Volume 28, Issue 3

In vivo assessment of dispersion affecting the propagation of visco-elastic waves in soft tissues is key to understand the rheology of human tissues. In this paper, the ability of the supersonic shear imaging (SSI) technique to generate planar shear waves propagating in tissues is fully exploited. First, by strongly limiting shear wave diffraction in the imaging plane, this imaging technique enables to discriminate between the usually concomitant influences of both medium rheological properties and diffraction affecting the shear wave dispersion. Second, transient propagation of these plane shear waves in soft tissues can be measured using echographic images acquired at very high frame. In vitro and in vivo experiments demonstrate that dispersion curves, which characterize the rheological behavior of tissues by measuring the frequency dependence of shear wave speed and attenuation, can be recovered in the 75-600 Hz frequency range. Based on a phase difference algorithm, the dispersion curves are computed in 1 cm 2 regions of interest from the acquired propagation movie. In vivo measurements in biceps brachii muscle and liver of three healthy volunteers show important differences in the rheological behavior of these different tissues. Liver tissue appears to be much more dispersive with a phase velocity ranging from ~ 1.5 m/s at 75 Hz to ~ 3 m/s at 500 Hz whereas muscle tissue shows an important anisotropy, shear waves propagating longitudinally to the muscular fibers are almost nondispersive while those propagating transversally are very dispersive with a shear wave speed ranging from 0.5 to 2 m/s between 75 and 500 Hz. The estimation of dispersion curves is local and can be performed separately in different regions of the organ. This signal processing approach based on the SSI modality introduces the new concept of In vivo shear wave spectroscopy (SWS) that could become an additional tool for tissue characterization. This paper demonstrates the in vivo ability of this SWS to quantify both local shear elasticity and dispersion in real time.

影响软组织中粘弹性波传播的色散现象的体内评估是理解人体组织流变学的关键。本文充分利用了超音速剪切成像（SSI）技术在组织中产生平面剪切波的能力。首先，通过强烈限制剪切波在成像平面内的衍射，该成像技术能够区分通常同时存在的介质流变特性和影响剪切波色散的衍射效应。其次，可以利用超高帧率获取的超声图像测量这些平面剪切波在软组织中的瞬态传播。体外和体内实验证明，通过测量剪切波速度和衰减的频率依赖性，可以在75-600 Hz频率范围内恢复表征组织流变行为的色散曲线。基于相位差算法，从获取的传播电影中在1 cm²的感兴趣区域计算色散曲线。在三名健康志愿者的肱二头肌和肝脏中的体内测量显示，这些不同组织的流变行为存在重要差异。肝脏组织表现出更强的色散性，相速度从75 Hz时的约1.5 m/s变化到500 Hz时的约3 m/s；而肌肉组织表现出显著的各向异性，沿肌纤维纵向传播的剪切波几乎无色散，而横向传播的剪切波色散很强，剪切波速度在75至500 Hz之间介于0.5至2 m/s。色散曲线的估计是局部的，可以在器官的不同区域分别进行。这种基于SSI模态的信号处理方法引入了体内剪切波光谱的新概念，可能成为组织表征的附加工具。本文展示了该SWS在体内实时量化局部剪切弹性和色散的能力。

Coregistered fluoro-deoxy-glucose (FDG) positron emission tomography/computed tomography (PET/CT) has shown potential to improve the accuracy of radiation targeting of head and neck cancer (HNC) when compared to the use of CT simulation alone. The objective of this study was to identify textural features useful in distinguishing tumor from normal tissue in head and neck via quantitative texture an...

共配准的氟脱氧葡萄糖（FDG）正电子发射断层扫描/计算机断层扫描（PET/CT）在提高头颈部癌（HNC）放射靶向准确性方面显示出潜力，与单独使用CT模拟相比。本研究的目的是通过定量纹理分析识别有助于区分头颈部肿瘤与正常组织的纹理特征...

