Mie Sato

Penalized-distance volumetric skeleton algorithm

Introduces a refined general definition of a skeleton that is based on a penalized distance function and that cannot create any of the degenerate cases of the earlier CEASAR (Center-line Extraction Algorithm-Smooth, Accurate and Robust) and TEASAR (Tree-structure Extraction Algorithm for Skeletons-Accurate and Robust) algorithms. Additionally, we provide an algorithm that finds the skeleton accurately and rapidly. Our solution is fully automatic, which frees the user from having to engage in manual data pre-processing. We present the accurate skeletons computed on a number of test data sets. The algorithm is very efficient, as demonstrated by the running times, which were all below seven minutes.

3D digital cleansing using segmentation rays

We propose a novel approach for segmentation and digital cleansing of endoscopic organs. Our method can be used for a variety of segmentation needs with little or no modification. It aims at fulfilling the dual and often conflicting requirements of a fast and accurate segmentation and also eliminates the undesirable partial volume effect which contemporary approaches cannot. For segmentation and digital cleansing, we use the peculiar characteristics exhibited by the intersection of any two distinct-intensity regions. To detect these intersections we cast rays through the volume, which we call the segmentation rays as they assist in the segmentation. We then associate a certain task of reconstruction and classification with each intersection the ray detects. We further use volumetric contrast enhancement to reconstruct surface lost by segmentation (if any), which aids in improving the quality of the volume rendering.

CEASAR: a smooth, accurate and robust centerline extraction algorithm

We present CEASAR, a centerline extraction algorithm that delivers smooth, accurate and robust results. Centerlines are needed for accurate measurements of length along winding tubular structures. Centerlines are also required in automatic virtual navigation through human organs, such as the colon or the aorta, as they are used to control movement and orientation of the virtual camera. We introduce a concise but general definition of a centerline, and provide an algorithm that finds the centerline accurately and rapidly. Our algorithm is provably correct for general geometries. Our solution is fully automatic, which frees the user from having to engage in data preprocessing. For a number of test datasets, we show the smooth and accurate centerlines computed by our CEASAR algorithm on a single 194 MHz MIPS R10000 CPU within five minutes.

TEASAR: tree-structure extraction algorithm for accurate and robust skeletons

We introduce the TEASAR algorithm which is a treestructure extraction algorithm delivering skeletons that are accurate and robust. Volumetric skeletons are needed for accurate measurements of length along branching and winding structures. Skeletons are also required in automatic virtual navigation, such as traveling through human organs (e.g., the colon) to control movement and orientation of the virtual camera. We introduce a concise but general definition of a skeleton, and provide an algorithm that finds the skeleton accurately and rapidly. Our solution is fully automatic, which frees the user from having to engage in data preprocessing. We present the accurate skeletons computed on a number of test datasets. The algorithm is efficient as demonstrated by the running times on a single 194 MHz MIPS R10000 CPU which were all below five minutes.

A gradient magnitude based region growing algorithm for accurate segmentation

An accurate segmentation is critical for clinical application of medical images. The undesirable partial-volume-effect, which lies on a boundary between a high intensity region and a low intensity region, makes unerring boundary determination a difficult task. A new approach to segmentation is required for removing the adverse effect on the boundary, which is unwanted especially from the point of view of volume rendering. Here, the authors propose a gradient magnitude based region growing algorithm for accurate segmentation. The gradient is useful for enhancing the boundary because it emphasizes the difference among voxel values. By analyzing the gradient magnitude, the authors can see the sufficient contrast which must be presented on the boundary region and they use this contrast to increase the accuracy of their segmentation method. The authors pay attention only to the boundary region, not to the whole large volumetric dataset itself, making it more computationally efficient.

A case study in selective visualization of unsteady 3D flow

In this case study, we explore techniques for the purpose of visualizing isolated flow structures in time-dependent data. Our primary industrial application is the visualization of the vortex rope, a rotating helical structure which builds up in the draft tube of a water turbine. The vortex rope can be characterized by high values of normalized helicity, which is a scalar field derived from the given CFD velocity data. In two related applications, the goal is to visualize the cavitation regions near the runner blades of a Kaplan turbine and a water pump, respectively. Again, the flow structure of interest can be defined by a scalar field, namely by low pressure values. We propose a particle seeding scheme based on quasi-random numbers, which minimizes visual artifacts such as clusters or patterns. By constraining the visualization to a region of interest, occlusion problems are reduced and storage efficiency is gained.

Interactive electronic biopsy for 3D virtual colonscopy

We propose an interactive electronic biopsy technique for more accurate colon cancer diagnoses by using advanced volume rendering technologies. The volume rendering technique defines a transfer function to map different ranges of sample values of the original volume data to different colors and opacities, so that the interior structure of the polyps can be clearly recognized by human eyes. Specifically, we provide a user- friendly interface for physicians to modify various parameters in the transfer function, so that the physician can interactively change the transfer function to observe the interior structures inside the abnormalities. Furthermore, to speed up the volume rendering procedure, we propose an efficient space-leaping technique by observing that the virtual camera parameters are often fixed when the physician modifies the transfer function. In addition, we provide an important tool to display the original 2D CT image at the current 3D camera position, so that the physician is able to double check the interior structure of a polyp with the density variation in the corresponding CT image for confirmation. Compared with the traditional biopsy in the procedure of optical colonoscopy, our method is more flexible, noninvasive, and therefore without risk.

Grasping a virtual object with a bare hand

We have been developed an augmented reality (AR) system that gives pseudo-haptic feedback when a user grasps a virtual object with a bare hand. In previous studies, pseudo-haptic feedback was emphasized by adding an auditory stimulus to visual information. However, the effective way of presenting the auditory stimulus has not been studied. Therefore, we investigate the type and presenting method of effective auditory stimulus that gives pseudo-haptic feedback.

AUTOMATIC FACIAL FEATURE EXTRACTION

Facial feature extraction is necessary for identification of an individual face on a computer. We propose an automatic facial feature extraction method that is robust in conditions of an input image. As facial features, the shape of facial parts is automatically extracted from a frontal face image. We experiment with input images of several resolutions that are taken with various types of cam- era. The accuracy of the extraction is shown by comparing our results with the corresponding manually extracted facial features.

A trial of navigation system using BLE beacon for sightseeing in traditional area of Nikko

We would like to explain the outline of a trial of navigation system using BLE beacon for sightseeing in traditional area of Nikko. We firstly explain the result of a research of characteristics of visitors to Nikko. From the questionnaire to visitors of Nikko, to support young people (20th) and foreigners by ICT is important. Especially to solve problems of transportation and to provide information of shopping and eating location are important. Also, to give them the culture and history in the approach to the Tosyogu-shrine is important. Then we designed a trial application that works with BLE beacon and performed trial to evaluate the usefulness of navigation system using BLE beacon for sightseeing in Nikko. We found that BLE beacon in outdoor worked well and if visitors are walking, they can find almost all beacons. If they move by bus, BLE beacon also work well.