Oxygen extraction fraction (OEF) and neural tissue susceptibility (χn) maps in representative cognitively Intact and impaired subjects. In cognitively intact subjects, OEF decreases with older age (A to B). In cognitively impaired subjects, OEF decreases with increased burden of white matter hyperintensities (WMH), measured as the volume of WMH as a percentage of whole brain volume on a fluid attenuated inversion recovery (FLAIR) sequence (C to E, D to F). Of note, OEF increases with cognitive impairment (A to C, B to D).