Sparse-then-dense alignment-based 3D map reconstruction method for endoscopic capsule robots

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Turan M., Pilavci Y. Y., Ganiyusufoglu I., Araujo H., Konukoglu E., Sitti M.

MACHINE VISION AND APPLICATIONS, vol.29, no.2, pp.345-359, 2018 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 29 Issue: 2
  • Publication Date: 2018
  • Doi Number: 10.1007/s00138-017-0905-8
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.345-359
  • Keywords: Endoscopic capsule robots, 3D map reconstruction, Sparse-then-dense feature tracking, ACTUATED SOFT CAPSULE, SHAPE, IMAGE
  • Middle East Technical University Affiliated: Yes


Despite significant progress achieved in the last decade to convert passive capsule endoscopes to actively controllable robots, robotic capsule endoscopy still has some challenges. In particular, a fully dense three-dimensional (3D) map reconstruction of the explored organ remains an unsolved problem. Such a dense map would help doctors detect the locations and sizes of the diseased areas more reliably, resulting in more accurate diagnoses. In this study, we propose a comprehensive medical 3D reconstruction method for endoscopic capsule robots, which is built in a modular fashion including preprocessing, keyframe selection, sparse-then-dense alignment-based pose estimation, bundle fusion, and shading-based 3D reconstruction. A detailed quantitative analysis is performed using a non-rigid esophagus gastroduodenoscopy simulator, four different endoscopic cameras, a magnetically activated soft capsule robot, a sub-millimeter precise optical motion tracker, and a fine-scale 3D optical scanner, whereas qualitative ex-vivo experiments are performed on a porcine pig stomach. To the best of our knowledge, this study is the first complete endoscopic 3D map reconstruction approach containing all of the necessary functionalities for a therapeutically relevant 3D map reconstruction.