List-mode processing provides an efficient way to deal with sparse projections in iterative image reconstruction for emission tomography. An issue often reported is the tremendous amount of computation required by such algorithm. Each recorded event requires several back- and forward line projections. We investigated the use of the programmable graphics processing unit (GPU) to accelerate the line...

列表模式处理提供了一种有效的方式来处理发射断层扫描迭代图像重建中的稀疏投影。经常被报道的问题是该算法所需的巨大计算量。每个记录的事件需要多次反向和正向线投影。我们研究了使用可编程图形处理单元（GPU）来加速线投影。

We describe a method for unsupervised region segmentation of an image using its spatial frequency domain representation. The algorithm was designed to process large sequences of real-time magnetic resonance (MR) images containing the 2-D midsagittal view of a human vocal tract airway. The segmentation algorithm uses an anatomically informed object model, whose fit to the observed image data is hie...

我们描述了一种利用图像空间频域表示进行无监督区域分割的方法。该算法旨在处理包含人类声道气道的二维正中矢状面视图的大量实时磁共振（MR）图像序列。分割算法使用了解剖学信息的目标模型，其对观测图像数据的拟合是分层的...

The work focuses on a unique medical repository of digital cervicographic images (“Cervigrams”) collected by the National Cancer Institute (NCI) in longitudinal multiyear studies. NCI, together with the National Library of Medicine (NLM), is developing a unique web-accessible database of the digitized cervix images to study the evolution of lesions related to cervical cancer. Tools are needed for ...

本工作聚焦于美国国家癌症研究所（NCI）在纵向多年研究中收集的一个独特的数字宫颈图像（“Cervigrams”）医学库。NCI与国家医学图书馆（NLM）合作，正在开发一个独特的网络可访问的数字宫颈图像数据库，以研究与宫颈癌相关的病变演变。需要工具来……

It is clinically important to quantify the geometric parameters of an abnormal vessel, as this information can aid radiologists in choosing appropriate treatments or apparatuses. Centerline and cross-sectional diameters are commonly used to characterize the morphology of vessel in various clinical applications. Due to the existence of stenosis or aneurysm, the associated vessel centerline is unabl...

临床上量化异常血管的几何参数很重要，因为这些信息可以帮助放射科医生选择合适的治疗方法或设备。中心线和横截面直径通常用于在各种临床应用中表征血管形态。由于存在狭窄或动脉瘤，相关血管中心线无法...

Contrast sensitivity of the human visual system is a characteristic that can adversely affect human performance in detection tasks. In this paper, we propose a method for incorporating human contrast sensitivity in anthropomorphic model observers. In our method, we model human contrast sensitivity using the Barten model with the mean luminance of a region of interest centered at the signal locatio...

人眼视觉系统的对比敏感度是一种可能对人在检测任务中的表现产生不利影响的特性。在本文中，我们提出了一种将人眼对比敏感度融入拟人化模型观察者的方法。在我们的方法中，我们使用Barten模型建模人眼对比敏感度，该模型以信号位置为中心的感兴趣区域的平均亮度为依据...

Signal dephasing due to field inhomogeneity and signal decay due to transverse relaxation lead to perturbations of the Fourier encoding commonly applied in magnetic resonance imaging. Hence, images acquired with long readouts suffer from artifacts such as blurring, distortion, and intensity variation. These artifacts can be removed in reconstruction, usually based on separately collected informati...

由于场不均匀性导致的信号去相位和横向弛豫导致的信号衰减会扰动磁共振成像中常用的傅里叶编码。因此，使用长读出序列采集的图像会出现模糊、失真和强度变化等伪影。这些伪影可以在重建中去除，通常基于单独收集的信息...

Multisource cone-beam computed tomography (CT) is an attractive approach of choice for superior temporal resolution, which is critically important for cardiac imaging and contrast enhanced studies. In this paper, we present a filtered-backprojection (FBP) algorithm for triple-source helical cone-beam CT. The algorithm is both exact and efficient. It utilizes data from three inter-helix PI-arcs ass...

