Molecular and Cellular Imaging with Targeted Contrast Ultrasound

Molecular imaging is an expanding field that involves the noninvasive detection of cellular and molecular mediators of disease using a range of imaging modalities. Molecular imaging using contrast-enhanced ultrasound relies on the detection of novel site-targeted ultrasound contrast agents. Gas-filled encapsulated microbubbles provide a sensitive and high-resolution ultrasound contrast agent, and site-targeted imaging is facilitated by the manipulation of the shell surface of these microbubbles. Nonmicrobubble agents such as immunoliposomes and small nanoemulsion agents have also been developed for targeting purposes. These contrast agents are retained within regions of a specific pathophysiological process, thereby allowing noninvasive phenotypic characterization of tissue. Since microbubbles are pure intravascular tracers, they provide an optimal agent to assess molecular processes occurring on the vascular endothelial surface. Accordingly, the pathologic states that have been targeted include inflammation, angiogenesis associated with ischemia and neoplasms, and thrombus formation. This review describes: 1) the potential clinical and research uses for targeted imaging; 2) strategies that have been employed for the creation of site-targeted ultrasound contrast agents; 3) the unique challenges for imaging targeted ultrasound contrast agents; and 4) initial results and experience in the imaging of molecular events in animal models of disease.     

Nonlocal Means-Based Speckle Filtering for Ultrasound Images

In image processing, restoration is expected to improve the qualitative inspection of the image and the performance of quantitative image analysis techniques. In this paper, an adaptation of the nonlocal (NL)-means filter is proposed for speckle reduction in ultrasound (US) images. Originally developed for additive white Gaussian noise, we propose to use a Bayesian framework to derive a NL-means filter adapted to a relevant ultrasound noise model. Quantitative results on synthetic data show the performances of the proposed method compared to well-established and state-of-the-art methods. Results on real images demonstrate that the proposed method is able to preserve accurately edges and structural details of the image.     

一种鲁棒的低对比度图像预处理算法

数字图像在采集过程中,由于照明或物体本身等原因,经常会出现目标区域对比度低、细节模糊的情况,需要经过进一步的预处理才能使用。灰度分段线性变换是一种较为有效的对比度拉升技术,它通过选择合理的分段点来实现图像增强。一种常见的分段点选择方法是以原始图像灰度值的最大和最小值为分段点,但它对整体动态范围较大的图像视觉效果改善有限。文中通过对图像直方图的分析,在其累积直方图上设定阈值来确定分段点是一种可行的方法,具有更好的鲁棒性。仿真实验结果表明,该算法能够有效地增强低对比度区域,为图像的进一步处理提供理想的结果。     

乳腺肿瘤超声图像纹理特征分析

提取乳腺肿瘤超声图像的肿瘤区域,计算乳腺肿瘤图像的纹理特征参数,研究纹理特征与肿瘤良恶性的关系。基于综合空间灰度共生矩阵计算11个乳腺肿瘤超声图像的纹理特征参数,然后分别利用模糊C均值和K-medoid聚类算法对乳腺肿瘤进行良恶性判别,同时,通过重复实验找到判别肿瘤良恶性的最佳特征参数组合。实验结果表明相关性、和方差、相关信息度量1和相关信息度量2四个特征参数组合的判别结果最好,达到了72.64%。因此,纹理特征在一定程度上能够反映良恶性乳腺肿瘤的区别,其对于鉴别乳腺肿瘤的良恶性是有效的。     

Mechanically Tunable Hollow Silica Ultrathin Nanoshells for Ultrasound Contrast Agents

Perfluoropentane (PFP) gas‐filled biodegradable iron‐doped silica nanoshells have been demonstrated as long‐lived ultrasound contrast agents. Nanoshells are synthesized by a sol–gel process with tetramethyl orthosilicate (TMOS) and iron ethoxide. Substituting a fraction of the TMOS with R‐substituted‐trialkoxysilanes produces ultrathin nanoshells with varying shell thicknesses and morphologies composed of fused nanoflakes. The ultrathin nanoshells have continuous ultrasound Doppler imaging lifetimes exceeding 3 h, are twice as bright using contrast‐specific imaging, and have decreased pressure thresholds compared to control nanoshells synthesized with just TMOS. Transmission electron microscopy shows that the R‐group‐substituted trialkoxysilanes can reduce the mechanically critical nanoshell layer to 1.4 nm. These ultrathin nanoshells have the mechanical behavior of weakly linked nanoflakes but the chemical stability of silica. The synthesis can be adapted for general fabrication of 3D nanostructures composed of nanoflakes, which have thicknesses from 1.4 to 3.8 nm and diameters from 2 to 23 nm.     

