Imaging Pseudo-Echoes Produced by a Frequency-Swept Pulse

J-Y. Park, M. Garwood Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, MN, United States Synopsis: Frequency-swept pulses, like the hyperbolic secant (HS1) pulse, are not typically employed for excitation in MRI. When used for excitation in gradient-echo imaging, the HS1 pulse does not produce a proper echo because the magnetization phase varies quadratically in space. Here, the phase profiles of HS1 are described analytically. It is shown that HS1 produces a “pseudo-echo” when used for excitation in a gradient-echo sequence. An image reconstruction method is developed to allow 3D pseudo-echo imaging using a sliding window function. This method makes it possible to take full advantage of HS1 for slab-selective 3D MR