title: Reproducibility of measurements of cerebral infarct volume on CT scans.
abstract: OBJECTIVE
  Infarct volume is increasingly used as an outcome measure in clinical trials of therapies for acute ischemic stroke. We tested which of 5 different methods to measure infarct size or volume on CT scans has the highest reproducibility.
  
  
  METHODS
  Infarct volume and total intracranial volume were measured with Leica Q500 MCP image analysis software, or with a caliper, on 38 CT scans of patients who participated in the Tirilazad Efficacy Stroke Study II (TESS II). The scans were performed 8 days (+/-2 days) after the onset of symptoms. The 5 methods tested were based on (1) semiautomated pixel thresholding, (2) manual tracing of the perimeter, (3) a stereological counting grid, (4) measurement of the 3 largest diameters, and (5) the single largest diameter. The measurements were performed independently by 2 observers; the first observer performed all measurements twice.
  
  
  RESULTS
  The single largest diameter did not correlate well with infarct volume. Of the other methods, manual tracing of the perimeter of the infarct had the lowest intraobserver and interobserver variability: coefficients of variation were 8.6% and 14.1%, respectively. For total intracranial volume, manual tracing also provided the highest reproducibility: intraobserver and interobserver coefficients of variation were 3.3% and 4.9%, respectively.
  
  
  CONCLUSIONS
  Manual tracing of the perimeter is the most reproducible method for measuring the volumes of the infarct and the total intracranial space in multicenter trials of therapies for acute ischemic stroke.
authors.affiliation: Department of Neurology, University Medical Center, Utrecht, Netherlands. h.b.vandeworp@neuro.azu.nl
authors.forename: H B
authors.initials: HB
authors.lastname: van der Worp
authors.forename: S P
authors.initials: SP
authors.lastname: Claus
authors.forename: P R
authors.initials: PR
authors.lastname: Bär
authors.forename: L M
authors.initials: LM
authors.lastname: Ramos
authors.forename: A
authors.initials: A
authors.lastname: Algra
authors.forename: J
authors.initials: J
authors.lastname: van Gijn
authors.forename: L J
authors.initials: LJ
authors.lastname: Kappelle
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001315:Australia; D001921:Brain / Q000000981:diagnostic imaging*; D002138:Calibration; D002544:Cerebral Infarction / Q000150:complications / Q000000981:diagnostic imaging* / Q000188:drug therapy; D005060:Europe; D006801:Humans; D007262:Infusions, Intravenous; D008875:Middle Aged; D009520:New Zealand; D015588:Observer Variation; D011281:Pregnatrienes / Q000008:administration & dosage; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D020521:Stroke / Q000150:complications / Q000000981:diagnostic imaging* / Q000188:drug therapy; D013997:Time Factors; D014057:Tomography, X-Ray Computed
chemical_list: D011281:Pregnatrienes; C053355:tirilazad