一种改进的基于差分曲率和对比度场的细节增强算法

针对图像细节增强过程中梯度对噪声敏感的缺点,本文提出了一种改进的基于差分曲率和对比度场的细节增强算法.首先,该算法利用差分曲率代替梯度值决定系数的放大倍数,以差分曲率作为自变量的放大系数函数考虑了更多的邻域像素,从而克服了图像梯度对噪声敏感的缺点;然后,利用该放大系数非线性地放大对比度场,并构造能量泛函;最后,通过变分方法得到增强后的图像.标准测试图像和工业X射线图像的实验结果表明,本文提出的算法在有效增强图像对比度的同时,能够较好地抑制噪声.     

双能X射线图像融合技术研究

在真双能X射线检测系统中，两次采集到的图像存在一定空间位置上的偏移，且现有的图像融合算法存在融合后图像有噪声和伪影的问题。提出了一种配准融合、降噪和增强双能量X射线图像的组合方案。首先采用SIFT算法对低能X图像和高能X图像进行配准处理，消除高低能图像间的位置偏差。接着采用基于像素的小波变换融合高低能图像。最后，使用基于背景减法的降噪技术处理融合后的图像，采用基于灰度级分组的技术对降噪后的图像进行增强处理。实验结果表明，最终图像不仅包含来自高低能图像的互补信息，而且达到了无背景噪声和对比度增强的效果。与其他组合方案比较，该组合方案处理所得的图像表现出更好的对比度和清晰度，因此该组合方案提高无损检测的成效，处理后的图像更有助于工作人员观察和解读。     

一种改进的基于差分曲率和对比度场的细节增强算法（英文）

针对图像细节增强过程中梯度对噪声敏感的缺点,本文提出了一种改进的基于差分曲率和对比度场的细节增强算法。首先,该算法利用差分曲率代替梯度值决定系数的放大倍数,以差分曲率作为自变量的放大系数函数考虑了更多的邻域像素,从而克服了图像梯度对噪声敏感的缺点;然后,利用该放大系数非线性地放大对比度场,并构造能量泛函;最后,通过变分方法得到增强后的图像。标准测试图像和工业X射线图像的实验结果表明,本文提出的算法在有效增强图像对比度的同时,能够较好地抑制噪声。     

射线图像增强技术仿真研究

图像增强在生物医学、无损检测、卫星遥感等领域得到广泛应用。对于低对比度射线图像而言,局部图像的反差较小是其特点。针对这一特点,将全局自适应均衡与局部动态增强相结合,通过增强倍数进行局部动态调整以适合各种对比度增强的要求。仿真结果表明,该算法能有效提高低对比度射线图像的整体对比度并同时突出细节。在实际应用中,对于其他成像技术的处理也有很好的参考价值。     

基于牙科X光片的多种直方图均衡化图像增强对比

牙科X光片在牙科疾病的诊断治疗中越来越重要。牙齿X光片机不像光学相机可以聚焦,常受低对比度和噪声的影响,很难直接借此识别疾病特征,常常需要对图片进行增强处理,故主要探讨一些适用于电子病例的牙科X光图像增强算法。算法主要有直方图均衡化、限制对比度自适应直方图均衡化、锐化中值滤波自适应直方图均衡化和改进的对比度自适应直方图均衡化方法。通过对这些算法处理后的牙科X光片图像的均方根误差(RMSE)、图像信噪比(SNR)和改善对比度指数(CII)以及视觉效果进行比较,发现用改进的对比度自适应直方图均衡化方法处理所得图像的均方根误差、改善对比度指数最小,图像信噪比最大,图像视觉效果清晰。     

封头焊缝的X射线图像分割与增强方法研究

针对现有大型封头焊缝X射线检测存在胶片成像成本高、人工识别缺陷效率低等问题,提出基于X射线数字图像自动采集方案,并设计焊缝图像自动处理识别方法。针对焊缝区域与背景差异特性,采用固步灰度梯度法提取焊缝区域;采用双边滤波融合算法、自适应高频图像信息增强算法,实现焊缝图像的降噪和缺陷细节对比度增强;最后结合封头焊缝类型及特点设计特征库,基于Canny算法组合树形分类器实现缺陷的特征提取和分类。实验结果表明,该方法对封头焊缝中的气孔、裂纹、未融合、夹杂、未焊透等五类典型缺陷特征提取效果满足判级要求。     

基于多帧图像焊缝缺陷轨迹跟踪的X射线实时检测技术

正基于X射线实时成像的焊缝缺陷在线检测是重要焊接结构连续生产过程中的关键环节,而动态图像处理技术是实现在线自动检测的关键。对于高噪声焊缝X射线实时图像,采用单帧图像处理算法无法克服缺陷误检与漏检之间的矛盾,需要研究多帧关联的图像处理方法。目前该领域已有的X射线多帧实时动态图像处理主要采用图像匹配方法或帧间缺陷匹配方法,前者在进行相关度计算时实时性较差,后者对低对比度缺陷容易产生漏检。另外,现有的焊缝缺陷检测图像处理算法对     

