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The current trend in attenuation correction for single photon emission computed tomography (SPECT) is to measure and reconstruct the attenuation coefficient map using a transmission scan, performed either sequentially or simultaneously with the emission scan. This approach requires dedicated hardware and increases the cost (and in some cases the scanning time) required to produce a clinical SPECT ...

当前单光子发射计算机断层扫描（SPECT）衰减校正的趋势是使用透射扫描测量和重建衰减系数图，该扫描可与发射扫描顺序或同时进行。这种方法需要专用硬件，并增加了临床SPECT...

The problem of parameter estimation from Rician distributed data (e.g., magnitude magnetic resonance images) is addressed. The properties of conventional estimation methods are discussed and compared to maximum-likelihood (ML) estimation which is known to yield optimal results asymptotically. In contrast to previously proposed methods, ML estimation is demonstrated to be unbiased for high signal-t...

本文讨论了从莱斯分布数据（例如，磁共振图像的幅度）进行参数估计的问题。讨论了传统估计方法的性质，并与已知渐近最优的最大似然（ML）估计进行了比较。与先前提出的方法相反，ML估计被证明在高信噪比条件下是无偏的...

This paper presents a new technique for the automatic model-based segmentation of three-dimensional (3-D) objects from volumetric image data. The development closely follows the seminal work of Taylor and Cootes on active shape models, but is based on a hierarchical parametric object description rather than a point distribution model. The segmentation system includes both the building of statistic...

本文提出了一种新的自动模型分割三维物体来自体积图像数据的技术。该发展紧密遵循Taylor和Cootes在主动形状模型方面的开创性工作，但基于分层参数化对象描述而非点分布模型。分割系统包括统计...

Proliferative diabetic retinopathy is a rare condition likely to lead to severe visual impairment. It is characterized by the development of abnormal new retinal vessels. We describe a method for automatically detecting new vessels on the optic disc using retinal photography. Vessel-like candidate segments are first detected using a method based on watershed lines and ridge strength measurement. F...

增殖性糖尿病视网膜病变是一种罕见的疾病，可能导致严重的视力损伤。其特征是异常新生视网膜血管的生成。我们描述了一种使用视网膜摄影自动检测视盘上新血管的方法。首先，基于分水岭线和脊强度测量的方法检测血管样候选段。

It is often desired to calculate line integrals through a field of reconstructed CT density pixels for the purpose of improving CT image quality. Two algorithms widely published and discussed in the past are known to either degrade spatial resolution or generate errors in the results due to the discontinuous "square pixel" modeling of the reconstructed image. An algorithm is described, based on li...

中文摘要翻译待生成

Reconstruction of images in electrical impedance tomography requires the solution of a nonlinear inverse problem on noisy data. This problem is typically ill-conditioned and requires either simplifying assumptions or regularization based on a priori knowledge. The authors present a reconstruction algorithm using neural network techniques which calculates a linear approximation of the inverse probl...

中文摘要翻译待生成

We show an iterative reconstruction framework for diffraction ultrasound tomography. The use of broad-band illumination allows significant reduction of the number of projections compared to straight ray tomography. The proposed algorithm makes use of forward nonuniform fast Fourier transform (NUFFT) for iterative Fourier inversion. Incorporation of total variation regularization allows the reducti...

我们展示了一种用于衍射超声层析成像的迭代重建框架。与直射线层析成像相比，使用宽带照明可以显著减少投影数量。所提出的算法利用前向非均匀快速傅里叶变换（NUFFT）进行迭代傅里叶反演。结合总变差正则化可以减少...

Radial basis functions are presented as a practical solution to the problem of interpolating incomplete surfaces derived from three-dimensional (3-D) medical graphics. The specific application considered is the design of cranial implants for the repair of defects, usually holes, in the skull. Radial basis functions impose few restrictions on the geometry of the interpolation centers and are suited to problems where the Interpolation centers do not form a regular grid. However, their high computational requirements have previously limited their use to problems where the number of interpolation centers is small (<300). Recently developed fast evaluation techniques have overcome these limitations and made radial basis interpolation a practical approach for larger data sets. In this paper radial basis functions are fitted to depth-maps of the skull's surface, obtained from X-ray computed tomography (CT) data using ray-tracing techniques. They are used to smoothly interpolate the surface of the skull across defect regions. The resulting mathematical description of the skull's surface can be evaluated at any desired resolution to be rendered on a graphics workstation or to generate instructions for operating a computer numerically controlled (CNC) mill.

