FIG 3. Signal intensity to white matter ratio. Measurements of signal intensity ratios of various anatomic structures in healthy volunteers at 30 min with the use of two types of masks show that CSF hyperintensity is significantly higher with the sealed mask compared with the loose mask (P < .01). PREPON, prepontine cistern; AMBIENT, ambient cistern; INTERPED, interpeduncular cistern; LAT.VENT, lateral ventricle; CHOROID.PL, choroid plexus; CONVEX, sulci over the convexity; GRAY, gray matter; EYE, vitreous of eye; WHITE, white matter.