Multidimensional excitation pulses based on spatiotemporal encoding concepts.

The understanding and control of spin dynamics play a fundamental role in modern NMR imaging, for devising new ways to monitor an object's density as well as for enabling the tailored excitation of spins in space. It has recently been shown that by relying on spatiotemporal encoding (SPEN), new forms of single-scan multidimensional NMR spectroscopy and imaging become feasible. The present study extends those imaging developments, by introducing a new class of multidimensional excitation pulses that relies on SPEN concepts. We focus in particular on a family of "hybrid" 2D radiofrequency (RF) pulses that operate in both direct and reciprocal excitation space, and which can spatially sculpt the spin magnetization in manners that are beyond the reach of sequential 1D pulse shaping. These SPEN-based 2D pulses are compatible with a majority of single- and multi-scan imaging techniques. Like the corresponding SPEN-based hybrid 2D acquisitions, these pulses can benefit from a high robustness against field inhomogeneities and/or offset effects that affect their k-space-based counterparts. These properties are analyzed, and illustrated with numerical simulations and model experiments.