title: Usefulness of z-score mapping for quantification of extent of hypoattenuation regions of hyperacute stroke in unenhanced computed tomography: analysis of radiologists' performance.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the usefulness of z-score mapping method on neuroradiologists' performance in quantification of the extent of hypoattenuation regions of hyperacute stroke on unenhanced computed tomographic (CT) images by using the Alberta Stroke Programme Early CT Score system.
  
  
  METHODS
  Twenty-one patients with infarction (<3 hours) were retrospectively selected. Five neuroradiologists interpreted CT images first without and then with z-score maps by using the Alberta Stroke Programme Early CT Score system. Their performances in the quantification of the extent of hypoattenuation were compared.
  
  
  RESULTS
  Average accuracies for the quantification without and with the z-score maps were 82.6% and 86.6%, respectively (P < 0.0001). The average area under the receiver operating characteristic curve for detection of focal hypoattenuation significantly increased from 0.883 to 0.925 (P = 0.01) by use of z-score maps.
  
  
  CONCLUSIONS
  The use of z-score mapping method has the potential to help neuroradiologists quantify the extent of hypoattenuation regions of hyperacute stroke on unenhanced CT images.
authors.affiliation: Department of Radiological Technology, Graduate School of Health Sciences, Niigata University, Niigata, Niigata, Japan. kiyurino1189@happy.odn.ne.jp
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Takahashi
authors.forename: Du-Yih
authors.initials: DY
authors.lastname: Tsai
authors.forename: Yongbum
authors.initials: Y
authors.lastname: Lee
authors.forename: Toshibumi
authors.initials: T
authors.lastname: Kinoshita
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Ishii
authors.forename: Hajime
authors.initials: H
authors.lastname: Tamura
authors.forename: Shoki
authors.initials: S
authors.lastname: Takahashi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002983:Clinical Competence; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D020521:Stroke / Q000000981:diagnostic imaging* / Q000473:pathology; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*