Volume 27, Issue 6

The objective of this work was to develop a methodology for measuring cartilage thickness in anatomically based subregions in the tibial and in the central weight-bearing femoral cartilage from magnetic resonance (MR) images. The tibial plateau was divided into a central area of the total subchondral bone area (tAB), and anterior, posterior, internal, and external subregions surrounding it. In the weight-bearing femoral condyles, central, internal, and external subregions were determined. The Euclidean distance between the tAB and cartilage surface was used for determining cartilage thickness. The reproducibility of the method was evaluated on test-retest data sets of 12 participants (six healthy, six with osteoarthritis). The subregion size was varied systematically to study the influence on the reproducibility. The size of the subregions was highly consistent under conditions of repositioning (standard deviation 0.0%-0.3%). The precision errors for regional mean cartilage thickness measurements ranged from 19 mum (1.5%) to 84 mum (4.7%). The computation of regional cartilage thickness values from segmented MR images is shown to be highly reproducible and robust under conditions of joint repositioning. In longitudinal studies, this technique may substantially enhance the ability of quantitative MRI to monitor structural changes in osteoarthritis at narrow time intervals.

本工作的目的是开发一种从磁共振图像中测量胫骨和股骨中央负重区软骨在解剖子区域中的厚度的方法。将胫骨平台分为总的软骨下骨面积（tAB）的中心区域以及围绕它的前、后、内、外子区域。在负重股骨髁中，确定了中央、内、外子区域。使用tAB和软骨表面之间的欧几里得距离来确定软骨厚度。在12名参与者（6名健康，6名骨关节炎）的重复测试数据集上评估了该方法的可重复性。系统性地改变子区域大小以研究对可重复性的影响。在重新定位条件下，子区域的大小高度一致（标准差0.0%-0.3%）。区域平均软骨厚度测量的精度误差范围为19微米（1.5%）至84微米（4.7%）。结果表明，从分割的MR图像计算区域软骨厚度值在关节重新定位条件下高度可重复且稳健。在纵向研究中，该技术可能显著增强定量MRI在窄时间间隔内监测骨关节炎结构变化的能力。

Quantitative analysis of dynamic processes in living cells by means of fluorescence microscopy imaging requires tracking of hundreds of bright spots in noisy image sequences. Deterministic approaches, which use object detection prior to tracking, perform poorly in the case of noisy image data. We propose an improved, completely automatic tracker, built within a Bayesian probabilistic framework. It...

利用荧光显微镜成像对活细胞动态过程进行定量分析需要在噪声图像序列中跟踪数百个亮点。在跟踪之前使用目标检测的确定性方法在噪声图像数据情况下性能较差。我们提出了一种改进的、完全自动的跟踪器，建立在贝叶斯概率框架内。它...

A fast and simple algorithm for designing time-optimal waveforms is presented. The algorithm accepts a given arbitrary multidimensional $k$-space trajectory as the input and outputs the time-optimal gradient waveform that traverses $k$-space along that path in minimum time. The algorithm is noniterative, and its run time is independent of the complexity of the curve, i.e., the number of switches ...

提出了一种快速简单的算法用于设计时间最优波形。该算法接受给定的任意多维$k$空间轨迹作为输入，并输出沿该路径以最小时间遍历$k$空间的时间最优梯度波形。该算法非迭代，其运行时间与曲线的复杂度无关，即与开关次数...

Adaptive imaging systems alter their data-acquisition configuration or protocol in response to the image information received. An adaptive pinhole single-photon emission computed tomography (SPECT) system might acquire an initial scout image to obtain preliminary information about the radiotracer distribution and then adjust the configuration or sizes of the pinholes, the magnifications, or the pr...

自适应成像系统根据接收到的图像信息改变其数据采集配置或协议。一种自适应针孔单光子发射计算机断层扫描（SPECT）系统可能会获取初始侦察图像以获得关于放射性示踪剂分布的初步信息，然后调整针孔的配置或尺寸、放大倍数或...

The distribution of water diffusion in biological tissues may be estimated by a 3-D Fourier transform (FT) of diffusion-weighted measurements in $q$-space. In this study, methods for estimating diffusion spectrum measures (the zero-displacement probability, the mean-squared displacement, and the orientation distribution function) directly from the $q$-space signals are described. These methods we...

生物组织中水扩散的分布可以通过对q空间中的扩散加权测量进行三维傅里叶变换（FT）来估计。本研究描述了直接从q空间信号估计扩散谱测量（零位移概率、均方位移和方向分布函数）的方法。这些方法我们...

This paper proposes a novel computational methodology for modelling the haemodynamic effects of endovascular coil embolization for cerebral aneurysms. We employ high-resolution 3-D angiographic data to reconstruct the intracranial geometry and we model the coiled part of the aneurysm as a porous medium, with porosity decreasing as coils are inserted. The actual dimensions of the coils employed are...

