Parallel Transmit Technology for High Field MRI

The success of parallel reconstruction methods and their impact on image encoding has sparked a great deal of interest in using the spatial distribution of transmit coils in an analogous fashion. Namely, by breaking down the transmit field into multiple regions each controlled by a separate transmit channel, spatial degrees of freedom are created that allow the spatial information in the array to be exploited in the excitation process. While a homogeneous birdcage-type body-coil driven by a single RF pulse waveform has served the MR community well, it does not possess spatial degrees of freedom, and subsequently works best for uniform excitations. Parallel excitation arrays and the potential to utilize the spatial information in an array during RF transmission offer the possibility to move beyond the uniform slice-select excitation, and to generate spatially tailored RF pulses; excitation pulses with a carefully controlled spatially varying flip angle or excitation phase that can mitigate artifacts or isolate specific anatomy. While the concept of spatially tailored Parallel Transmit Technology for High Field MRI