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图像分割是计算机图像识别和理解的基础,本文提出一种基于色彩特征的彩色多普勒图像分割和基于频域双线性插值的图像旋转与用户交互式剪切相结合的图像分析方法,通过计算彩色超声医学图像的三基色R,G,B的色彩特征,提取出感兴趣的区域并实现了图像的分割,实验证明这是快速可行的彩色分割方法。 相似文献
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早在50年代前期,超声就被研究并作为医学上的一种诊断工具。随着超声诊断技术的发展,超声医学诊断成为一门专门的医学诊断技术,并形成一个独立的分支。B超图像是由医学B型超声扫描仪(Ultrasound—B-mode Scanner)采用脉冲回波法对被测物体进行扫描,通过对所得的回波数据重建而形成的一类医学图像,它的主要成像原理是运用超声在人体组织中传播特性(速度、反射率、吸收率等)的不同,将其转化为一定的可显信号,在显示器上反映出来。文章对该类图像在计算机上重建的算法进行了研究,对各种算法分析、比较,最后提出比较合理的适应于计算机上实时重建B超图像的算法。 相似文献
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针对摩擦振动特征难以有效提取的问题,提出利用连续小波变换(CWT)时频谱图像和图像处理技术提取摩擦振动特征参数的方法。运用CWT变换绘制6S50MC船用柴油机缸套-活塞环试样摩擦振动信号的时频谱图,再用图像分割技术提取振动特征体及相应的特征参数,探讨特征参数与不同润滑剂润滑条件下缸套-活塞环摩擦振动特性的内在联系。结果表明,随着摩擦磨损过程的进行,摩擦振动信号特征参数出现规律性变化;不同润滑工况下的特征参数呈现出明显的差异,反映了摩擦磨损的状态。振动特征体特征参数能定量刻画摩擦振动信号的特征。 相似文献
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本文介绍了利用模糊逻辑控制理论提高B型超声图像横向分辨力的方法,文章中介绍了变孔径技术,电子聚焦时原理及动态实时聚焦。 相似文献
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由于对比度低和噪声强等特点,超声图像分割很难达到满意的效果,针对这一状况,将Gabor滤波器结合形态学操作应用到超声图像中目标的边界提取。首先对原始图像做预处理,去噪增强,然后再利用Gabor滤波进行目标区域特征提取,再经形态学腐蚀、膨胀等操作平滑图像,最后由sobel算子提取最终的边界图像。该法的关键之处在于Gabor滤波器尺度参数的选择,通过实验和分析得出了一组最佳尺度参数,取得了良好的分割效果,同时也验证了这一方法在超声图像分割中的实用性。 相似文献
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Lizzi FL Rorke MC King DL Feleppa EJ Kalisz A Sokil-Melgar JB Nowakowski J 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1992,39(2):212-226
Data obtained from a scanning laser acoustic microscope (SLAM) were used to examine several aspects of ultrasonic backscattering from the liver. Phase interferograms from normal and abnormal human-liver specimens were digitized, and a series of algorithms was used to compute images of propagation velocity within the specimens. The propagation velocity images were then employed to simulate A- and B-mode results. These initial simulations were used to investigate how ultrasonic echo signals are related to tissue microstructure. Among the topics examined were B-mode speckling, frequency and beamwidth effects, and angulation dependencies. 相似文献
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Stoitsis J. Golemati S. Nikita K. S. 《IEEE transactions on instrumentation and measurement》2006,55(6):1944-1952
Improvements in medical imaging technology have greatly contributed to early disease detection and diagnosis. However, the accuracy of an examination depends on both the quality of the images and the ability of the physician to interpret those images. Use of output from computerized analysis of an image may facilitate the diagnostic tasks and, potentially improve the overall interpretation of images and the subsequent patient care. In this paper, Analysis, a modular software system designed to assist interpretation of medical images, is described in detail. Analysis allows texture and motion estimation of selected regions of interest (ROIs). Texture features can be estimated using first-order statistics, second-order statistics, Laws' texture energy, neighborhood gray-tone difference matrix, gray level difference statistics, and the fractal dimension. Motion can be estimated from temporal image sequences using block matching or optical flow. Image preprocessing, manual and automatic definition of ROIs, and dimensionality reduction and clustering using fuzzy c-means, are also possible within Analysis. An important feature of Analysis is the possibility for online telecollaboration between health care professionals under a secure framework. To demonstrate the applicability and usefulness of the system in clinical practice, Analysis was applied to B-mode ultrasound images of the carotid artery. Diagnostic tasks included automatic segmentation of the arterial wall in transverse sections, selection of wall and plaque ROIs in longitudinal sections, estimation of texture features in different image areas, motion analysis of tissue ROIs, and clustering of the extracted features. It is concluded that Analysis can provide a useful platform for computerized analysis of medical images and support of diagnosis 相似文献
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Shankar P.M. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2009,56(10):2086-2096
