Fluid-attenuated inversion recovery (FLAIR) is a magnetic resonance imaging sequence with an

inversion recovery Inversion recovery is a magnetic resonance imaging sequence that provides high contrast between tissue and lesion. It can be used to provide high T1 weighted image, high T2 weighted image, and to suppress the signals from fat, blood, or cerebros ...

set to null fluids. For example, it can be used in brain imaging to suppress

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...

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

multiple sclerosis Multiple sclerosis (MS) is an autoimmune disease resulting in damage to myelinthe insulating covers of nerve cellsin the brain and spinal cord. As a demyelinating disease, MS disrupts the nervous system's ability to Action potential, transmit ...

(MS) plaques. It was invented by

Graeme Bydder Graham or Graeme may refer to: People * Graham (given name), an English-language given name * Graham (surname), an English-language surname * Graeme (surname), an English-language surname * Graham (musician) (born 1979), Burmese singer * Clan ...

, Joseph Hajnal, and Ian Young in the early 1990s. 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 c ...

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 inj ...

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, intense headache, vomiting and neck stiffness and occasion ...

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