Volume 25, Issue 10

Reconstructing low-dose X-ray computed tomography (CT) images is a noise problem. This work investigated a penalized weighted least-squares (PWLS) approach to address this problem in two dimensions, where the WLS considers first- and second-order noise moments and the penalty models signal spatial correlations. Three different implementations were studied for the PWLS minimization. One utilizes a Markov random field (MRF) Gibbs functional to consider spatial correlations among nearby detector bins and projection views in sinogram space and minimizes the PWLS cost function by iterative Gauss-Seidel algorithm. Another employs Karhunen-Loeve (KL) transform to de-correlate data signals among nearby views and minimizes the PWLS adaptively to each KL component by analytical calculation, where the spatial correlation among nearby bins is modeled by the same Gibbs functional. The third one models the spatial correlations among image pixels in image domain also by a MRF Gibbs functional and minimizes the PWLS by iterative successive over-relaxation algorithm. In these three implementations, a quadratic functional regularization was chosen for the MRF model. Phantom experiments showed a comparable performance of these three PWLS-based methods in terms of suppressing noise-induced streak artifacts and preserving resolution in the reconstructed images. Computer simulations concurred with the phantom experiments in terms of noise-resolution tradeoff and detectability in low contrast environment. The KL-PWLS implementation may have the advantage in terms of computation for high-resolution dynamic low-dose CT imaging.

重建低剂量X射线计算机断层扫描（CT）图像是一个噪声问题。本研究探讨了一种惩罚加权最小二乘（PWLS）方法，以二维方式解决此问题，其中WLS考虑了一阶和二阶噪声矩，惩罚项则对信号空间相关性建模。研究了三种不同的PWLS最小化实现方法。一种是利用马尔可夫随机场（MRF）吉布斯泛函来考虑正弦图空间中相邻探测器箱和投影视角之间的空间相关性，并通过迭代高斯-赛德尔算法最小化PWLS代价函数。另一种采用卡洛南-洛伊（KL）变换来消除邻近视角数据信号的相关性，并通过解析计算自适应地最小化每个KL分量的PWLS，其中相邻箱之间的空间相关性由相同的吉布斯泛函建模。第三种是在图像域中同样通过MRF吉布斯泛函对图像像素间的空间相关性建模，并通过迭代逐次超松弛算法最小化PWLS。在这三种实现中，均选择了二次泛函正则化用于MRF模型。体模实验表明，这三种基于PWLS的方法在抑制噪声引起的条纹伪影和保持重建图像分辨率方面性能相当。计算机模拟在噪声-分辨率权衡和低对比度环境下的可检测性方面与体模实验结果一致。KL-PWLS实现在计算方面可能具有优势，适用于高分辨率动态低剂量CT成像。

Functional and structural maps, such as a curvature, cortical thickness, and functional magnetic resonance imaging (MRI) maps, indexed over the local coordinates of the cortical manifold play an important role in neuropsychiatric studies. Due to the highly convoluted nature of the cerebral cortex and image quality, these functions are generally uninterpretable without proper methods of association...

功能和结构图，如曲率、皮质厚度和功能磁共振成像（MRI）图，索引在皮质流形的局部坐标上，在神经精神研究中发挥重要作用。由于大脑皮层的高度卷曲特性和图像质量，这些功能在没有适当的关联方法的情况下通常难以解释...

We propose a new electrocardiographic (ECG) inverse approach for imaging the three-dimensional (3-D) ventricular activation sequence based on the modeling and estimation of the equivalent current density throughout the entire volume of the ventricular myocardium. The spatio-temporal coherence of the ventricular excitation process has been utilized to derive the activation time from the estimated t...

我们提出一种新的心电图（ECG）逆问题方法，用于基于整个心室心肌体积内等效电流密度的建模和估计来成像三维心室激动序列。利用心室激动过程的时空相干性，从估计的...

Mixture models are commonly used in the statistical segmentation of images. For example, they can be used for the segmentation of structural medical images into different matter types, or of statistical parametric maps into activating and nonactivating brain regions in functional imaging. Spatial mixture models have been developed to augment histogram information with spatial regularization using ...

混合模型常用于图像的统计分割。例如，它们可用于将结构医学图像分割成不同的物质类型，或将统计参数图分割为功能成像中的激活和非激活脑区域。空间混合模型已被开发出来，通过空间正则化增强直方图信息，使用...

The study of cerebral microvascular networks requires high-resolution images. However, to obtain statistically relevant results, a large area of the brain (several square millimeters) must be analyzed. This leads us to consider huge images, too large to be loaded and processed at once in the memory of a standard computer. To consider a large area, a compact representation of the vessels is require...

脑微血管网络的研究需要高分辨率图像。然而，为了获得统计上相关的结果，必须分析大脑的大面积区域（几平方毫米）。这导致我们需要考虑巨大的图像，这些图像太大，无法一次性加载到标准计算机的内存中进行处理。为了考虑大面积区域，需要一种紧凑的血管表示...

We have developed a method and a device entitled prostate mechanical imager (PMI) for the real-time imaging of prostate using a transrectal probe equipped with a pressure sensor array and position tracking sensor. PMI operation is based on measurement of the stress pattern on the rectal wall when the probe is pressed against the prostate. Temporal and spatial changes in the stress pattern provide ...

