title: Feasibility of respiratory motion-compensated stereoscopic X-ray tracking for bronchoscopy.
abstract: OBJECTIVE
  Precise localization in bronchoscopy is challenging, particularly for peripheral lesions that cannot be reached by conventional bronchoscopes with a large working channel. Existing navigation methods are hampered by respiratory motion, e.g., in the lower lobes. We present an image-guided approach that considers respiratory motion and can localize instruments.
  
  
  METHODS
  We developed a rigid chest marker containing steel balls visible in X-ray images and a pattern for passive tracking with an optical camera system. An experimental setup to evaluate stereoscopic localization and to mimic chest motion was established in our interventional suite. The marker motion was recorded, and X-ray images were acquired from different angles using a standard C-arm. All coordinates were expressed with respect to the stationary tracking camera. The feasibility of motion-compensated stereoscopic localization was assessed.
  
  
  RESULTS
  The orientation of the C-arm could be established with a mean error of less than 1°. Triangulation based on two different X-ray images from different angles resulted in a mean error of 1.8 (±0.7) mm. A similar result was obtained when the marker was moved between X-ray acquisitions, and the mean error was 1.6 (±1.4) mm. The latencies were approximately 80 and 380 ms for tracking camera and X-ray imaging, respectively. Stereoscopic localization of a moving target was feasible.
  
  
  CONCLUSIONS
  The system presents a flexible alternative for precise stereoscopic localization of a bronchoscope or instruments using a standard C-arm. We demonstrated the ability to track multiple moving markers and to compensate for respiratory motion.
authors.affiliation: Medical Robotics Group, Institute for Robotics and Cognitive Systems, University of Lübeck, Lübeck, Germany.
authors.forename: Nikolas
authors.initials: N
authors.lastname: Leßmann
authors.forename: Daniel
authors.initials: D
authors.lastname: Drömann
authors.forename: Alexander
authors.initials: A
authors.lastname: Schlaefer
mesh_terms: D059925:Anatomic Landmarks / Q000000981:diagnostic imaging*; D016477:Artifacts; D001999:Bronchoscopy / Q000379:methods*; D005240:Feasibility Studies; D006801:Humans; D019047:Phantoms, Imaging; D011859:Radiography; D015656:Respiratory Mechanics