We compare two methods for estimating local SAR with virtual observation points (VOPs) in a commercial and a self-built 8Tx/32Rx head coil, respectively. The commercial coil relies on a constant safety factor that reduces the hardware power limits in each transmit channel, where the self-built coil derives the VOPs from coil electromagnetic field (EMF) simulations. We show the use of both coils in vivo with MPRAGE using Universal and subject-specific pTx pulses. The EMF-based VOPs, used with the self-built coil, resulted in a lower local SAR estimate for a similar image quality, providing more flexibility in pulse sequence design.
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