Quantitative evaluation of age-related white matter microstructural changes on MRI by multifractal analysis.

Multifractal analysis has been applied to evaluate biological tissues, which are composed of complex structures. We carried out multifractal analyses in a group of healthy young and elderly subjects to examine age-related white matter microstructural changes on T2-weighted MR images without any visible abnormal intensity, and to correlate such changes with age-related cognitive decline. Comparison between the two age groups showed that Deltaalpha (established as the most suitable index of heterogeneity in our previous report) in the frontal region was significantly higher in the elderly group, but no significant group difference was found in Deltaalpha in the parieto-occipital region. The Trail-Making Test score (a measure of executive dysfunction) was significantly higher in the elderly group. In the elderly group, the Trail-Making Test score was positively correlated with Deltaalpha in the frontal region, but not in the parieto-occipital region. These results suggest that microstructural changes in the white matter preferentially occur in the frontal region with normal aging, and these changes are associated with executive cognitive decline reflective of frontal-subcortical dysfunction.