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Transmit $B_1^+$ field homogenization in high-field ( ${>}3.0$ T) human magnetic resonance imaging (MRI) is challenging due to radio-frequency wavelength effects. An approach based on appropriately coupling surface coils to a volume coil was investigated. Electromagnetic simulation results demonstrated the feasibility and effectiveness of this method in proton MRI of the human head at 7.0 T.

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Large-tip-angle multidimensional radio-frequency (RF) pulse design is a difficult problem, due to the nonlinear response of magnetization to applied RF at large tip-angles. In parallel excitation, multidimensional RF pulse design is further complicated by the possibility for transmit field patterns to change between subjects, requiring pulses to be designed rapidly while a subject lies in the scan...

大翻转角多维射频（RF）脉冲设计是一个难题，因为在大翻转角下磁化对施加RF的响应是非线性的。在并行激励中，由于发射场模式可能在不同受试者之间变化，需要受试者在扫描过程中快速设计脉冲，这使得多维RF脉冲设计更加复杂。

The recently developed S-transform (ST) combines features of the Fourier and Wavelet transforms; it reveals frequency variation over both space and time. It is a potentially powerful tool that can be applied to medical image processing including texture analysis and noise filtering. However, calculation of the ST is computationally intensive, making conventional implementations too slow for many m...

最近开发的S变换（ST）结合了傅里叶变换和小波变换的特性；它揭示了频率在空间和时间上的变化。这是一个潜在强大的工具，可应用于医学图像处理，包括纹理分析和噪声滤波。然而，ST的计算量很大，使得传统实现对于许多医学应用而言太慢。

A statistical method for detecting activated pixels in functional MRI (fMRI) data is presented. In this method, the fMRI time series measured at each pixel is modeled as the sum of a response signal which arises due to the experimentally controlled activation-baseline pattern, a nuisance component representing effects of no interest, and Gaussian white noise. For periodic activation-baseline patte...

提出了一种用于检测功能磁共振成像（fMRI）数据中激活像素的统计方法。在该方法中，每个像素处的fMRI时间序列被建模为响应信号（由实验控制的激活-基线模式引起）、不感兴趣的干扰效应和高斯白噪声之和。对于周期性激活-基线模式...

The radial derivative of the three-dimensional (3-D) radon transform of an object is an important intermediate result in many analytically exact cone-beam reconstruction algorithms. The authors briefly review Grangeat's (1991) approach for calculating radon derivative data from cone-beam projections and then present a new, efficient method for 3-D radon inversion, i.e., reconstruction of the image...

物体的三维Radon变换的径向导数是许多解析精确锥束重建算法中的重要中间结果。作者简要回顾了Grangeat（1991）从锥束投影计算Radon导数数据的方法，然后提出了一种新的、高效的三维Radon反演方法，即图像重建...

Fractal analysis of bone X-ray images has received much interest recently for the diagnosis of bone disease. Here, the authors propose a fractal analysis of bone X-ray tomographic microscopy (XTM) projections. The aim of the study is to establish whether or not there is a correlation between three-dimensional (3-D) trabecular changes and two-dimensional (2-D) fractal descriptors. Using a highly co...

骨X射线图像的分形分析近来在骨病诊断中受到广泛关注。本文作者提出对骨X射线断层显微镜（XTM）投影进行分形分析。研究旨在确定三维（3-D）小梁变化与二维（2-D）分形描述符之间是否存在相关性。利用高度共...

An analytical framework of error propagation for diffusion tensor imaging (DTI) is presented. Using this framework, any uncertainty of interest related to the diffusion tensor elements or to the tensor-derived quantities such as eigenvalues, eigenvectors, trace, fractional anisotropy (FA), and relative anisotropy (RA) can be analytically expressed and derived from the noisy diffusion-weighted sign...

提出了一种针对扩散张量成像（DTI）的误差传播分析框架。利用该框架，任何与扩散张量元素或张量衍生量（如特征值、特征向量、迹、分数各向异性（FA）和相对各向异性（RA））相关的不确定性都可以从噪声扩散加权信号中解析表达和推导出来。

A method is presented for correcting PET images for the blurring caused by variations in the depth-of-interaction in position-sensitive gamma ray detectors. The method uses an empirically determined, tabulated relationship between depth-of-interaction and most probable pulse-height to estimate the unknown depth from the measured pulse-height for each detected gamma ray. In the case of one fine-cut...

