Popular Articles

Presents a dual-energy (DE) transmission computed tomography (CT) reconstruction method. It is statistically motivated and features nonnegativity constraints in the density domain. A penalized weighted least squares (PWLS) objective function has been chosen to handle the non-Poisson noise added by amorphous silicon (aSi:H) detectors. A Gauss-Seidel algorithm has been used to minimize the objective...

提出了一种双能量（DE）透射计算机断层扫描（CT）重建方法。该方法基于统计原理，具有密度域非负约束的特点。选择惩罚加权最小二乘（PWLS）目标函数来处理非晶硅（aSi:H）探测器引入的非泊松噪声。采用高斯-赛德尔算法来最小化目标函数...

In magnetic resonance imaging (MRI), the spatial inhomogeneity of the static magnetic field can cause degraded images if the reconstruction is based on inverse Fourier transformation. This paper presents and discusses a range of fast reconstruction algorithms that attempt to avoid such degradation by taking the field inhomogeneity into account. Some of these algorithms are new, others are modified...

在磁共振成像（MRI）中，如果重建基于逆傅里叶变换，静态磁场的空间不均匀性可能导致图像质量下降。本文介绍并讨论了一系列快速重建算法，这些算法通过考虑场不均匀性来避免这种退化。其中一些算法是新的，另一些则是经过改进的...

This paper outlines a simple, fast, and accurate method for automatically locating the nipple on digitized mammograms that have been segmented to reveal the skin-air interface. If the average gradient of the intensity is computed in the direction normal to the interface and directed inside the breast, it is found that there is a sudden and distinct change in this parameter close to the nipple. A n...

本文概述了一种简单、快速且准确的方法，用于在已分割以显示皮肤-空气界面的数字化乳腺X线照片上自动定位乳头。如果计算垂直于界面方向并指向乳房内部的平均强度梯度，就会发现该参数在乳头附近发生突然而明显的变化。一

The steady-state magnetizations in three versions of rapid NMR imaging using small flip angles and short repetition intervals are studied. It is shown that in the original version, the estimation using (1 - E1) sin α/(1 - E1 cos α) contains errors that depend on the increment of the phase rotation angle arising from the phase encoding process. The modified version of rapid imaging, where the phase...

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Echo-planar imaging (EPI) is a fast nuclear magnetic resonance imaging (MRI) method. Unfortunately, local magnetic field inhomogeneities induced mainly by the subject's presence cause significant geometrical distortion, predominantly along the phase-encoding direction, which must be undone to allow for meaningful further processing. So far, this aspect has been too often neglected. In this paper, ...

回波平面成像（EPI）是一种快速的核磁共振成像（MRI）方法。不幸的是，主要由受试者存在引起的局部磁场不均匀性会导致显著的几何畸变，主要沿相位编码方向，必须进行校正才能进行有意义的进一步处理。到目前为止，这一方面常常被忽视。在本文中，……

Presents two new methods for robust parameter estimation of mixtures in the context of magnetic resonance (MR) data segmentation. The head is constituted of different types of tissue that can be modeled by a finite mixture of multivariate Gaussian distributions. The authors' goal is to estimate accurately the statistics of desired tissues in presence of other ones of lesser interest. These latter ...

针对磁共振（MR）数据分割中的混合模型，提出了两种新的鲁棒参数估计方法。头部由不同类型的组织构成，这些组织可以用多元高斯分布的有限混合来建模。作者的目标是在存在其他不太感兴趣的组织的情况下，准确估计所需组织的统计量。这些后者……

Methods of quantitative emission computed tomography require compensation for linear photon attenuation. A current trend in single-photon emission computed tomography (SPECT) and positron emission tomography (PET) is to employ transmission scanning to reconstruct the attenuation map. Such an approach, however, considerably complicates both the scanner design and the data acquisition protocol. A dr...

定量发射计算机断层扫描方法需要对线性光子衰减进行补偿。当前单光子发射计算机断层扫描（SPECT）和正电子发射断层扫描（PET）的一个趋势是使用透射扫描来重建衰减图。然而，这种方法大大复杂化了扫描仪设计和数据采集协议。一个...

The problem of precise spatial localization of spectral information in magnetic resonance (MR) spectroscopic imaging is addressed. A novel method, called GSLIM (generalized spectral location by imaging), is proposed to make possible the marriage of high-resolution proton imaging with spectroscopic imaging and localization. This method improves on the conventional Fourier series inversion method us...

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Breast cancer continues to be a significant public health problem in the United States. Approximately, 182,000 new cases of breast cancer are diagnosed and 46,000 women die of breast cancer each year. Even more disturbing is the fact that one out of eight women in the United States will develop breast cancer at some point during her lifetime. Since the cause of breast cancer remains unknown, prima...

