Estimation of Electric Field Maps from B1+ and Transceive Phase Measurements for Local SAR Evaluation

Alessandro Sbrizzi¹, Hans Hoogduin, Jan J. Lagendijk, Peter R. Luijten, Cornelis A. van den Berg²

To compute the SAR, the electric fields generated by the RF coil should be estimated. In this work, we show how to extract this information from B1+ and treansceive phase measurements. The reconstruction of the complex z-component of the electric fields is done on the basis of a 3D model. The electromagnetic fields can be efficiently expressed in terms of few ad hoc constructed basis functions. The expansions coefficients are found by fitting the measured data to the model. Numerical simulations and in vivo measurements confirm the validity of the method for a 2ch 7T transceive birdcage headcoil.