Steady‐state sequence synthesis and its application to efficient fat‐suppressed imaging

Abstract A new synthesis algorithm, based on the Shinnar‐Le Roux (SLR) transform, can be used to generate fully refocused steady‐state pulse sequences with arbitrary magnetization profiles as a function of off‐resonant precession. This is accomplished by appropriate periodic oscillation of the RF excitation magnitude and phase from echo to echo. The technique is applied to the design of refocused steady‐state free precession (SSFP) sequences with flat profiles, providing the opportunity for banding‐artifact‐free imaging with steady‐state contrast. The algorithm is also used to generate refocused‐SSFP sequences with an arbitrarily broad region of attenuated signal. These sequences are implemented and applied to the problem of steady‐state fat suppression. Preliminary results show signal levels that agree well with theory, and a broad region of suppressed signal at each echo. Total imaging time is kept identical to that of a standard refocused‐SSFP experiment through echo equalization and interleaving. 3D images from the leg of a normal volunteer acquired in 44 s demonstrate the applicability of the technique to fat‐suppressed imaging. Magn Reson Med 50:550–559, 2003. © 2003 Wiley‐Liss, Inc.