Magnetic resonance imaging of a body uses steady state free precession
with material separation for the selective imaging of two species, such
as blood or fat. The refocusing property of SSFP is used with signal
phase detection to suppress either water or lipid. Phase and/or frequency
of the RF excitation pulse and repetition time are selected so that
resonant frequencies of water, fw, and lipid, fl, are on opposite sides
of the signal null frequency.
