title: Evaluation of 4 three-dimensional representation algorithms in capsule endoscopy images.
abstract: OBJECTIVE
  To evaluate the three-dimensional (3-D) representation performance of 4 publicly available Shape-from-Shading (SfS) algorithms in small-bowel capsule endoscopy (SBCE).
  
  
  METHODS
  SfS techniques recover the shape of objects using the gradual variation of shading. There are 4 publicly available SfS algorithms. To the best of our knowledge, no comparative study with images obtained during clinical SBCE has been performed to date. Three experienced reviewers were asked to evaluate 54 two-dimensional (2-D) images (categories: protrusion/inflammation/vascular) transformed to 3-D by the aforementioned SfS 3-D algorithms. The best algorithm was selected and inter-rater agreement was calculated.
  
  
  RESULTS
  Four publicly available SfS algorithms were compared. Tsai's SfS algorithm outperformed the rest (selected as best performing in 45/54 SBCE images), followed by Ciuti's algorithm (best performing in 7/54 images) and Torreão's (in 1/54 images). In 26/54 images; Tsai's algorithm was unanimously selected as the best performing 3-D representation SfS software. Tsai's 3-D algorithm superiority was independent of lesion category (protrusion/inflammatory/vascular; P = 0.678) and/or CE system used to obtain the 2-D images (MiroCam/PillCam; P = 0.558). Lastly, the inter-observer agreement was good (kappa = 0.55).
  
  
  CONCLUSIONS
  3-D representation software offers a plausible alternative for 3-D representation of conventional capsule endoscopy images (until optics technology matures enough to allow hardware enabled-"real" 3-D reconstruction of the gastrointestinal tract).
authors.affiliation: Alexandros Karargyris, National Library of Medicine, National Institutes of Health, Bethesda, MD 20892, United States.
authors.forename: Alexandros
authors.initials: A
authors.lastname: Karargyris
authors.forename: Emanuele
authors.initials: E
authors.lastname: Rondonotti
authors.forename: Giovanna
authors.initials: G
authors.lastname: Mandelli
authors.forename: Anastasios
authors.initials: A
authors.lastname: Koulaouzidis
mesh_terms: D000328:Adult; D000465:Algorithms; D053704:Capsule Endoscopy; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D007421:Intestine, Small / Q000473:pathology*; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012984:Software
keywords: Advance; Algorithm; Capsule endoscopy; Reconstruction; Small-bowel; Software; Technology; Three-dimensional