SAR in interleaved excitation of an MRI RF array

We have numerically investigated the safety implications of interleaved RF excitation, as proposed by Avdievitch (2011), when used with multi-row near field arrays at 300 MHz. In most configurations, for both circular polarized excitation and static RF shimming, interleaved excitation resulted in multiplication of power deposited in the entire human tissue by a factor approximately equal to the number of interleaves, and a significant increase of specific absorption ratio averaged over 10 gram of tissue (SAR_10g). However, for a specific configuration, in which interleaved excitation at each time step resulted in significant power reflected by the entire array, and RF excitation profiles that were well separated in space, the SAR_10g remained practically the same as with simultaneous excitation.