title: DWI intensity values predict FLAIR lesions in acute ischemic stroke.
abstract: OBJECTIVE
  In acute stroke, the DWI-FLAIR mismatch allows for the allocation of patients to the thrombolysis window (<4.5 hours). FLAIR-lesions, however, may be challenging to assess. In comparison, DWI may be a useful bio-marker owing to high lesion contrast. We investigated the performance of a relative DWI signal intensity (rSI) threshold to predict the presence of FLAIR-lesions in acute stroke and analyzed its association with time-from-stroke-onset.
  
  
  METHODS
  In a retrospective, dual-center MR-imaging study we included patients with acute stroke and time-from-stroke-onset ≤12 hours (group A: n = 49, 1.5T; group B: n = 48, 3T). DW- and FLAIR-images were coregistered. The largest lesion extent in DWI defined the slice for further analysis. FLAIR-lesions were identified by 3 raters, delineated as regions-of-interest (ROIs) and copied on the DW-images. Circular ROIs were placed within the DWI-lesion and labeled according to the FLAIR-pattern (FLAIR+ or FLAIR-). ROI-values were normalized to the unaffected hemisphere. Adjusted and nonadjusted receiver-operating-characteristics (ROC) curve analysis on patient level was performed to analyze the ability of a DWI- and ADC-rSI threshold to predict the presence of FLAIR-lesions. Spearman correlation and adjusted linear regression analysis was performed to assess the relationship between DWI-intensity and time-from-stroke-onset.
  
  
  RESULTS
  DWI-rSI performed well in predicting lesions in FLAIR-imaging (mean area under the curve (AUC): group A: 0.84; group B: 0.85). An optimal mean DWI-rSI threshold was identified (A: 162%; B: 161%). ADC-maps performed worse (mean AUC: A: 0.58; B: 0.77). Adjusted regression models confirmed the superior performance of DWI-rSI. Correlation coefficents and linear regression showed a good association with time-from-stroke-onset for DWI-rSI, but not for ADC-rSI.
  
  
  CONCLUSIONS
  An easily assessable DWI-rSI threshold identifies the presence of lesions in FLAIR-imaging with good accuracy and is associated with time-from-stroke-onset in acute stroke. This finding underlines the potential of a DWI-rSI threshold as a marker of lesion age.
authors.affiliation: Center for Stroke Research Berlin (CSB), Charité-Universitätsmedizin, Berlin, Germany; Department of Neurology, Charité-Universtitätsmedizin, Berlin, Germany.
authors.forename: Vince I
authors.initials: VI
authors.lastname: Madai
authors.affiliation: Center for Stroke Research Berlin (CSB), Charité-Universitätsmedizin, Berlin, Germany.
authors.forename: Ivana
authors.initials: I
authors.lastname: Galinovic
authors.affiliation: Center for Stroke Research Berlin (CSB), Charité-Universitätsmedizin, Berlin, Germany; Department for Biostatistics and Clinical Epidemiology, Charité-Universitätsmedizin, Berlin, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Grittner
authors.affiliation: Center for Stroke Research Berlin (CSB), Charité-Universitätsmedizin, Berlin, Germany; Max-Planck-Institute for Neurological Research, Cologne, Germany.
authors.forename: Olivier
authors.initials: O
authors.lastname: Zaro-Weber
authors.affiliation: Center for Stroke Research Berlin (CSB), Charité-Universitätsmedizin, Berlin, Germany; Department for Biostatistics and Clinical Epidemiology, Charité-Universitätsmedizin, Berlin, Germany.
authors.forename: Alice
authors.initials: A
authors.lastname: Schneider
authors.affiliation: Center for Stroke Research Berlin (CSB), Charité-Universitätsmedizin, Berlin, Germany.
authors.forename: Steve Z
authors.initials: SZ
authors.lastname: Martin
authors.affiliation: Center for Stroke Research Berlin (CSB), Charité-Universitätsmedizin, Berlin, Germany; Fraunhofer MEVIS, Bremen, Germany.
authors.forename: Federico C
authors.initials: FC
authors.lastname: von Samson-Himmelstjerna
authors.affiliation: Center for Stroke Research Berlin (CSB), Charité-Universitätsmedizin, Berlin, Germany; Department of Neurology, Charité-Universtitätsmedizin, Berlin, Germany.
authors.forename: Katharina L
authors.initials: KL
authors.lastname: Stengl
authors.affiliation: Center for Stroke Research Berlin (CSB), Charité-Universitätsmedizin, Berlin, Germany; Department of Neurology, Charité-Universtitätsmedizin, Berlin, Germany.
authors.forename: Matthias A
authors.initials: MA
authors.lastname: Mutke
authors.affiliation: Department of Radiology, Krankenhaus Ludmillenstift, Meppen, Germany.
authors.forename: Walter
authors.initials: W
authors.lastname: Moeller-Hartmann
authors.affiliation: Center for Stroke Research Berlin (CSB), Charité-Universitätsmedizin, Berlin, Germany; Department of Neurology, Charité-Universtitätsmedizin, Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Ebinger
authors.affiliation: Center for Stroke Research Berlin (CSB), Charité-Universitätsmedizin, Berlin, Germany.
authors.forename: Jochen B
authors.initials: JB
authors.lastname: Fiebach
authors.affiliation: Center for Stroke Research Berlin (CSB), Charité-Universitätsmedizin, Berlin, Germany; Department of Neurology, Charité-Universtitätsmedizin, Berlin, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Sobesky
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D020521:Stroke / Q000175:diagnosis*; D013997:Time Factors