title: Associations between diffusion and perfusion parameters, N-acetyl aspartate, and lactate in acute ischemic stroke.
abstract: OBJECTIVE
  In acute ischemic stroke, the amount of neuronal damage in hyperintense areas on MR diffusion imaging (DWI) is unclear. We used spectroscopic imaging to measure N-acetyl aspartate (NAA, a marker of normal neurons) and lactate (a marker of ischemia) to compare with diffusion and perfusion values in the diffusion lesion in acute ischemic stroke.
  
  
  METHODS
  We recruited patients with acute ischemic stroke prospectively and performed MR diffusion weighted (DWI), perfusion, and spectroscopic imaging. We coregistered the images, outlined the visible diffusion lesion, and extracted metabolite, perfusion, and apparent diffusion coefficient (ADC) values from the diffusion lesion.
  
  
  RESULTS
  42 patients were imaged, from 1.5 to 24 hours after stroke. In the DWI lesion, although NAA was reduced, there was no correlation between NAA and ADC or perfusion values. However, raised lactate correlated with reduced ADC (Spearman rho=0.32, P=0.04) and prolonged mean transit time (MTT, rho=0.31, P=0.04). Increasing DWI lesion size was associated with lower NAA and higher lactate (rho=-0.44, P=0.003; rho=0.49, P=0.001 respectively); NAA fell with increasing times to imaging (rho=-0.3, P=0.03), but lactate did not change.
  
  
  CONCLUSIONS
  Although larger confirmatory studies are needed, the correlation of ADC and MTT with lactate but not NAA suggests that ADC and MTT are better markers of the presence of ischemia than of cumulative neuronal loss. Further studies should define more precisely the rate of neuronal loss and relationship to diffusion and perfusion parameters with respect to the depth and duration of ischemia.
authors.affiliation: Division of Clinical Neurosciences, University of Edinburgh, Western General Hospital, UK.
authors.forename: Vera
authors.initials: V
authors.lastname: Cvoro
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Wardlaw
authors.forename: Ian
authors.initials: I
authors.lastname: Marshall
authors.forename: Paul A
authors.initials: PA
authors.lastname: Armitage
authors.forename: Carly S
authors.initials: CS
authors.lastname: Rivers
authors.forename: Mark E
authors.initials: ME
authors.lastname: Bastin
authors.forename: Trevor K
authors.initials: TK
authors.lastname: Carpenter
authors.forename: Karolina
authors.initials: K
authors.lastname: Wartolowska
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Farrall
authors.forename: Martin S
authors.initials: MS
authors.lastname: Dennis
mesh_terms: D000208:Acute Disease; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D002545:Brain Ischemia / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D016923:Cell Death; D002560:Cerebrovascular Circulation / Q000502:physiology*; D038524:Diffusion Magnetic Resonance Imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019344:Lactic Acid / Q000378:metabolism*; D016014:Linear Models; D011446:Prospective Studies; D020521:Stroke / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology
chemical_list: D001224:Aspartic Acid; D019344:Lactic Acid; C000179:N-acetylaspartate