Fat suppression techniques take of two (2) characteristics. First, the difference in precession frequency between water and fat, which is utilized in chemical/spectral (pre)saturation, Dixon/IDEAL and water excitation techniques. Second, the difference in T1 relaxation times between water and fat, which is utilized by STIR sequence. Finally, there are hybrid techniques, which combine the two aforementioned characteristics. SPIR and SPAIR are part of this third category of techniques (figure).