径向基函数被提出作为解决三维医学图形中不完整表面插值问题的实用方法。具体应用考虑的是设计颅骨植入物以修复颅骨中的缺损（通常是孔洞）。径向基函数对插值中心的几何形状限制很少，适用于插值中心不形成规则网格的问题。然而，它们的高计算要求此前限制了其应用，仅能处理插值中心数量较少（<300）的问题。最近开发的快速评估技术克服了这些限制，使径向基插值成为处理更大数据集的实用方法。本文中，径向基函数被拟合到通过射线追踪技术从X射线计算机断层扫描（CT）数据获得的颅骨表面深度图上，用于平滑插值缺损区域的颅骨表面。由此得到的颅骨表面数学描述可以在任何所需分辨率下进行评估，以便在图形工作站上渲染，或生成用于操作计算机数控铣床的指令。

Derives approximate analytical expressions for the local impulse response and covariance of images reconstructed from fully three-dimensional (3-D) positron emission tomography (PET) data using maximum a posteriori (MAP) estimation. These expressions explicitly account for the spatially variant detector response and sensitivity of a 3-D tomograph. The resulting spatially variant impulse response and covariance are computed using 3-D Fourier transforms. A truncated Gaussian distribution is used to account for the effect on the variance of the nonnegativity constraint used in MAP reconstruction. Using Monte Carlo simulations and phantom data from the microPET small animal scanner, the authors show that the approximations provide reasonably accurate estimates of contrast recovery and covariance of MAP reconstruction for priors with quadratic energy functions. They also describe how these analytical results can be used to achieve near-uniform contrast recovery throughout the reconstructed volume.

推导了使用最大后验（MAP）估计从全三维（3-D）正电子发射断层扫描（PET）数据重建图像的局部脉冲响应和协方差的近似解析表达式。这些表达式明确考虑了三维断层扫描仪的空间变化探测器响应和灵敏度。使用三维傅里叶变换计算得到的空间变化脉冲响应和协方差。采用截断高斯分布来解释MAP重建中非负性约束对方差的影响。通过蒙特卡罗模拟和来自microPET小动物扫描仪的体模数据，作者表明这些近似方法能够为具有二次能量函数的先验提供对比度恢复和协方差的合理准确估计。他们还描述了如何利用这些分析结果在整个重建体积中实现接近均匀的对比度恢复。

A new statistical approach to phase correction in NMR imaging is proposed. The proposed scheme consists of first-and zero-order phase corrections each by the inverse multiplication of estimated phase error. The first-order error is estimated by the phase of autocorrelation calculated from the complex valued phase distorted image while the zero-order correction factor is extracted from the histogra...

中文摘要翻译待生成

Quantification of the degree of stenosis or vessel dimensions are important for diagnosis of vascular diseases and planning vascular interventions. Although diagnosis from three-dimensional (3-D) magnetic resonance angiograms (MRA's) is mainly performed on two-dimensional (2-D) maximum intensity projections, automated quantification of vascular segments directly from the 3-D dataset is desirable t...

量化狭窄程度或血管尺寸对于诊断血管疾病和规划血管介入治疗非常重要。尽管从三维（3-D）磁共振血管造影（MRA）图像进行诊断主要基于二维（2-D）最大强度投影，但直接从三维数据集自动量化血管段是理想的...

Algebraic reconstruction methods, such as the algebraic reconstruction technique (ART) and the related simultaneous ART (SART), reconstruct a two-dimensional (2-D) or three-dimensional (3-D) object from its X-ray projections. The algebraic methods have, in certain scenarios, many advantages over the more popular Filtered Backprojection approaches and have also recently been shown to perform well f...

代数重建方法，如代数重建技术(ART)及其相关的同步ART(SART)，通过X射线投影重建二维或三维物体。在某些情况下，代数方法比更流行的滤波反投影方法具有许多优点，并且最近也被证明在...中表现良好。

It is known that when a tissue is subjected to movements such as rotation, shearing, scaling, etc., changes in speckle patterns that result act as a noise source, often responsible for most of the displacement-estimate variance. From a modeling point of view, these changes can be thought of as resulting from two mechanisms: one is the motion of the speckles and the other, the alterations of their ...

已知当组织受到旋转、剪切、缩放等运动时，产生的散斑图案变化会作为噪声源，通常是位移估计方差的主要来源。从建模角度来看，这些变化可归因于两种机制：一是散斑的运动，二是其形状的改变。

Presents the use of an entropy focus criterion to enable automatic focusing of motion corrupted magnetic resonance images. The authors demonstrate the principle using illustrative examples from cooperative volunteers. Their technique can determine unknown patient motion or use knowledge of motion from other measures as a starting estimate. The motion estimate is used to compensate the acquired dat...

介绍了使用熵聚焦准则来自动聚焦运动污染的磁共振图像。作者通过合作志愿者的示例说明了该原理。他们的技术可以确定未知的患者运动，或利用来自其他测量的运动知识作为初始估计。运动估计用于补偿采集的数据...

