Volume 23, Issue 7

Characterizing the performance of image segmentation approaches has been a persistent challenge. Performance analysis is important since segmentation algorithms often have limited accuracy and precision. Interactive drawing of the desired segmentation by human raters has often been the only acceptable approach, and yet suffers from intra-rater and inter-rater variability. Automated algorithms have been sought in order to remove the variability introduced by raters, but such algorithms must be assessed to ensure they are suitable for the task. The performance of raters (human or algorithmic) generating segmentations of medical images has been difficult to quantify because of the difficulty of obtaining or estimating a known true segmentation for clinical data. Although physical and digital phantoms can be constructed for which ground truth is known or readily estimated, such phantoms do not fully reflect clinical images due to the difficulty of constructing phantoms which reproduce the full range of imaging characteristics and normal and pathological anatomical variability observed in clinical data. Comparison to a collection of segmentations by raters is an attractive alternative since it can be carried out directly on the relevant clinical imaging data. However, the most appropriate measure or set of measures with which to compare such segmentations has not been clarified and several measures are used in practice. We present here an expectation-maximization algorithm for simultaneous truth and performance level estimation (STAPLE). The algorithm considers a collection of segmentations and computes a probabilistic estimate of the true segmentation and a measure of the performance level represented by each segmentation. The source of each segmentation in the collection may be an appropriately trained human rater or raters, or may be an automated segmentation algorithm. The probabilistic estimate of the true segmentation is formed by estimating an optimal combination of the segmentations, weighting each segmentation depending upon the estimated performance level, and incorporating a prior model for the spatial distribution of structures being segmented as well as spatial homogeneity constraints. STAPLE is straightforward to apply to clinical imaging data, it readily enables assessment of the performance of an automated image segmentation algorithm, and enables direct comparison of human rater and algorithm performance.

表征图像分割方法的性能一直是一个持续的挑战。性能分析很重要，因为分割算法通常精度和准确度有限。由人类评分员交互式绘制所需分割通常曾是唯一可接受的方法，但存在评分员内和评分员间的变异性。为了消除评分员引入的变异性，人们寻求自动化算法，但必须评估这些算法以确保它们适合任务。生成医学图像分割的评分员（人类或算法）的性能难以量化，因为难以获得或估计临床数据的已知真实分割。尽管可以构建物理和数字幻影，其真实值已知或易于估计，但由于难以构建再现临床数据中观察到的全部成像特征及正常和病理解剖变异性的幻影，此类幻影不能完全反映临床图像。与评分员的分割集合进行比较是一种有吸引力的替代方案，因为它可以直接在相关临床成像数据上进行。然而，用于比较这些分割的最合适的度量或度量集尚未明确，实际中使用了多种度量。我们在此提出一种用于同时真实值及性能水平估计的期望最大化算法（STAPLE）。该算法考虑一个分割集合，计算真实分割的概率估计以及每个分割所代表的性能水平的度量。集合中每个分割的来源可以是经过适当训练的人类评分员或一个自动化分割算法。通过估计分割的最优组合，根据估计的性能水平对每个分割进行加权，并结合被分割结构的空间分布先验模型以及空间同质性约束，形成真实分割的概率估计。STAPLE易于应用于临床成像数据，能够方便地评估自动化图像分割算法的性能，并实现人类评分员与算法性能的直接比较。

The problem this paper addresses is how to use the two-dimensional D-bar method for electrical impedance tomography with experimental data collected on finitely many electrodes covering a portion of the boundary of a body. This requires an approximation of the Dirichlet-to-Neumann, or voltage-to-current density map, defined on the entire boundary of the region, from a finite number of matrix eleme...

本文解决的问题是，如何利用二维D-bar方法对电阻抗断层成像进行处理，该方法使用在覆盖身体边界一部分的有限个电极上收集的实验数据。这需要从有限数量的矩阵元素近似定义在区域整个边界上的Dirichlet-to-Neumann或电压-电流密度映射...

A statistical method for the evaluation of image registration for a series of images based on the assessment of consistency properties of the registration results is proposed. Consistency is defined as the residual error of the composition of cyclic registrations. By combining the transformations of different algorithms the consistency error allows a quantitative comparison without the use of grou...

提出了一种基于图像配准结果一致性属性评估的图像配准统计方法。一致性定义为循环配准组合的残差。通过结合不同算法的变换，一致性误差可以在不使用金标准的情况下进行定量比较。

Ultrasound is a main noninvasive modality for the assessment of the heart function. Wall tracking from ultrasound data is, however, inherently difficult due to weak echoes, clutter, poor signal-to-noise ratio, and signal dropouts. To cope with these artifacts, pretrained shape models can be applied to constrain the tracking. However, existing methods for incorporating subspace shape constraints in...

超声是评估心脏功能的主要无创模态。然而，由于弱回声、杂波、低信噪比和信号丢失，从超声数据进行心肌壁跟踪固有地困难。为了应对这些伪影，可以应用预训练的形状模型来约束跟踪。然而，现有的结合子空间形状约束的方法在...

A method is presented to interpolate between neighboring slices in a grey-scale tomographic data set. Spatial correspondence between adjacent slices is established using a nonrigid registration algorithm based on B-splines which optimizes the normalized mutual information similarity measure. Linear interpolation of the image intensities is then carried out along the directions calculated by the re...

提出了一种在灰度断层数据集中对相邻切片进行插值的方法。利用基于B样条的非刚体配准算法建立相邻切片之间的空间对应关系，该算法优化了归一化互信息相似性度量。然后沿着由配准计算出的方向对图像强度进行线性插值...

