Optimal surface segmentation in volumetric images--a graph-theoretic approach

Efficient segmentation of globally optimal surfaces representing object boundaries in volumetric data sets is important and challenging in many medical image analysis applications. We have developed an optimal surface detection method capable of simultaneously detecting multiple interacting surfaces, in which the optimality is controlled by the cost functions designed for individual surfaces and by several geometric constraints defining the surface smoothness and interrelations. The method solves the surface segmentation problem by transforming it into computing a minimum s-t cut in a derived arc-weighted directed graph. The proposed algorithm has a low-order polynomial time complexity and is computationally efficient. It has been extensively validated on more than 300 computer-synthetic volumetric images, 72 CT-scanned data sets of different-sized plexiglas tubes, and tens of medical images spanning various imaging modalities. In all cases, the approach yielded highly accurate results. Our approach can be readily extended to higher-dimensional image segmentation.     

A hybrid multi-group approach for privacy-preserving data mining

In this paper, we propose a hybrid multi-group approach for privacy preserving data mining. We make two contributions in this paper. First, we propose a hybrid approach. Previous work has used either the randomization approach or the secure multi-party computation (SMC) approach. However, these two approaches have complementary features: the randomization approach is much more efficient but less accurate, while the SMC approach is less efficient but more accurate. We propose a novel hybrid approach, which takes advantage of the strength of both approaches to balance the accuracy and efficiency constraints. Compared to the two existing approaches, our proposed approach can achieve much better accuracy than randomization approach and much reduced computation cost than SMC approach. We also propose a multi-group scheme that makes it flexible for the data miner to control the balance between data mining accuracy and privacy. This scheme is motivated by the fact that existing randomization schemes that randomize data at individual attribute level can produce insufficient accuracy when the number of dimensions is high. We partition attributes into groups, and develop a scheme to conduct group-based randomization to achieve better data mining accuracy. To demonstrate the effectiveness of the proposed general schemes, we have implemented them for the ID3 decision tree algorithm and association rule mining problem and we also present experimental results.

A hybrid evolutionary approach to segmentation of non-stationary signals

Automatic segmentation of non-stationary signals such as electroencephalogram (EEG), electrocardiogram (ECG) and brightness of galactic objects has many applications. In this paper an improved segmentation method based on fractal dimension (FD) and evolutionary algorithms (EAs) for non-stationary signals is proposed. After using Kalman filter (KF) to reduce existing noises, FD which can detect the changes in both the amplitude and frequency of the signal is applied to reveal segments of the signal. In order to select two acceptable parameters of FD, in this paper two authoritative EAs, namely, genetic algorithm (GA) and imperialist competitive algorithm (ICA) are used. The proposed approach is applied to synthetic multi-component signals, real EEG data, and brightness changes of galactic objects. The proposed methods are compared with some well-known existing algorithms such as improved nonlinear energy operator (INLEO), Varri?s and wavelet generalized likelihood ratio (WGLR) methods. The simulation results demonstrate that segmentation by using KF, FD, and EAs have greater accuracy which proves the significance of this algorithm.     

A hybrid approach to feature segmentation of triangle meshes

Segmentation of a polygonal mesh is a method of breaking the mesh down into ‘meaningful’ connected subsets of meshes called regions or features. Several methods have been proposed in the past and they are either vertex based or edge based. The vertex method used here is based on the watershed segmentation scheme which appears prominently in the image segmentation literature and was later applied to the 3D segmentation problem [9] and [10]. Its main drawback is that it is a vertex based method and no hard boundaries (edges) are created for the features or regions. Edge based methods rely on the dihedral angle between polygon faces to determine if the common edge should be classified as a Feature Edge. However, this method results in many disconnected edges and thereby incomplete feature loops.We propose a hybrid method which takes advantage of both methods mentioned earlier and create regions with complete feature loops. Satisfactory results have been achieved for both CAD parts as well as other laser scanned objects such as bones and ceramic vessels.     

Classification of functional data: A segmentation approach

We suggest a classification and feature extraction method on functional data where the predictor variables are curves. The method, called functional segment discriminant analysis (FSDA), combines the classical linear discriminant analysis and support vector machine. FSDA is particularly useful for irregular functional data, characterized by spatial heterogeneity and local patterns like spikes. FSDA not only reduces the computation and storage burden by using a fraction of the spectrum, but also identifies important predictors and extracts features. FSDA is highly flexible, easy to incorporate information from other data sources and/or prior knowledge from the investigators. We apply FSDA to two public domain data sets and discuss the understanding developed from the study.     