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Cochlear implantation is the standard treatment for profound hearing loss, Preimplantation and postimplantation spiral computed tomography (CT) is essential in several key clinical and research aspects. The maximum image resolution with commercial spiral CT scanners is insufficient to define clearly anatomical features and implant electrode positions in the inner ear, In this paper, the authors de...

人工耳蜗植入是治疗重度听力损失的标准方法，术前和术后螺旋计算机断层扫描（CT）在多个关键的临床和研究方面至关重要。商用螺旋CT扫描仪的最大图像分辨率不足以清晰定义内耳的解剖结构和植入电极位置。在本文中，作者...

In cone-beam computerized tomography (CT), projections acquired with the focal spot constrained on a planar orbit cannot provide a complete set of data to reconstruct the object function exactly. There are severe distortions in the reconstructed noncentral transverse planes when the cone angle is large. In this work, a new method is proposed which can obtain a complete set of data by acquiring con...

在锥束计算机断层扫描（CT）中，焦点在平面轨道上采集的投影无法提供完整的数据集来精确重建物体函数。当锥角较大时，重建的非中心横向平面存在严重畸变。本文提出了一种新方法，通过采集...

The authors present a new algorithm to enhance the edges and contrast of chest and breast radiographs while minimally amplifying image noise. The algorithm consists of a linear combination of an original image and two smoothed images obtained from it by using different masks and parameters, followed by the application of nonlinear contrast stretching. The result is an image which retains the high ...

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True three dimensional (3-D) volume reconstruction from fully 3-D data in positron emission tomography (PET) has only a limited clinical use because of its large computational burden. Fourier rebinning (FORE) of the fully 3-D data into a set of 2-D sinogram data decomposes the 3-D reconstruction process into multiple 2-D reconstructions of decoupled 2-D image slices, thus substantially decreasing ...

真正的三维（3-D）体积重建在全三维正电子发射断层扫描（PET）数据中由于巨大的计算负担而仅具有有限的临床应用。将全三维数据通过傅里叶重排（FORE）分解为一组二维正弦图数据，将三维重建过程分解为多个解耦的二维图像切片的二维重建，从而大大减少计算量。

A technique is presented for automatic detection of the longitudinal fissure in tomographic scans of the brain. The technique utilizes the planar nature of the fissure and is a three-dimensional variant of the Hough transform principle. Algorithmic and computational aspects of the technique are discussed. Results and performance on coronal and transaxial magnetic resonance data show that the algor...

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Optoacoustic tomography (OAT), also known as photoacoustic tomography, is an emerging computed biomedical imaging modality that exploits optical contrast and ultrasonic detection principles. Iterative image reconstruction algorithms that are based on discrete imaging models are actively being developed for OAT due to their ability to improve image quality by incorporating accurate models of the im...

光声层析成像（OAT），也称为光声断层扫描，是一种新兴的计算生物医学成像模式，利用光学对比度和超声检测原理。基于离散成像模型的迭代图像重建算法正在积极开发中，因为它们能够通过纳入准确的成像模型来提高图像质量...

Active model-based segmentation has frequently been used in medical image processing with considerable success. Although the active model-based method was initially viewed as an optimization problem, most researchers implement it as a partial differential equation solution. The advantages and disadvantages of the active model-based method are distinct: speed and stability. To improve its performan...

基于活动模型的图像分割在医学图像处理中经常被使用，并取得了相当大的成功。尽管基于活动模型的方法最初被视为优化问题，但大多数研究人员将其实现为偏微分方程解。基于活动模型的方法的优缺点很明显：速度和稳定性。为了提高其性能...

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。

A new scheme for denoising magnetic resonance spectroscopy (MRS) signals is presented. This scheme is based on projecting noisy MRS signals in different domains, consecutively, and performing noise filtering operations in these domains. The domains are chosen such that the noise portion, which is inseparable from the desired signal in one domain, is separable in the other. A set of stable, linear,...

提出了一种用于磁共振波谱（MRS）信号去噪的新方案。该方案基于将噪声MRS信号连续投影到不同域中，并在这些域中执行噪声滤波操作。选择这些域使得在一个域中与期望信号不可分离的噪声部分在另一个域中是可分离的。一组稳定的、线性的...

