title: Magnetic resonance perfusion-weighted imaging of acute cerebral infarction: effect of the calculation methods and underlying vasculopathy.
abstract: OBJECTIVE
  Various calculation methods are available to estimate the transit-time on MR perfusion-weighted imaging (PWI). Each method may affect the results of PWI. Steno-occlusive disease in the parent vessels is another factor that may affect the results of the PWI. The purpose of this study was to elucidate the effect of the calculation methods and underlying vasculopathy on PWI.
  
  
  METHODS
  From a pool of 113 patients who had undergone PWI during the study period, a total of 12 patients with nonlacunar ischemic strokes who were scanned within 24 hours after onset of symptom were selected for the study. The patient population consisted of 6 patients who had extracranial internal carotid artery stenosis (>70%) and 6 individuals without stenosis. Seven different postprocessing methods were evaluated: first moment, ratio of area to peak, time to peak (TTP), relative TTP, arrival time, full-width at half-maximum, and deconvolution methods. Follow-up MR or CT images were used to determine the areas that evolved into infarcts, which served as the gold standard. Sensitivity and specificity of each transit time technique were calculated.
  
  
  RESULTS
  Calculation methods with high sensitivity were the first moment (sensitivity, 74%), TTP (sensitivity, 77%), and deconvolution methods (sensitivity, 81% to 94%). Between the 2 groups with and without internal carotid artery stenosis, the specificity of most of the techniques was lower in the internal carotid artery stenosis group. The first moment and deconvolution methods maintained relatively high specificity even in the stenosis group.
  
  
  CONCLUSIONS
  The calculation technique and presence of underlying vasculopathy have a direct impact on the results of PWI. The methods with high sensitivity even in the presence of steno-occlusive disease were the first moment and deconvolution methods with arterial input function derived from the peri-infarct arteries; the deconvolution method was the superior choice because of higher lesion conspicuity.
authors.affiliation: Massachusetts General Hospital NMR Center, Harvard Medical School, Boston, USA. kyamada@koto.kpu-m.ac.jp
authors.forename: Kei
authors.initials: K
authors.lastname: Yamada
authors.forename: Ona
authors.initials: O
authors.lastname: Wu
authors.forename: R Gilberto
authors.initials: RG
authors.lastname: Gonzalez
authors.forename: Dirk
authors.initials: D
authors.lastname: Bakker
authors.forename: Leif
authors.initials: L
authors.lastname: Østergaard
authors.forename: William A
authors.initials: WA
authors.lastname: Copen
authors.forename: Robert M
authors.initials: RM
authors.lastname: Weisskoff
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Rosen
authors.forename: Katsumi
authors.initials: K
authors.lastname: Yagi
authors.forename: Tsunehiko
authors.initials: T
authors.lastname: Nishimura
authors.forename: A Gregory
authors.initials: AG
authors.lastname: Sorensen
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D002545:Brain Ischemia / Q000175:diagnosis; D016893:Carotid Stenosis / Q000175:diagnosis*; D002544:Cerebral Infarction / Q000175:diagnosis*; D003951:Diagnostic Errors; D004058:Diffusion; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007700:Kinetics; D008875:Middle Aged; D008962:Models, Theoretical; D010477:Perfusion; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D020521:Stroke / Q000175:diagnosis; D014057:Tomography, X-Ray Computed