MS Lesions in Fluid Attenuated Inversion Recovery Images

Abstract

Fluid attenuated inversion recovery (FLAIR) MR sequences produce heavily T2-weighted images by nulling the signal from cerebrospinal fluid (CSF), using an inversion time that usually ranges from 1,800 to 2,500 ms (Adams and Melhem 1999). By suppressing the signal intensity of bulk water, FLAIR images increase the conspicuousness of lesions located in the periventricular area. Tissue water is also affected, therefore FLAIR images provide a better lesion contrast than do PD- or T2-weighted images, particularly in gray matter (up to 30%, Yousry et al.). This technique was first reported by Hajnal et al. (1992). Because of its unique characteristics in identifying lesions close to the ventricles, juxtacortical, and especially cortical regions, it has attracted strong attention of radiologists for its clinical utility. Unfortunately, FLAIR images are less sensitive in the depiction of lesions involving brainstem and cerebellum, so lesion load may be underestimated in the posterior fossa (Gawne-Cain et al. 1998).