Presents a framework for designing fast and monotonic algorithms for transmission tomography penalized-likelihood image reconstruction. The new algorithms are based on paraboloidal surrogate functions for the log likelihood, Due to the form of the log-likelihood function it is possible to find low curvature surrogate functions that guarantee monotonicity. Unlike previous methods, the proposed surr...

提出了一种用于透射断层扫描惩罚似然图像重建的快速单调算法设计框架。新算法基于对数似然的抛物面替代函数，由于对数似然函数的形式，可以找到保证单调性的低曲率替代函数。与先前方法不同，所提出的替代...

A direct (noniterative) reconstruction algorithm for electrical impedance tomography in the two-dimensional (2-D), cross-sectional geometry is reviewed. New results of a reconstruction of a numerically simulated phantom chest are presented. The algorithm is based on the mathematical uniqueness proof by A.I. Nachman [1996] for the 2-D inverse conductivity problem. In this geometry, several of the c...

回顾了一种用于二维（2-D）横截面几何的电阻抗断层成像的直接（非迭代）重建算法。给出了数值模拟的胸部体模重建的新结果。该算法基于A.I. Nachman [1996] 对二维逆电导率问题的数学唯一性证明。在这种几何结构中，几个...

Knowledge-based segmentation has been explored significantly in medical imaging. Prior anatomical knowledge can be used to define constraints that can improve performance of segmentation algorithms to physically corrupted and incomplete data. In this paper, the objective is to introduce such knowledge-based constraints while preserving the ability of dealing with local deformations. Toward this en...

基于知识的分割在医学影像中已得到广泛探索。先验解剖知识可用于定义约束，从而提高分割算法在处理物理损坏和不完整数据时的性能。本文旨在引入此类基于知识的约束，同时保留处理局部变形的能力。为此...

Microscopy cell image analysis is a fundamental tool for biological research. In particular, multivariate fluorescence microscopy is used to observe different aspects of cells in cultures. It is still common practice to perform analysis tasks by visual inspection of individual cells which is time consuming, exhausting and prone to induce subjective bias. This makes automatic cell image analysis essential for large scale, objective studies of cell cultures. Traditionally the task of automatic cell analysis is approached through the use of image segmentation methods for extraction of cells' locations and shapes. Image segmentation, although fundamental, is neither an easy task in computer vision nor is it robust to image quality changes. This makes image segmentation for cell detection semi-automated requiring frequent tuning of parameters. We introduce a new approach for cell detection and shape estimation in multivariate images based on the sliding band filter (SBF). This filter's design makes it adequate to detect overall convex shapes and as such it performs well for cell detection. Furthermore, the parameters involved are intuitive as they are directly related to the expected cell size. Using the SBF filter we detect cells' nucleus and cytoplasm location and shapes. Based on the assumption that each cell has the same approximate shape center in both nuclei and cytoplasm fluorescence channels, we guide cytoplasm shape estimation by the nuclear detections improving performance and reducing errors. Then we validate cell detection by gathering evidence from nuclei and cytoplasm channels. Additionally, we include overlap correction and shape regularization steps which further improve the estimated cell shapes. The approach is evaluated using two datasets with different types of data: a 20 images benchmark set of simulated cell culture images, containing 1000 simulated cells; a 16 images Drosophila melanogaster Kc167 dataset containing 1255 cells, stained for DNA and actin. Both image datasets present a difficult problem due to the high variability of cell shapes and frequent cluster overlap between cells. On the Drosophila dataset our approach achieved a precision/recall of 95%/69% and 82%/90% for nuclei and cytoplasm detection respectively and an overall accuracy of 76%.

显微细胞图像分析是生物学研究的基本工具。特别是，多变量荧光显微镜用于观察培养细胞的不同方面。目前，通过视觉检查单个细胞来执行分析任务仍然是常见做法，这既耗时又容易产生主观偏差。这使得自动细胞图像分析对于大规模、客观的细胞培养研究至关重要。传统上，自动细胞分析的任务通过使用图像分割方法提取细胞的位置和形状来实现。图像分割虽然是基础，但在计算机视觉中并非易事，也不鲁棒于图像质量变化。这使得用于细胞检测的图像分割半自动化，需要频繁调整参数。本文提出了一种基于滑动带滤波器（SBF）的多变量图像中细胞检测和形状估计的新方法。该滤波器的设计使其足以检测整体凸形状，因此在细胞检测中表现良好。此外，涉及的参数直观，因为它们直接与预期的细胞大小相关。使用SBF滤波器，我们检测细胞核和细胞质的位置和形状。基于每个细胞在细胞核和细胞质荧光通道中具有近似相同形状中心的假设，我们通过核检测指导细胞质形状估计，提高性能并减少误差。然后通过从核和细胞质通道收集证据来验证细胞检测。此外，我们还包括重叠校正和形状正则化步骤，进一步改进估计的细胞形状。该方法使用两个不同类型的数据集进行评估：一个包含1000个模拟细胞的20张模拟细胞培养图像基准集；一个包含1255个细胞、标记DNA和肌动蛋白的16张黑腹果蝇Kc167数据集。由于细胞形状的高度变异和细胞之间频繁的簇重叠，这两个图像数据集都提出了难题。在果蝇数据集上，我们的方法在核检测和细胞质检测上分别达到了95%/69%和82%/90%的精确率/召回率，总体准确率为76%。

