Fluid-attenuated inversion recovery (FLAIR): clinical prospectus of current and future applications

A relative weakness of the traditional spin-echo technique, and particularly of the newer "FAST" or "TURBO" spin-echo sequences, has been diminished conspicuousness of lesions affecting the peripheral cortical mantle or those located in the periventricular region. This is a consequence of partial volume effects and high cerebrospinal fluid (CSF) signal adjacent to pathologic regions. Fluid-attenuated inversion recovery (FLAIR) is a magnetic resonance imaging (MRI) sequence that produces strong T2 weighting, suppresses the CSF signal, and minimizes contrast between gray matter and white matter. This effect produces images with significantly increased lesion-to-background CSF contrast and enhances the visibility of lesions as well as their detectability, particularly in the peripheral subcortical and periventricular regions. Applications are evolving, though preliminary reports highlight the superiority of FLAIR in the evaluation of infarction, multiple sclerosis, metastatic disease, tuberous sclerosis, and, possibly, subarachnoid hemorrhage. Early reports also address the application of FLAIR to imaging of the spinal cord. Modified versions of FLAIR are currently being developed; these modifications will further shorten acquisition times and eliminate pulsation artifacts. FLAIR may ultimately supplant conventional spin-echo imaging in routine MR screening of the brain.