title: Automated analysis of perfusion weighted MRI using asymmetry in vascular territories.
abstract: OBJECTIVE
  To determine the feasibility of automatic vascular territory region of interest (ROI) construction as a method for standardized quantification of cerebral blood flow (CBF) images.
  
  
  METHODS
  An algorithm for automatic construction of vascular territory ROIs was performed on 10 healthy controls and 25 patients with perfusion abnormalities identified by retrospective chart review. The ROIs were used to quantify perfusion asymmetry for each territory, and perfusion asymmetry was compared in the two cohorts and against blinded neuroradiologist interpretation. The algorithm was additionally applied to a separate cohort of 23 prospectively enrolled patients and perfusion asymmetry was correlated against clinical variables.
  
  
  RESULTS
  There was significantly greater perfusion asymmetry in territories graded by neuroradiologists as hypoperfused compared to those graded as normally perfused (p<.05) and compared to healthy volunteers (p<.01). An ROC analysis showed that perfusion asymmetry was sensitive and specific for identifying hypoperfusion in vascular territories (84.9% sensitivity and 90.5% specificity for a threshold asymmetry index of .829). In the prospective cohort, perfusion asymmetry was correlated with initial NIH stroke scale (NIHSS) (p<.01) and length of stay (p<.05).
  
  
  CONCLUSIONS
  Automatic construction of vascular territory ROIs and calculation of perfusion asymmetry is a feasible method for analyzing CBF images. Because the technique is rapid and minimizes bias, it can facilitate analysis of larger scale research studies.
authors.affiliation: Department of Radiology, Northwestern University Feinberg School of Medicine, 737N Michigan Suite 1600, Chicago, IL, USA.
authors.forename: Neil R
authors.initials: NR
authors.lastname: Chatterjee
authors.affiliation: Department of Radiology, Northwestern University Feinberg School of Medicine, 737N Michigan Suite 1600, Chicago, IL, USA.
authors.forename: Sameer A
authors.initials: SA
authors.lastname: Ansari
authors.affiliation: Department of Radiology, Northwestern University Feinberg School of Medicine, 737N Michigan Suite 1600, Chicago, IL, USA.
authors.forename: Parmede
authors.initials: P
authors.lastname: Vakil
authors.affiliation: Department of Neurology, Northwestern University Feinberg School of Medicine, Abbott Hall Suite 1123, 710 N Lake Shore Drive, Chicago, IL, USA.
authors.forename: Shyam
authors.initials: S
authors.lastname: Prabhakaran
authors.affiliation: Department of Radiology, Northwestern University Feinberg School of Medicine, 737N Michigan Suite 1600, Chicago, IL, USA. Electronic address: t-carroll@northwestern.edu.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Carroll
authors.affiliation: Department of Radiology, Northwestern University Feinberg School of Medicine, 737N Michigan Suite 1600, Chicago, IL, USA.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Hurley
mesh_terms: D000465:Algorithms; D002560:Cerebrovascular Circulation / Q000502:physiology*; D015331:Cohort Studies; D005240:Feasibility Studies; D006801:Humans; D018810:Magnetic Resonance Angiography; D015588:Observer Variation; D011446:Prospective Studies; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D020521:Stroke / Q000175:diagnosis* / Q000503:physiopathology*
keywords: Cerebral blood flow; Image analysis; Perfusion weighted MRI; Stroke