Inversion-recovery suppresses the signal of certain tissues as a function of their relaxation time T1. So by choosing a short inversion time, the short T1 tissue signal is suppressed.
The TI corresponding to fat signal suppression is 150 ms at 1.5 T: the sequences using this TI are STIR sequences.
This technique is effective for large volumes and has low dependency on magnetic field heterogeneities.
However, inversion-recovery alters the contrasts and the technique is only employed for sequences with DP or T2 weighting.
It is not recommended for studies after Gadolinium chelate injection as Gadolinium reduces the relaxation time T1 of the tissues: the risk being that the signal from Gadolinium-enhanced lesions is also suppressed.