乳腺癌在美国仍然是一个重大的公共卫生问题。每年约有182,000例新发乳腺癌病例被诊断，46,000名女性死于乳腺癌。更令人不安的是，美国每八名女性中就有一人在其一生中的某个阶段会患上乳腺癌。由于乳腺癌的病因尚不明确，因此...

Respiratory motion during the collection of computed tomography (CT) projections generates structured artifacts and a loss of resolution that can render the scans unusable. This motion is problematic in scans of those patients who cannot suspend respiration, such as the very young or intubated patients. Here, the authors present an algorithm that can be used to reduce motion artifacts in CT scans ...

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The authors describe a new approach to imaging neural current sources from measurements of the magnetoencephalogram (MEG) associated with sensory, motor, or cognitive brain activation. Many previous approaches to this problem have concentrated on the use of weighted minimum norm (WMN) inverse methods. While these methods ensure a unique solution, they do not introduce information specific to the M...

作者描述了一种从与感觉、运动或认知脑激活相关的脑磁图（MEG）测量中成像神经电流源的新方法。许多先前的方法都集中在使用加权最小范数（WMN）逆方法。虽然这些方法确保了唯一解，但它们没有引入M...

In this paper implicit representations of deformable models for medical image enhancement and segmentation are considered. The advantage of implicit models over classical explicit models is that their topology can be naturally adapted to objects in the scene. A geodesic formulation of implicit deformable models is especially attractive since it has the energy minimizing properties of classical mod...

本文考虑用于医学图像增强和分割的可变形模型的隐式表示。隐式模型相对于经典显式模型的优势在于其拓扑结构可以自然地适应场景中的物体。隐式可变形模型的测地线公式尤其吸引人，因为它具有经典模型的能量最小化特性……

The authors have applied mathematical morphology for fractal analysis on bone X-ray images. The digitized gray level image is treated as a three-dimensional surface whose fractal dimension is calculated by performing a series of dilations on this surface and plotting the area of the resulting set of surfaces against the size of the structuring element. This approach has the added advantage of enco...

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A new two-stage approach for nonlinear brain image registration is proposed. In the first stage, an active contour algorithm is used to establish a homothetic one-to-one map between a set of region boundaries in two images to be registered. This mapping is used in the second step: a two-dimensional transformation which is based on an elastic body deformation. This method is tested by registering m...

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It is well understood that binary classifiers have two implicit objective functions (sensitivity and specificity) describing their performance. Traditional methods of classifier training attempt to combine these two objective functions (or two analogous class performance measures) into one so that conventional scalar optimization techniques can be utilized. This involves incorporating a priori inf...

众所周知，二元分类器有两个隐含的目标函数（灵敏度和特异度）来描述其性能。传统的分类器训练方法试图将这两个目标函数（或两个类似的类别性能度量）合并为一个，以便使用传统的标量优化技术。这涉及引入先验信息...

In the rapidly evolving field of intravascular ultrasound (IVUS), the assessment of vessel morphology still lacks a geometrically correct three-dimensional (3-D) reconstruction. The IVUS frames are usually stacked up to form a straight vessel, neglecting curvature and the axial twisting of the catheter during the pullback. The authors' method combines the information about vessel cross sections ob...

在快速发展的血管内超声（IVUS）领域，血管形态评估仍缺乏几何正确的三维（3-D）重建。IVUS图像帧通常被堆叠成一条笔直的血管，忽略了导管回撤过程中的弯曲和轴向扭转。作者的方法结合了关于血管横截面的信息，...

A new implementation of the minimum spanning tree (MST) phase unwrapping method is presented. The time complexity of the MST method is reduced from O(n/sup 2/) to O(n log/sub 2/ n), where n is the number of pixels in the phase map. Typical 256/spl times/256 phase maps from magnetic resonance imaging can be unwrapped in seconds, compared with tens of minutes with the O(n/sup 2/) implementation. Thi...

提出了一种新的最小生成树（MST）相位展开方法的实现。该方法的时间复杂度从O(n²)降低到O(n log₂ n)，其中n是相位图中的像素数。典型的256×256磁共振相位图可以在几秒内展开，而O(n²)的实现则需要几十分钟。

The authors examine the spatial resolution and variance properties of PET images reconstructed using maximum a posteriori (MAP) or penalized-likelihood methods. Resolution is characterized by the contrast recovery coefficient (CRC) of the local impulse response. Simplified approximate expressions are derived for the local impulse response CRCs and variances for each voxel. Using these results the authors propose a practical scheme for selecting spatially variant smoothing parameters to optimize lesion detectability through maximization of the local CRC-to-noise ratio in the reconstructed image.

