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A central issue of parallel RF transmission is the SAR management toensure patient safety. The additional degrees of freedom availablein parallel transmission hamper straight-forward SAR estimations asapplied for single channel transmission. As an alternative to the usually applied model-based SAR estimation, a new method has been proposed to estimate SAR from the acquired B1 maps. This B1-based SAR determination has been successfully tested for quadrature (single channel) excitation in vivo and non-quadrature (multi-channel) excitation in a phantom study. This study adapts B1-based SAR determination for non-quadrature excitation in vivo. To this goal, the local SAR inthighs and pelvis of a volunteer is investigated and compared withresults of corresponding FDTD simulations based on the same volunteer.

Transmit SENSE is typically applied to improve spatially selective RF pulses in two or three dimensions. This study investigates the application of Transmit SENSE to one-dimensional RF pulses. For these RF pulses, Transmit SENSE is applicable in case of large B1 variations across the slice or slab to be excited. Typically, such large B1 variations are found across the slabs excited in 3D volume imaging orin the framework of the REgional Saturation Technique (REST). 1D Transmit SENSE can improve the excitation slab profile, and particularly can result in a significant reduction of RF power and the relatedspecific absorption rate (SAR). Since the involved RF pulses have the same duration as standard slice-selection pulses, they can easilybe incorporated in standard sequences without changing sequence timing. The approach was tested using synthetic and realistic coil sensitivity profiles.