共查询到20条相似文献,搜索用时 15 毫秒
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In this paper, we introduce a novel parametric finite element method for segmentation of three-dimensional images. We consider a piecewise constant version of the Mumford–Shah and the Chan–Vese functionals and perform a region-based segmentation of 3D image data. An evolution law is derived from energy minimization problems which push the surfaces to the boundaries of 3D objects in the image. We propose a parametric scheme which describes the evolution of parametric surfaces. An efficient finite element scheme is proposed for a numerical approximation of the evolution equations. Since standard parametric methods cannot handle topology changes automatically, an efficient method is presented to detect, identify and perform changes in the topology of the surfaces. One main focus of this paper are the algorithmic details to handle topology changes like splitting and merging of surfaces and change of the genus of a surface. Different artificial images are studied to demonstrate the ability to detect the different types of topology changes. Finally, the parametric method is applied to segmentation of medical 3D images. 相似文献
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基于变宽邻域图割和活动轮廓的目标分割方法 总被引:1,自引:1,他引:1
基于图割的活动轮廓算法是一个结合图割优化工具和活动轮廓模型迭代变形思想的目标分割算法。针对算法在迭代过程中对已达目标边界的活动轮廓线所在邻域重复切割的不足,将活动轮廓线分为已达目标曲线段和未达目标曲线段,仅对未达目标曲线段进行膨胀得到可变宽度轮廓线邻域,从而减少了对邻域的切割时间。实验表明,改进算法效率提高为原来的2~3倍。 相似文献
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基于高斯混合模型的活动轮廓模型脑MRI分割 总被引:2,自引:0,他引:2
传统的活动轮廓模型用于图像分割往往基于目标的边界信息,在图像含有强噪音或目标具有弱边界时很难得到真实解.引入高斯混合模型构造新的约束项,在新的约束项作用下模型可以减少噪音的影响,并防止从弱边界泄漏.高斯混合模型求解通常使用Expectation-maximization(EM)算法,该算法是局部优化算法,且对初值敏感.因此引入粒子群算法,并提出一种改进的算法,利用该算法的全局优化性求解高斯混合模型的参数,以提高参数精度.对脑核磁共振图像(MRI)分割实验表明该模型具有较好的分割效果. 相似文献
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医学图像轮廓跟踪的广义模糊粒子滤波方法 总被引:5,自引:0,他引:5
在医学图像运动跟踪领域,轮廓线跟踪是描绘边缘运动的有力手段.为避免观测噪声的影响,增加轮廓的时空局部约束并利用粒子滤波(PF)技术解决该类跟踪问题是非常有效的.为更好地优化计算PF的重要比率(IR)以提高粒子滤波器的性能,该文提出了广义模糊粒子滤波(GFPF)方法,通过与当前较好的无迹粒子滤波(UPF)相比较,GFPF显示了很好的效果;另外,在似然估计方面,GFPF提供了独特的似然轮廓估计算法.理论和试验证明,GFPF不仅能够很好地解决动态轮廓跟踪问题,还为当前各种PF算法的IR计算提供了全新的解决途径. 相似文献
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We present a framework for incorporating prior information about high-probability shapes in the process of contour extraction
and object recognition in images. Here one studies shapes as elements of an infinite-dimensional, non-linear quotient space,
and statistics of shapes are defined and computed intrinsically using differential geometry of this shape space. Prior models
on shapes are constructed using probability distributions on tangent bundles of shape spaces. Similar to the past work on
active contours, where curves are driven by vector fields based on image gradients and roughness penalties, we incorporate
the prior shape knowledge in the form of vector fields on curves. Through experimental results, we demonstrate the use of
prior shape models in the estimation of object boundaries, and their success in handling partial obscuration and missing data.
Furthermore, we describe the use of this framework in shape-based object recognition or classification. 相似文献
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Ketut Fundana Niels C. Overgaard Anders Heyden 《International Journal of Computer Vision》2008,80(3):289-299
In this paper we address the problem of segmentation in image sequences using region-based active contours and level set methods.