红外序列图像的双滤波侧抑制边缘检测算法

针对红外图像的特点，重点研究了采用双滤波的方法及侧抑制网络的“突出边框，增强反差”的功能，提出一种图像边缘检测方法．对噪声有一定的抑帆作用，边缘检测果明显。还结合序列图像的相关性，运用免疫计算方法，分割出目标运动区域，形成目标模板，然后在运动序列的各帧动态更新模板。最后得到具有低对比度、低信噪比、边缘模糊的红外图像目标的序列边缘。     

Adaptive Polarization Contrast Techniques for Through-Wall Microwave Imaging Applications

In this paper, we describe and utilize polarization contrast techniques of the adaptive polarization difference imaging algorithm and its transient modification for through-wall microwave imaging (TWMI) applications. Originally developed for optical imaging and sensing of polarization information in nature, this algorithm is modified to serve for target detection purposes in a through-wall environment. The proposed techniques exploit the polarization statistics of the observed scene for the detection and identification of changes within the scene and are not only capable of mitigating and substantially removing the wall effects but also useful in detecting motion, when conventional Doppler techniques are not applicable. Applications of the techniques to several TWMI scenarios including both homogeneous and periodic wall cases are presented.     

一种基于网络矢量图形SVG仿真展示光栅图像的有效方法

提出了一种基于网络矢量图形SVG 展示光栅图像的方法(简称为SRRI).首先研究了光栅图像和SVG图形的结构组成,同时依据局部特征(灰度、颜色或者梯度等)相似性将图像分割成若干个互不相交的区域;然后提取每个区域的边缘,并对边缘进行合并、压缩;最后使用SVG 代码描述分割后的区域边缘形状和颜色特征,并依据区域同质特征将SVG代码进行合并和压缩.通过数字文物图像集和标准图像数据集进行实验,表明SRRI方法对于粗纹理图像和相似图案较多的文物数字图像,其存储容量小,展示效果好.     

一种有效的基于变长包的IEEE 802.11系统性能分析方法

本文对DCF的退避过程建立马尔可夫链模型,通过理论分析,估计出了在各个站点运行不同业务、有着不同的包长分布的情况下,系统吞吐量及各个站点占有的网络带宽。在通过仿真工具NS-2进行验证后,取得了较为准确的结果。系统吞吐量及各个站点占用带宽情况的估计,在网络规划、接纳控制、切换等过程中都有非常重要的意义。     

基于辐射对比度的变发射率舰船的红外隐身研究

利用固定发射率的红外隐身涂料无法实现全天候舰船红外隐身。以小于0.04的目标与背景的辐射对比度作为红外隐身的评判标准,通过计算分析目标与背景的红外特征模型,得到了实现红外隐身所需的目标表面发射率变化范围,提出利用电致变色材料来改变目标表面的平均发射率。与固定发射率的普通红外隐身涂料相比,改变发射率后的红外隐身涂料的隐身效率有了很大的改善,基本能满足目标的全天候红外隐身要求。     

一种快速有效的红外图像中海天线提取算法

针对海天红外图像的特点,提出一种快速有效的海天线提取方法.首先通过模板运算在大尺度上对图像进行预处理来增强海天线区域的图像梯度值,然后为了减小水面波纹和噪声的干扰,设计了一种非线性分割方法对图像进行处理,最后对图像进行行扫描找出海天线的位置.实验结果验证了该方法的简单有效性,抗干扰能力强,易于工程上应用.     

