title: A method for detecting undisplayed regions in virtual colonoscopy and its application to quantitative evaluation of fly-through methods.
abstract: OBJECTIVE
  When virtual endoscopy is used as a diagnostic tool, especially as a tool for detecting colon polyps, the user often performs automated fly-through based on automatically generated paths. In the case of automated fly-through in the colon, there are some blind areas at the backs of folds. The aim of this study is to detect undisplayed regions during fly-through and to perform quantitative evaluation.
  
  
  METHODS
  Undisplayed regions are detected by marking displayed triangles for surface rendering or displayed voxels for volume rendering. The voxels or triangles not having displayed marks are considered to be undisplayed triangles or voxels. Various kinds of automated fly-through paths generated from medial axes of the colon and flattened views of the colon from the viewpoint of the rate of undisplayed regions are evaluated.
  
  
  RESULTS
  The experiment results show that about 30% of colon regions are classified as undisplayed regions by the conventional automated fly-through along the medial axis and that the flattened view results in very few undisplayed regions.
  
  
  CONCLUSIONS
  There is a possibility that the automated fly-through methods may cause many undisplayed regions.
authors.affiliation: Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Kensaku
authors.initials: K
authors.lastname: Mori
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Hasegawa
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Suenaga
authors.forename: Jun-ichiro
authors.initials: J
authors.lastname: Toriwaki
mesh_terms: D003111:Colonic Polyps / Q000175:diagnosis*; D003113:Colonoscopy / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D014057:Tomography, X-Ray Computed; D014584:User-Computer Interface