The problem of reconstruction in positron emission tomography (PET) is basically estimating the number of photon pairs emitted from the source. Using the concept of the maximum-likelihood (ML) algorithm, the problem of reconstruction is reduced to determining an estimate of the emitter density that maximizes the probability of observing the actual detector count data over all possible emitter dens...

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Interior-point methods have been successfully applied to a wide variety of linear and nonlinear programming applications. This paper presents a class of algorithms, based on path-following interior-point methodology, for performing regularized maximum-likelihood (ML) reconstructions on three-dimensional (3-D) emission tomography data. The algorithms solve a sequence of subproblems that converge to...

内点方法已成功应用于各种线性和非线性规划问题。本文提出了一类基于路径跟踪内点方法的算法，用于在三维发射断层扫描数据上执行正则化最大似然重建。这些算法求解一系列子问题，这些子问题收敛到...

Digital image-based elasto-tomography (DIET) is a prototype system for breast cancer screening. A breast is imaged while being vibrated, and the observed surface motion is used to infer the internal stiffness of the breast, hence identifying tumors. This paper describes a computer vision system for accurately measuring 3-D surface motion. A model-based segmentation is used to identify the profile ...

基于数字图像的弹性断层扫描(DIET)是一种用于乳腺癌筛查的原型系统。在乳房振动时对其进行成像，通过观察到的表面运动来推断乳房内部硬度，从而识别肿瘤。本文描述了一种用于精确测量三维表面运动的计算机视觉系统。采用基于模型的分割来识别轮廓……

A new imaging modality is introduced to image electrical conductivity of biological tissues via contactless measurements. This modality uses magnetic excitation to induce currents inside the body and measures the magnetic fields of the induced currents. In this study, the mathematical basis of the methodology is analyzed and numerical models are developed to simulate the imaging system. The induce...

介绍了一种新的成像模态，通过非接触测量对生物组织的电导率进行成像。该模态利用磁激励在体内感应电流，并测量感应电流产生的磁场。本研究分析了该方法的数学基础，并开发了数值模型来模拟成像系统。感应...

Accurate detection of vessel boundaries is particularly important for a precise extraction of vasculatures in magnetic resonance angiography (MRA). In this paper, we propose the use of weighted local variance (WLV)-based edge detection scheme for vessel boundary detection in MRA. The proposed method is robust against changes of intensity contrast of edges and capable of giving high detection respo...

准确检测血管边界对于磁共振血管成像（MRA）中血管的精确提取尤为重要。本文提出使用基于加权局部方差（WLV）的边缘检测方案用于MRA中的血管边界检测。该方法对边缘强度对比度的变化具有鲁棒性，并且能够给出高检测响应...

Identification of anatomical features is a necessary step for medical image analysis. Automatic methods for feature identification using conventional pattern recognition techniques typically classify an object as a member of a predefined class of objects, but do not attempt to recover the exact or approximate shape of that object. For this reason, such techniques are usually not sufficient to iden...

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Earlier investigations with BGO positron emission tomography (PET) scanners showed that the scatter correction technique based on multiple acquisitions with different energy windows are problematic to implement because of the poor energy resolution of BGO (22%), particularly for whole-body studies. The authors believe that these methods are likely to work better with NaI(Tl) because of the better ...

早期使用BGO正电子发射断层扫描（PET）扫描仪的研究表明，基于不同能量窗口多次采集的散射校正技术由于BGO的能量分辨率较差（22%），特别是在全身研究中实施起来存在问题。作者认为这些方法在使用NaI(Tl)时可能会更有效，因为其能量分辨率更好...

Considers the direct Fourier methods (DFM's) for reconstructing an image from its given X-ray projections. The main purpose here is to use concepts from numerical analysis to estimate the errors in the methods. The authors also suggest an alternative to the interpolations involved in the DFM's and estimate the number of terms involved. Realizing that one of the main reasons for the degradation of ...

考虑使用直接傅里叶方法（DFM）从给定的X射线投影重建图像。这里的主要目的是使用数值分析的概念来估计方法中的误差。作者还提出了DFM中涉及的插值的替代方案，并估计了涉及的项数。意识到...