Robustness of 300MHz 8-channel dual-row transmit arrays for MRI

We evaluated how magnetic resonance imaging robustness depends on dual-row transmit array geometry, head size, position of a head inside the array and array tuning condition. A clear winner was not found. For overlapped arrays, different tuning conditions resulted in larger peak-to-peak variation for circular polarization excitation, but B₁+ (averaged over the volume of interest) decrease was as a bit less for excitations that minimized B₁+ root-mean-square inhomogeneity as compared with non-overlapped arrays. For the non-overlapped array, the safety excitation efficiency was better if the distance between the crown of the head and the end of the array was small. Decreasing the distance to the array shield resulted in improved array robustness at the cost of decreased B₁+.