Fat suppression is useful for example to distinguish active inflammation in the intestines from fat deposition such as can be caused by long-standing (but possibly inactive) inflammatory bowel disease, but also obesity, chemotherapy and celiac disease. Without fat suppression techniques, fat and fluid will have similar signal intensities on fast spin-echo sequences.
Techniques to suppress fat on MRI mainly include:
* Identifying fat by the chemical shift of its atoms, causing different time-dependent phase shifts compared to water.
* Frequency-selective saturation of the spectral peak of fat by a "fat sat" pulse before imaging.
* Short tau inversion recovery (STIR), a T1-dependent method
* Spectral presaturation with inversion recovery (SPIR)