Multi-Dimensional Refocusing Pulses for Parallel Transmission by Optimal Control

Weiran Deng¹, Cungeng Yang¹, V. Andrew Stenger¹

Multi-dimensioanl refocusing RF pulses for parallel transmission are useful for spin-echo imaging at high magnetic fields. The design of such pulses is challenging because it requires a nonlinear approach to "pancake-flip" the spins with different in-plane phases. We designed a refocusing pulse with 2D spiral k-space trajectory for eight transmitters using a two-process optimal control approach that flips the Y-component of spins from the +Y to -Y direction and leaves the X-component intact. The performance of the pulse was demonstrated using Bloch equation simulation.