Short TI Inversion Recovery
A fat suppression method suitable for large fields-of-view, or regions of higher magnetic susceptibility variation.
A 180 degree inversion prepulse is used to invert all magnetisation. Then imaging proceeds after a delay (the inversion time, or TI), when the longitudinal recovery of fat magnetisation has reached the null point: when Mz = 0. This means that, for fat, there will be no magnetisation ready to flip into the x-y plane for measurement, and so fat will not provide a signal; it will be dark.
Tissues with a T1 relaxation time different to fat have a signal, because they either have not yet reached the null point, or have recovered past it. When the excitation pulse for imaging is applied, there is magnetisation available to flip into the x-y plane for these tissues, and a signal is detected.
The inversion time can be set to different values, suitable to null other tissues with a different T1 relaxation time. For example, FLAIR uses a long TI.
“[Ian Young’s] group sustained low field imaging and kept it competitive with a series of technical developments including fat suppression with STIR.”
“Ian was described as the Father of Clinical MRI.”Graeme Bydder, co-author with Ian Young on the 1985 STIR paper