title: Age-related apparent diffusion coefficient changes in the normal brain.
abstract: OBJECTIVE
  To measure the mean diffusional age-related changes of the brain over the full human life span by using diffusion-weighted spin-echo single-shot echo-planar magnetic resonance (MR) imaging and sequential whole-brain apparent diffusion coefficient (ADC) histogram analysis and, secondarily, to build mathematical models of these normal age-related changes throughout human life.
  
  
  METHODS
  After obtaining institutional review board approval, a HIPAA-compliant retrospective search was conducted for brain MR imaging studies performed in 2007 for various clinical indications. Informed consent was waived. The brain data of 414 healthy subjects (189 males and 225 females; mean age, 33.7 years; age range, 2 days to 89.3 years) were obtained with diffusion-weighted spin-echo single-shot echo-planar MR imaging. ADC histograms of the whole brain were generated. ADC peak values, histogram widths, and intracranial volumes were plotted against age, and model parameters were estimated by using nonlinear regression.
  
  
  RESULTS
  Four different stages were identified for aging changes in ADC peak values, as characterized by specific mathematical terms: There were age-associated exponential decays for the maturation period and the development period, a constant term for adulthood, and a linear increase for the senescence period. The age dependency of ADC peak value was simulated by using four-term six-coefficient function, including biexponential and linear terms. This model fit the data very closely (R(2) = 0.91).
  
  
  CONCLUSIONS
  Brain diffusivity as a whole demonstrated age-related changes through four distinct periods of life. These results could contribute to establishing an ADC baseline of the normal brain, covering the full human life span.
authors.affiliation: Department of Radiology, Boston Medical Center, Boston University School of Medicine, 820 Harrison Ave, FGH Bldg, 3rd Floor, Boston, MA 02118, USA. memi.watanabe@bmc.org
authors.forename: Memi
authors.initials: M
authors.lastname: Watanabe
authors.forename: Osamu
authors.initials: O
authors.lastname: Sakai
authors.forename: Al
authors.initials: A
authors.lastname: Ozonoff
authors.forename: Steven
authors.initials: S
authors.lastname: Kussman
authors.forename: Hernán
authors.initials: H
authors.lastname: Jara
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D000465:Algorithms; D001921:Brain / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D038524:Diffusion Magnetic Resonance Imaging; D017352:Echo-Planar Imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D012016:Reference Values; D012189:Retrospective Studies