Biomedical subjects

J Toriwaki

Publications and source records attributed to J Toriwaki.

At least 19 recordsLinked to original sources

PubMed2002

Tracking of a bronchoscope using epipolar geometry analysis and intensity-based image registration of real and virtual endoscopic images.

This paper describes a method for tracking the camera motion of a flexible endoscope, in particular a bronchoscope, using epipolar geometry analysis and intensity-based image registration. The method proposed here does not use a positional sensor attached to the endoscope. Instead, it tracks camera motion using real endoscopic (RE) video images obtained at the time of the procedure and X-ray CT images acquired before the endoscopic examination. A virtual endoscope system (VES) is used for generating virtual endoscopic (VE) images. The basic idea of this tracking method is to find the viewpoint and view direction of the VES that maximizes a similarity measure between the VE and RE images. To assist the parameter search process, camera motion is also computed directly from epipolar geometry analysis of the RE video images. The complete method consists of two steps: (a) rough estimation using epipolar geometry analysis and (b) precise estimation using intensity-based image registration. In the rough registration process, the method computes camera motion from optical flow patterns between two consecutive RE video image frames using epipolar geometry analysis. In the image registration stage, we search for the VES viewing parameters that generate the VE image that is most similar to the current RE image. The correlation coefficient and the mean square intensity difference are used for measuring image similarity. The result obtained in the rough estimation process is used for restricting the parameter search area. We applied the method to bronchoscopic video image data from three patients who had chest CT images. The method successfully tracked camera motion for about 600 consecutive frames in the best case. Visual inspection suggests that the tracking is sufficiently accurate for clinical use. Tracking results obtained by performing the method without the epipolar geometry analysis step were substantially worse. Although the method required about 20 s to process one frame, the results demonstrate the potential of image-based tracking for use in an endoscope navigation system.

Algorithms↗

PubMed2001

[Virtual bronchoscope system].

In this article, we describe the features of Virtual Bronchoscope System(VBS) and its practical use. VBS is constructed based on 3-D chest CT images. The bronchus region is automatically extracted from 3-D chest CT images by a three-dimensional region growing method. The surface rendering is employed for construction of virtualized tracheo-bronchial tree. It gives us an environment where we can observe inside the bronchi from an arbitrary viewpoint and a view direction. By mouse operation, the user can control the viewpoint and the view direction to fly through inside the airway in real time. VBS is applicable for a variety of purposes such as diagnosis, surgical planning, informed consent, education and training. One of extension of this system is a teaching tool for medical students. In the module for educational use, we have developed four functions for using the system as a teaching tool as follows: (a) automated display of bronchial anatomical names, (b) presenting questions about the currently observed branch in the endoscopic view, (c) display of the path which the user should follow, and (d) display of a question about the location of the artificially created tumor in the bronchus. These functions use the processed results of automated anatomical labeling. The method proposed here combines the knowledge based processing technique 'automated labeling of bronchial branch' and the novel visualization technique 'virtual bronchoscope'. This is one of new teaching tools of medical images. We conclude that this virtual bronchoscope system might have an important role in the medial students' education.

Bronchi↗

PubMed2000

Automated anatomical labeling of the bronchial branch and its application to the virtual bronchoscopy system.

This paper describes a method for the automated anatomical labeling of the bronchial branch extracted from a three-dimensional (3-D) chest X-ray CT image and its application to a virtual bronchoscopy system (VBS). Automated anatomical labeling is necessary for implementing an advanced computer-aided diagnosis system of 3-D medical images. This method performs the anatomical labeling of the bronchial branch using the knowledge base of the bronchial branch name. The knowledge base holds information on the bronchial branch as a set of rules for its anatomical labeling. A bronchus region is automatically extracted from a given 3-D CT image. A tree structure representing the essential structure of the extracted bronchus is recognized from the bronchus region. Anatomical labeling is performed by comparing this tree structure of the bronchus with the knowledge base. As an application, we implemented the function to automatically present the anatomical names of the branches that are shown in the currently rendered image in real time on the VBS. The result showed that the method could segment about 57% of the branches from CT images and extracted a tree structure of about 91% in branches in the segmented bronchus. The anatomical labeling method could assign the correct branch name to about 93% of the branches in the extracted tree structure. Anatomical names were appropriately displayed in the endoscopic view.

Algorithms↗

PubMed1998

Virtualized angioscopy of the thoracic aorta in a rabbit model of atherosclerosis.

The purpose of this study was to apply virtual reality technology to spiral computed tomographic (CT) angiogram images in a rabbit model of atherosclerosis and to correlate the images with histopathologic evaluation of the aorta. Image data were transferred to the virtual endoscope system in a graphics workstation. "Virtualized angioscopy" includes an interactive graphic user interface, which controls the viewpoint, the direction of the observation, and rendering and navigation functions. The virtual angioscopy system demonstrated irregularities of the luminal surface of the ascending aorta and a smooth luminal surface in the descending aorta. These observations were correlated with histopathologic findings. The results of this study indicate that the potential and real benefits of virtualized angioscopy far outweigh several technical limitations.

Angioscopy↗

PubMed1991

[Problems of three-dimensional hepatic imaging and surgical planning system].

Explore the source record for details and available documents.

Computer Simulation↗

PubMed1989

[A hip joint surgical planning system using 3-D images].

This paper describes a hip joint surgical simulation system using a three-dimensional image (X-ray CT images). We developed this system in cooperation with surgeons, and we have already applied it to several clinical examples. According to a surgeon who used our system for actual surgical plannings, most of the hip joint surgeries operated at the present time can be simulated. Our system has useful functions in order to plan surgeries such as interference check in movement of a bone and display of the attached surface of bone. We show an actual surgical planning process performed by the surgeon with our system.

Computer Simulation↗

PubMed1988