introduction: nowadays virtual colonoscopy has become a reliable and efficient method of detecting primary stages of colon cancer such as polyp detection. one of the most important and crucial stages of virtual colonoscopy is colon segmentation because an incorrect segmentation may lead to a misdiagnosis.  materials and methods: in this work, a hybrid method based on geometric deformable models...

Purpose: To evaluate the implications of differences between contours drawn manually and contours generated automatically by deformable image registration for four-dimensional (4D) treatment planning. Methods and Materials: In 12 lung cancer patients intensity-modulated radiotherapy (IMRT) planning was performed for both manual contours and automatically generated (‘‘auto’’) contours in mid and...

Orientation discrimination and tilt aftereffects (TAEs) were measured to determine if the orientation of luminance and illusory contours are processed by separate mechanisms. The assumption was made that if a single mechanism supports the perception of both types of contours, then illusory and luminance contours that support the same level of orientation discrimination will be equally effective...

We describe an approach to define contours of 3D vector fields and employ them as an interactive flow visualization tool. Although contours are well-defined and commonly used for surfaces and 3D scalar fields, they have no straightforward extension in vector fields. Our approach is to extract and visualize specific stream lines which show the most similar behavior to contours on surfaces. This ...

Illusory contours where no contrast exists in the image can be seen between pairs of spatially separate but aligned inducing real contours defined either by pictorial cues (luminance contrasts or offset gratings), kinetic contrast, or binocular disparity contrast. In previous studies it has been shown that the detection of a thin luminous line is facilitated when the line is superimposed on ill...

Active contour, or snake, is an energy minimizing spline that is useful in image boundary detection. Active contours are stimulated by internal forces, image forces and external forces which maintain the shape of the contours while attract the contours to some desired features, usually edges. Problems in implementing active contours such as convergence and initialization have motivated research...

In this paper we propose a new technique for outlines of objects detection. We exploit the set of contours computed using the image analogies principle. A set of artificial patterns are used to locate contours of any query image, each one permits the location of contours corresponding to a specific intensity variation. We studied these contours and a theoretical foundation is proposed to explai...

Previous literature suggests that low-level stimulus properties determine the detection performance of contours and are used to define different contour types. Here we investigated the processing of different types of contours under conscious and unconscious conditions. In Experiment 1, we adopted an inattentional blindness paradigm and showed that collinear contours (i.e., a contour type that ...

This paper presents a new method for reconstructing piecewise linear surfaces from planar polygonal contours that branch. For non-branching contours, experience has shown that the piecewise linear surface of minimum surface area which connects a pair of contours often provides a good solution. The current algorithm extends this idea by searching for the surface of minimal area which connects tw...

In this paper we study the exact contours of a piecewise trilinear scalar field. We show how to represent these contours exactly as trimmed surfaces of triangular rational cubic Bézier patches. As part of this, we introduce an extension of the marching cubes algorithm which gives a topologically exact triangular approximation of the contours for any case. Finally, we modify the exact contours t...