平板探测器坏像素校正方法研究

讨论X射线系统中平板探测器的坏像素产生原因并归纳分类。研究坏像素的探测、校正矩阵的生成和对坏像素的校正方法。通过仿真模型对所提出的校正算法进行了验证,通过比较重建图像的信噪比对该算法的效果进行了评估。研究结果表明,平板探测器的制造缺陷等固有噪声源将在重建图像中被增强,并表现为大量的条纹和环形伪影;通过校正,重建图像中的上述伪影明显减少,图像质量得到改善,且系统的低对比度探测能力也得到相应提高。     

X射线无损探伤技术在变电站运行状态GIS检测中的应用

现有变电站运行状态GIS检测工作,难以确保所有高压输电站都能实现每年一次的检修工作,因此研究了X射线无损探伤技术,并将其应用在变电站运行状态GIS检测中。预先设计了X射线防护装置,屏蔽高压电磁脉冲对X射线机的干扰;在此基础上,构建X射线相机模型,并选择合适的管电压、管电流,明确工件对比度和成像板灵敏度;通过几何变换、灰度变换、图像平滑和阈值分割手段,处理GIS检测图像,实现检测变电站运行状态。实验测试结果可知,当施加电压超过150kV时,无防护装置的X射线机被高压脉冲干扰,无法显示检测结果;而有防护装置的测试组中,当施加电压超过330kV时,X射线机依旧可以显示GIS检测结果。可见此次应用的X射线无损探伤技术,在防护装置的辅助下,可以更好地实现变电站运行状态检测。     

一种改进的图像模糊增强法

基于医学图像对比度差以致正常组织和病态组织难以区分,本文在讨论了Pal.King模糊增强的基础上,对模糊算法进行了改进,改进后的模糊算法效果明显,能增强图像细微细节,提高图像的对比度,改善图像视觉效果,提高诊断的准确性.     

Evaluation of X‐ray tomography contrast agents: A review of production,protocols, and biological applications

X‐ray computed tomography is a strong tool that finds many applications both in medical applications and in the investigation of biological and nonbiological samples. In the clinics, X‐ray tomography is widely used for diagnostic purposes whose three‐dimensional imaging in high resolution helps physicians to obtain detailed image of investigated regions. Researchers in biological sciences and engineering use X‐ray tomography because it is a nondestructive method to assess the structure of their samples. In both medical and biological applications, visualization of soft tissues and structures requires special treatment, in which special contrast agents are used. In this detailed report, molecule‐based and nanoparticle‐based contrast agents used in biological applications to enhance the image quality were compiled and reported. Special contrast agent applications and protocols to enhance the contrast for the biological applications and works to develop nanoparticle contrast agents to enhance the contrast for targeted drug delivery and general imaging applications were also assessed and listed.     

Simultaneous phase and amplitude extraction from a single defocused image of a homogeneous object

We demonstrate simultaneous phase and amplitude extraction from a single defocused image of a homogeneous object. Subject to the assumptions explicitly stated in the derivation, the algorithm solves the twin‐image problem of in‐line holography and is capable of analysing data obtained using X‐ray microscopy, electron microscopy, neutron microscopy or visible‐light microscopy, especially as they relate to defocus and point projection methods. Our simple, robust, non‐iterative and computationally efficient method is applied to data obtained using an X‐ray phase contrast ultramicroscope.     

Visualization of water drying in porous materials by X‐ray phase contrast imaging

We present in this study results from X‐ray tomographic microscopy with synchrotron radiation performed both in attenuation and phase contrast modes on a limestone sample during two stages of water drying. No contrast agent was used in order to increase the X‐ray attenuation by water. We show that only by using the phase contrast mode it is possible to achieve enough water content change resolution to investigate the drying process at the pore‐scale. We performed 3D image analysis of the time‐differential phase contrast tomogram. We show by the results of such analysis that it is possible to obtain a reliable characterization of the spatial redistribution of water in the resolved pore system in agreement with what expected from the theory of drying in porous media and from measurements performed with other approaches. We thus show the potential of X‐ray phase contrast imaging for pore‐scale investigations of reactive water transport processes which cannot be imaged by adding a contrast agent for exploiting the standard attenuation contrast imaging mode.     

基于平稳小波的维纳滤波射线图像去噪算法研究

将维纳滤波的原理应用到基于平稳小波的X射线图像去噪过程,研究了一种基于平稳小波的X射线图像维纳滤波去噪方法.实验证明:该方法不仅能有效消除Gibbs现象,而且能够在有效滤除噪声的同时,很好地保持X射线图像的细节部分信息.     

