title: The relative effect of vendor variability in CT perfusion results: a method comparison study.
abstract: OBJECTIVE
  There are known interoperator, intraoperator, and intervendor software differences that can influence the reproducibility of quantitative CT perfusion values. The purpose of this study was to determine the relative impact of operator and software differences in CT perfusion variability.
  
  
  METHODS
  CT perfusion imaging data were selected for 11 patients evaluated for suspected ischemic stroke. Three radiologists each independently postprocessed the source data twice, using four different vendor software applications. Results for cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) were recorded for the lentiform nuclei in both hemispheres. Repeated variables multivariate analysis of variance was used to assess differences in the means of CBV, CBF, and MTT. Bland-Altman analysis was used to assess agreement between pairs of vendors, readers, and read times.
  
  
  RESULTS
  Choice of vendor software, but not interoperator or intraoperator disagreement, was associated with significant variability (p < 0.001) in CBV, CBF, and MTT. The mean difference in CT perfusion values was greater for pairs of vendors than for pairs of operators.
  
  
  CONCLUSIONS
  Different vendor software applications do not generate quantitative perfusion results equivalently. Intervendor difference is, by far, the largest cause of variability in perfusion results relative to interoperator and intraoperator difference. Caution should be exercised when interpreting quantitative CT perfusion results because these values may vary considerably depending on the postprocessing software.
authors.affiliation: Department of Radiology, Thomas Jefferson University Hospital, Ste 1080B, Main Bldg, 132 S Tenth St, Philadelphia, PA 19107-5244, USA.
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Zussman
authors.forename: Garen
authors.initials: G
authors.lastname: Boghosian
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Gorniak
authors.forename: Mark E
authors.initials: ME
authors.lastname: Olszewski
authors.forename: Katrina M
authors.initials: KM
authors.lastname: Read
authors.forename: Khan M
authors.initials: KM
authors.lastname: Siddiqui
authors.forename: Adam E
authors.initials: AE
authors.lastname: Flanders
mesh_terms: D000704:Analysis of Variance; D001810:Blood Volume; D002560:Cerebrovascular Circulation; D006801:Humans; D015588:Observer Variation; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012984:Software; D020521:Stroke / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods*