Simultaneous Multi-Slice Parallel RF Excitation with In-Plane B1+ Homogenization

Xiaoping Wu¹, Sebastian Schmitter¹, Edward J. Auerbach¹, Steen Moeller¹, Kamil Ugurbil¹, Pierre-Francois Van de Moortele¹

Simultaneous multi-band (MB) RF excitation, along with subsequent unaliasing via parallel imaging principles, provides an effective means to accelerate volume coverage along the slice direction. Recently, the approach has been exploited with significant success in functional and diffusion-weighted imaging studies of the brain. So far this technique has only been demonstrated in the context of single channel transmit. In this study, we extend this technique to multi-channel transmit and introduce parallel transmit (pTX) MB pulse design in order to tackle the issues of B1+ inhomogeneity at high and ultrahigh field strengths, and RF power deposition. The new extension is validated in the human brain at 7T and is demonstrated capable of providing good B1+ homogenization in addition to simultaneous MB excitation without necessitating the use of higher RF energy relative to a single channel application.