Phase-Compensated Spin-Echo Sequence Using Hyperbolic Secant Pulses for Both Excitation and Refocusing
Park J, Garwood M
Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota
Frequency-modulated (FM) pulses are frequently used for refocusing to overcome problems due to RF inhomogeneity and to achieve broad bandwidth. An even number of FM pulses have previously been used in spin-echo sequences to cancel the non-linear phase of the transverse magnetization produced by individual pulses. FM pulses have also been applied for both excitation and refocusing, whereby each pulse compensates the phase of the other. Here, the phase profiles are analytically described when hyperbolic secant (HS) pulses are used for excitation and refocusing, and the exact condition for achieving phase compensation is derived for spin-echo imaging using HS pulses.