title: Quantitative assessment of the ischemic brain by means of perfusion-related parameters derived from perfusion CT.
abstract: OBJECTIVE
  Besides the delineation of hypoperfused brain tissue, the characterization of ischemia with respect to severity is of major clinical relevance, because the degree of hypoperfusion is the most critical factor in determining whether an ischemic lesion becomes an infarct or represents viable brain tissue. CT perfusion imaging yields a set of perfusion related parameters which might be useful to describe the hemodynamic status of the ischemic brain. Our objective was to determine whether measurements of the relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV), and relative time to peak (rTP) can be used to differentiate areas undergoing infarction from reversible ischemic tissue.
  
  
  METHODS
  In 34 patients with acute hemispheric ischemic stroke <6 hours after onset, perfusion CT was used to calculate rCBF, rCBV, and rTP values from areas of ischemic cortical and subcortical gray matter. Results were obtained separately from areas of infarction and noninfarction, according to the findings on follow-up imaging studies. The efficiency of each parameter to predict tissue outcome was tested.
  
  
  RESULTS
  There was a significant difference between infarct and peri-infarct tissue for both rCBF and rCBV but not for rTP. Threshold values of 0.48 and 0.60 for rCBF and rCBV, respectively, were found to discriminate best between areas of infarction and noninfarction, with the efficiency of the rCBV being slightly superior to that of rCBF. The prediction of tissue outcome could not be increased by using a combination of various perfusion parameters.
  
  
  CONCLUSIONS
  The assessment of cerebral ischemia by means of perfusion parameters derived from perfusion CT provides valuable information to predict tissue outcome. Quantitative analyses of the severity of ischemic lesions should be implemented into the diagnostic management of stroke patients.
authors.affiliation: Departments of Radiology and Nuclear Medicine, Ruhr-University Bochum, Germany. matthias.koenig@ruhr-uni-bochum.de
authors.forename: M
authors.initials: M
authors.lastname: Koenig
authors.forename: M
authors.initials: M
authors.lastname: Kraus
authors.forename: C
authors.initials: C
authors.lastname: Theek
authors.forename: E
authors.initials: E
authors.lastname: Klotz
authors.forename: W
authors.initials: W
authors.lastname: Gehlen
authors.forename: L
authors.initials: L
authors.lastname: Heuser
mesh_terms: D000368:Aged; D001783:Blood Flow Velocity; D001810:Blood Volume; D001921:Brain / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000473:pathology; D002545:Brain Ischemia / Q000175:diagnosis* / Q000628:therapy; D002404:Catheterization; D002560:Cerebrovascular Circulation; D003287:Contrast Media / Q000493:pharmacokinetics; D016002:Discriminant Analysis; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D015912:Thrombolytic Therapy; D010959:Tissue Plasminogen Activator / Q000008:administration & dosage; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media; D010959:Tissue Plasminogen Activator