title: Arterial input function placement for accurate CT perfusion map construction in acute stroke.
abstract: OBJECTIVE
  The objective of our study was to evaluate the effect of varying arterial input function (AIF) placement on the qualitative and quantitative CT perfusion parameters.
  
  
  METHODS
  Retrospective analysis of CT perfusion data was performed on 14 acute stroke patients with a proximal middle cerebral artery (MCA) clot. Cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) maps were constructed using a systematic method by varying only the AIF placement in four positions relative to the MCA clot including proximal and distal to the clot in the ipsilateral and contralateral hemispheres. Two postprocessing software programs were used to evaluate the effect of AIF placement on perfusion parameters using a delay-insensitive deconvolution method compared with a standard deconvolution method.
  
  
  RESULTS
  One hundred sixty-eight CT perfusion maps were constructed for each software package. Both software programs generated a mean CBF at the infarct core of < 12 mL/100 g/min and a mean CBV of < 2 mL/100 g for AIF placement proximal to the clot in the ipsilateral hemisphere and proximal and distal to the clot in the contralateral hemisphere. For AIF placement distal to the clot in the ipsilateral hemisphere, the mean CBF significantly increased to 17.3 mL/100 g/min with delay-insensitive software and to 19.4 mL/100 g/min with standard software (p < 0.05). The mean MTT was significantly decreased for this AIF position. Furthermore, this AIF position yielded qualitatively different parametric maps, being most pronounced with MTT and CBF. Overall, CBV was least affected by AIF location.
  
  
  CONCLUSIONS
  For postprocessing of accurate quantitative CT perfusion maps, laterality of the AIF location is less important than avoiding AIF placement distal to the clot as detected on CT angiography. This pitfall is less severe with deconvolution-based software programs using a delay-insensitive technique than with those using a standard deconvolution method.
authors.affiliation: Department of Radiology, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Rafael M
authors.initials: RM
authors.lastname: Ferreira
authors.forename: Michael H
authors.initials: MH
authors.lastname: Lev
authors.forename: Gregory V
authors.initials: GV
authors.lastname: Goldmakher
authors.forename: Shahmir
authors.initials: S
authors.lastname: Kamalian
authors.forename: Pamela W
authors.initials: PW
authors.lastname: Schaefer
authors.forename: Karen L
authors.initials: KL
authors.lastname: Furie
authors.forename: R Gilberto
authors.initials: RG
authors.lastname: Gonzalez
authors.forename: Pina C
authors.initials: PC
authors.lastname: Sanelli
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002533:Cerebral Angiography / Q000379:methods*; D005260:Female; D006801:Humans; D020244:Infarction, Middle Cerebral Artery / Q000150:complications / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D020521:Stroke / Q000000981:diagnostic imaging* / Q000209:etiology*; D014057:Tomography, X-Ray Computed / Q000379:methods*
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