Broadband nuclear magnetic resonance pulses with two-dimensional spatial selectivity

Two-dimensional spatial localization can be achieved using a single nuclear magnetic resonance (NMR) pulse if the pulse is applied in the presence of a magnetic field gradient which is reorienting through two dimensions. The application of these pulses to whole-body NMR imaging systems is hampered, however, by amplitude and slew-rate constraints on the magnetic field gradients, resulting in longer pulses with relatively limited bandwidth. We describe here a variable rate method for shortening these pulses by as much as 36% for pulses limited by slew rate and 55% for pulses limited by gradient amplitude, without changing their spatial excitation profiles on resonance.