title: A hybrid plaque characterization method using intravascular ultrasound images.
abstract: BACKGROUND
  Intravascular ultrasound (IVUS) is an invasive imaging modality that provides high resolution cross-sectional images permitting detailed evaluation of the lumen, outer vessel wall and plaque morphology and evaluation of its composition. Over the last years several methodologies have been proposed which allow automated processing of the IVUS data and reliable segmentation of the regions of interest or characterization of the type of the plaque.
  
  
  OBJECTIVE
  In this paper we present a novel methodology for the automated identification of different plaque components in grayscale IVUS images.
  
  
  METHODS
  The proposed method is based on a hybrid approach that incorporates both image processing techniques and classification algorithms and allows classification of the plaque into three different categories: Hard Calcified, Hard-Non Calcified and Soft plaque. Annotations by two experts on 8 IVUS examinations were used to train and test our method.
  
  
  RESULTS
  The combination of an automatic thresholding technique and active contours coupled with a Random Forest classifier provided reliable results with an overall classification accuracy of 86.14%.
  
  
  CONCLUSIONS
  The proposed method can accurately detect the plaque using grayscale IVUS images and can be used to assess plaque composition for both clinical and research purposes.
authors.affiliation: Unit of Medical Technology and Intelligent Information Systems, Department of Materials Science and Engineering, University of Ioannina, Ioannina, Greece.
authors.forename: Lambros S
authors.initials: LS
authors.lastname: Athanasiou
authors.forename: Petros S
authors.initials: PS
authors.lastname: Karvelis
authors.forename: Antonis I
authors.initials: AI
authors.lastname: Sakellarios
authors.forename: Themis P
authors.initials: TP
authors.lastname: Exarchos
authors.forename: Panagiotis K
authors.initials: PK
authors.lastname: Siogkas
authors.forename: Vassilis D
authors.initials: VD
authors.lastname: Tsakanikas
authors.forename: Katerina K
authors.initials: KK
authors.lastname: Naka
authors.forename: Christos V
authors.initials: CV
authors.lastname: Bourantas
authors.forename: Michail I
authors.initials: MI
authors.lastname: Papafaklis
authors.forename: Georgia
authors.initials: G
authors.lastname: Koutsouri
authors.forename: Lampros K
authors.initials: LK
authors.lastname: Michalis
authors.forename: Oberdan
authors.initials: O
authors.lastname: Parodi
authors.forename: Dimitrios I
authors.initials: DI
authors.lastname: Fotiadis
mesh_terms: D000465:Algorithms; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D058226:Plaque, Atherosclerotic / Q000145:classification* / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D018084:Ultrasonography, Interventional / Q000379:methods*