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The estimation of parameters in radio-tracer models from positron emission tomography (PET) data by nonlinear least squares (NLS) often leads to results with unacceptable mean square error (MSE) characteristics. The introduction of constraints on parameters has the potential to address this problem. We examine a ridge regression technique that augments the standard NLS criterion by the addition of a term which penalizes estimates which deviate from physiologically reasonable values. A variation on a plug-in methodology of Hoerl et al. (1975) is examined for data-dependent selection of the degree of reliance to place on the penalizing term. A simulation study is carried out to evaluate the performance of this approach in the context of estimation of kinetic constants in the three-compartment model used to analyze data from PET studies with fluoro-deoxyglucose (FDG). The results show that, over a range of realistic noise levels, the ridge regression procedure can be expected to reduce the root MSE of parameter estimates by 60%. This result is not found to be substantially dependent on the precise formulation of the penalty function used. Thus, the use of ridge regression for the estimation of kinetic parameters in PET studies is thus considered to be a promising tool.

通过非线性最小二乘法(NLS)从正电子发射断层扫描(PET)数据估计放射性示踪剂模型中的参数通常会导致具有不可接受的均方误差(MSE)特性的结果。引入参数约束有可能解决这个问题。我们研究了一种岭回归技术，该技术通过添加...

A computerized approach to the problem of the assessment of skeletal maturity in pediatric radiology is presented. A CR (computed radiography) hand image to be analyzed is first standardized to obtain a left hand, upright, PA view. Then the phalangeal region of interest is defined and thresholded. After the separation of the third finger, the lengths of the distal, middle, and proximal phalanx are measured automatically. Using the standard phalangeal length table, the skeletal age is estimated. The assessed age has been compared to the estimates obtained by a radiologist using the atlas matching method as well as the chronological age. >

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We present a new approach to anisotropic diffusion based on a multidirectional diffusion flux. The diffusion flux is decomposed in an orthogonal basis, effectively enabling enhancement of contours as well as diffusion along the contours. To this end, we have selected a three-dimensional basis that depicts the directions of principal curvature and has an interesting interpretation in the context of the vessels. The diffusion function associated to each vector of the basis depends on the first-order derivative of the intensity in this direction, instead of the traditional norm of the smoothed gradient. Accordingly, we present the results of a restoration of computed tomography data of the liver.

我们提出了一种基于多方向扩散通量的各向异性扩散新方法。扩散通量在正交基上分解，有效地实现了轮廓增强以及沿轮廓的扩散。为此，我们选择了一个三维基，该基描述了主曲率方向，并在……背景下具有有趣的解释。

In this paper, we present a fast numerical algorithm for solving total variation and $\ell_1$ (TVL1) based image reconstruction with application in partially parallel magnetic resonance imaging. Our algorithm uses variable splitting method to reduce computational cost. Moreover, the Barzilai–Borwein step size selection method is adopted in our algorithm for much faster convergence. Experimental results on clinical partially parallel imaging data demonstrate that the proposed algorithm requires much fewer iterations and/or less computational cost than recently developed operator splitting and Bregman operator splitting methods, which can deal with a general sensing matrix in reconstruction framework, to get similar or even better quality of reconstructed images.

在本文中，我们提出了一种快速数值算法，用于求解基于全变差和ℓ1（TVL1）的图像重建问题，并将其应用于部分并行磁共振成像。我们的算法采用变量分裂方法来降低计算成本。此外，我们在算法中采用了Barzilai-Borwein步长选择方法以实现更快的收敛速度。实验结果...

Equalizing image noise has been shown to be an important step in automatic detection of microcalcifications in digital mammograms. In this study, an accurate adaptive approach for noise equalization is presented and investigated. No additional information obtained from phantom recordings is improved in the method, which makes the approach robust and independent of film type and film development characteristics. Furthermore, it is possible to apply the method on direct digital mammograms as well. In this study, the adaptive approach is optimized by investigating a number of alternative approaches to estimate the image noise. The estimation of high-frequency noise as a function of the grayscale is improved by a new technique for dividing the grayscale in sample intervals and by using a model for additive high-frequency noise. It is shown that the adaptive noise equalization gives substantially better detection results than does a fixed noise equalization. A large database of 245 digitized mammograms with 341 clusters was used for evaluation of the method.

研究表明，均衡图像噪声是数字乳腺X线图像中微钙化自动检测的重要步骤。本文提出并研究了一种精确的自适应噪声均衡方法。该方法无需从体模记录中获取额外信息，使得该方法稳健且独立于胶片类型和胶片显影过程。

We propose a method to simulate atrophy and other similar volumetric change effects on medical images. Given a desired level of atrophy, we find a dense warping deformation that produces the corresponding levels of volumetric loss on the labeled tissue using an energy minimization strategy. Simulated results on a real brain image indicate that the method generates realistic images of tissue loss. ...