本文提出了一种新颖的计算方法，用于模拟血管内线圈栓塞治疗脑动脉瘤的血流动力学效应。我们利用高分辨率三维血管造影数据重建颅内几何结构，并将动脉瘤的线圈部分建模为多孔介质，其孔隙率随着线圈的插入而降低。所用线圈的实际尺寸为...

Gridding microarray images remains, at present, a major bottleneck. It requires human intervention which causes variations of the gene expression results. In this paper, an original and fully automatic approach for accurately locating a distorted grid structure in a microarray image is presented. The gridding process is expressed as an optimization problem which is solved by using a genetic algori...

目前，微阵列图像的网格化仍然是一个主要瓶颈。它需要人工干预，这会导致基因表达结果的变异。本文提出了一种原始且全自动的方法，用于准确定位微阵列图像中失真的网格结构。网格化过程被表述为一个优化问题，并通过遗传算法求解。

Diffusion tensor magnetic resonance imaging (DT-MRI) is capable of providing quantitative insights into tissue microstructure in the brain. An important piece of information offered by DT-MRI is the directional preference of diffusing water molecules within a voxel. Building upon this local directional information, DT-MRI tractography attempts to construct global connectivity of white matter tract...

扩散张量磁共振成像（DT-MRI）能够提供关于大脑组织微结构的定量见解。DT-MRI提供的一个重要信息是体素内水分子扩散的方向偏好。基于这种局部方向信息，DT-MRI纤维束成像试图构建白质纤维束的全局连接...

We describe a process aiming to construct a 3-D geometric model of the human normal intracranial venous system from MRA data. An analysis of geometric properties of the intracranial veins and sinuses results in proposing three models: circular, elliptic, and free-shape. We formulate a rule based on which a suitable geometric venous model can be selected. The cross-sectional shape of different part...

我们描述了一种旨在从MRA数据构建人体正常颅内静脉系统三维几何模型的过程。分析了颅内静脉和静脉窦的几何特性，提出了三种模型：圆形、椭圆和自由形状。我们制定了一个规则，基于该规则可以选择合适的几何静脉模型。不同部位的横截面形状...

Inspired by Paragious and Deriche's work, which unifies boundary-based and region-based image partition approaches, we integrate the snake model and the Fisher criterion to capture, respectively, the boundary information and region information of microarray images. We then use the proposed algorithm to segment the spots in the microarray images, and compare our results with those obtained by comme...

受Paragious和Deriche工作的启发，该方法统一了基于边界和基于区域的图像分割方法，我们整合了蛇模型和费希尔准则，以分别捕获微阵列图像的边界信息和区域信息。然后，我们使用所提出的算法分割微阵列图像中的斑点，并将我们的结果与常见的分割方法进行比较。

This paper unifies our earlier work on detection of brain activation (Rajapakse and Piyaratna, 2001) and connectivity (Rajapakse and Zhou, 2007) in a probabilistic framework for analyzing effective connectivity among activated brain regions from functional magnetic resonance imaging (fMRI) data. Interactions among brain regions are expressed by a dynamic Bayesian network (DBN) while contextual dep...

本文统一了我们早期关于脑激活检测（Rajapakse 和 Piyaratna, 2001）和连接性（Rajapakse 和 Zhou, 2007）的工作，提出一个概率框架来分析功能性磁共振成像（fMRI）数据中激活脑区之间的有效连接。脑区之间的相互作用通过动态贝叶斯网络（DBN）表示，而上下文依赖……

Voxel-based reconstructions in diffuse optical tomography (DOT) using a quadratic regularization functional tend to produce very smooth images due to the attenuation of high spatial frequencies. This then causes difficulty in estimating the spatial extent and contrast of anomalous regions such as tumors. Given an assumption that the target image is piecewise constant, we can employ a parametric mo...

使用二次正则化函数的漫射光学层析成像（DOT）中的基于体素的重建往往会因高频空间衰减而产生非常平滑的图像。这导致难以估计异常区域（如肿瘤）的空间范围和对比度。假设目标图像是分段常数，我们可以采用参数化模型...

This paper describes a dynamic vector model for modelling the electromagnetic characteristics of microstrip radio-frequency (RF) resonators for high field magnetic resonance imaging (MRI). A biological tissue-equivalent load having a circular cross section is assumed in the analysis. The dynamic model uses the well-known Green's function for cylindrically stratified media to characterize all six c...

本文描述了一种用于高场磁共振成像（MRI）中微带射频谐振器电磁特性建模的动态向量模型。分析中假设了具有圆形截面的生物组织等效负载。动态模型利用著名的圆柱层状介质格林函数来表征所有六个分量...

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