title: Regional and global changes in cerebral diffusion with normal aging.
abstract: OBJECTIVE
  We used quantitative diffusion MR imaging to investigate the microstructural changes that occur in white matter during normal aging in order to identify regional changes in anisotropy and to quantify global microstructural changes by use of whole-brain diffusion histograms.
  
  
  METHODS
  Full diffusion tensor MR imaging was performed in 20 healthy volunteers, 20 to 91 years old. Thirteen subjects also underwent high-resolution T1-weighted imaging, so that diffusion images could be coregistered and standardized to normal coordinates for statistical probability mapping. Relative anisotropy (RA) was calculated, as was linear regression of RA with age for each pixel; pixels with a significant correlation coefficient were displayed. For histographic analysis, the average apparent diffusion coefficient (ADC) histograms were calculated on a pixel-by-pixel basis. Subjects were divided into two equal groups by the median age (55 years) of the population and plotted for statistical comparison.
  
  
  RESULTS
  Regional analysis showed statistically significant decreases in RA with increasing age in the periventricular white matter, frontal white matter, and genu and splenium of the corpus callosum, despite the absence of signal abnormalities on visual inspection of conventional images. Significant increases in RA were found in the internal capsules bilaterally. ADC histograms showed higher mean ADC and reduced peak height and skew in the older age group on group comparisons.
  
  
  CONCLUSIONS
  Quantitative diffusion histograms correlate with normal aging and may provide a global assessment of normal age-related changes and serve as a standard for comparison with neurodegenerative diseases.
authors.affiliation: Department of Radiology, Mount Sinai School of Medicine, New York, NY, USA.
authors.forename: A O
authors.initials: AO
authors.lastname: Nusbaum
authors.forename: C Y
authors.initials: CY
authors.lastname: Tang
authors.forename: M S
authors.initials: MS
authors.lastname: Buchsbaum
authors.forename: T C
authors.initials: TC
authors.lastname: Wei
authors.forename: S W
authors.initials: SW
authors.lastname: Atlas
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D016880:Anisotropy; D001921:Brain / Q000033:anatomy & histology* / Q000254:growth & development*; D004058:Diffusion; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012016:Reference Values