Volume 31, Issue 9

Although diagnostic medical imaging provides enormous benefits in the early detection and accuracy diagnosis of various diseases, there are growing concerns on the potential side effect of radiation induced genetic, cancerous and other diseases. How to reduce radiation dose while maintaining the diagnostic performance is a major challenge in the computed tomography (CT) field. Inspired by the compressive sensing theory, the sparse constraint in terms of total variation (TV) minimization has already led to promising results for low-dose CT reconstruction. Compared to the discrete gradient transform used in the TV method, dictionary learning is proven to be an effective way for sparse representation. On the other hand, it is important to consider the statistical property of projection data in the low-dose CT case. Recently, we have developed a dictionary learning based approach for low-dose X-ray CT. In this paper, we present this method in detail and evaluate it in experiments. In our method, the sparse constraint in terms of a redundant dictionary is incorporated into an objective function in a statistical iterative reconstruction framework. The dictionary can be either predetermined before an image reconstruction task or adaptively defined during the reconstruction process. An alternating minimization scheme is developed to minimize the objective function. Our approach is evaluated with low-dose X-ray projections collected in animal and human CT studies, and the improvement associated with dictionary learning is quantified relative to filtered backprojection and TV-based reconstructions. The results show that the proposed approach might produce better images with lower noise and more detailed structural features in our selected cases. However, there is no proof that this is true for all kinds of structures.

尽管诊断性医学成像在多种疾病的早期检测和准确诊断中提供了巨大益处，但人们对辐射诱导的遗传性、癌性及其他疾病的潜在副作用越来越担忧。如何在保持诊断性能的同时降低辐射剂量是计算机断层扫描（CT）领域的一个主要挑战。受压缩感知理论的启发，基于全变差（TV）最小化的稀疏约束已在低剂量CT重建中取得了有希望的结果。与TV方法中使用的离散梯度变换相比，字典学习被证明是一种有效的稀疏表示方式。另一方面，在低剂量CT情况下，考虑投影数据的统计特性也很重要。最近，我们开发了一种基于字典学习的低剂量X射线CT方法。本文详细介绍了该方法并通过实验进行了评估。在我们的方法中，将冗余字典的稀疏约束纳入统计迭代重建框架的目标函数中。字典可以在图像重建任务前预定义，也可以在重建过程中自适应定义。我们开发了一种交替最小化方案来最小化目标函数。我们使用动物和人类CT研究中收集的低剂量X射线投影来评估我们的方法，并相对于滤波反投影和基于TV的重建量化了字典学习的改进。结果表明，在我们选择的案例中，所提出的方法可能产生噪声更低、结构特征更详细的更好图像。然而，没有证据表明这对所有类型的结构都成立。

Partial separability (PS) and sparsity have been previously used to enable reconstruction of dynamic images from undersampled (k,t)-space data. This paper presents a new method to use PS and sparsity constraints jointly for enhanced performance in this context. The proposed method combines the complementary advantages of PS and sparsity constraints using a unified formulation, achieving significan...

部分可分离性和稀疏性先前已被用于从欠采样的(k,t)-空间数据重建动态图像。本文提出了一种新方法，通过统一公式结合部分可分离性和稀疏性约束的互补优势，以实现更好的性能。该方法显著提高了...

Fast and accurate tissue elasticity imaging is essential in studying dynamic tissue mechanical properties. Various ultrasound shear elasticity imaging techniques have been developed in the last two decades. However, to reconstruct a full field-of-view 2-D shear elasticity map, multiple data acquisitions are typically required. In this paper, a novel shear elasticity imaging technique, comb-push ul...

快速准确的組織彈性成像对于研究动态组织力学特性至关重要。在过去二十年中，已经发展了多种超声剪切弹性成像技术。然而，为了重建全视野的二维剪切弹性图，通常需要多次数据采集。本文提出了一种新型剪切弹性成像技术——组合推压超声...

Compressed sensing (CS) has been used for accelerating magnetic resonance imaging acquisitions, but its use in applications with rapid spatial phase variations is challenging, e.g., proton resonance frequency shift (PRF-shift) thermometry and velocity mapping. Previously, an iterative MRI reconstruction with separate magnitude and phase regularization was proposed for applications where magnitude ...

压缩感知（CS）已用于加速磁共振成像采集，但在具有快速空间相位变化的应用中（例如质子共振频率偏移（PRF偏移）测温术和速度图）其使用具有挑战性。之前，有人提出了一种带有幅度和相位分离正则化的迭代MRI重建方法，用于幅度...等应用。

Electrical impedance tomography (EIT) is a low-cost, noninvasive and radiation free medical imaging modality for monitoring ventilation distribution in the lung. Although such information could be invaluable in preventing ventilator-induced lung injury in mechanically ventilated patients, clinical application of EIT is hindered by difficulties in interpreting the resulting images. One source of th...

电气阻抗断层成像（EIT）是一种低成本、无创、无辐射的医学成像方式，用于监测肺部的通气分布。尽管这些信息对于预防机械通气患者发生呼吸机相关性肺损伤可能是无价的，但EIT的临床应用因难以解释所得图像而受到阻碍。其中一个来源是...

A novel game-theoretic framework for landmark-based image segmentation is presented. Landmark detection is formulated as a game, in which landmarks are players, landmark candidate points are strategies, and likelihoods that candidate points represent landmarks are payoffs, determined according to the similarity of image intensities and spatial relationships between the candidate points in the targ...

