We present a novel pipeline for computer-aided detection (CAD) of colonic polyps by integrating texture and shape analysis with volume rendering and conformal colon flattening. Using our automatic method, the 3D polyp detection problem is converted into a 2D pattern recognition problem. The colon surface is first segmented and extracted from the CT data set of the patient's abdomen, which is then mapped to a 2D rectangle using conformal mapping. This flattened image is rendered using a direct volume rendering technique with a translucent electronic biopsy transfer function. The polyps are detected by a 2D clustering method on the flattened image. The false positives are further reduced by analyzing the volumetric shape and texture features. Compared with shape based methods, our method is much more efficient without the need of computing curvature and other shape parameters for the whole colon surface. The final detection results are stored in the 2D image, which can be easily incorporated into a virtual colonoscopy (VC) system to highlight the polyp locations. The extracted colon surface mesh can be used to accelerate the volumetric ray casting algorithm used to generate the VC endoscopic view. The proposed automatic CAD pipeline is incorporated into an interactive VC system, with a goal of helping radiologists detect polyps faster and with higher accuracy.
Figure 1: Simplifying the zero-isosurface of a directed distance volume of 256 3 using our topology-preserving isosurface simplification algorithm. Although the cylinders and the box are very close to each other, they don't touch, and thus there are several disconnected surface components in this volume. Note that disconnected surface components are assigned different materials and are clustered independently.
ABSTRACTWe present a fast, topology-preserving approach for isosurface simplification. The underlying concept behind our approach is to preserve the disconnected surface components in cells during isosurface simplification. We represent isosurface components in a novel representation, called enhanced cell, where each surface component in a cell is represented by a vertex and its connectivity information. A topology-preserving vertex clustering algorithm is applied to build a vertex octree. An enhanced dual contouring algorithm is applied to extract error-bounded multiresolution isosurfaces from the vertex octree while preserving the finest resolution isosurface topology. Cells containing multiple vertices are properly handled during contouring. Our approach demonstrates better results than existing octree-based simplification techniques.
Wayfinding system" is an interdisciplinary research between the environment design and human interface of information system. The design of EXIT is to efficiently help people to identify the emergency exit when the accident occurred. In this paper, eye tracking techniques are utilized to aided EXIT design in the wayfinding system. The mobile eye tracking was used to collect the human eye movement data in the building where different EXIT designs were displayed. While the stationary eye tracking techniques was used to collect the eye movement data on the same building's EXIT designs on virtual 3D sketches to get the quantitative data comparing with the mobile eye tracker. Finally, some general conclusions were obtained from the views of visual elements selecting, EXIT appearance design and EXIT's placement in the building, which is very valuable and can be commonly referred in wayfinding system. The research methods in the paper is very original and has not been mentioned in other papers of the related fields before, which is well worthy data and empirical methodologies can be introduced in wayfinding and space decision making research.
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