title: Accuracy of Non-Enhanced CT in Detecting Early Ischemic Edema Using Frequency Selective Non-Linear Blending.
abstract: OBJECTIVE
  Ischemic brain edema is subtle and hard to detect by computed tomography within the first hours of stroke onset. We hypothesize that non-enhanced CT (NECT) post-processing with frequency-selective non-linear blending ("best contrast"/BC) increases its accuracy in detecting edema and irreversible tissue damage (infarction).
  
  
  METHODS
  We retrospectively analyzed the NECT scans of 76 consecutive patients with ischemic stroke (exclusively middle cerebral artery territory-MCA) before and after post-processing with BC both at baseline before reperfusion therapy and at follow-up (5.73±12.74 days after stroke onset) using the Alberta Stroke Program Early CT Score (ASPECTS). We assessed the differences in ASPECTS between unprocessed and post-processed images and calculated sensitivity, specificity, and predictive values of baseline NECT using follow-up CT serving as reference standard for brain infarction.
  
  
  RESULTS
  NECT detected brain tissue hypoattenuation in 35 of 76 patients (46.1%). This number increased to 71 patients (93.4%) after post-processing with BC. Follow-up NECT confirmed brain infarctions in 65 patients (85.5%; p = 0.012). Post-processing increased the sensitivity of NECT for brain infarction from 35/65 (54%) to 65/65 (100%), decreased its specificity from 11/11 (100%) to 7/11 (64%), its positive predictive value (PPV) from 35/35 (100%) to 65/69 (94%) and increased its accuracy 46/76 (61%) to 72/76 (95%).
  
  
  CONCLUSIONS
  This post-hoc analysis suggests that post-processing of NECT with BC may increase its sensitivity for ischemic brain damage significantly.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Eberhard Karls-University Tuebingen, D-72076, Tuebingen, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Bier
authors.affiliation: Department of Diagnostic and Interventional Radiology, Eberhard Karls-University Tuebingen, D-72076, Tuebingen, Germany.
authors.forename: Malte N
authors.initials: MN
authors.lastname: Bongers
authors.affiliation: Siemens AG Healthcare, Imaging & Therapy Systems Computed Tomography & Radiation Oncology, Siemensstr. 1, D-91301, Forchheim, Germany.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Ditt
authors.affiliation: Department of Neuroradiology, Eberhard Karls-University Tuebingen, D-72076, Tuebingen, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Bender
authors.affiliation: Department of Neuroradiology, Eberhard Karls-University Tuebingen, D-72076, Tuebingen, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Ernemann
authors.affiliation: Department of Diagnostic and Interventional Radiology, Eberhard Karls-University Tuebingen, D-72076, Tuebingen, Germany.
authors.forename: Marius
authors.initials: M
authors.lastname: Horger
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001929:Brain Edema / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D020521:Stroke / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000592:standards*
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