Contact X‐ray microscopy of living cells by using LiF crystal as imaging detector

In this paper, the use of lithium fluoride (LiF) as imaging radiation detector to analyse living cells by single‐shot soft X‐ray contact microscopy is presented. High resolved X‐ray images on LiF of cyanobacterium Leptolyngbya VRUC135, two unicellular microalgae of the genus Chlamydomonas and mouse macrophage cells (line RAW 264.7) have been obtained utilizing X‐ray radiation in the water window energy range from a laser plasma source. The used method is based on loading of the samples, the cell suspension, in a special holder where they are in close contact with a LiF crystal solid‐state X‐ray imaging detector. After exposure and sample removal, the images stored in LiF by the soft X‐ray contact microscopy technique are read by an optical microscope in fluorescence mode. The clear image of the mucilaginous sheath the structure of the filamentous Leptolyngbya and the visible nucleolus in the macrophage cells image, are noteworthiness results. The peculiarities of the used X‐ray radiation and of the LiF imaging detector allow obtaining images in absorption contrast revealing the internal structures of the investigated samples at high spatial resolution. Moreover, the wide dynamic range of the LiF imaging detector contributes to obtain high‐quality images. In particular, we demonstrate that this peculiar characteristic of LiF detector allows enhancing the contrast and reveal details even when they were obscured by a nonuniform stray light.     

Three‐dimensional imaging of whole mouse models: comparing nondestructive X‐ray phase‐contrast micro‐CT with cryotome‐based planar epi‐illumination imaging

In this study, we compare two evolving techniques for obtaining high‐resolution 3D anatomical data of a mouse specimen. On the one hand, we investigate cryotome‐based planar epi‐illumination imaging (cryo‐imaging). On the other hand, we examine X‐ray phase‐contrast micro‐computed tomography (micro‐CT) using synchrotron radiation. Cryo‐imaging is a technique in which an electron multiplying charge coupled camera takes images of a cryo‐frozen specimen during the sectioning process. Subsequent image alignment and virtual stacking result in volumetric data. X‐ray phase‐contrast imaging is based on the minute refraction of X‐rays inside the specimen and features higher soft‐tissue contrast than conventional, attenuation‐based micro‐CT. To explore the potential of both techniques for studying whole mouse disease models, one mouse specimen was imaged using both techniques. Obtained data are compared visually and quantitatively, specifically with regard to the visibility of fine anatomical details. Internal structure of the mouse specimen is visible in great detail with both techniques and the study shows in particular that soft‐tissue contrast is strongly enhanced in the X‐ray phase images compared to the attenuation‐based images. This identifies phase‐contrast micro‐CT as a powerful tool for the study of small animal disease models.     

Size-selective colloidal-gold localization in transmission X-ray microscopy

Colloidal gold is a useful marker for functional‐imaging experiments in transmission X‐ray microscopy. Due to the low contrast of gold particles with small diameters it is necessary to develop a powerful algorithm to localize the single gold particles. The presented image‐analysis algorithm for identifying colloidal gold particles is based on the combination of a threshold with respect to the local absorption and shape discrimination, realized by fitting a Gaussian profile to the identified regions of interest. The shape discrimination provides the possibility of size‐selective identification and localization of single colloidal gold particles down to a diameter of 50 nm. The image‐analysis algorithm, therefore, has potential for localization studies of several proteins simultaneously and for localization of fiducial markers in X‐ray tomography.     

Wavelet-based image restoration for compact X-ray microscopy

Compact water‐window X‐ray microscopy with short exposure times will always be limited on photons owing to sources of limited power in combination with low‐efficency X‐ray optics. Thus, it is important to investigate methods for improving the signal‐to‐noise ratio in the images. We show that a wavelet‐based denoising procedure significantly improves the quality and contrast in compact X‐ray microscopy images. A non‐decimated, discrete wavelet transform (DWT) is applied to original, noisy images. After applying a thresholding procedure to the finest scales of the DWT, by setting to zero all wavelet coefficients of magnitude below a prescribed value, the inverse DWT to the thresholded DWT produces denoised images. It is concluded that the denoising procedure has potential to reduce the exposure time by a factor of 2 without loss of relevant image information.     

Application of sensitive,high‐resolution imaging at a commercial lab‐based X‐ray micro‐CT system using propagation‐based phase retrieval

Several dedicated commercial lab‐based micro‐computed tomography (μCT) systems exist, which provide high‐resolution images of samples, with the capability to also deliver in‐line phase contrast. X‐ray phase contrast is particularly beneficial when visualizing very small features and weakly absorbing samples. The raw measured projections will include both phase and absorption effects. Extending our previous work that addressed the optimization of experimental conditions at the commercial ZEISS Xradia 500 Versa system, single‐distance phase‐contrast imaging is demonstrated on complex biological and material samples. From data captured at this system, we demonstrate extraction of the phase signal or the correction of the mixed image for the phase shift, and show how this procedure increases the contrast and removes artefacts. These high‐quality images, measured without the use of a synchrotron X‐ray source, demonstrate that highly sensitive, micrometre‐resolution imaging of 3D volumes is widely accessible using commercially advanced laboratory devices.     

A study of the human hair structure with a Zernike phase contrast X-ray microscope

We have observed the internal structure of human hair shafts with a transmission Zernike phase contrast hard X‐ray microscope. Due to the high spatial resolution and the high contrast of the microscope, we could image scales, macrofibrils, medulla and melanin without staining. The structure of a black hair shaft is compared with that of a white one.