我们提出了一种方法，用于模拟医学图像上的萎缩和其他类似的体积变化效应。给定所需的萎缩水平，我们使用能量最小化策略，找到一种密集的扭曲变形，在标记的组织上产生相应水平的体积损失。在实际脑图像上的模拟结果表明，该方法生成了逼真的组织损失图像。

The high computational cost of data processing in volume PET imaging is still hindering the routine application of this successful technique, especially in the case of dynamic studies. This paper describes two new algorithms based on an exact rebinning equation, which can be applied to accelerate the processing of three-dimensional (3-D) PET data. The first algorithm, FOREPROJ, is a fast-forward p...

体积PET成像中数据处理的高计算成本仍然阻碍着这一成功技术的常规应用，尤其是在动态研究中。本文描述了两种基于精确重排方程的新算法，可用于加速三维PET数据的处理。第一种算法FOREPROJ是一种快速前向投影...

A multiresolution statistical method for identifying clinically normal tissue in digitized mammograms is used to construct an algorithm for separating normal regions from potentially abnormal regions; that is, small regions that may contain isolated calcifications. This is the initial phase of the development of a general method for the automatic recognition of normal mammograms. The first step is...

一种用于识别数字化乳腺X线摄影中临床正常组织的多元统计方法，用于构建一种将正常区域与可能异常区域（即可能含有孤立钙化点的小区域）分离的算法。这是开发自动识别正常乳腺X线图像通用方法的初始阶段。第一步是...

The majority of functional magnetic resonance imaging (fMRI) studies obtain functional information using statistical tests based on the magnitude image reconstructions. Recently, a complex correlation (CC) test was proposed based on the complex image data in order to take advantage of phase information in the signal. However, the CC test ignores additional phase information in the baseline compone...

大多数功能磁共振成像（fMRI）研究使用基于幅度图像重建的统计检验来获取功能信息。最近，提出了基于复数图像数据的复数相关（CC）测试，以利用信号中的相位信息。然而，CC测试忽略了基线分量中的额外相位信息...

A regularized color clustering algorithm is proposed to solve the color clustering problem in medical image database. By incorporating both measures of cluster separability and cluster compactness, regularized color clustering allows the automatic extraction of significant color groups with varying populations. Experimental results in different color spaces show that the regularized color clusteri...

提出了一种正则化颜色聚类算法来解决医学图像数据库中的颜色聚类问题。通过同时考虑聚类分离度和聚类紧致度，正则化颜色聚类能够自动提取具有不同种群数量的重要颜色组。在不同颜色空间中的实验结果表明，正则化颜色聚类...

Reduction of eddy currents by a temporal compensation of the input current waveform to the gradient coil is studied with an analytic solution. The technique is the inverse filtering of the eddy-current affected field response, which is calculated from the diffusion equation. The limitation of the temporal compensation due to the spatially variant eddy currents is also investigated for whole-body d...

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Subject motion during brain imaging studies can adversely affect the images through loss of resolution and other artifacts related to movement. The authors have developed and tested a device to measure head motion externally in real-time during emission computed tomographic (ECT) brain imaging studies, to be used eventually to correct ECT data for that motion. The system is based on optical triang...

在脑成像研究中，受试者的运动会由于分辨率损失和其他与运动相关的伪影而对图像产生不利影响。作者开发并测试了一种设备，可以在发射计算机断层扫描（ECT）脑成像研究中实时外部测量头部运动，最终用于校正ECT数据中的运动。该系统基于光学三角测量...

It is well known that the energy dependence of X-ray attenuation can be used to characterize materials. Yet, even with energy discriminating photon counting X-ray detectors, it is still unclear how to best form energy dependent measurements for spectral imaging. Common ideas include binning photon counts based on their energies and detectors with both photon counting and energy integrating electro...

众所周知，X射线衰减的能量依赖性可用于表征材料。然而，即使使用能量分辨光子计数X射线探测器，尚不清楚如何最好地形成用于光谱成像的能量依赖性测量。常见的想法包括根据能量对光子计数进行分箱，以及使用同时具有光子计数和能量积分功能的探测器...

A barrier to the adoption of non-Cartesian parallel magnetic resonance imaging for real-time applications has been the times required for the image reconstructions. These times have exceeded the underlying acquisition time thus preventing real-time display of the acquired images. We present a reconstruction algorithm for commodity graphics hardware (GPUs) to enable real time reconstruction of sens...

非笛卡尔并行磁共振成像在实时应用中的障碍之一是图像重建所需的时间。这些时间超过了底层采集时间，从而阻止了采集图像的实时显示。我们提出了一种用于商用图形硬件（GPU）的重建算法，以实现灵敏度的实时重建...