作者研究了使用最大后验（MAP）或惩罚似然方法重建的PET图像的空间分辨率和方差特性。分辨率通过局部脉冲响应的对比度恢复系数（CRC）来表征。推导了每个体素的局部脉冲响应CRC和方差的简化近似表达式。利用这些结果，作者提出了一种实用的方案，通过最大化重建图像中的局部CRC与噪声比，来选择空间变化的平滑参数以优化病灶可检测性。

In this paper a temporal learning-filtering procedure is applied to refine the left ventricle (LV) boundary detected by an active-contour model. Instead of making prior assumptions about the LV shape or its motion, this information is incrementally gathered directly from the images and is exploited to achieve more coherent segmentation. A Hough transform technique is used to find an initial approx...

本文应用时间学习-滤波程序来优化由主动轮廓模型检测到的左心室（LV）边界。不是对LV形状或运动做出先验假设，而是直接从图像中逐步收集这些信息，并利用它们实现更一致的分割。使用霍夫变换技术来找到初始近似...

A model for the scattering of ultrasound from breast tissue is proposed. The model is based on the use of non-Rayleigh statistics, specifically the K distribution to describe the backscattered echo from the tissue. A multiparameter test based on this model has been designed to characterize the tissue. The data from the B-scan images of the breasts of 6 different patients were analyzed using this m...

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Analyzes B-spline interpolation techniques of degree 2, 4, and 5 with respect to all criteria that have been applied to evaluate various interpolation schemes in a recently published survey on image interpolation in medical imaging (Lehmann et al., 1999). It is shown that high-degree B-spline interpolation has superior Fourier properties, smallest interpolation error, and reasonable computing time...

分析了次数为2、4和5的B样条插值技术，这些技术均符合最近发表的关于医学成像中图像插值的综述（Lehmann等人，1999年）中用于评估各种插值方案的所有标准。研究表明，高次B样条插值具有优越的傅里叶性质、最小的插值误差以及合理的计算时间。

For newly developed iterative Newton-Kantorovitch reconstruction techniques, the quality of the final image depends on both experimental and model noise. Experimental noise is inherent to any experimental acquisition scheme, while model noise refers to the accuracy of the numerical model, used in the reconstruction process, to reproduce the experimental setup. This paper provides a systematic asse...

对于新发展的迭代牛顿-坎托罗维奇重建技术，最终图像的质量取决于实验噪声和模型噪声。实验噪声是任何实验采集方案固有的，而模型噪声指的是重建过程中用于再现实验设置的数值模型的精度。本文提供了一种系统的评估...

The gain achieved in image quality by utilizing, in the image forming process, the time-of-flight information (TOF) of positron annihilation photons between their inception and detection was measured experimentally by means of a positron emission tomograph (PET)-Super PETT I. The measurements were carried out by imaging a 35 cm cylindrical uniform phantom containing different positron activity con...

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The authors assess the value of magnetic resonance (MR) image texture in Alzheimer's disease (AD) both as a diagnostic marker and as a measure of progression. T/sub 1/-weighted MR scans were acquired from 40 normal controls and 24 AD patients. These were split into a training set (20 controls, 40 AD) and a test set (20 controls, 14 AD). In addition, five control subjects and five AD patients were ...

作者评估了磁共振（MR）图像纹理在阿尔茨海默病（AD）中作为诊断标志物和进展衡量指标的价值。从40名正常对照和24名AD患者中获取了T1加权MR扫描。这些数据被分为训练集（20名对照，40名AD）和测试集（20名对照，14名AD）。此外，还有5名对照和5名AD患者...

Traditional space-invariant regularization methods in tomographic image reconstruction using penalized-likelihood estimators produce images with nonuniform spatial resolution properties. The local point spread functions that quantify the smoothing properties of such estimators are space variant, asymmetric, and object-dependent even for space invariant imaging systems. The authors propose a new quadratic regularization scheme for tomographic imaging systems that yields increased spatial uniformity and is motivated by the least-squares fitting of a parameterized local impulse response to a desired global response. The authors have developed computationally efficient methods for PET systems with shift-invariant geometric responses. They demonstrate the increased spatial uniformity of this new method versus conventional quadratic regularization schemes in simulated PET thorax scans.

在采用惩罚似然估计器的层析图像重建中，传统的空间不变正则化方法会产生空间分辨率不均匀的图像。即使是空间不变的成像系统，量化此类估计器平滑特性的局部点扩散函数也是空间可变、非对称且依赖于物体的。作者针对层析成像系统提出了一种新的二次正则化方案，该方案通过将参数化局部脉冲响应的最小二乘拟合到期望的全局响应，从而提高空间均匀性。作者为具有移不变几何响应的PET系统开发了计算高效的方法。他们在模拟PET胸部扫描中展示了这种新方法相比传统二次正则化方案在空间均匀性上的提升。