title: Comparison of computed tomographic and magnetic resonance perfusion measurements in acute ischemic stroke: back-to-back quantitative analysis.
abstract: OBJECTIVE
  Magnetic resonance perfusion (MRP) and computed tomographic perfusion (CTP) are being increasingly applied in acute stroke trials and clinical practice, yet the comparability of their perfusion values is not well validated. The aim of this study was to validate the comparability of CTP and MRP measures.
  
  
  METHODS
  A 3-step approach was used. Step 1 was a derivation step, where we analyzed 45 patients with acute ischemic stroke who had both CTP and MRP performed within 2 hours of each other and within 9 hours of stroke onset. In this step, we derived the optimal perfusion map with the least difference between MRP and CTP. In step 2, the optimal map was validated on whole-brain perfusion data of 15 patients. Step 3 was to apply the optimal perfusion map to define cross-modality reperfusion from acute CTP to 24-hour MRP in 45 patients and, in turn, to assess how accurately this predicted 3-month clinical outcome.
  
  
  RESULTS
  Among 8 different perfusion maps included in this study, time to peak of the residual function (T(max)) was the only one with a nonsignificant difference between CTP and MRP in delineating perfusion defects. This was validated on whole-brain perfusion data, showing high concordance of T(max) between the 2 modalities (concordance correlation coefficient of Lin, >0.91); the best concordance was at 6 s. At T(max)>6 s threshold, MRP and CTP reached substantial agreement in mismatch classification (κ >0.61). Cross-modality reperfusion calculated by T(max)>6 s strongly predicted good functional outcome at 3 months (area under the curve, 0.979; P<0.05).
  
  
  CONCLUSIONS
  MRP and CTP can be used interchangeably if one uses T(max) measurement.
authors.affiliation: From the Stroke Research Program, Hunter Medical Research Institute (L.L., A.B., C.R.L., M.W.P.) and Department of Neurology, John Hunter Hospital (C.R.L., M.W.P.), The University of Newcastle, Newcastle, New South Wales, Australia.
authors.forename: Longting
authors.initials: L
authors.lastname: Lin
authors.affiliation: From the Stroke Research Program, Hunter Medical Research Institute (L.L., A.B., C.R.L., M.W.P.) and Department of Neurology, John Hunter Hospital (C.R.L., M.W.P.), The University of Newcastle, Newcastle, New South Wales, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Bivard
authors.affiliation: From the Stroke Research Program, Hunter Medical Research Institute (L.L., A.B., C.R.L., M.W.P.) and Department of Neurology, John Hunter Hospital (C.R.L., M.W.P.), The University of Newcastle, Newcastle, New South Wales, Australia.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Levi
authors.affiliation: From the Stroke Research Program, Hunter Medical Research Institute (L.L., A.B., C.R.L., M.W.P.) and Department of Neurology, John Hunter Hospital (C.R.L., M.W.P.), The University of Newcastle, Newcastle, New South Wales, Australia. mark.parsons@hnehealth.nsw.gov.au.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Parsons
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002533:Cerebral Angiography; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography; D008875:Middle Aged; D012189:Retrospective Studies; D020521:Stroke / Q000000981:diagnostic imaging* / Q000503:physiopathology; D013997:Time Factors; D014057:Tomography, X-Ray Computed
keywords: perfusion imaging; reperfusion; stroke