We propose a method for enforcing topology preservation and smoothness onto a given displacement field. We first analyze the conditions for topology preservation on two- and three-dimensional displacement fields over a discrete rectangular grid. We then pose the problem of finding the closest topology preserving displacement field in terms of its complete set of gradients, which we later solve usi...

我们提出了一种方法，用于在给定的位移场上强制保持拓扑和光滑性。我们首先分析了在离散矩形网格上二维和三维位移场保持拓扑的条件。然后，我们提出了根据其完整的梯度集寻找最接近的保持拓扑位移场的问题，随后我们通过...解决该问题。

The likelihood ratio, or ideal observer, decision rule is known to be optimal for two-class classification tasks in the sense that it maximizes expected utility (or, equivalently, minimizes the Bayes risk). Furthermore, using this decision rule yields a receiver operating characteristic (ROC) curve which is never above the ROC curve produced using any other decision rule, provided the observer's m...

似然比（即理想观察者）决策规则已知在二类分类任务中是最优的，因为它最大化期望效用（或者等价地，最小化贝叶斯风险）。此外，使用该决策规则得到的接收者操作特征（ROC）曲线永远不会高于使用任何其他决策规则得到的ROC曲线，前提是观察者的m...

In this paper, we present a new method for reconstructing three-dimensional (3-D) left ventricular myocardial strain from tagged magnetic resonance (MR) image data with a 3-D B-spline deformation model. The B-spline model is based on a cylindrical coordinate system that more closely fits the morphology of the myocardium than previously proposed Cartesian B-spline models and does not require explic...

本文提出了一种利用三维B样条变形模型从标记磁共振（MR）图像数据重建左心室心肌三维应变的新方法。该B样条模型基于圆柱坐标系，比先前提出的笛卡尔B样条模型更贴合心肌形态，且无需显式...

This paper presents a modified Uniform Cramer-Rao bound (UCRB) for studying estimator spatial resolution and variance tradeoffs. We proposed to use a resolution constraint that is imposed on mean gradient vectors of achieved estimators and derived the minimum achievable variance for any estimator satisfies this resolution constraint. This approach partially overcomes the limitations of the former ...

本文提出了一种改进的均匀Cramer-Rao界（UCRB），用于研究估计器空间分辨率和方差的权衡。我们建议使用一个施加于已实现估计器的平均梯度向量上的分辨率约束，并推导出满足该分辨率约束的任何估计器的最小可实现方差。这种方法部分克服了先前方法的局限性...

Peripheral enhancement and tilt correction of unprocessed digital mammograms was achieved with a new reversible algorithm. This method has two major advantages for image visualization. First, the display dynamic range can be relatively small, and second, adjustment of the overall luminance to inspect details is not required in most cases. The correction is useful for preprocessing in computer-aide...

通过一种新的可逆算法实现了未处理数字乳腺X线图像的外围增强和倾斜校正。该方法在图像可视化方面有两个主要优点。首先，显示动态范围可以相对较小；其次，在大多数情况下不需要调整整体亮度来检查细节。该校正对于计算机辅助预处理非常有用。

An analysis of the kinetics of myocardial contrast enhancement is an important component of myocardial perfusion studies. The contrast enhancement can be modeled by a linear time-invariant system, and the myocardial impulse response, calculated by deconvolution of the measured tissue response with an arterial input, gives a direct estimate of myocardial blood flow. In this paper, we analyze the ef...

心肌对比增强动力学分析是心肌灌注研究的重要组成部分。对比增强可通过线性时不变系统建模，通过将测量到的组织响应与动脉输入进行反卷积计算心肌脉冲响应，可直接估计心肌血流量。本文分析了...

The objective of the current study is to develop an automatic tool to identify microbiological data types using computer-vision and statistical modeling techniques. Bacteriophage (phage) typing methods are used to identify and extract representative profiles of bacterial types out of species such as the Staphylococcus aureus. Current systems rely on the subjective reading of profiles by a human ex...

当前研究的目标是利用计算机视觉和统计建模技术开发一种自动工具来识别微生物数据类型。噬菌体分型方法用于识别和提取诸如金黄色葡萄球菌等物种中细菌类型的代表性特征。当前系统依赖于人类对特征的主观解读。

This paper is built upon the assumption that in electrical impedance tomography, vectors of voltages and currents are linearly dependent through a resistance matrix. This linear relationship was confirmed experimentally and may be derived analytically under certain assumptions regarding electrodes (Isaacson, 1991). Given measurement data consisting of voltages and currents, we treat this relations...

本文基于以下假设：在电阻抗断层成像中，电压和电流向量通过电阻矩阵线性相关。这一线性关系已通过实验证实，并在一定电极假设下可解析推导（Isaacson, 1991）。给定由电压和电流组成的测量数据，我们将此关系...

Investigations into the method of generalized projections (MGP) as a ghost correction method for interleaved EPI are described. The technique is image-based and does not require additional reference scans. The algorithm was found to be more effective if a priori knowledge was incorporated to reduce the degrees of freedom, by modeling the ghosting as arising from a small number of phase offsets. In...

描述了将广义投影法(MGP)作为交错EPI鬼影校正方法的研究。该技术基于图像，不需要额外的参考扫描。研究发现，如果加入先验知识，通过将鬼影建模为来自少量相位偏移，从而减少自由度，则该算法更为有效。

Provides a listing of current committee members and society officers.

提供当前委员会成员和学会官员的列表。

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这些页面有意留白。

Presents the table of contents for this issue of the periodical.

展示了本期的目录。

Provides notice of upcoming conference events of interest to practitioners and researchers.

为从业者和研究人员提供即将召开的会议活动通知。

Provides instructions and guidelines to prospective authors who wish to submit manuscripts.

为希望提交手稿的潜在作者提供说明和指南。