We propose a novel method for variational segmentation of image sequences containing nonrigid, moving objects. The method
is based on the classical Chan-Vese model augmented with a novel frame-to-frame interaction term, which allow us to update
the segmentation result from one image frame to the next using the previous segmentation result as a shape prior. The interaction
term is constructed to be pose-invariant and to allow moderate deformations in shape. It is expected to handle the appearance
of occlusions which otherwise can make segmentation fail. The performance of the model is illustrated with experiments on
synthetic and real image sequences. 相似文献
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In this paper we consider the problem of reconstructing triangular surfaces from given contours. An algorithm solving this problem must decide which contours of two successive slices should be connected by the surface (branching problem) and, given that, which vertices of the assigned contours should be connected for the triangular mesh (correspondence problem). We present a new approach that solves both tasks in an elegant way. The main idea is to employ discrete distance fields enhanced with correspondence information. This allows us not only to connect vertices from successive slices in a reasonable way but also to solve the branching problem by creating intermediate contours where adjacent contours differ too much. Last but not least we show how the 2D distance fields used in the reconstruction step can be converted to a 3D distance field that can be advantageously exploited for distance calculations during a subsequent simplification step. 相似文献
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基于图划分的形状统计主动轮廓模型心脏MR图像分割 总被引:1,自引:0,他引:1
为有效分析心脏功能,高精度分割左、右心室是必要的.心脏MR图像中存在图像灰度不均,左、右心室及周围其它组织灰度接近,存在弱边缘、边缘断裂及噪声造成边缘模糊等现象,给精确分割左、右心室轮廓带来困难.本文在基于图划分的主动轮廓方法基础上,通过对训练形状进行配准及变化模式分析,定义左、右心室轮廓形状变化允许空间,提出基于图划分的形状统计主动轮廓模型来分割心脏MR图像.该方法通过图划分理论将图像分割问题转化为最优化问题,所以能够得到全局最优解,具有较大的捕捉范围.还引入形状统计来引导曲线的演化,有效处理曲线演化时存在的边缘泄漏问题,提高分割精度.实验结果表明,本文方法较以往方法具有更高的分割精度和更好的稳定性,为临床应用提供一种较可行的方法. 相似文献
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如何表示曲面上的曲线,在处理诸如数控加工中的路径设计以及CAD/CAM等领域频繁出现的曲面裁剪问题时显得日益重要.给出了数据点的切方向(切方向及曲率向量或测地曲率值)指定而G1连续(G2连续)插值曲面上任意点列的方法.作为曲面上曲线插值问题的特例,还讨论了曲面上曲线的混合问题.基本思想是借助于微分几何的有关结论,曲面上曲线的插值问题被转化为其参数平面上类似的曲线插值问题.该方法能够用二维隐式方程来表示曲面上的插值曲线,从而把在显示该曲线时所面对的曲面求交的几何问题转化为计算隐式曲线的代数问题.实验证明该方法是可行的,而且适用于CAD/CAM及计算机图形学等领域. 相似文献
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Chunlin Wu Juyong Zhang Yuping Duan Xue-Cheng Tai 《Journal of scientific computing》2012,50(1):145-166
Recently total variation (TV) regularization has been proven very successful in image restoration and segmentation. In image
restoration, TV based models offer a good edge preservation property. In image segmentation, TV (or vectorial TV) helps to
obtain convex formulations of the problems and thus provides global minimizations. Due to these advantages, TV based models
have been extended to image restoration and data segmentation on manifolds. However, TV based restoration and segmentation
models are difficult to solve, due to the nonlinearity and non-differentiability of the TV term. Inspired by the success of
operator splitting and the augmented Lagrangian method (ALM) in 2D planar image processing, we extend the method to TV and
vectorial TV based image restoration and segmentation on triangulated surfaces, which are widely used in computer graphics
and computer vision. In particular, we will focus on the following problems. First, several Hilbert spaces will be given to
describe TV and vectorial TV based variational models in the discrete setting. Second, we present ALM applied to TV and vectorial
TV image restoration on mesh surfaces, leading to efficient algorithms for both gray and color image restoration. Third, we
discuss ALM for vectorial TV based multi-region image segmentation, which also works for both gray and color images. The proposed
method benefits from fast solvers for sparse linear systems and closed form solutions to subproblems. Experiments on both
gray and color images demonstrate the efficiency of our algorithms. 相似文献
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Lisitsyn V. M. Obrosov K. V. Safonov V. A. 《Journal of Computer and Systems Sciences International》2019,58(6):945-959
Journal of Computer and Systems Sciences International - An analytical solution of the problem of estimating the coordinates of the axis of a cylindrical surface and its radius by processing range... 相似文献
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融合局部和全局图像信息的活动轮廓模型 总被引:3,自引:0,他引:3
为了克服局部图像拟合模型对轮廓初始化敏感的不足,结合改进C-V模型,提出一种融合局部和全局图像信息的活动轮廓模型.首先由改进C-V模型的全局灰度拟合力和局部图像拟合模型的局部灰度拟合力的一个线性组合来构造水平集演化力,然后通过调整这2个拟合力的权重以提升该模型对轮廓初始化的灵活性,最后利用高斯滤波正则水平集函数法实现水平集函数的正则化.实验结果表明,对于一些真实和人造图像,文中模型显示了对轮廓初始化的鲁棒性,以及较好地处理灰度不均图像的能力. 相似文献
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窄带主动轮廓模型及在医学和纹理图像局部分割中的应用 总被引:1,自引:0,他引:1
提出一种新的基于二值水平集的窄带主动轮廓模型用于局部分割.通过对二值水平集进行形态学膨胀和腐蚀操作, 提出一种稳定灵活可控的窄带控制方案,该方案可使得曲线进化精度从一个像素宽度灵活变化到任意大小. 考虑到局部分割一般要求初始轮廓置于待分割目标内部并不断膨胀进化直至目标边缘,本文提出用形态学闭运算作为新的曲线平滑方案. 与传统的高斯平滑和曲率平滑方案相比,形态学闭运算不仅能够更好地促进曲线的膨胀进化,而且有利于保持水平集函数的二值性. 此外,本文提出的方法是一种通用的自然框架,可以根据不同的需求设计不同的速度函数. 为了证明所提出的局部分割框架的有效性和鲁棒性,本文以医学图像和纹理图像为例分别设计了两个速度函数: 一个是融合了磁共振脑图像的非严格对称信息的速度函数用于大脑皮质下结构的局部分割;另一个是融合了局部熵和局部梯 度算子的速度函数用于纹理图像的局部分割. 在合成图像、医学图像和纹理图像上的实验证明了本文方法在局部分割中的有效性和鲁棒性. 相似文献
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Intersection of Parametric Surfaces by Means of Look-Up Tables 总被引:1,自引:0,他引:1