A systematic design procedure for selective pulses in NMR imaging.
Spectral tailoring of an amplitude-modulated radio-frequency (RF) pulse may be used to modify the slice-profile produced by a selective excitation sequence. Optimisation of the profile by intuitive means is difficult, however, due to the non-linearity of the magnetisation's response. A design procedure is presented which uses computer-simulation to calculate the response to an arbitrary RF envelope, and alters systematically the shape of the envelope in order to optimise the slice-profile. Two forms of modulation function are suggested, both based on a truncated-sinc, and the simulated response to optimised 90 degrees and 180 degrees pulses is shown. The effect on the slice-profile of RF magnetic field inhomogeneity is discussed.
D004574:Electromagnetic Fields; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D012984:Software