Volume 20, Issue 5

A fully automated approach to segmentation of the left and right cardiac ventricles from magnetic resonance (MR) images is reported. A novel multistage hybrid appearance model methodology is presented in which a hybrid active shape model/active appearance model (AAM) stage helps avoid local minima of the matching function. This yields an overall more favorable matching result. An automated initialization method is introduced making the approach fully automated. The authors' method was trained in a set of 102 MR images and tested in a separate set of 60 images. In all testing cases, the matching resulted in a visually plausible and accurate mapping of the model to the image data. Average signed border positioning errors did not exceed 0.3 mm in any of the three determined contours-left-ventricular (LV) epicardium, LV and right-ventricular (RV) endocardium. The area measurements derived from the three contours correlated well with the independent standard (r=0.96, 0.96, 0.90), with slopes and intercepts of the regression lines close to one and zero, respectively. Testing the reproducibility of the method demonstrated an unbiased performance with small range of error as assessed via Bland-Altman statistic. In direct border positioning error comparison, the multistage method significantly outperformed the conventional AAM (p<0.001). The developed method promises to facilitate fully automated quantitative analysis of LV and RV morphology and function in clinical setting.

报道了一种从磁共振（MR）图像中自动分割左右心室的完全自动化方法。提出了一种新颖的多阶段混合外观模型方法，其中混合主动形状模型/主动外观模型（AAM）阶段有助于避免匹配函数的局部最小值，从而产生更好的整体匹配结果。引入了一种自动初始化方法，使该方法完全自动化。作者的方法在102张MR图像上训练，并在另外60张图像上测试。在所有测试案例中，匹配结果在视觉上合理且精确地将模型映射到图像数据上。在确定的三个轮廓——左心室（LV）心外膜、左心室和右心室（RV）心内膜——中，平均有符号边界定位误差不超过0.3 mm。从三个轮廓导出的面积测量值与独立标准高度相关（r=0.96, 0.96, 0.90），回归线的斜率和截距分别接近1和0。通过Bland-Altman统计评估，该方法的重现性测试显示出无偏性能且误差范围小。在直接边界定位误差比较中，多阶段方法显著优于传统AAM（p<0.001）。所开发的方法有望促进临床环境中LV和RV形态和功能的完全自动化定量分析。

A method is proposed for three-dimensional (3-D) texture analysis of magnetic resonance imaging brain datasets. It is based on extended, multisort co-occurrence matrices that employ intensity, gradient and anisotropy image features in a uniform way. Basic properties of matrices as well as their sensitivity and dependence on spatial image scaling are evaluated. The ability of the suggested 3-D text...

提出了一种针对磁共振成像脑数据集的三维纹理分析方法。该方法基于扩展的多排序共现矩阵，以统一的方式利用强度、梯度及各向异性图像特征。评估了矩阵的基本属性及其对空间图像缩放的敏感性和依赖性。所提出的三维纹理...

A new method for medical image registration is formulated as a minimization problem involving robust estimators. The authors propose an efficient hierarchical optimization framework which is both multiresolution and multigrid. An anatomical segmentation of the cortex is introduced in the adaptive partitioning of the volume on which the multigrid minimization is based. This allows to limit the esti...

一种新的医学图像配准方法被表述为涉及鲁棒估计的最小化问题。作者提出了一种高效的分层优化框架，该框架同时具有多分辨率和多重网格特性。在基于多重网格最小化的体积自适应分区中引入了皮质的解剖分割。这使得能够限制估计...

The maximum-likelihood (ML) expectation-maximization (EM) [ML-EM] algorithm is being widely used for image reconstruction in positron emission tomography. The algorithm is strictly valid if the data are Poisson distributed. However, it is also often applied to processed sinograms that do not meet this requirement. This may sometimes lead to suboptimal results: streak artifacts appear and the algor...

最大似然（ML）期望最大化（EM）[ML-EM]算法正被广泛用于正电子发射断层扫描图像重建。如果数据呈泊松分布，该算法严格有效。然而，它也经常应用于不满足此要求的已处理正弦图。这有时会导致次优结果：出现条纹伪影，并且算法...

Fractal analysis of bone X-ray images has received much interest recently for the diagnosis of bone disease. Here, the authors propose a fractal analysis of bone X-ray tomographic microscopy (XTM) projections. The aim of the study is to establish whether or not there is a correlation between three-dimensional (3-D) trabecular changes and two-dimensional (2-D) fractal descriptors. Using a highly co...

骨X射线图像的分形分析近来在骨病诊断中受到广泛关注。本文作者提出对骨X射线断层显微镜（XTM）投影进行分形分析。研究旨在确定三维（3-D）小梁变化与二维（2-D）分形描述符之间是否存在相关性。利用高度共...

Computed tomography (CT) provides the most reliable method to detect emphysema in vivo. Commonly used methods only calculate the area of low attenuation [pixel index (PI)], while a radiologist considers the bullous morphology of emphysema. The PI is a good, well-known measure of emphysema. But it is not able to detect emphysema in cases in which emphysema and fibrosis occur at the same time. This ...

计算机断层扫描（CT）是检测体内肺气肿最可靠的方法。常用方法仅计算低衰减区域[像素指数（PI）]，而放射科医生会考虑肺气肿的泡状形态。PI是衡量肺气肿的良好且众所周知的指标，但在肺气肿和纤维化同时发生时无法检测肺气肿。

The authors propose a flexible, comprehensive approach for analysis of [/sup 15/O]-water positron emission tomography (PET) brain images using a penalized version of linear discriminant analysis (PDA). They applied it to scans from 20 subjects (eight scans/subject) performing a finger movement task and analyzed: (1) two classes to obtain a covariance-normalized baseline-activation image, and (2) e...

作者提出了一种灵活、全面的方法，用于分析[15O]-水正电子发射断层扫描（PET）脑图像，该方法使用惩罚线性判别分析（PDA）。他们将其应用于20名受试者（每人八次扫描）进行手指运动任务的扫描，并分析了：(1) 两类以获得协方差归一化的基线激活图像，以及(2) ...

Presents a contextual clustering procedure for statistical parametric maps (SPM) calculated from time varying three-dimensional images. The algorithm can be used for the detection of neural activations from functional magnetic resonance images (fMRI). An important characteristic of SPM is that the intensity distribution of background (nonactive area) is known whereas the distributions of activatio...

提出了一种用于从随时间变化的三维图像计算出的统计参数图的上下文聚类过程。该算法可用于从功能磁共振图像中检测神经激活。统计参数图的一个重要特征是背景（非活动区域）的强度分布已知，而激活区域的分布...