Fluid attenuated inversion recovery
Citation, DOI, disclosures and article data
At the time the article was created Mohammad Taghi Niknejad had no recorded disclosures.
View Mohammad Taghi Niknejad's current disclosuresAt the time the article was last revised Raymond Chieng had no financial relationships to ineligible companies to disclose.
View Raymond Chieng's current disclosures- FLAIR sequence
- Fluid attenuation inversion recovery sequence
- Fluid attenuation inversion recovery (FLAIR)
- Fluid-attenuated inversion recovery (FLAIR)
Fluid attenuated inversion recovery (FLAIR) is a special inversion recovery sequence with a long inversion time. This removes signal from the cerebrospinal fluid in the resulting images 1. Brain tissue on FLAIR images appears similar to T2 weighted images with grey matter brighter than white matter but CSF is dark instead of bright.
Physics
To null the signal from fluid, the inversion time (TI) of the FLAIR pulse sequence is adjusted such that at equilibrium there is no net transverse magnetization of fluid.
Clinical use
The FLAIR sequence is part of almost all protocols for imaging the brain, particularly useful in the detection of subtle changes at the periphery of the hemispheres and in the periventricular region close to CSF.
FLAIR is able to show lower concentration gadolinium compared to T1-weighted post Gadolinium imaging. In three-dimensional (3D) FLAIR imaging, foci of leptomeningeal enhancement can be seen in multiple sclerosis. Such enhancement is due to fluid leakage secondary to inflammation of the blood vessels 6.
The usefulness of FLAIR sequences has been evaluated in many diseases of the central nervous system such as 2-4:
Post-contrast FLAIR images have been included in protocols to assess leptomeningeal diseases, such as meningitis 5.
References
- 1. Okuda T, Korogi Y, Shigematsu Y et-al. Brain lesions: when should fluid-attenuated inversion-recovery sequences be used in MR evaluation?. Radiology. 1999;212 (3): 793-8. Radiology (full text) - Pubmed citation
- 2. Bakshi R, Ariyaratana S, Benedict RH et-al. Fluid-attenuated inversion recovery magnetic resonance imaging detects cortical and juxtacortical multiple sclerosis lesions. Arch. Neurol. 2001;58 (5): 742-8. Pubmed citation
- 3. Okuda T, Korogi Y, Ikushima I et-al. Use of fluid-attenuated inversion recovery (FLAIR) pulse sequences in perinatal hypoxic-ischaemic encephalopathy. Br J Radiol. 1998;71 (843): 282-90. Br J Radiol (abstract) - Pubmed citation
- 4. Bangerter NK, Hargreaves BA, Gold GE et-al. Fluid-attenuated inversion-recovery SSFP imaging. J Magn Reson Imaging. 2006;24 (6): 1426-31. J Magn Reson Imaging (full text) - doi:10.1002/jmri.20743 - Pubmed citation
- 5. Vaswani AK, Nizamani WM, Ali M et-al. Diagnostic Accuracy of Contrast-Enhanced FLAIR Magnetic Resonance Imaging in Diagnosis of Meningitis Correlated with CSF Analysis. ISRN Radiol. 2014;2014: 578986. doi:10.1155/2014/578986 - Free text at pubmed - Pubmed citation
- 6. Titelbaum D, Engisch R, Schwartz E et al. Leptomeningeal Enhancement on 3D‐FLAIR MRI in Multiple Sclerosis: Systematic Observations in Clinical Practice. J Neuroimaging. 2020;30(6):917-29. doi:10.1111/jon.12774 - Pubmed
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- Pineal and tectal plate protocol (MRI)
- Brain screen protocol (MRI)
- Short tau inversion recovery
- Double doughnut sign
- Bilateral temporal lobe T2 hyperintensity
- 3D fast spin echo (MRI sequence)
- Stroke protocol (MRI)
- Cerebral cortical T2 hyperintensity
- T2/FLAIR mismatch sign
- Diffuse axonal injury
- Turbo inversion recovery magnitude
- V sign (midbrain)
- Medical abbreviations and acronyms (F)
- White matter tracts
- Artery of Percheron territory infarct
- FLAIR vascular hyperintensities
- Inflammatory cerebral amyloid angiopathy
- Brain tumour protocol (MRI)
- Bright rim sign (DNET)
- Hyperintense vessel sign
- MCA infarction with subarachnoid FLAIR vascular hyperintensities
- Subarachnoid FLAIR vascular hyperintensities
- Thalamic aphasia
- Subarachnoid FLAIR vascular hyperintensities
- Epstein-Barr virus encephalitis
- Posterior reversible encephalopathy syndrome (PRES)
- Posterior reversible encephalopathy syndrome (PRES)
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