6] pulses with regard to amplitude and phase perturbations. In this work, we investigated the behavior of the local SAR regarding perturbed spoke k-space trajectory based excitation pulses [7] designed using simulated field maps.