  Multiple sclerosis (MS) is a demyelinating disease that affects more than 2
million people worldwide. The most used imaging technique to help in its
diagnosis and follow-up is magnetic resonance imaging (MRI). Fluid Attenuated
Inversion Recovery (FLAIR) images are usually acquired in the context of MS
because lesions often appear hyperintense in this particular image weight,
making it easier for physicians to identify them. Though lesions have a bright
intensity profile, it may overlap with white matter (WM) and gray matter (GM)
tissues, posing difficulties to be accurately segmented. In this sense, we
propose a lesion enhancement technique to dim down WM and GM regions and
highlight hyperintensities, making them much more distinguishable than other
tissues. We applied our technique to the ISBI 2015 MS Lesion Segmentation
Challenge and took the average gray level intensity of MS lesions, WM and GM on
FLAIR and enhanced images. The lesion intensity profile in FLAIR was on average
25% and 19% brighter than white matter and gray matter, respectively;
comparatively, the same profile in our enhanced images was on average 444% and
264% brighter. Such results mean a significant improvement on the intensity
distinction among these three clusters, which may come as aid both for experts
and automated techniques. Moreover, a byproduct of our proposal is that the
enhancement can be used to automatically estimate a mask encompassing WM and MS
lesions, which may be useful for brain tissue volume assessment and improve MS
lesion segmentation accuracy in future works.
