Fluid-attenuated inversion recovery

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:

${\displaystyle {\textrm {TI}}=\ln(2)\cdot T_{1},\,}$

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.[2]

The FLAIR sequence analysis has been especially useful in the evaluation and study of CNS disorders, involving:[2]

• Lacunar infarction
• Multiple sclerosis (MS) plaques
• Subarachnoid haemorrhage
• Head trauma
• Meningitis and other leptomeningeal diseases*

* Post-contrast FLAIR images have been added to diagnosis protocol for accurate medical assessment.[2]

• 
  Axial fluid-attenuated inversion recovery MRI image demonstrating tumor-related infiltration involving lenticular nuclei (Arrow).
• 
  Axial fluid-attenuated inversion recovery MRI image demonstrating tumor-related infiltration involving both temporal lobes (Short arrow), and the substantia nigra (Long arrow).

• Relaxation (NMR)