A SAR Prediction Concept for Parallel Transmission MRI

The speci c absorption rate (SAR) is a limiting factor in higheld MR. SAR estimation is typically performed by numerical simulations using generic human body models. However, SAR concepts for single-channel RF transmission cannot be directly applied for multi-channel systems. In this study, a novel and comprehensive SAR prediction concept for parallel RF transmission MRI is presented, based on pre-calculated B1 and electric elds obtained from EM simulations of multiple numerical body models. The application of so-called Q-matrices and further computational optimizations allow for real-time SAR prediction prior to scanning. This SAR prediction concept was fully integrated into an 8-channel whole body MRI system and facilitates selection of di erent body models and body positions. Experimental validation of the global SAR in phantoms showed good qualitative and quantitative agreement. Also an initial in vivo validation showed good qualitative agreement between simulated and measured B1. The feasibility and practicability of this SAR prediction concept was shown, paving the way for safe parallel RF transmission in higheld MR.

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