title: Apparent diffusion coefficient thresholds and diffusion lesion volume in acute stroke.
abstract: BACKGROUND
  Apparent diffusion coefficient (ADC) thresholds are used to determine acute stroke lesion volume, but the reliability of this approach and comparability to the volume of the magnetic resonance diffusion-weighted imaging (MR-DWI) hyperintense lesion is unclear.
  
  
  METHODS
  We prospectively recruited and clinically assessed patients who had experienced acute ischemic stroke and performed DWI less than 24 hours and at 3 to 7 days after stroke. We compared the volume of the manually outlined DW hyperintense lesion (reference standard) with lesion volumes derived from 3 commonly used ADC thresholds: .55 × 10(-3)/mm(2)/second(-1), .65 × 10(-3)/mm(2)/second(-1), and .75 × 10(-3)/mm(2)/second(-1), with and without "editing" of erroneous tissue. We compared the volumes obtained by reference standard, "raw," and "edited" thresholds.
  
  
  RESULTS
  Among 33 representative patients, the acute DWI lesion volume was 15,284 mm(3); the median unedited/edited ADC volumes were 52,972/2786 mm(3), 92,707/6,987 mm(3), and 227,681/unmeasureable mm(3) (.55 × 10(-3)/mm(2)/second(-1), .65 × 10(-3)/mm(2)/second(-1), and .75 × 10(-3)/mm(2)/second(-1) thresholds, respectively). Subacute lesions gave similar differences. These differences between edited and unedited diffusion-weighted imaging and ADC volumes were statistically significant.
  
  
  CONCLUSIONS
  Threshold-derived ADC volumes require substantial manual editing to avoid over- or underestimating the visible DWI lesion and should be used with caution.
authors.affiliation: Brain Research Imaging Centre, Division of Clinical Neurosciences, University of Edinburgh, Western General Hospital, Edinburgh, Scotland, United Kingdom; Scottish Imaging Network, A Platform for Scientific Collaboration (SINAPSE).
authors.forename: Ralph G R
authors.initials: RG
authors.lastname: Thomas
authors.forename: G Katherine
authors.initials: GK
authors.lastname: Lymer
authors.forename: Paul A
authors.initials: PA
authors.lastname: Armitage
authors.forename: Francesca M
authors.initials: FM
authors.lastname: Chappell
authors.forename: Trevor
authors.initials: T
authors.lastname: Carpenter
authors.forename: Bartosz
authors.initials: B
authors.lastname: Karaszewski
authors.forename: Martin S
authors.initials: MS
authors.lastname: Dennis
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Wardlaw
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000503:physiopathology*; D002545:Brain Ischemia / Q000503:physiopathology*; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D020521:Stroke / Q000503:physiopathology*