The spatial Bessel filters are studied for their ability to reduce ultrasonic speckle and enhance the boundaries of regions of interest (ROI) in medical B-mode images. Using the concept of the heterogeneity index, a new parameter is defined to provide a quantitative measure of the edge visibility. It is hypothesized that this edge visibility parameter will be almost equal to unity if the ROI does not contain a boundary and greater than unity when the ROI contains a boundary. Analyses of 2 computer-synthesized images containing speckle and B-mode images of tissue-mimicking phantoms were carried out. The improvement in contrast and enhancement in edge visibility were estimated. In addition, parametric images containing a map of the edge visibility were created that showed clear boundaries. The quantitative measures strongly support the visual perception of contrast and enhanced edge visibility provided by the spatial Bessel filters. Results demonstrate the potential use of Bessel spatial filters in providing speckle reduction along with the ability to enhance the boundaries of regions of interest in B-mode images. 相似文献
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Zemp RJ Abbey CK Insana MF 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2003,50(6):642-654
Linear equations for modeling echo signals from shift-variant systems forming ultrasonic B-mode, Doppler, and strain images are analyzed and extended. The approach is based on a solution to the homogeneous wave equation for random inhomogeneous media. When the system is shift-variant, the spatial sensitivity function-defined as a spatial weighting function that determines the scattering volume for a fixed point of time-has advantages over the point-spread function traditionally used to analyze ultrasound systems. Spatial sensitivity functions are necessary for determining statistical moments in the context of rigorous image quality assessment, and they are time-reversed copies of point-spread functions for shift variant systems. A criterion is proposed to assess the validity of a local shift-invariance assumption. The analysis reveals realistic situations in which in-phase signals are correlated to the corresponding quadrature signals, which has strong implications for assessing lesion detectability. Also revealed is an opportunity to enhance near- and far-field spatial resolution by matched filtering unfocused beams. The analysis connects several well-known approaches to modeling ultrasonic echo signals. 相似文献
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Montaldo G. Tanter M. Bercoff J. Benech N. Fink M. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2009,56(3):489-506
The emergence of ultrafast frame rates in ultrasonic imaging has been recently made possible by the development of new imaging modalities such as transient elastography. Data acquisition rates reaching more than thousands of images per second enable the real-time visualization of shear mechanical waves propagating in biological tissues, which convey information about local viscoelastic properties of tissues. The first proposed approach for reaching such ultrafast frame rates consists of transmitting plane waves into the medium. However, because the beamforming process is then restricted to the receive mode, the echographic images obtained in the ultrafast mode suffer from a low quality in terms of resolution and contrast and affect the robustness of the transient elastography mode. It is here proposed to improve the beamforming process by using a coherent recombination of compounded plane-wave transmissions to recover high-quality echographic images without degrading the high frame rate capabilities. A theoretical model is derived for the comparison between the proposed method and the conventional B-mode imaging in terms of contrast, signal-to-noise ratio, and resolution. Our model predicts that a significantly smaller number of insonifications, 10 times lower, is sufficient to reach an image quality comparable to conventional B-mode. Theoretical predictions are confirmed by in vitro experiments performed in tissue-mimicking phantoms. Such results raise the appeal of coherent compounds for use with standard imaging modes such as B-mode or color flow. Moreover, in the context of transient elastography, ultrafast frame rates can be preserved while increasing the image quality compared with flat insonifications. Improvements on the transient elastography mode are presented and discussed. 相似文献