A hybrid approach for classification of rare class data

Learning of rare class data is a challenging problem in field of classification process. A rare class or imbalanced class learning is the common problem faced by many real-world applications, because of this many researcher work focused on this issue. Rare class data always generate wrong results because of overwhelming accuracy of minority class by majority class. There are lots of methods been proposed to handle imbalanced class or rare class or skew class problem. This paper proposes a hybrid method, i. e. classification- and clustering-based method, solving rare class problem. This proposed hybrid method uses k-means, ensemble and divide and merge methods. This method tries to improve detection rate of every class. For experimental work, the proposed method is tested on real datasets. The experimental results show that proposed method works well as compared with other algorithms.     

面向数据稀疏问题的个性化组合推荐研究

协同过滤技术是推荐系统中应用最为广泛的算法,其面临着数据稀疏性问题、冷启动、规模可扩展性等问题。工作体现在两点:一是在基于项的协同过滤模型中,改进了项间的相似度计算方法,相比调整余弦方法仅考虑一个要素,包含了三个要素:两项的具有共同用户的评分、共同评分用户数量、非共同评分用户数量;二是组合基于用户、基于项和基于奇异值分解的协同过滤推荐,通过多模型组合提高推荐性能。实验结果表明在基于项过滤中MAE指标上提高了4.30%。进一步,加权的组合多种模型方法比基于项方法提高了1.26%。     

A fast display method for volumetric data

Presented is a fast display method for volumetric data sets, which involves a slicebased method for extracting potentially visible voxels to represent visible surfaces. For a given viewing direction, the number of visible voxels can be trimmed further by culling most of the voxels not visible from that direction. The entire 3D array of voxels is also present for invasive operations and direct access to interior structures. This approach has been integrated on a low-cost graphic engine as an interactive system for craniofacial surgical planning that is currently in clinical use.     

A scalable sparse Cholesky based approach for learning high-dimensional covariance matrices in ordered data

Machine Learning - Covariance estimation for high-dimensional datasets is a fundamental problem in machine learning, and has numerous applications. In these high-dimensional settings the number of...     

基于多级混合模型的图像分割方法

本文研究了典型的基于区域的图像分割方法主动形状模型(Active Shape Model,ASM)和基于边缘的图像分割snake算法,分析了算法适用条件和各自的优缺点.结合snake模型与主动形状模型,提出了一种基于多级混合模型的图像分割方法:首先使用ASM,获得的时目标图像位置和形态的最佳估计,并通过snake算法对匹配的结果进行二次调整,获取可以精确描述图像边缘信息的模型.试验表明了该方法的有效性.     

Computing on rays: A parallel approach for surface mesh modeling from multi-material volumetric data

Ray representation (Ray-rep) of a solid has been studied and used in the solid modeling community for many years because of its compactness and simplicity. This paper presents a parallel approach for mesh surface modeling from multi-material volume data using an extended Ray-rep as an intermediate, where every homogeneous region is enclosed by a set of two-manifold surface meshes on the resultant model. The approach consists of three major algorithms: firstly, an algorithm is developed to convert the given multi-material volumetric data into a Ray-rep for heterogeneous solid; secondly, filtering algorithm is exploited to process the rays of heterogeneous solid in parallel; and lastly, the adaptive mesh surfaces are generated from the Ray-rep through a dual-contouring like algorithm. Here the intermediate surfaces between two constituent materials can be directly extracted without building the volumetric mesh, and the manifold topology is preserved on each surface patch. Furthermore, general offset surface can be easily computed in this paradigm by designing a special parallel operator for the rays.     

混合云存储中网络稀疏大数据渗透迁移算法

当前方法没有考虑到特殊样本数据筛查的问题,导致数据渗透迁移完整度不高,所用时间较长,为此提出一种混合云存储中网络稀疏大数据渗透迁移算法.在主成分分析算法中引入信息熵的思想,对网络稀疏大数据进行降维处理,将降维结果与信息熵进行结合;筛选网络稀疏大数据的特征,将网络稀疏大数据中存在的无用特征进行剔除;计算网络稀疏大数据的敏...     

Global segmentation and curvature analysis of volumetric data sets using trivariate B-spline functions

This paper presents a method to globally segment volumetric images into regions that contain convex or concave (elliptic) iso-surfaces, planar or cylindrical (parabolic) iso-surfaces, and volumetric regions with saddle-like (hyperbolic) iso-surfaces, regardless of the value of the iso-surface level. The proposed scheme relies on a novel approach to globally compute, bound, and analyze the Gaussian and mean curvatures of an entire volumetric data set, using a trivariate B-spline volumetric representation. This scheme derives a new differential scalar field for a given volumetric scalar field, which could easily be adapted to other differential properties. Moreover, this scheme can set the basis for more precise and accurate segmentation of data sets targeting the identification of primitive parts. Since the proposed scheme employs piecewise continuous functions, it is precise and insensitive to aliasing.     

