title: CT angiography source images acquired with a fast-acquisition protocol overestimate infarct core on diffusion weighted images in acute ischemic stroke.
abstract: OBJECTIVE
  Studies have demonstrated that computed tomography (CT) angiography source images (CTA-SI) acquired under near-steady-state contrast concentration provide infarct core estimates equivalent to diffusion-weighted images (DWI). We sought to test this relationship using our current CTA protocol optimized for faster scan acquisition.
  
  
  METHODS
  Forty-eight consecutive acute ischemic stroke patients met the following criteria: fast-acquisition CTA and magnetic resonance imaging (MRI) within 9 hours of symptom onset, CTA-to-MRI interval under 2 hours, and anterior circulation vessel occlusion. Collaterals were graded on CTA, and lesion volumes were calculated on CTA-SI, DWI, and MR mean transit time (MTT) maps.
  
  
  RESULTS
  The mean CTA-to-MRI interval was 36 minutes (± 18 minutes). In paired analysis, lesion volumes on CTA-SI were significantly larger than on DWI (45.6 cm3 vs. 29.9 cm3; P < .0001). In 14 (29.2%) cases, there was major CTA-SI overestimation (>25 cm3 difference) of the DWI lesion. Lower collateral score (P = .001), higher National Institutes of Health stroke scale (NIHSS) score (P = .01), older age (P = .01), and proximal occlusion (P < .05) were univariate predictors of major overestimation, with collateral score being the only independent predictor. The interobserver agreement was worse for CTA-SI than for DWI (P < .001 for limits of agreement).
  
  
  CONCLUSIONS
  CTA-SI performed using a fast-acquisition protocol overestimates the infarct core on DWI. Substantial differences are observed in over 25% of cases, and are associated with reduced collateralization.
authors.affiliation: Division of Neuroradiology, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA. ajyoo@partners.org
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Yoo
authors.forename: Ranliang
authors.initials: R
authors.lastname: Hu
authors.forename: Reza
authors.initials: R
authors.lastname: Hakimelahi
authors.forename: Michael H
authors.initials: MH
authors.lastname: Lev
authors.forename: Raul G
authors.initials: RG
authors.lastname: Nogueira
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Hirsch
authors.forename: R Gilberto
authors.initials: RG
authors.lastname: González
authors.forename: Pamela W
authors.initials: PW
authors.lastname: Schaefer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000175:diagnosis* / Q000000981:diagnostic imaging; D002533:Cerebral Angiography / Q000379:methods*; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007479:Iopamidol; D008297:Male; D020521:Stroke / Q000175:diagnosis* / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007479:Iopamidol; D019786:Gadolinium DTPA