Fluid-attenuated inversion recovery (FLAIR) is an

MRI sequence An MRI sequence in magnetic resonance imaging (MRI) is a particular setting of pulse sequences and pulsed field gradients, resulting in a particular image appearance. A multiparametric MRI is a combination of two or more sequences, and/or includin ...

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 bra ...

(CSF) effects on the image, so as to bring out the periventricular hyperintense lesions, such as

multiple sclerosis Multiple (cerebral) sclerosis (MS), also known as encephalomyelitis disseminata or disseminated sclerosis, is the most common demyelinating disease, in which the insulating covers of nerve cells in the brain and spinal cord are damaged. This d ...

(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 Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural openi ...

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 Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...

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