Extracting curve-skeletons from digital shapes using occluding contours

Curve-skeletons are compact and semantically relevant shape descriptors, able to summarize both topology and pose of a wide range of digital objects. Most of the state-of-the-art algorithms for their computation rely on the type of geometric primitives used and sampling frequency. In this paper we introduce a formally sound and intuitive definition of curve-skeleton, then we propose a novel method for skeleton extraction that rely on the visual appearance of the shapes. To achieve this result we inspect the properties of occluding contours, showing how information about the symmetry axes of a 3D shape can be inferred by a small set of its planar projections. The proposed method is fast, insensitive to noise, capable of working with different shape representations, resolution insensitive and easy to implement

3D Geometric Analysis of Tubular Objects based on Surface Normal Accumulation

This paper proposes a simple and efficient method for the reconstruction and extraction of geometric parameters from 3D tubular objects. Our method constructs an image that accumulates surface normal information, then peaks within this image are located by tracking. Finally, the positions of these are optimized to lie precisely on the tubular shape centerline. This method is very versatile, and is able to process various input data types like full or partial mesh acquired from 3D laser scans, 3D height map or discrete volumetric images. The proposed algorithm is simple to implement, contains few parameters and can be computed in linear time with respect to the number of surface faces. Since the extracted tube centerline is accurate, we are able to decompose the tube into rectilinear parts and torus-like parts. This is done with a new linear time 3D torus detection algorithm, which follows the same principle of a previous work on 2D arc circle recognition. Detailed experiments show the versatility, accuracy and robustness of our new method.Comment: in 18th International Conference on Image Analysis and Processing, Sep 2015, Genova, Italy. 201

Correcting curvature-density effects in the Hamilton-Jacobi skeleton

The Hainilton-Jacobi approach has proven to be a powerful and elegant method for extracting the skeleton of two-dimensional (2-D) shapes. The approach is based on the observation that the normalized flux associated with the inward evolution of the object boundary at nonskeletal points tends to zero as the size of the integration area tends to zero, while the flux is negative at the locations of skeletal points. Nonetheless, the error in calculating the flux on the image lattice is both limited by the pixel resolution and also proportional to the curvature of the boundary evolution front and, hence, unbounded near endpoints. This makes the exact location of endpoints difficult and renders the performance of the skeleton extraction algorithm dependent on a threshold parameter. This problem can be overcome by using interpolation techniques to calculate the flux with subpixel precision. However, here, we develop a method for 2-D skeleton extraction that circumvents the problem by eliminating the curvature contribution to the error. This is done by taking into account variations of density due to boundary curvature. This yields a skeletonization algorithm that gives both better localization and less susceptibility to boundary noise and parameter choice than the Hamilton-Jacobi method

Gap Filling of 3-D Microvascular Networks by Tensor Voting

We present a new algorithm which merges discontinuities in 3-D images of tubular structures presenting undesirable gaps. The application of the proposed method is mainly associated to large 3-D images of microvascular networks. In order to recover the real network topology, we need to fill the gaps between the closest discontinuous vessels. The algorithm presented in this paper aims at achieving this goal. This algorithm is based on the skeletonization of the segmented network followed by a tensor voting method. It permits to merge the most common kinds of discontinuities found in microvascular networks. It is robust, easy to use, and relatively fast. The microvascular network images were obtained using synchrotron tomography imaging at the European Synchrotron Radiation Facility. These images exhibit samples of intracortical networks. Representative results are illustrated

Enhancement of virtual colonoscopy system.

Colorectal cancer is the fourth most common cancer, and the fourth leading cause of cancer related death in the United States. It also happens to be one of the most preventable cancers provided an individual performs a regular screening. For years colonoscopy via colonoscope was the only method for colorectal cancer screening. In the past decade, colonography or virtual colonoscopy (VC) has become an alternative (or supplement) to the traditional colonoscopy. VC has become a much researched topic since its introduction in the mid-nineties. Various visualization methods have been introduced including: traditional flythrough, colon flattening, and unfolded-cube projection. In recent years, the CVIP Lab has introduced a patented visualization method for VC called flyover. This novel visualization method provides complete visualization of the large intestine without significant modification to the rendered three-dimensional model. In this thesis, a CVIP Lab VC interface was developed using Lab software to segment, extract the centerline, split (for flyover), and visualize the large intestine. This system includes adaptive level sets software to perform large intestine segmentation, and CVIP Lab patented curve skeletons software to extract the large intestine centerline. This software suite has not been combined in this manner before so the system stands as a unique contribution to the CVIP Lab colon project. The system is also a novel VC pipeline when compared to other academic and commercial VC methods. The complete system is capable of segmenting, finding the centerline, splitting, and visualizing a large intestine with a limited number of slices (~350 slices) for VC in approximately four and a half minutes. Complete CT scans were also validated with the centerline extraction external to the system (since the curve skeletons code used for centerline extraction cause memory exceptions because of high memory utilization)