提出了一种新颖的基于博弈论的标志点图像分割框架。标志点检测被建模为一个博弈，其中标志点是玩家，候选点是策略，候选点代表标志点的似然度为收益，该收益根据目标图像中候选点之间的图像强度相似性和空间关系来确定。

Quantitative positron emission tomography (PET) imaging relies on accurate attenuation correction. Predicting attenuation values from magnetic resonance (MR) images is difficult because MR signals are related to proton density and relaxation properties of tissues. Here, we propose a method to derive the attenuation map from a transmission scan. An annulus transmission source is positioned inside t...

定量正电子发射断层扫描（PET）成像依赖于准确的衰减校正。从磁共振（MR）图像预测衰减值很困难，因为MR信号与组织的质子密度和弛豫特性有关。在这里，我们提出了一种从透射扫描中获取衰减图的方法。一个环形透射源被放置在...

Cine displacement encoding with stimulated echoes (DENSE) is a magnetic resonance (MR) method that directly encodes tissue displacement into MR phase images. This technique has successfully interrogated many forms of tissue motion, but is most commonly used to evaluate cardiac mechanics. Currently, motion analysis from cine DENSE images requires manually delineated anatomical structures. An automa...

刺激回波编码位移的磁共振电影成像（DENSE）是一种将组织位移直接编码到MR相位图像中的磁共振方法。该技术已成功用于研究多种形式的组织运动，但最常用于评估心脏力学。目前，从电影DENSE图像进行运动分析需要手动描绘解剖结构。一种自动化的...

In medical image segmentation, tumors and other lesions demand the highest levels of accuracy but still call for the highest levels of manual delineation. One factor holding back automatic segmentation is the exemption of pathological regions from shape modelling techniques that rely on high-level shape information not offered by lesions. This paper introduces two new statistical shape models (SSM...

在医学图像分割中，肿瘤和其他病变要求最高的精度，但仍然需要最高水平的手工勾画。阻碍自动分割的一个因素是病理区域不受依赖于病变未提供的高层形状信息的形状建模技术的约束。本文介绍了两种新的统计形状模型（SSM...

The three-dimensional cardiac electrical imaging (3DCEI) technique was previously developed to estimate the initiation site(s) of cardiac activation and activation sequence from the noninvasively measured body surface potential maps (BSPMs). The aim of this study was to develop and evaluate the capability of 3DCEI in mapping the transmural distribution of extracellular potentials and localizing in...

三维心脏电生理成像（3DCEI）技术先前被开发用于从无创测量的体表电位图（BSPMs）估计心脏激活的起始点（s）和激活序列。本研究的目的是开发和评估3DCEI在映射透壁细胞外电位分布和定位...

The entry process of virus particles into cells is decisive for infection. In this work, we investigate fusion of virus particles with the cell membrane via time-lapse fluorescence microscopy. To automatically identify fusion for single particles based on their intensity over time, we have developed a layered probabilistic approach. The approach decomposes the action of a single particle into thre...

病毒颗粒进入细胞的过程对于感染至关重要。在这项工作中，我们通过延时荧光显微镜研究病毒颗粒与细胞膜的融合。为了根据单个颗粒的强度随时间变化自动识别其融合过程，我们开发了一种分层概率方法。该方法将单个颗粒的作用分解为三个步骤：初始化、追踪和融合检测。我们使用概率模型对每个步骤进行建模，并通过最大似然估计进行参数推断。在合成数据和真实数据上的实验表明，该方法能够可靠地识别病毒-细胞融合事件。

In clinical oncology, positron emission tomography (PET) imaging can be used to assess therapeutic response by quantifying the evolution of semi-quantitative values such as standardized uptake value, early during treatment or after treatment. Current guidelines do not include metabolically active tumor volume (MATV) measurements and derived parameters such as total lesion glycolysis (TLG) to chara...

在临床肿瘤学中，正电子发射断层扫描（PET）成像可用于通过量化早期治疗期间或治疗后标准化摄取值等半定量值的演变来评估治疗反应。当前的指南不包括代谢活性肿瘤体积（MATV）测量和衍生参数（如总病灶糖酵解（TLG））来表征...

We provide a general form for many reconstruction estimators of emission tomography. These estimators include Shepp and Vardi's maximum likelihood (ML) estimator, the quadratic weighted least squares (WLS) estimator, Anderson's WLS estimator, and Liu and Wang's multi-objective estimator, and others. We derive a generic update rule by constructing a surrogate function. This work is inspired by the ...

我们为发射断层成像的许多重建估计器提供了一种通用形式。这些估计器包括Shepp和Vardi的最大似然（ML）估计器、二次加权最小二乘（WLS）估计器、Anderson的WLS估计器、Liu和Wang的多目标估计器等。通过构造代理函数，我们推导出了一个通用的更新规则。这项工作受...启发。

In the above titled paper (ibid., vol. 31, no. 7, pp. 1396-1403, July 2012), there were errors in equations (7a) and (7b). The corrected equations are presented here.

在上述题名论文（同上，第31卷，第7期，第1396-1403页，2012年7月）中，方程(7a)和(7b)存在错误。现给出修正后的方程。

Provides a listing of current committee members and society officers.

提供当前委员会成员和学会官员的列表。

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

介绍本期期刊的目录。

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