title: Feasibility of obtaining quantitative 3-dimensional information using conventional endoscope: a pilot study.
abstract: OBJECTIVE
  Three-dimensional (3D) imaging is gaining popularity and has been partly adopted in laparoscopic surgery or robotic surgery but has not been applied to gastrointestinal endoscopy. As a first step, we conducted an experiment to evaluate whether images obtained by conventional gastrointestinal endoscopy could be used to acquire quantitative 3D information.
  
  
  METHODS
  Two endoscopes (GIF-H260) were used in a Borrmann type I tumor model made of clay. The endoscopes were calibrated by correcting the barrel distortion and perspective distortion. Obtained images were converted to gray-level image, and the characteristics of the images were obtained by edge detection. Finally, data on 3D parameters were measured by using epipolar geometry, two view geometry, and pinhole camera model.
  
  
  RESULTS
  The focal length (f) of endoscope at 30 mm was 258.49 pixels. Two endoscopes were fixed at predetermined distance, 12 mm (d(12)). After matching and calculating disparity (v2-v1), which was 106 pixels, the calculated length between the camera and object (L) was 29.26 mm. The height of the object projected onto the image (h) was then applied to the pinhole camera model, and the result of H (height and width) was 38.21 mm and 41.72 mm, respectively. Measurements were conducted from 2 different locations. The measurement errors ranged from 2.98% to 7.00% with the current Borrmann type I tumor model.
  
  
  CONCLUSIONS
  It was feasible to obtain parameters necessary for 3D analysis and to apply the data to epipolar geometry with conventional gastrointestinal endoscope to calculate the size of an object.
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Jong Jin
authors.initials: JJ
authors.lastname: Hyun
authors.forename: Hoon Jai
authors.initials: HJ
authors.lastname: Chun
authors.forename: Bora
authors.initials: B
authors.lastname: Keum
authors.forename: Yeon Seok
authors.initials: YS
authors.lastname: Seo
authors.forename: Yong Sik
authors.initials: YS
authors.lastname: Kim
authors.forename: Yoon Tae
authors.initials: YT
authors.lastname: Jeen
authors.forename: Hong Sik
authors.initials: HS
authors.lastname: Lee
authors.forename: Soon Ho
authors.initials: SH
authors.lastname: Um
authors.forename: Chang Duck
authors.initials: CD
authors.lastname: Kim
authors.forename: Ho Sang
authors.initials: HS
authors.lastname: Ryu
authors.forename: Jong-Wook
authors.initials: JW
authors.lastname: Lim
authors.forename: Dong-Gi
authors.initials: DG
authors.lastname: Woo
authors.forename: Young-Joong
authors.initials: YJ
authors.lastname: Kim
authors.forename: Myo-Taeg
authors.initials: MT
authors.lastname: Lim