Wavelet Techniques for Medical Images Performance Analysis and Observations with EZW and Underwater Image Processing

Massive multiple-input multiple output (mMIMO) is considered as one of the most in demand and innovative technologies for the fifth-generation wireless communication systems. This paper attempts to frame a mMIMO system model, intends to improve the spectral efficiency, energy efficiency and performance gain. Here, the system performance achievements are premeditated in a multi-cell downlink mMIMO system under the core considerations such as “imperfect channel estimation, perfect channel estimation and the effect of interference among cells due to pilot sequences contamination”. The performance gains such as “spatial multiplexing gain, array gain and spatial diversity gain” are considered to maximize in this paper. For attaining this multi-objective function, an improved meta-heuristic algorithm called rider optimization algorithm (ROA) known as trial-based ROA adopted, and analyse the performance of the proposed model by comparing over existing models.

     

Effective GPS Jamming Techniques for UAVs Using Low-Cost SDR Platforms

Lately, a rising number of incidents between unmanned aerial vehicles (UAVs) and airplanes have been reported in airports and airfields. In order to help cope with the problem of unauthorized UAV operations, in this paper we evaluate the use of low cost SDR platforms (software defined radio) for the implementation of a jammer able to generate an effective interfering signal aimed at the GPS navigation system. Using a programmable BladeRF x40 platform from Nuand and the GNU radio software development toolkit, several interference techniques were studied and evaluated, considering the spectral efficiency, energy efficiency and complexity. It was shown that the tested approaches are capable of stopping the reliable reception of the radionavigation signal in real-life scenarios, neutralizing the capacity for autonomous operation of the vehicle.

     

Information Theory-Based Approach for Contrast Analysis in Polarimetric and/or Interferometric SAR Images

We propose a new approach for evaluating the contribution of the different channels of polarimetric and interferometric synthetic aperture radar (PolInSAR) images. For that purpose, we demonstrate that the Bhattacharyya distance between the probability density functions of neighboring regions in the image provides an efficient scalar contrast measure. We show that the analysis of this contrast measure allows one to precisely characterize the contribution of each channel for different system configurations, including intensity, polarimetric, and interferometric images. We illustrate this approach using a real synthetic aperture radar image to compare several polarimetric system architectures. Since PolInSAR imaging configurations can correspond to complex and expensive systems, the proposed method can be helpful in system imaging optimization.      

基于局部形状结构分类的心血管内超声图像中-外膜边界检测

本文提出了一种基于局部形状结构分类的心血管内超声（Intravascular Ultrasound,IVUS）图像中-外膜边界检测方法.首先利用k-均值（k-means）聚类方法,确定局部形状结构类别;其次通过类别标号索引图像块,并对其进行积分通道特征和自相似性特征提取,构建多分类随机决策森林模型;最后由分类模型寻找IVUS图像的关键点,采用曲线拟合方法,实现IVUS图像中-外膜边界检测.实验结果表明,本文方法能够有效地解决IVUS图像中斑块、伪影和血管分支等造成边缘难以准确检测的问题,与已有算法相比,其JM （Jaccard Measure,JM）达到了88.9%,PAD （Percentage of Area Difference,PAD）降低了19.1%,HD （Hausdorff Distance,HD）减少了9.7%,更准确地识别目标边界的关键点,成功地检测出完整的中-外膜边界.     

三种光电外壳光窗封接工艺的强度对比分析

从理论上分析了带光窗外壳的三种制作方式在成型变形上的不同,并对各自进行了强冲击应力模拟分析,最后通过锤击试验对理论分析进行验证,实验结果与结论分析一致,得出金属钎焊管帽抵抗外力的效果最好,高温管帽次之,高频管帽相对较差.     

Classification of Amniotic Fluid Level Using Bi-LSTM with Homomorphic filter and Contrast Enhancement Techniques

Wireless Personal Communications - Ultrasound scan plays a predominant role in assisting the health care provider for monitoring pregnancy. This methods is employed for providing insights about...     

心脏B超轮廓光流场的一种检测方法

本文介绍一种心脏Ｂ超轮廓光流场的检测方法－－边缘聚类中心匹配法，这是变形体光流场的一种检测方法。文章还介绍这种方法被应用于检测心脏机构轮廓光流场的实际操作与结果。