title: Automatic path searching for interactive navigation support within virtual medical 3-dimensional objects.
abstract: OBJECTIVE
  This article proposes the use of a disembodied autonomous actor for navigation support within complex virtual medical objects reconstructed from Computed Tomography or Magnetic Resonance Imaging. Such objects are often maze-like, and users risk getting lost within them during Virtual Reality sessions. Therefore, users need paths for guided fly-throughs when performing non-invasive diagnostic tasks.
  
  
  METHODS
  We present a synthetic vision-based actor capable of finding collision-free paths from a given position to a goal point in environments containing loops and impasses. When navigating, the actor voxelizes the virtual environment and searches for collision-free paths in voxel space by using a back tracking search algorithm. Automata and rules control its search behaviour. The resulting paths can be used in dedicated virtual endoscopy applications.
  
  
  RESULTS
  Our path search method has been tested within a variety of tubular virtual anatomical structures in 3D such as aortas, colons, or blood vessels of the brain. The actor finds paths within reasonable time limits, even when considering complex anatomical surface models.
  
  
  CONCLUSIONS
  The method may be used as a valuable tool for assisting virtual endoscopic diagnostic and screening activities in the near future.
authors.affiliation: University of Zurich, Department of Informatics, Zurich, Switzerland. noser@ifi.unizh.ch
authors.forename: Hansrudi
authors.initials: H
authors.lastname: Noser
authors.forename: Christian
authors.initials: C
authors.lastname: Stern
authors.forename: Peter
authors.initials: P
authors.lastname: Stucki
mesh_terms: D000465:Algorithms; D001011:Aorta / Q000033:anatomy & histology; D001185:Artificial Intelligence; D001921:Brain / Q000098:blood supply; D003106:Colon / Q000033:anatomy & histology; D003196:Computer Graphics; D003198:Computer Simulation; D004724:Endoscopy; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D025321:Surgery, Computer-Assisted; D014057:Tomography, X-Ray Computed; D014132:Trachea / Q000033:anatomy & histology; D014584:User-Computer Interface