RF Concatenation with Spiral In-And-Out Trajectory for Two-Dimensional Large-Tip-Angle Excitation

Seung-Kyun Lee¹, Dan Xu², W A. Grissom³, Ileana Hancu¹, Mika W. Vogel⁴

We demonstrate that the time-reversed RF concatenation principle, which was previously considered in one-dimensional non-adiabatic inversion pulse design, can be extended to multi-dimensional and multi-coil excitation pulses. We present general analytical formulation of the concatenation principle, and demonstrate its use in (i) simulated inversion in 8-channel parallel transmit, and (ii) in-vivo inversion experiment on a single channel system with a human subject. The off-resonance field sensitivity, which is a drawback of the concatenation method in one dimension, is significantly reduced for two-dimensional excitation when a spiral in- and out- trajectory is employed.