title: Variability in the measurement of minimum fibrous cap thickness and reproducibility of fibroatheroma classification by optical coherence tomography using manual versus semi-automatic assessment.
abstract: OBJECTIVE
  The minimum fibrous cap thickness (FCT) is considered a major criterion of coronary plaque vulnerability according to autopsy studies. We aimed to assess the reproducibility in the measurement of the optical coherence tomography (OCT)-detected minimum FCT and the agreement in the classification of thin-cap fibroatheroma (TCFA), by a software-based semi-automatic method compared with the manual method.
  
  
  RESULTS
  A total of 50 frames with fibroatheromas (FA) were randomly selected from the Integrated Biomarker Imaging Study-4 (IBIS-4). Two experienced OCT analysts independently measured the minimum FCT at two different time points, manually and by three different semi-automatic software-based algorithms, based on the assessment of light intensity along the axial scan line. A TCFA was defined as an FA with minimum FCT <65 μm. The inter- and intra-observer reproducibility of the manual measurement of the minimum FCT was moderate with an intra-class correlation coefficient (ICC) of 0.71 and 0.79, respectively. The corresponding ICCs by either one of the three semi-automatic algorithms were 0.99. When categorising FA according to the minimum FCT based on the manual assessment, the inter- and intra-observer agreement was poor (κ=0.23) and moderate (κ=0.50), respectively. In contrast, the semi-automatic assessment showed perfect agreement for both inter- and intra-observer assessments (κ=0.90-1.00 and 1.00, respectively).
  
  
  CONCLUSIONS
  While semi-automatic assessment of FCT and TCFA classification was associated with excellent reproducibility and agreement, manual measurements were associated with a moderate reproducibility and agreement in the quantification of FCT and classification of TCFA.
authors.affiliation: Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Maria D
authors.initials: MD
authors.lastname: Radu
authors.forename: Kyohei
authors.initials: K
authors.lastname: Yamaji
authors.forename: Hector M
authors.initials: HM
authors.lastname: García-García
authors.forename: Serge
authors.initials: S
authors.lastname: Zaugg
authors.forename: Masanori
authors.initials: M
authors.lastname: Taniwaki
authors.forename: Konstantinos C
authors.initials: KC
authors.lastname: Koskinas
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Serruys
authors.forename: Stephan
authors.initials: S
authors.lastname: Windecker
authors.forename: Jouke
authors.initials: J
authors.lastname: Dijkstra
authors.forename: Lorenz
authors.initials: L
authors.lastname: Räber
mesh_terms: D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D015588:Observer Variation; D058226:Plaque, Atherosclerotic / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence