Fluid-attenuated inversion recovery (FLAIR) is an MRI sequence with an inversion recovery set to null fluids. For example, it can be used in brain imaging to suppress

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the ...

(CSF) effects on the image, so as to bring out the periventricular hyperintense lesions, such as multiple sclerosis (MS) plaques. It was invented by Dr. Graeme Bydder. FLAIR can be used with both three-dimensional imaging (3D FLAIR) or two dimensional imaging (2D FLAIR).

Technique

By carefully choosing the inversion time (TI), the signal from any particular tissue can be nulled. The appropriate TI depends on the tissue via the formula: :

\textrm = \ln(2) \cdot T_1,\,

in other words, one should typically use a TI of around 70% of the ''T₁'' value. In the case of CSF suppression, one aims for ''T₁''-weighted images, which prioritize the signal of fat over that of water. Therefore, if the long TI (inversion time) is adjusted to a zero crossing point for water (none of its signal is visible), the signal of the CSF is theoretically being "erased," from the derived image.

Clinical applications

The FLAIR sequence analysis has been especially useful in the evaluation and study of CNS disorders, involving: * Lacunar infarction * Multiple sclerosis (MS) plaques *

Subarachnoid haemorrhage Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain. Symptoms may include a severe headache of rapid onset, vomiting, decreased level of cons ...

Head trauma A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inju ...

* Meningitis and other leptomeningeal diseases* * Post-contrast FLAIR images have been added to diagnosis protocol for accurate medical assessment. File:Gliomatosis cerebri2.jpg, Axial fluid-attenuated inversion recovery MRI image demonstrating tumor-related infiltration involving lenticular nuclei (Arrow). File:Gliomatosis cerebri.jpg, Axial fluid-attenuated inversion recovery MRI image demonstrating tumor-related infiltration involving both temporal lobes (Short arrow), and the substantia nigra (Long arrow).

Technique

Clinical applications

See also

References

Further reading