我们开发了一种名为前列腺机械成像仪的方法和设备，用于使用配备压力传感器阵列和位置跟踪传感器的经直肠探头对前列腺进行实时成像。前列腺机械成像的操作基于当探头压向前列腺时对直肠壁上应力模式的测量。应力模式的时间和空间变化提供了...

A reconstruction algorithm to simultaneously estimate the shape and location of three-dimensional breast cancer tumor is presented and its utility is analyzed. The approach is based on a spherical harmonic decomposition to capture the shape of the tumor. We combine a gradient descent optimization method with a direct electromagnetic solver to determine the coefficients in the harmonic expansion as...

提出了一种同时估计三维乳腺癌肿瘤形状和位置的重建算法，并分析了其实用性。该方法基于球谐分解来捕捉肿瘤的形状。我们将梯度下降优化方法与直接电磁求解器相结合，以确定谐波展开中的系数...

Elasticity imaging is a burgeoning medical imaging field. Many methods have been proposed that impart a force to tissue and measure the mechanical response. One method, vibro-acoustography, uses the ultrasound radiation force to harmonically vibrate tissue and measure the resulting acoustic emission field with a nearby hydrophone. Another method, vibrometry, uses the ultrasound radiation force acc...

弹性成像是一个新兴的医学成像领域。许多方法已被提出，通过对组织施加力并测量机械响应。一种方法，振动声成像，使用超声辐射力使组织谐波振动，并用附近的水听器测量由此产生的声发射场。另一种方法，振动测量法，使用超声辐射力...

Use of iterative algorithms to reconstruct three-dimensional (3-D) positron emission tomography (PET) data requires the computation of the system probability matrix. The pure geometrical contribution can easily be approximated by the length-of-intersection (LOI) between lines-of-response (LOR) and individual voxels. However, more accurate geometrical projectors are desirable. Therefore, we have de...

使用迭代算法重建三维（3-D）正电子发射断层扫描（PET）数据需要计算系统概率矩阵。纯几何贡献可以通过响应线（LOR）与单个体素之间的相交长度（LOI）来近似。然而，需要更精确的几何投影器。因此，我们...

In this paper, a multiport driving mechanism is numerically implemented at ultra high-field (UHF) magnetic resonance imaging (MRI) to provide 1) homogenous whole-slice (axial, sagittal, or coronal) and 2) highly localized radio frequency (RF) field excitation within the same slices, all with the same RF transmit array (here chosen to be a standard transverse electromagnetic (TEM) resonator/coil). ...

在本文中，在超高场（UHF）磁共振成像（MRI）中数值实现了一种多端口驱动机制，以提供1）均匀的全切片（轴向、矢状或冠状）和2）在同一切片内高度局部的射频（RF）场激励，所有这些都使用相同的射频发射阵列（这里选择标准横向电磁（TEM）谐振器/线圈）。

Linear model observers based on statistical decision theory have been used successfully to predict human visual detection of aperiodic signals in a variety of noisy backgrounds. However, some models have included nonlinearities such as a transducer or nonlinear decision rules to handle intrinsic uncertainty. In addition, masking models used to predict human visual detection of signals superimposed...

基于统计决策理论的线性模型观察者已被成功用于预测人类在各种噪声背景下的非周期信号视觉检测。然而，一些模型包含了非线性元素，如转换函数或非线性决策规则，以处理内在不确定性。此外，用于预测人类视觉检测叠加信号的掩蔽模型...

Poisson's equation, a fundamental partial differential equation in classical physics, has a number of properties that are interesting for shape analysis. In particular, the equipotential sets of the solution graph become smoother as the potential increases. We use the displacement map, the length of the streamlines formed by the gradient field of the solution, to measure the "complexity" (or smoot...

泊松方程是经典物理学中的一个基本偏微分方程，具有许多对形状分析感兴趣的性质。特别地，解图的等势集随着势的增加变得更加平滑。我们使用位移图（即解的梯度场形成的流线长度）来衡量'复杂性'（或平滑度）...

We address the problem of image formation in transmission tomography when metal objects of known composition and shape, but unknown pose, are present in the scan subject. Using an alternating minimization (AM) algorithm, derived from a model in which the detected data are viewed as Poisson-distributed photon counts, we seek to eliminate the streaking artifacts commonly seen in filtered back projec...

我们解决了在扫描对象中存在已知成分和形状但未知姿态的金属物体时透射断层成像中的图像形成问题。使用交替最小化（AM）算法，该算法源自将检测数据视为泊松分布光子计数的模型，我们旨在消除在滤波反投影中常见的条纹伪影...

In picture archiving and communications systems (PACS), images need to be displayed in standardized ways for radiologists' interpretations. However, for most radiographs acquired via computed radiography (CR), digital radiography (DR), or digitized films, the image orientation is undetermined because of the variations in examination conditions and patients' situations. To address this problem, an ...

在图像存档与通信系统(PACS)中，图像需要以标准化的方式显示，以供放射科医生解读。然而，对于大多数通过计算机放射摄影(CR)、数字放射摄影(DR)或数字化胶片获取的X光片，由于检查条件和患者情况的差异，图像方向是不确定的。为了解决这个问题，一种...

Provides instructions and guidelines to prospective authors who wish to submit manuscripts.

为希望投稿的作者提供说明和指南。

Provides a listing of publications staff, current committee members and society officers.

提供出版工作人员、现任委员会成员和学会官员的列表。

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Presents the table of contents for this issue of the periodical.

介绍本期期刊的目录。