title: Color-coded cerebral computed tomographic angiography: implementation of a convolution-based algorithm and first clinical evaluation in patients with acute ischemic stroke.
abstract: OBJECTIVE
  The objective of this study was to develop a new method of displaying dynamic cerebral computed tomographic (CT) angiography (CTA) data sets in which the time delay to maximum enhancement (Tdelay) is displayed in a range of colors (color-coded CT angiography [cCTA]).
  
  
  METHODS
  This institutional review board-approved study included multiparametric CT data sets from 16 patients with different types of supra-aortic large vessel occlusions. Color-coded CT angiography was reconstructed from CT perfusion raw data sets. All voxel enhancement curves were fitted to f(t) = α · AIFmtt(t - Δt), with AIFmtt(t), indicating enhancement of AIF dilated by convolution with boxcar function (with mean transit time [mtt]); α, scaling factor; and [INCREMENT]t, transition along the time. The time delay to maximum enhancement was defined as Tdelay = Δt +0.5 · mtt. Values of Tdelay were color-coded and superimposed on temporal maximum intensity projections CTA resulting in colored angiographic composite images. For a pilot clinical evaluation, diagnostic confidence in determining the pathology, quality of the visualization of leptomeningeal collaterals, and additional diagnostic information were assessed.
  
  
  RESULTS
  The reconstruction of cCTA was technically feasible in all 16 patients. Both diagnostic confidence (P < 0.01) and the quality of the visualization of collaterals (P < 0.0001) were significantly higher when using the combination of single-phase CTA and cCTA compared with single-phase CTA alone. Additional diagnostic information was obtained with cCTA regarding occlusion type (reader 1: 5 cases and reader 2: 4 cases), differentiation between arteries and veins (11/13), differentiation between antegrade and retrograde filling (12/13), as well as leptomeningeal collateralization (13/14).
  
  
  CONCLUSIONS
  Color-coded CT angiography is a technically feasible technique that provides additional information on cerebral hemodynamics in ischemic stroke patients.
authors.affiliation: From the *Institute for Clinical Radiology, †Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, Departments of ‡Neurology, and §Neuroradiology, Ludwig Maximilians University Hospital Munich; and ∥Siemens AG, Healthcare Sector, Erlangen, Germany.
authors.forename: Kolja M
authors.initials: KM
authors.lastname: Thierfelder
authors.forename: Lukas
authors.initials: L
authors.lastname: Havla
authors.forename: Sebastian E
authors.initials: SE
authors.lastname: Beyer
authors.forename: Birgit
authors.initials: B
authors.lastname: Ertl-Wagner
authors.forename: Felix G
authors.initials: FG
authors.lastname: Meinel
authors.forename: Louisa
authors.initials: L
authors.lastname: von Baumgarten
authors.forename: Hendrik
authors.initials: H
authors.lastname: Janssen
authors.forename: Hendrik
authors.initials: H
authors.lastname: Ditt
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.forename: Wieland H
authors.initials: WH
authors.lastname: Sommer
mesh_terms: D000328:Adult; D000465:Algorithms; D002533:Cerebral Angiography / Q000379:methods*; D002536:Cerebral Arteries / Q000000981:diagnostic imaging*; D003116:Color; D005260:Female; D006801:Humans; D008297:Male; D010865:Pilot Projects; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D020521:Stroke / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*