Volume 20, Issue 4

Breast tissue deformation modeling has recently gained considerable interest in various medical applications. A biomechanical model of the breast is presented using a finite element (FE) formulation. Emphasis is given to the modeling of breast tissue deformation which takes place in breast imaging procedures. The first step in implementing the FE modeling (FEM) procedure is mesh generation. For objects with irregular and complex geometries such as the breast, this step is one of the most difficult and tedious tasks. For FE mesh generation, two automated methods are presented which process MRI breast images to create a patient-specific mesh. The main components of the breast are adipose, fibroglandular and skin tissues. For modeling the adipose and fibroglandular tissues, we used eight noded hexahedral elements with hyperelastic properties, while for the skin, we chose four noded hyperelastic membrane elements. For model validation, an MR image of an agarose phantom was acquired and corresponding FE meshes were created. Based on assigned elasticity parameters, a numerical experiment was performed using the FE meshes, and good results were obtained. The model was also applied to a breast image registration problem of a volunteer's breast. Although qualitatively reasonable, further work is required to validate the results quantitatively.

乳房组织变形建模最近在各种医学应用中引起了广泛关注。本文提出了一种使用有限元公式的乳房生物力学模型。重点是对乳房成像过程中发生的乳房组织变形进行建模。实施有限元建模的第一步是网格生成。对于像乳房这样具有不规则和复杂几何形状的物体，这一步是最困难和最繁琐的任务之一。对于有限元网格生成，提出了两种自动化方法，它们处理MRI乳房图像以创建患者特定的网格。乳房的主要组成部分是脂肪、纤维腺体和皮肤组织。对于脂肪和纤维腺体组织的建模，我们使用了具有超弹性特性的八节点六面体单元，而对于皮肤，我们选择了四节点超弹性膜单元。为了模型验证，获取了琼脂糖体模的MR图像，并创建了相应的有限元网格。基于分配的弹性参数，使用有限元网格进行了数值实验，并获得了良好的结果。该模型还应用于一名志愿者乳房的图像配准问题。虽然定性上合理，但需要进一步工作来定量验证结果。

The maximum-likelihood (ML) approach in emission tomography provides images with superior noise characteristics compared to conventional filtered backprojection (FBP) algorithms. The expectation-maximization (EM) algorithm is an iterative algorithm for maximizing the Poisson likelihood in emission computed tomography that became very popular for solving the ML problem because of its attractive the...

发射断层成像中的最大似然（ML）方法相比传统的滤波反投影（FBP）算法能提供具有更优噪声特性的图像。期望最大化（EM）算法是一种用于最大化发射计算机断层成像中泊松似然的迭代算法，由于其吸引人的特性而非常流行于解决ML问题...

This paper presents a deformable model for automatically segmenting brain structures from volumetric magnetic resonance (MR) images and obtaining point correspondences, using geometric and statistical information in a hierarchical scheme. Geometric information is embedded into the model via a set of affine-invariant attribute vectors, each of which characterizes the geometric structure around a po...

本文提出了一种可变形模型，用于从体积磁共振（MR）图像中自动分割脑结构并获得点对应关系，采用层次化方案利用几何和统计信息。几何信息通过一组仿射不变属性向量嵌入到模型中，每个向量描述一个点周围的几何结构...

This paper describes fusion of three-dimensional (3-D) ultrasound (US) and magnetic resonance imaging (MRI) data sets, without the assistance of external fiducial markers or external position sensors. Fusion of these two modalities combines real-time 3-D ultrasound scans of soft tissue with the larger anatomical framework from MRI. The complementary information available from multiple imaging moda...

本文描述了在不使用外部基准标记或外部位置传感器的情况下，三维超声与磁共振成像数据集的融合。这两种模态的融合将软组织的实时三维超声扫描与MRI提供的更大解剖框架相结合。多模态成像提供的互补信息...

This paper presents a statistical model supported approach for enhanced segmentation and extraction of suspicious mass areas from mammographic images. With an appropriate statistical description of various discriminate characteristics of both true and false candidates from the localized areas, an improved mass detection may be achieved in computer-assisted diagnosis (CAD). In this study, one type ...

本文提出了一种基于统计模型的方法，用于从乳腺X线图像中增强分割和提取可疑肿块区域。通过对局部区域内真假候选的各种判别特征进行适当的统计描述，可以在计算机辅助诊断（CAD）中实现改进的肿块检测。在本研究中，一种类型……

For pt.I see ibid., vol.20, no.4, p.289-301 (2001). Based on the enhanced segmentation of suspicious mass areas, further development of computer-assisted mass detection may be decomposed into three distinctive machine learning tasks: (1) construction of the featured knowledge database; (2) mapping of the classified and/or unclassified data points in the datahase; and (3) development of an intellig...

第一部分见同上，第20卷，第4期，第289-301页（2001年）。基于对可疑肿块区域的增强分割，计算机辅助肿块检测的进一步开发可分解为三个独特的机器学习任务：（1）构建特征知识数据库；（2）映射数据库中已分类和/或未分类的数据点；（3）开发智能...

Certain diseases cause permanent changes to the shapes and densities of nailfold capillaries and, therefore, nailfold capillaroscopy is important as a tool for diagnosing and monitoring these diseases. The first aim of the project is to resolve differences in terminology that have developed over the years in previous work. We propose a taxonomy for nailfold capillaries that cover six descriptive c...

某些疾病会导致甲襞毛细血管的形状和密度发生永久性变化，因此甲襞毛细血管镜检查作为诊断和监测这些疾病的工具非常重要。该项目的首要目标是解决以往工作中长期存在的术语差异。我们提出了一种涵盖六种描述性特征的甲襞毛细血管分类法...

The determination of the sources of electric activity inside the brain from electric and magnetic measurements on the surface of the head is known to be an ill-posed problem. In this paper, a new algorithm which takes temporal a priori information modeled by the smooth activation model into account is described and compared with existing algorithms such as Tikhonov-Phillips.

从头部表面的电学和磁学测量确定脑内电活动的源是一个已知的不适定问题。本文描述了一种考虑由平滑激活模型建模的时间先验信息的新算法，并与Tikhonov-Phillips等现有算法进行了比较。

The algorithm we consider here is a block-iterative (or ordered subset) version of the inferior point algorithm for transmission reconstruction. Our algorithm is an interior point method because each vector of the iterative sequence {x/sup k/}, k= 0, 1, 2,..., satisfies the constraints a/sub j/<x/sub j//sup k/<b/sub j/, j=1,..., J. Because it is a block-iterative algorithm that reconstructs the tr...

我们在此考虑的算法是用于透射重建的劣点算法的块迭代（或有序子集）版本。我们的算法是一种内点法，因为迭代序列{x/sup k/}, k=0,1,2,...的每个向量都满足约束a/sub j/<x/sub j//sup k/<b/sub j/, j=1,...,J。由于它是一种块迭代算法，重建了tr...

Estimation of current or potential distribution on the cortex is used to obtain information about neural sources from the scalp recorded electroencephalogram. If the active sources in the brain are superficial, the estimated field distribution on the cortex also yields information about the active source configuration. In these cases, these methods can be used as source localization methods. In th...

利用头皮记录的脑电图（EEG）估计皮层上的电流或电位分布，以获取神经源的信息。如果大脑中的活动源是浅表的，则估计的皮层场分布也能提供活动源配置的信息。在这些情况下，这些方法可作为源定位方法使用。在...