title: Fully automated tracking of cardiac structures using radiopaque markers and high-frequency videofluoroscopy in an in vivo ovine model: from three-dimensional marker coordinates to quantitative analyses.
abstract: OBJECTIVE
  Recently, algorithms were developed to track radiopaque markers in the heart fully automated. However, the methodology did not allow to assign the exact anatomical location to each marker. In this case study we describe the steps from the generation of three-dimensional marker coordinates to quantitative data analyses in an in vivo ovine model.
  
  
  METHODS
  In one adult sheep, twenty silver balls were sutured to the right side of the heart: 10 to the tricuspid annulus, one to the anterior tricuspid leaflet and nine to the epicardial surface of the right ventricle. In addition, 13 cylindrical tantalum markers were implanted into the left ventricle. Data were acquired with a biplanar X-ray acquisition system (Neurostar R, Siemens AG, 500 Hz). Radiopaque marker coordinates were determined fully automated using novel tracking algorithms.
  
  
  RESULTS
  The anatomical marker locations were identified using a 3-dimensional model of a single frame containing all tracked markers. First, cylindrical markers were manually separated from spherical markers, thus allowing to distinguish right from left heart markers. The fast moving leaflet marker was identified by using video loops constructed of all recorded frames. Rotation of the 3-dimensional model allowed the identification of the precise anatomical position for each marker. Data sets were then analyzed quantitatively using customized software.
  
  
  CONCLUSIONS
  The method presented in this case study allowed quantitative data analyses of radiopaque cardiac markers that were tracked fully automated with high temporal resolution. However, marker identification still requires substantial manual work. Future improvements including the implication of marker identification algorithms and data analysis software could allow almost real-time quantitative analyses of distinct cardiac structures with high temporal and spatial resolution.
authors.affiliation: Department of Cardiothoracic Surgery, University Hospital Jena, 07747 Jena, Germany ; Department of Cardiovascular Surgery, University Heart Center Freiburg - Bad Krozingen, Freiburg, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bothe
authors.affiliation: Institute of Laboratory Animals Science, Friedrich-Schiller-University, Jena, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Schubert
authors.affiliation: Department of Cardiothoracic Surgery, University Hospital Jena, 07747 Jena, Germany.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Diab
authors.affiliation: Department of Cardiothoracic Surgery, University Hospital Jena, 07747 Jena, Germany.
authors.forename: Gloria
authors.initials: G
authors.lastname: Faerber
authors.affiliation: Department of Cardiothoracic Surgery, University Hospital Jena, 07747 Jena, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Bettag
authors.affiliation: Computer Vision Group, Friedrich Schiller University, Jena, Germany.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Institute of Systematic Zoology and Evolutionary Biology, Friedrich Schiller University, Jena, Germany.
authors.forename: Martin S
authors.initials: MS
authors.lastname: Fischer
authors.affiliation: Computer Vision Group, Friedrich Schiller University, Jena, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Denzler
authors.affiliation: Department of Cardiothoracic Surgery, University Hospital Jena, 07747 Jena, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Doenst
keywords: Cardiac mechanics; Cardiac surgery; Large animal model; Radiopaque marker tracking; Tricuspid valve complex