Stereoscopic liver surface reconstruction

Abstract

The paper presents a practical approach to measuring liver motion, both respiratory and laparoscopic, with a tool guided in the operating room. The presented method is based on standard operating room equipment, i.e. rigid laparoscopic cameras and a single incision laparoscopic surgery trocar. The triangulation algorithm is used and stereo correspondence points are marked manually by two independent experts. To calibrate the cameras two perpendicular chessboards, a pinhole camera model and a Tsai algorithm are used. The data set consists of twelve real liver surgery video sequences: ten open surgery and two laparoscopic, gathered from different patients. The setup equipment and methodology are presented. The proposed evaluation method based on both calibration points of the chessboard reconstruction and measurements made by the Polaris Vicra tracking system are used as a reference system. In the analysis stage we focused on two specific goals, measuring respiration and laparoscopic tool guided liver motions. We have presented separate examples for left and right liver lobes. It is possible to reconstruct liver motion using the SILS trocar. Our approach was made without additional position or movement sensors. Diffusion of cameras and laser for distance measurement seems to be less practical for in vivo laparoscopic data, but we do not exclude exploring such sensors in further research.

Keywords: 3D reconstruction; abdominal surgery; liver motion.

Figure 1

Setup diagram

Figure 2

Stereo camera setup

Figure 3

The geometric interpretation of a triangulation of point X with known cameras C, C’

Figure 4

Picture of the liver during surgery

Figure 5

Zoomed pixel values – imshow and local extrema – red rectangles

Figure 6

Picture of the liver with the selected points of interest – imtool