A segmentation approach for file broadcast scheduling

We study the broadcast scheduling problem in which clients send their requests to a server in order to receive some files available on the server. The server may be scheduled in a way that several requests are satisfied in one broadcast. When files are transmitted over computer networks, broadcasting the files by fragmenting them provides flexibility in broadcast scheduling that allows the optimization of per user response time. The broadcast scheduling algorithm, then, is in charge of determining the number of segments of each file and their order of transmission in each round of transmission. In this paper, we obtain a closed form approximation formula which approximates the optimal number of segments for each file, aiming at minimizing the total response time of requests. The obtained formula is a function of different parameters including those of underlying network as well as those of requests arrived at the server. Based on the obtained approximation formula we propose an algorithm for file broadcast scheduling which leads to total response time which closely conforms to the optimum one. We use extensive simulation and numerical study in order to evaluate the proposed algorithm which reveals high accuracy of obtained analytical approximation. We also investigate the impact of various headers that different network protocols add to each file segment. Our segmentation approach is examined for scenarios with different file sizes at the range of 100 KB to 1 GB. Our results show that for this range of file sizes the segmentation approach shows on average 13% tolerance from that of optimum in terms of total response time and the accuracy of the proposed approach is growing by increasing file size. Besides, using proposed segmentation in this work leads to a high Goodput of the scheduling algorithm.     

Volume models for volumetric data

Given a set of points on the boundary of an object derived from volumetric data, how can one represent the object and, in particular visualize it from these points? This problem is addressed by our research on the representation of points at the boundary of an object as a union of simple boundary primitives. We use volumetric data in the customary sense, but an additional feature for our purpose is the availability of an inside-outside test for any point within the volume. Our problem is, therefore, a restricted form of the general problem of visualizing an arbitrary cloud of points. Representing and visualizing can be vague concepts. As an intuitive example of the kind of representation we are looking for, assume we have data somehow representing a human head. In the first approximation, the head can be represented by a sphere. The surface area and the volume of the sphere give us rough, but useful, estimates of the corresponding properties for the head. At the same time, the position and radius of the sphere give us an idea of the translation and scaling to apply to get the head in some canonical position. If, instead, we fit an ellipsoid, the additional degrees of freedom might let us obtain the parameters of the rotations to apply. Of course, we cannot independently obtain estimates for the scaling, volume, or area. The obtainable estimates depend on the context. Whereas human perception deals very well with these ambiguities, computer visualization tends to fall short. The new representation of volumetric data based on union of spheres shows promise in achieving stability     

An approach for temporal analysis of email data based on segmentation

Many kinds of information are hidden in email data, such as the information being exchanged, the time of exchange, and the user IDs participating in the exchange. Analyzing the email data can reveal valuable information about the social networks of a single user or multiple users, the topics being discussed, and so on. In this paper, we describe a novel approach for temporally analyzing the communication patterns embedded in email data based on time series segmentation. The approach computes egocentric communication patterns of a single user, as well as sociocentric communication patterns involving multiple users. Time series segmentation is used to uncover patterns that may span multiple time points and to study how these patterns change over time. To find egocentric patterns, the email communication of a user is represented as an item-set time series. An optimal segmentation of the item-set time series is constructed, from which patterns are extracted. To find sociocentric patterns, the email data is represented as an item-setgroup time series. Patterns involving multiple users are then extracted from an optimal segmentation of the item-setgroup time series. The proposed approach is applied to the Enron email data set, which produced very promising results.     

Region based techniques for segmentation of volumetric histo-pathological images

In this article we have presented the application of three region based segmentation techniques namely, seeded volume growing, constrained erosion-dilation techniques and 3-D watershed algorithm. The algorithms are suitably extended to apply on 3-D histo-pathological images. Suitable modifications and extension for each algorithm is done to obtain better segmentation. A quantitative as well as qualitative comparison of the three methods is presented. Modifications to these algorithms for obtaining better results are discussed. The modifications include, (1) design of adaptive similarity measures to control the seeded volume growing and (2) rule-based merging of the over-segmented cells in the case of the 3-D watershed algorithm. Some results and quantitative study is also presented.