Ultrasonic measurements of human carotid and femoral artery walls are conventionally obtained by manually tracing interfaces between tissue layers. The drawbacks of this method are the interobserver variability and inefficiency. Here, the authors present a new automated method which reduces these problems. By applying a multiscale dynamic programming (DP) algorithm, approximate vessel wall positio...

超声测量人类颈动脉和股动脉壁的传统方法是通过手动追踪组织层之间的界面。这种方法的缺点是观察者间差异和效率低下。本文作者提出了一种新的自动化方法，减少了这些问题。通过应用多尺度动态规划算法，近似血管壁位置...

Functional magnetic resonance images (fMRI's) provide high-resolution datasets which allow researchers to obtain accurate delineation and sensitive detection of activation areas involved in cognitive processes. To preserve the resolution of this noninvasive technique, refined methods are required in the analysis of the data. In this paper, the authors first discuss the widely used methods based on...

功能磁共振成像（fMRI）提供高分辨率数据集，使研究人员能够获得认知过程中激活区域的准确描绘和敏感检测。为了保持这种无创技术的分辨率，在数据分析中需要精细的方法。本文首先讨论了基于...的广泛使用的方法。

Multiple sclerosis (MS) is a disease of the white matter. Magnetic resonance imaging (MRI) is proven to be a sensitive method of monitoring the progression of this disease and of its changes due to treatment protocols. Quantification of the severity of the disease through estimation of MS lesion volume via MR imaging is vital for understanding and monitoring the disease and its treatment. This pap...

多发性硬化（MS）是一种白质疾病。磁共振成像（MRI）已被证明是一种监测该疾病进展及其因治疗方案变化而改变的敏感方法。通过MRI估计MS病变体积来量化疾病严重程度对于理解和监测疾病及其治疗至关重要。本文...

From a set of longitudinal three-dimensional scans of the same anatomical structure, the authors have accurately modeled the temporal shape and size changes using a linear shape model. On a total of 31 computed tomography scans of the mandible from six patients, 14,851 semilandmarks are found automatically using shape features and a new algorithm called geometry-constrained diffusion. The semiland...

作者利用一组同一解剖结构的纵向三维扫描，通过线性形状模型精确模拟了时间上的形状和大小变化。基于六名患者的31次下颌骨CT扫描，使用形状特征和一种名为几何约束扩散的新算法自动找到了14851个半地标。半地标...

Describes a system that is being used to segment gray matter from magnetic resonance imaging (MRI) and to create connected cortical representations for functional MRI visualization (fMRI). The method exploits knowledge of the anatomy of the cortex and incorporates structural constraints into the segmentation. First, the white matter and cerebral spinal fluid (CSF) regions in the MR volume are segm...

描述了一种系统，该系统用于从磁共振成像（MRI）中分割灰质，并创建用于功能磁共振成像可视化（fMRI）的连通皮层表示。该方法利用了皮层解剖学知识，并在分割中加入了结构约束。首先，在MR体积中分割白质和脑脊液（CSF）区域...

This paper presents microwave tomographic reconstructions of the complex permittivity of lossy dielectric objects immersed in water from experimental multiview near-field data obtained with a 2.35-GHz planar active microwave camera. An iterative reconstruction algorithm based on the Levenberg-Marquardt method was used to solve the nonlinear matrix equation which results when applying a moment meth...

本文介绍了利用2.35 GHz平面有源微波相机获得的实验多视近场数据，对浸没在水中的有耗介电物体的复介电常数进行微波层析重建。采用基于Levenberg-Marquardt方法的迭代重建算法来求解应用矩量法时产生的非线性矩阵方程...

By exploiting the correlation of ultrasound speckle patterns that result from scattering by underlying tissue elements, two-dimensional tissue motion theoretically can be recovered by tracking the apparent movement of the associated speckle patterns. Speckle tracking, however, is an ill-posed inverse problem because of temporal decorrelation of the speckle patterns and the inherent low signal-to-n...

通过利用由底层组织元素散射产生的超声斑点模式的相关性，理论上可以通过跟踪相关斑点模式的表观运动来恢复二维组织运动。然而，由于斑点模式的时间去相关性和固有的低信噪比，斑点跟踪是一个不适定的逆问题。