title: Uncinate fasciculus-correlated cognition in Alzheimer's disease: a diffusion tensor imaging study by tractography.
abstract: BACKGROUND
  Neuroimaging studies show increased diffusivity and decreased anisotropy in Alzheimer's disease (AD) patients by diffusion tensor imaging (DTI). Previous reports have analyzed a correlation with cognitive function and DTI parameters, but their results are inconsistent. A reason for this might be a region of interest (ROI) method, used to calculate parameters for DTI, because this method has various usages of how to place a ROI and includes summations of values for various neuronal fiber tracts, resulting in contamination of unintended fibers. To improve the instability with ROI placement, a tractography-based method might be useful. Our coworker reported decreased fractional anisotropy (FA) and increased apparent diffusion coefficient (ADC) of uncinate fasciculus (UF) in patients with AD by tractography. To confirm whether DTI parameter values are related to severity of cognitive function in patients with AD, we measured mean diffusion anisotropy and diffusivity of coregistered voxels along the tracking lines (i.e. tract of interest) of UF.
  
  
  METHODS
  The subjects were 30 patients with probable AD (NINCDS-ADRDA criteria). Assessment of cognitive function was carried out according to the Mini-Mental State Examination (MMSE) and the Alzheimer's Disease Assessment Scale-cognitive component-Japanese version (ADAS-Jcog). A 1.5-T clinical magnetic resonance unit was used to obtain diffusion tensor images. Diffusion tensors were computed and fiber-tract maps were created using 'dTV II' DTI software developed by Masutani et al. We measured mean FA and ADC values along the bilateral UF.
  
  
  RESULTS
  FA values were positively correlated with MMSE score (r= 0.67) and were negatively correlated with ADAS-Jcog score (r=-0.62), while ADC values were negatively correlated with MMSE score (r=-0.58) and were positively correlated with ADAS-Jcog score (r= 0.59).
  
  
  CONCLUSIONS
  FA and ADC values might reflect the severity of cognitive dysfunction. The tract-of-interest method might be a useful tool for objectively evaluating DTI parameters in AD.
authors.affiliation: Sakai City Mental Health Center, Sakai, Japan. mmorikaw@naramed-u.ac.jp
authors.forename: Masayuki
authors.initials: M
authors.lastname: Morikawa
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Kiuchi
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Taoka
authors.forename: Kiyoyuki
authors.initials: K
authors.lastname: Nagauchi
authors.forename: Kimihiko
authors.initials: K
authors.lastname: Kichikawa
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Kishimoto
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000150:complications / Q000473:pathology*; D016880:Anisotropy; D003072:Cognition Disorders / Q000209:etiology / Q000473:pathology; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D005625:Frontal Lobe / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D013702:Temporal Lobe / Q000473:pathology*