title: Utilizing dual energy CT to improve CT diagnosis of posterior fossa ischemia.
abstract: OBJECTIVE
  Evaluation of posterior fossa ischemia on conventional CT is limited. The goal of our study was to determine if virtual monochromatic CT increases the diagnostic accuracy for the detection of posterior infarcts relative to standard CT while using diffusion-weighted MRI as a reference standard.
  
  
  METHODS
  Thirty consecutive subjects who meet the following inclusion criteria were retrospectively enrolled: (1) symptoms of posterior fossa stroke (e.g. vertigo, fainting, and dizziness), (2) unenhanced dual-energy CT of the head performed upon admission to the emergency department, and (3) MRI of the brain within 7 days following the CT. Eight of the 30 subjects were determined to have MRI diffusion-weighted imaging findings consistent with acute posterior fossa ischemia. Monochromatic energy reconstructions at 60, 80, 100, 120keV and the clinical CT were interpreted independently by two fellowship-trained neuroradiologists, who assessed the images for posterior fossa infarcts and for imaging quality.
  
  
  RESULTS
  Reconstructions obtained at 80keV provided the best artifact reduction and overall maximization of image quality and were statistically significantly better than standard head CT (P<0.001). Sensitivity, specificity, positive predictive value, and negative predictive value were at least not less than standard CT, and there was a trend toward better values at 100keV (P=0.096).
  
  
  CONCLUSIONS
  Monoenergetic 80 or 100keV reconstructions may improve the detection of posterior fossa ischemia compared to conventional CT. However, if clinical suspicion for posterior fossa ischemia warrants, a brain MRI with diffusion-weighted imaging should still be obtained, even in the presence of a negative dual energy CT of the brain.
authors.affiliation: Department of radiology, university of Virginia, Charlottesville, VA, United States.
authors.forename: H R
authors.initials: HR
authors.lastname: Hixson
authors.affiliation: Department of radiology, university of Virginia, Charlottesville, VA, United States.
authors.forename: C
authors.initials: C
authors.lastname: Leiva-Salinas
authors.affiliation: Department of radiology, university of Virginia, Charlottesville, VA, United States.
authors.forename: S
authors.initials: S
authors.lastname: Sumer
authors.affiliation: Department of biostatistics, university of Virginia, Charlottesville, VA, United States.
authors.forename: J
authors.initials: J
authors.lastname: Patrie
authors.affiliation: Department of biostatistics, university of Virginia, Charlottesville, VA, United States.
authors.forename: W
authors.initials: W
authors.lastname: Xin
authors.affiliation: Department of radiology, neuroradiology section, Stanford university, Stanford, California, Canada. Electronic address: max.wintermark@gmail.com.
authors.forename: M
authors.initials: M
authors.lastname: Wintermark
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D001921:Brain / Q000000981:diagnostic imaging*; D002545:Brain Ischemia / Q000000981:diagnostic imaging*; D003388:Cranial Fossa, Posterior / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult
keywords: CT; DWI; Dual-energy CT; MRI; Posterior fossa; Stroke