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Abbey CK Nguyen NQ Insana MF 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2012,59(6):1115-1126
Transmitted pressure pulses in ultrasonic B-mode imaging systems are commonly characterized by their center frequency and bandwidth. Both parameters are associated with tradeoffs in spatial resolution and signal-to-noise in ultrasonic system design, with no general understanding of where they are optimal when applied to specific clinical exams. We use the ideal observer and simple psychophysical studies with human observers to evaluate the efficiency of information transfer in B-mode imaging as a function of the transmitted pulse center frequency and fractional bandwidth. Our approach uses a statistical model of backscatter relevant to breast imaging, and a 2-D model of pulse propagation based on Rayleigh-Sommerfeld diffraction theory. The statistics of the backscattered signal are combined in an ideal observer calculation that quantifies the task-relevant information contained in the radio-frequency (RF) signal after delay-and-sum beamforming. This is followed by a psychophysical evaluation of observer performance on B-mode envelope-detected images in three simple tasks. This experimental design allows us to track the flow of diagnostic information through RF acquisition and subsequent reading of the envelope image. In a low-contrast detection task and a high-contrast boundary discrimination task, optimal efficiency for human observers is observed at the highest center frequencies tested (15 MHz) and at moderate bandwidth (40%). For detection of scattering material in a high-contrast hypoechoic lesion, optimal efficiency was observed at lower center frequencies (5 MHz) and higher bandwidth (80%). The ideal observer analysis shows that this task dependence does not arise in the acquisition stage, where efficiency is maximized at 15 MHz with bandwidths of 60% or greater, but rather in the subsequent processing and reading of the envelope image. In addition, at higher frequencies more information is lost in the processing and reading than in the acquisition of reflected signals. 相似文献
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Dumont Douglas Dahl Jeremy Miller Elizabeth Allen Jason Fahey Brian Trahey Gregg 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2009,56(5):931-944
Acoustic radiation force impulse (ARFI) imaging characterizes the mechanical properties of tissue by measuring displacement resulting from applied ultrasonic radiation force. In this paper, we describe the current status of ARFI imaging for lower-limb vascular applications and present results from both tissue-mimicking phantoms and in vivo experiments. Initial experiments were performed on vascular phantoms constructed with polyvinyl alcohol for basic evaluation of the modality. Multilayer vessels and vessels with compliant occlusions of varying plaque load were evaluated with ARFI imaging techniques. Phantom layers and plaque are well resolved in the ARFI images, with higher contrast than B-mode, demonstrating the ability of ARFI imaging to identify regions of different mechanical properties. Healthy human subjects and those with diagnosed lower-limb peripheral arterial disease were imaged. Proximal and distal vascular walls are well visualized in ARFI images, with higher mean contrast than corresponding B-mode images. ARFI images reveal information not observed by conventional ultrasound and lend confidence to the feasibility of using ARFI imaging during lower-limb vascular workup. 相似文献
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键合点剪切强度是衡量键合质量的重要指标之一,以引线键合系统超声波发生器电信号作为信息载体,研究了超声电信号的特征提取方法以及在键合强度识别方面的应用。针对超声电信号的瞬态特性,提出一种基于信号子频带包络分段的特征提取方法。该方法将超声电信号滤波后的子频带包络分成信号上升、稳定和衰减三个阶段,提取每个阶段的敏感波形特征来表征键合过程。为了消除特征中的冗余信息并实现特征降维,采用了主分量分析(PCA)技术进行特征选择。建立了人工神经网络系统(ANN)对提取的特征进行识别,通过实验数据分析,验证了本文方法的有效性。 相似文献