Understanding steady-state free precession: A geometric perspective

Steady-state free precession (SSFP) sequences are becoming more common in clinical and research studies. Though there have been mathematical treatments of SSFP signals, a simple and/or intuitive understanding of how such signals are established is lacking in the literature. In this work, the classical picture of a spin system is used to develop an analysis of the behavior of magnetization in phase space. This leads to a geometric description that demonstrates the essential features of SSFP signals. This analysis yields an intuitive understanding of SSFP signal formation and the intricate interactions between the choice of flip angle, pulse repetition time, relaxation effects, and phase-cycling patterns on the final SSFP signal. (c) 2005 Wiley Periodicals, Inc.