title: Iron deposition influences the measurement of water diffusion tensor in the human brain: a combined analysis of diffusion and iron-induced phase changes.
abstract: BACKGROUND
  This study aims to evaluate the impact of iron deposition during aging on the measurement of water diffusion in the brain.
  
  
  METHODS
  Diffusion tensor images (DTI) and phase images collected from a group of healthy adults from 23 to 72 years old were retrospectively analyzed. The axial diffusivity, radial diffusivity, mean diffusivity (MD), and fractional anisotropy (FA) in the frontal white matter and deep gray matter nuclei were calculated. The phase changes in these regions were used to estimate local iron concentration. Pearson correlation analysis was used to evaluate the age dependence of DTI metrics and iron concentration. Multiple linear regression models were then built to examine the independent effect of age and iron deposition on DTI metrics.
  
  
  RESULTS
  Age-related iron deposition occurred in the putamen (r = 0.680, P < 0.001) and frontal white matter (r = 0.333, P = 0.007). In the putamen, FA increased with elevated iron concentration (P = 0.042) excluding the effect of age, and MD decreased with iron deposition with marginal statistical significance (P = 0.067). In the frontal white matter, increase in iron level was also associated with a decrease in MD and an increase in FA. Moreover, radial diffusivity was more reduced than axial diffusivity as local iron concentration increased.
  
  
  CONCLUSIONS
  Iron deposition in the brain during aging decreases water diffusion and increases the degree of anisotropy. Caution is needed when using DTI metrics for diagnosis of various neurological diseases involving abnormal iron deposition.
authors: Department of Radiology, Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, Zhejiang Province, China, 310009. xxjmailbox@163.com.
authors: Xiaojun
authors: X
authors: Xu
authors: Department of Radiology, First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.
authors: Qidong
authors: Q
authors: Wang
authors: College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China.|University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
authors: Jianhui
authors: J
authors: Zhong
authors: Department of Radiology, Second Affiliated Hospital, Zhejiang University School of Medicine, 88 Jiefang Road, Hangzhou, Zhejiang Province, China, 310009.
authors: Minming
authors: M
authors: Zhang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D001834:Body Water / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D004058:Diffusion; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007501:Iron / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution; D014867:Water; D055815:Young Adult
chemical_list: D014867:Water; D007501:Iron
keywords: Brain aging; Brain iron; Diffusion tensor