Real-4D parallel transmit pulse design for slab-selective uniform water excitation: demonstration in humans at 7T

Motivation: Effective slab-selective uniform water excitation is lacking when pursuing mesoscale BOLD functional MRI (fMRI) at ultrahigh field. Goal(s): To propose a new parallel transmit (pTx) pulse design for achieving slab-selective uniform water excitation in layer fMRI. Approach: Real-4D spatial spectral (spsp) pTx pulses were designed by formulating the design problem in 1D spectral and 3D spatial domains, with the goal of eliminating undesired fat excitation when using traditional pTx approaches based on spoke trajectories. Our new design was validated using both simulation and experiments. Results: In both simulation and experiments, our design method outperformed existing approaches, producing slab-selective uniform water excitation. Impact: Our new design method provides an effective solution for slab-selective uniform water excitation with no out-of-slab fat excitation, holding a promise to many applications including mesoscale fMRI and fat-free body imaging at ultrahigh field.