title: Image-based electrode array tracking for epicardial electrophysiological mapping in minimally invasive arrhythmia surgery.
abstract: OBJECTIVE
  Electrophysiological mapping is effective in realizing a precise minimally invasive arrhythmia surgery. Recently, an epicardial electrophysiological mapping system for minimally invasive arrhythmia surgery was reported. The system requires a small electrode array, a tracking system and a global mapping algorithm. The optical tracking system employed in the research requires line of sight and complicated configuration. This paper proposes a new tracking method for locating an electrode array.
  
  
  METHODS
  We developed a small electrode array and optical markers. Center points of respective optical markers and the electrode array are tracked via an endoscopic stream and calculated in image space. The orientation of the electrode array is calculated using the dot product between the vector joining two center points of two upper optical markers and the vector joining two end points of the longest edge of the electrode array.
  
  
  RESULTS
  Mean tracking errors of position and orientation of the electrode array were 0.51 mm and 0.64°, respectively. And the processing time was constant at 46 ms per frame. Our method could successfully track the electrode array on the epicardium during in vivo experiment and a global epicardial electrophysiological map was reconstructed from separately measured epicardial electrograms by the small electrode array.
  
  
  CONCLUSIONS
  An image-based tracking method for locating an electrode array was proposed. Tracking accuracy, processing time and applicability to surgical environment of our method proved to be acceptable. Consequently, our method enables the electrode array tracking system to be simplified with no separate tracking system.
authors.affiliation: Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo Bunkyo, Tokyo, Japan. kimhongho@bmpe.t.u-tokyo.ac.jp
authors.forename: Hongho
authors.initials: H
authors.lastname: Kim
authors.forename: Paul
authors.initials: P
authors.lastname: de Lange
authors.forename: Takehiro
authors.initials: T
authors.lastname: Ando
authors.forename: Sanghyun
authors.initials: S
authors.lastname: Joung
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Taniguchi
authors.forename: Hongen
authors.initials: H
authors.lastname: Liao
authors.forename: Shunei
authors.initials: S
authors.lastname: Kyo
authors.forename: Minoru
authors.initials: M
authors.lastname: Ono
authors.forename: Shinichi
authors.initials: S
authors.lastname: Takamoto
authors.forename: Etsuko
authors.initials: E
authors.lastname: Kobayashi
authors.forename: Ichiro
authors.initials: I
authors.lastname: Sakuma
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000503:physiopathology* / Q000601:surgery; D006348:Cardiac Surgical Procedures / Q000379:methods*; D004195:Disease Models, Animal; D004566:Electrodes; D056149:Epicardial Mapping / Q000295:instrumentation*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D019060:Minimally Invasive Surgical Procedures; D015203:Reproducibility of Results; D013552:Swine