多源锥束计算机断层扫描（CT）因其优越的时间分辨率而成为一种有吸引力的选择，这对于心脏成像和对比增强研究至关重要。本文提出了一种用于三源螺旋锥束CT的滤波反投影（FBP）算法。该算法既精确又高效，利用三个螺旋间PI弧的数据。

We introduce a fluid mechanics based tractography method for estimating the most likely connection paths between points in diffusion tensor imaging (DTI) volumes. We customize the Navier–Stokes equations to include information from the diffusion tensor and simulate an artificial fluid flow through the DTI image volume. We then estimate the most likely connection paths between points in the DTI vol...

我们介绍了一种基于流体力学的纤维追踪方法，用于估计扩散张量成像（DTI）体积中点之间最可能的连接路径。我们定制纳维-斯托克斯方程以包含扩散张量的信息，并通过DTI图像体积模拟人工流体流动。然后，我们估计DTI体积中点之间最可能的连接路径。

In this paper, we propose an automated approach for the joint detection of major sulci on cortical surfaces. By representing sulci as nodes in a graphical model, we incorporate Markovian relations between sulci and formulate their detection as a maximum a posteriori (MAP) estimation problem over the joint space of major sulci. To make the inference tractable, a sample space with a finite number of...

本文提出了一种在皮质表面上联合检测主要脑沟的自动化方法。通过将脑沟表示为图模型中的节点，我们融合了脑沟之间的马尔可夫关系，并将其检测问题表述为主要脑沟联合空间上的最大后验估计问题。为了使推理可行，我们构建了一个有限数量的样本空间。

In diffuse optical imaging (DOI) data analysis, the functional response is contaminated with physiological noise as in functional magnetic resonance imaging (fMRI). In this work we extend a previously proposed method for fMRI to estimate the parameters of a linear model of DOI time series. The regression is performed in the wavelet domain to infer drift coefficients at different scales and to esti...

在扩散光学成像（DOI）数据分析中，功能响应受到生理噪声的污染，如同功能磁共振成像（fMRI）一样。在这项工作中，我们将先前为fMRI提出的方法扩展到估计DOI时间序列线性模型的参数。在小波域中进行回归，以推断不同尺度的漂移系数并估计...

Visualization and quantification of small structures with computed tomography (CT) is hampered by the limited spatial resolution of the system. Histogram-based selective deblurring (HiSD) is a deconvolution method that restores small high-density structures, i.e., calcifications, of a CT image, using the high-intensity voxel information of the deconvolved image, while preserving the original houns...

计算机断层扫描（CT）对微小结构的可视化和定量受限于系统的空间分辨率。基于直方图的选择性去模糊化（HiSD）是一种反卷积方法，利用反卷积图像的高强度体素信息恢复CT图像中的小高密度结构（即钙化），同时保留原始的亨氏...

Magnetic resonance imaging (MRI) uses applied spatial variations in the magnetic field to encode spatial position. Therefore, nonuniformities in the main magnetic field can cause image distortions. In order to correct the image distortions, it is desirable to simultaneously acquire data with a field map in registration. We propose a joint estimation (JE) framework with a fast, noniterative approac...

磁共振成像利用施加的磁场空间变化来编码空间位置。因此，主磁场的不均匀性会导致图像失真。为了校正图像失真，最好同时获取配准的场图数据。我们提出了一种联合估计框架，采用快速非迭代方法...

Arthroplasty, the implantation of prostheses into joints, is a surgical procedure that is affecting a larger and larger number of patients over time. As a result, it is increasingly important to develop imaging techniques to noninvasively examine joints with prostheses after surgery, both statically and dynamically in 3-D. The static problem is considered here, with the aim to create a 3-D shape m...

关节置换术，即将假体植入关节的手术，随着时间的推移，影响的患者数量越来越多。因此，开发非侵入性成像技术来在术后对带假体的关节进行静态和动态三维检查变得越来越重要。本文考虑静态问题，旨在创建三维形状模型...

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