In a T2 weighted FLAIR sequence, what is suppressed to highlight long T2 pathologies?

In a T2 weighted FLAIR (Fluid-Attenuated Inversion Recovery) sequence, cerebrospinal fluid (CSF) is specifically suppressed to enhance the visibility of long T2 pathologies. This suppression is crucial because the natural high signal intensity of CSF could obscure or mask abnormalities present in the brain tissue, such as lesions associated with multiple sclerosis, edema, and other conditions where fluid dynamics are altered.

By removing the CSF signal, the FLAIR sequence allows for clearer identification and assessment of these pathologies in the brain, making it a vital tool in neuroimaging. Long T2 pathologies are better appreciated against the darker background created by the suppressed CSF signal, thereby improving diagnostic accuracy. This targeted suppression distinguishes FLAIR from standard T2-weighted sequences, where CSF is evident and can lead to less contrast in the evaluation of brain lesions.