This paper describes a new approach to reconstruction of the conductivity field in electrical impedance tomography. Our goal is to improve the tradeoff between the quality of the images and the numerical complexity of the reconstruction method. In order to reduce the computational load, we adopt a linearized approximation to the forward problem that describes the relationship between the unknown c...

本文描述了一种在电阻抗断层成像中重建电导率场的新方法。我们的目标是改善图像质量与重建方法数值复杂度之间的权衡。为了降低计算负荷，我们采用正向问题的线性化近似，描述未知电导率与测量数据之间的关系。

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 order to demonstrate the growth of the medical image registration field over the past decades, this paper presents the number of journal publications on this topic since 1988 until 2002. In a similar manner, trends in topics within the field of medical image registration are detected. Publications on computed tomography (CT) and magnetic resonance imaging (MRI) are rather constant through the y...

为了展示过去几十年医学图像配准领域的发展，本文介绍了1988年至2002年间关于该主题的期刊发表数量。类似地，检测了医学图像配准领域内的主题趋势。关于计算机断层扫描（CT）和磁共振成像（MRI）的出版物数量多年来相当稳定...

A high spatial resolution brain positron tomograph, the ECAT 953B/31, is presented. The machine consists of two 76.5 cm diameter rings (patient port diameter: 36 cm) made of 24 8*8 BGO detector blocks each, each block being coupled to four 1 in/sup 2/ Hammamatsu phototubes. The machine has 15 9 cm*1 mm motorized removable septa, which allows reconstruction of 31 slices 3.375 mm apart. The transaxi...

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For implementations of iterative reconstruction algorithms that rotate the image matrix, the characteristics of the rotator may affect the reconstruction quality. Desirable qualities for the rotator include: (1) preservation of global and local image counts; (2) accurate count positioning; (3) a uniform and predictable amount of blurring due to the rotation. A new rotation method for iterative rec...

对于旋转图像矩阵的迭代重建算法的实现，旋转器的特性可能会影响重建质量。旋转器所需的特性包括：(1) 保持全局和局部图像计数；(2) 准确的计数定位；(3) 由于旋转而产生的均匀且可预测的模糊量。一种用于迭代重...

Nuclear magnet resonance (NMR) imaging in the presence of large static field nonuniformity is presented. The method involves three steps: field mapping, imaging by a conventional method, and image restoration from nonuniform field influence. Two-dimensional experiments are performed to demonstrate effectiveness of this method, as well as to clarify practical problems in employing the method. Exper...

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Phase contrast magnetic resonance imaging (MRI) can provide in vivo myocardial velocity field measurements. These data allow densely spaced material points to be tracked throughout the whole heart cycle using, for example, the Fourier tracking algorithm. To process the tracking results for myocardial deformation and strain quantification, the authors developed a method that is based on fitting the...

相位对比磁共振成像（MRI）可以提供体内心肌速度场测量。这些数据允许使用例如傅里叶跟踪算法在整个心动周期中追踪密集分布的物质点。为了处理追踪结果以量化心肌变形和应变，作者开发了一种基于拟合...的方法。

Presents the design of a positron emission tomograph (PET) with flexible geometry dedicated to in vivo studies of small animals (TierPET). The scanner uses two pairs of detectors. Each detector consists of 400 small individual yttrium aluminum perovskite (YAP) scintillator crystals of dimensions 2/spl times/2/spl times/15 mm/sup 3/, optically isolated and glued together, which are coupled to posit...

介绍一种用于小动物体内研究的柔性几何正电子发射断层扫描仪（TierPET）的设计。该扫描仪使用两对探测器。每个探测器由400个尺寸为2×2×15 mm³的小型钇铝钙钛矿（YAP）闪烁晶体组成，这些晶体光学隔离并粘合在一起，耦合到正电子...

Locally adaptive image binarization with a sliding-window threshold can be an effective tool for various image processing tasks. We have used the method for the detection of bone ridges in radiotherapy portal images. However, a straight-forward implementation of sliding-window processing is too time consuming for routine use. Therefore, we have developed a new thresholding criterion suitable for i...

局部自适应图像二值化使用滑动窗口阈值可以有效地处理各种图像处理任务。我们已将该方法用于放疗门户图像中骨脊的检测。然而，滑动窗口处理的直接实现对于常规使用来说过于耗时。因此，我们开发了一种新的阈值化准则，适用于...

The fast Hartley transform (FHT) is used to transform two-dimensional image data. Because the Hartley transform is real-valued, it does not require complex operations. Both spectra and autocorrelations of two-dimensional ultrasound images of normal and abnormal livers were computed.<>

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