Volume 19, Issue 1

The authors have been developing general user steered image segmentation strategies for routine use in applications involving a large number of data sets. In the past, they have presented three segmentation paradigms: live wire, live lane, and a three-dimensional (3-D) extension of the live-wire method. Here, they introduce an ultra-fast live-wire method, referred to as live wire on the fly for further reducing user's time compared to the basic live-wire method. In live wire, 3-D/four-dimensional (4-D) object boundaries are segmented in a slice-by-slice fashion. To segment a two-dimensional (2-D) boundary, the user initially picks a point on the boundary and all possible minimum-cost paths from this point to all other points in the image are computed via Dijkstra's algorithm. Subsequently, a live wire is displayed in real time from the initial point to any subsequent position taken by the cursor. If the cursor is close to the desired boundary, the live wire snaps on to the boundary. The cursor is then deposited and a new live-wire segment is found next. The entire 2-D boundary is specified via a set of live-wire segments in this fashion. A drawback of this method is that the speed of optimal path computation depends on image size. On modestly powered computers, for images of even modest size, some sluggishness appears in user interaction, which reduces the overall segmentation efficiency. In this work, the authors solve this problem by exploiting some known properties of graphs to avoid unnecessary minimum-cost path computation during segmentation. In live wire on the fly, when the user selects a point on the boundary the live-wire segment is computed and displayed in real time from the selected point to any subsequent position of the cursor in the image, even for large images and even on low-powered computers. Based on 492 tracing experiments from an actual medical application, the authors demonstrate that live wire on the fly is 1.331 times faster than live wire for actual segmentation for varying image sizes, although the pure computational part alone is found to be about 120 times faster.

作者一直致力于开发通用的用户引导图像分割策略，用于涉及大量数据集的常规应用。过去，他们提出了三种分割范式：活动线、活动车道以及活动线方法的三维（3-D）扩展。在此，他们介绍了一种超快速的活动线方法，称为即时活动线，以进一步减少用户时间相比基本活动线方法。在活动线中，3-D/四维（4-D）物体边界以逐切片方式分割。为了分割二维（2-D）边界，用户首先在边界上选取一个点，然后通过Dijkstra算法计算从该点到图像中所有其他点的所有最小代价路径。随后，从初始点到光标随后位置的即时活动线实时显示。如果光标接近期望边界，活动线会捕捉到边界上。然后放置光标，接着找到新的活动线段。整个二维边界通过一组活动线段以这种方式指定。该方法的缺点是，最优路径计算的速度取决于图像大小。在性能一般的计算机上，即使是中等大小的图像，用户交互也会出现一些迟缓，这降低了整体分割效率。在本工作中，作者通过利用图的一些已知属性来避免分割过程中不必要的代价路径计算，从而解决了这个问题。在即时活动线中，当用户在边界上选择一个点时，活动线段从所选点到图像中光标随后位置实时计算并显示，即使对于大图像和低性能计算机也是如此。基于来自实际医学应用的492次追踪实验，作者证明，对于不同图像大小的实际分割，即时活动线比活动线快1.331倍，尽管纯计算部分本身大约快120倍。

This paper presents a new reconstruction algorithm for both single- and dual-energy computed tomography (CT) imaging. By incorporating the polychromatic characteristics of the X-ray beam into the reconstruction process, the algorithm is capable of eliminating beam hardening artifacts. The single energy version of the algorithm assumes that each voxel in the scan field can be expressed as a mixture...

本文提出了一种用于单能量和双能量计算机断层扫描（CT）成像的新型重建算法。通过将X射线束的多色特性纳入重建过程，该算法能够消除射束硬化伪影。该算法的单能量版本假设扫描场中的每个体素可以表示为混合物...

Proposes and validates the hypothesis that one can use differential shape properties of the myocardial surfaces to recover dense field motion from standard three-dimensional (3-D) image sequences (MRI and CT). Quantitative measures of left ventricular regional function can be further inferred from the point correspondence maps. The noninvasive, algorithm-derived results are validated on two levels...

提出并验证了一种假设，即可以利用心肌表面的微分形状特性从标准三维（3-D）图像序列（MRI和CT）中恢复密集场运动。进一步可以从点对应图中推断出左心室区域功能的定量测量。无创、算法推导的结果在两个层面上得到验证...

Introduces a computer-aided atlas-based functional neurosurgery methodology and describes NeuroPlanner, a software system which supports it. NeuroPlanner provides four groups of functions: (1) data-related for data reading, interpolation, reformatting, and image processing; (2) atlas-related for multiple atlases reading, atlas-to-data global and local registrations, two way anatomical indexing, an...

介绍了一种基于计算机辅助图谱的功能神经外科学方法，并描述了支持该方法的软件系统NeuroPlanner。NeuroPlanner提供四组功能：（1）数据相关功能，用于数据读取、插值、重格式化和图像处理；（2）图谱相关功能，用于多图谱读取、图谱到数据的全局和局部配准、双向解剖索引等。

Describes a probabilistic framework for modeling single-trial functional magnetic resonance (fMR) images based on a parametric model for the hemodynamic response and Markov random field (MRF) image models. The model is fitted to image data by maximizing a lower bound on the log likelihood. The result is an approximate maximum a posteriori estimate of the joint distribution over the model parameter...

描述了一个基于血流动力学反应参数模型和马尔可夫随机场(MRF)图像模型对单次试验功能磁共振图像进行概率建模的框架。该模型通过最大化对数似然的下界来拟合图像数据。结果是对模型参数联合分布的近似最大后验估计。

Volume rendering is a visualization technique that has important applications in diagnostic radiology and in radiotherapy but has not achieved widespread use due, in part, to the lack of volumetric analysis tools for comparison of volume rendering to conventional visualization techniques. The volume rendering quantification algorithm (VRQA), a technique for three-dimensional (3-D) reconstruction o...

体积渲染是一种可视化技术，在诊断放射学和放射治疗中具有重要应用，但尚未得到广泛使用，部分原因是缺乏用于比较体积渲染与传统可视化技术的体积分析工具。体积渲染量化算法（VRQA）是一种用于三维（3D）重建的技术...

Because an image can be reconstructed from knowledge of its Radon transform (RT), the task of reconstructing an image is tantamount to that of estimating its RT. Based upon the Fourier diffraction projection (FDP) theorem, from the statistical perspective of unbiased reduction of image variance, the author previously proposed an infinite family of estimation methods for obtaining the RT from the s...

由于图像可以从其Radon变换（RT）的知识重建，重建图像的任务等同于估计其RT。基于傅里叶衍射投影（FDP）定理，从无偏减少图像方差的统计角度出发，作者先前提出了一个无限族的估计方法来从s...