Published online Nov 28, 2013. doi: 10.3748/wjg.v19.i44.8028
Revised: September 20, 2013
Accepted: October 19, 2013
Published online: November 28, 2013
Processing time: 161 Days and 9.4 Hours
AIM: 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).
CONCLUSION: 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).
Core tip: Accurate three-dimensional (3-D) reconstruction of the gastrointestinal tract requires the use of stereo-cameras that can simulate human binocular vision. In the absence of such technology in capsule endoscopy, we rely on software approaches [such as the Shape-from-Shading (SfS) algorithms] to obtain 3-D representation of digestive tract structures. In the present study, we evaluated the use of 4 publically available SfS in capsule endoscopy. 3 experienced/experts reviewers concluded that Tsai’s approach is the best of the four available algorithms.