Method for improved multiband excitation profiles using the Shinnar-Le Roux transform

A method to design multiband RF pulses for magnetic resonance imaging is de scribed. The method is based on the Shinnar-Le Roux transform and involves a phase correction that provides control over the phase of the excited band s. The theory behind the method and this phase correction is outlined. The method is demonstrated with the design of RF pulses for Hadamard encoding a nd Haar wavelet encoding. Experimentally measured excitation profiles and i mages for RF pulses designed with the new method are compared to those desi gned by the conventional method. The conventional method is shown to result in distortion of the excitation profile when the bands are closely spaced. A 78% reduction in this distortion is attributed to the new method. This t ranslates into a 52% reduction of out-of-slice signal in Haar wavelet encod ing. (C) 1999 Wiley-Liss, Inc.