Camera motion tracking of real endoscope by using virtual endoscopy system and texture information

Abstract

This paper proposes an improved method for camera motion tracking of a real endoscope based on registration endoscopic images and Computerized Tomography (CT) images. Camera motion estimation is a fundamental function of an endoscope navigation system, which provides useful navigation information to medical doctors during endoscopic examinations. Our previous method consists of two steps: (1) rough estimation of camera motion using optical flow information and (2) precise estimation performed by the image based registration technique. The problem of the previous method was that only the forward and the backward motion of the camera were estimated by the optical flow information. To solve this problem, the proposed method effectively uses the change in texture information on real endoscopic video images and estimates the camera motion by mapping the texture to the organ's 3-D shape generated from the CT images. We roughly estimate the all motion of the camera using texture information of the organ's wall, then the precise estimation is performed by using image based registration method. We applied the proposed method to the real bronchoscopic video images and 3-D X-ray CT images. The results sowed that the proposed method was superior to our previous method in many cases.