title: Minimum detectable difference of MR diffusion maps in acute ischemic stroke.
abstract: OBJECTIVE
  To determine the minimum detectable difference (MDD) and investigate variability of region-of-interest (ROI) analysis of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) in acute ischemic stroke.
  
  
  METHODS
  Ten patients with acute stroke (<24 hours) and moderate-to-large infarcts were imaged using a fast diffusion tensor technique. Four observers repeated three trials, during which each of two ROI types (free-hand polygon and ellipse) were drawn in white and gray matter (WM and GM) on FA and ADC maps. Analysis-of-variance techniques examined tissue and ROI type effects as well as inter- and intraobserver variability. F-tests examined the variability differences between ROI types.
  
  
  RESULTS
  The MDD for ADC was 0.160 x 10(-3) mm(2) s(-1) in WM and 0.212 x 10(-3) mm(2) s(-1) in GM. The FA MDD was 0.19 in WM and 0.10 in GM. Tissue but not ROI type affected the mean values for both ADC and FA maps. Intraobserver reliability was substantial, while interobserver reliability was poor-to-moderate. No variability differences were found by ROI types.
  
  
  CONCLUSIONS
  The MDD for WM and GM in normal and ischemic tissue were calculated. Inter- and intraobserver variability and tissue type affect ROI analysis of ADC and FA maps.
authors.affiliation: Seaman Family MR Research Centre, Foothills Medical Centre, Calgary Health Region, Calgary, Alberta, Canada.
authors.forename: Ashley D
authors.initials: AD
authors.lastname: Harris
authors.forename: Mirthula
authors.initials: M
authors.lastname: Govindaraj
authors.forename: Richard
authors.initials: R
authors.lastname: Frayne
mesh_terms: D000208:Acute Disease; D000368:Aged; D000369:Aged, 80 and over; D002544:Cerebral Infarction / Q000175:diagnosis*; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation