X‐ray dynamical diffraction Fraunhofer holography

An X‐ray dynamical diffraction Fraunhofer holographic scheme is proposed. Theoretically it is shown that the reconstruction of the object image by visible light is possible. The spatial and temporal coherence requirements of the incident X‐ray beam are considered. As an example, the hologram recording as well as the reconstruction by visible light of an absolutely absorbing wire are discussed.     

Numerical reconstruction of an object image using an X‐ray dynamical diffraction Fraunhofer hologram

A numerical method of reconstruction of an object image using an X‐ray dynamical diffraction Fraunhofer hologram is presented. Analytical approximation methods and numerical methods of iteration are discussed. An example of a reconstruction of an image of a cylindrical beryllium wire is considered. The results of analytical approximation and zero‐order iteration coincide with exact values of the amplitude complex transmission coefficient of the object as predicted by the resolution limit of the scheme, except near the edges of the object. Calculations of the first‐ and second‐order iterations improve the result at the edges of the object. This method can be applied for determination of the complex amplitude transmission coefficient of amplitude as well as phase objects. It can be used in X‐ray microscopy.     

基于小波变换的X射线图像超动态范围重建

针对小动态范围X射线成像设备提出一种X射线图像超动态范围重建方法.将成像对象进行两次不同球管电压下的低剂量曝光,对两次曝光得到的图像进行多分辨率小波分解.根据一定规则重构分解系数,将重构的系数进行小波逆变换重建一幅宽动态范围图像.实验表明,该方法能有效扩展图像的灰度动态范围,并且两次低剂量曝光并未增加患者皮肤表面吸收剂量.      

XDesign: an open‐source software package for designing X‐ray imaging phantoms and experiments

The development of new methods or utilization of current X‐ray computed tomography methods is impeded by the substantial amount of expertise required to design an X‐ray computed tomography experiment from beginning to end. In an attempt to make material models, data acquisition schemes and reconstruction algorithms more accessible to researchers lacking expertise in some of these areas, a software package is described here which can generate complex simulated phantoms and quantitatively evaluate new or existing data acquisition schemes and image reconstruction algorithms for targeted applications.     

Single‐cell resolution in high‐resolution synchrotron X‐ray CT imaging with gold nanoparticles

Gold nanoparticles are excellent intracellular markers in X‐ray imaging. Having shown previously the suitability of gold nanoparticles to detect small groups of cells with the synchrotron‐based computed tomography (CT) technique both ex vivo and in vivo, it is now demonstrated that even single‐cell resolution can be obtained in the brain at least ex vivo. Working in a small animal model of malignant brain tumour, the image quality obtained with different imaging modalities was compared. To generate the brain tumour, 1 × 10⁵ C6 glioma cells were loaded with gold nanoparticles and implanted in the right cerebral hemisphere of an adult rat. Raw data were acquired with absorption X‐ray CT followed by a local tomography technique based on synchrotron X‐ray absorption yielding single‐cell resolution. The reconstructed synchrotron X‐ray images were compared with images obtained by small animal magnetic resonance imaging. The presence of gold nanoparticles in the tumour tissue was verified in histological sections.     

Object image correction using an X‐ray dynamical diffraction Fraunhofer hologram

Taking into account background correction and using Fourier analysis, a numerical method of an object image correction using an X‐ray dynamical diffraction Fraunhofer hologram is presented. An example of the image correction of a cylindrical beryllium wire is considered. A background correction of second‐order iteration leads to an almost precise reconstruction of the real part of the amplitude transmission coefficient and improves the imaginary part compared with that without a background correction. Using Fourier analysis of the reconstructed transmission coefficient, non‐physical oscillations can be avoided. This method can be applied for the determination of the complex amplitude transmission coefficient of amplitude as well as phase objects, and can be used in X‐ray microscopy.     

衍射增强成像信息分离方法研究

衍射增强成像（DEI）是一种功能强大的相位衬度成像技术,对于软组织,它能获得比基于吸收的传统X射线成像技术更高的衬度.研究了一种基于DEI的信息分离方法,它能同时获得三种参数图像,即吸收像、折射像和小角散射像.信息分离利用解析方程求解,获得的参数图像质量取决于在三个不同的分析晶体角度处获得的DEI图像.利用矩阵条件数对方程求解的稳定性进行了讨论,推导出理论上的折射角和小角散射宽度的最大值.最后,利用豚鼠耳蜗DEI图像对研究结果进行了验证. 关键词： 信息分离 衍射增强成像 矩阵条件数 豚鼠耳蜗     

Enhancements in full‐field PIXE imaging—Large area elemental mapping with increased lateral resolution devoid of optics artefacts

The combination of a pn‐junction charge‐coupled device‐based pixel detector with a poly‐capillary X‐ray optics was installed and examined at the Helmholtz‐Zentrum Dresden‐Rossendorf. The set‐up is intended for particle‐induced X‐ray emission imaging to survey the trace elemental composition of flat/polished geological samples. In the standard configuration, a straight X‐ray optics (20 μm capillary diameter) is used to guide the emitted photons from the sample towards the detector with nearly 70 000 pixels. Their dimensions of 48 × 48 μm² are the main limitation of the lateral resolution. This limitation can be bypassed by applying a dedicated subpixel algorithm to recalculate the footprint of the photon's electron cloud in the detector. The lateral resolution is then mainly determined by the capillary's diameter. Nevertheless, images are still superimposed by the X‐ray optics pattern. The optics' capillaries are grouped in hexagonal bundles resulting in a reduced transmission of X‐rays in the boundary regions. This influence can be largely suppressed by combining a series of short measurements at slightly shifted positions using a precision stage and correcting the image data for this shifting. The use of a subpixel grid for the image reconstruction allows a further increase of the spatial resolution. This approach of image‐stacking and multiframe super‐resolution in combination with the subpixel correction algorithm is presented and illustrated with experimental data. Additionally, a flat‐field correction is shown to remove the remaining imaging inhomogeneity caused by non‐uniform X‐ray transmission. The described techniques can be used for all X‐ray spectrometry methods using an X‐ray camera to obtain high‐quality elemental images.     

3D imaging of a rice pollen grain using transmission X‐ray microscopy

For the first time, the three‐dimensional (3D) ultrastructure of an intact rice pollen cell has been obtained using a full‐field transmission hard X‐ray microscope operated in Zernike phase contrast mode. After reconstruction and segmentation from a series of projection images, complete 3D structural information of a 35 µm rice pollen grain is presented at a resolution of ～100 nm. The reconstruction allows a clear differentiation of various subcellular structures within the rice pollen grain, including aperture, lipid body, mitochondrion, nucleus and vacuole. Furthermore, quantitative information was obtained about the distribution of cytoplasmic organelles and the volume percentage of each kind of organelle. These results demonstrate that transmission X‐ray microscopy can be quite powerful for non‐destructive investigation of 3D structures of whole eukaryotic cells.     

位相恢复法与X射线激光等离子体密度诊断

 详细介绍了XUV波段Gabor全息及位相恢复法去除Gabor全息孪生像的全部过程,分析了X射线激光Gabor全息术对等离子体和实验条件的要求,编程对全息图的制作、反演以及位相恢复法的全过程进行了模拟,并对三个模型进行了计算比较。     

基于倒置结构的直接体积重建

通过多个点状探测器在三维空间中的适当分布的排列,得到了基于倒置结构Ｘ射线锥形束投影的直接体积重建三维成像七锥形束边界重建相结合,针对倒置结构构造的重建算法及其数值仿真表明,新的成像模式相对于传统的锥形束边界重建,在实际存在Ｘ射线投影噪声情形下有明显的优点。     

惯性约束聚变靶三维成像研究

利用计算机层析技术，采用乘代数重建法，编制出三维图像重建程序ＣＴ３Ｄ，通过五个方位对“星光Ⅱ”装置的惯性约束聚变靶进行Ｘ光成像，重建出靶等离子体的三维图像，获得了较好的结果，表明该技术在惯性约束聚变实验中应用的可能性。     

Multivariate analysis of hyperspectral hard X‐ray images

This article describes methods to analyse and process hyperspectral hard X‐ray imaging data. We focus on the use of multivariate techniques that exploit the spectral information to make informed decisions on the material content within each pixel of an X‐ray image. These analysis methods have the ability to auto‐segment data without prior knowledge of the sample composition or structure, and are particularly useful for studying completely unknown, diluted or complex specimens. We demonstrate the methods on a variety of hard X‐ray images including X‐ray fluorescence and absorption data recorded using a hard X‐ray imaging spectrometer. The multivariate methods described are very powerful with the ability to segment, distinguish and, in some cases, identify different materials within a single X‐ray image. Potential uses of hyperspectral X‐ray imaging are discussed varying from materials science to industrial or security applications. Copyright © 2013 John Wiley & Sons, Ltd.     

数字重现无透镜傅里叶变换X射线全息的实验模拟研究

参照无透镜傅里叶变换（ＬＬＦＴ）Ｘ射线全息图的记录光路，采用可见光源模拟研究了无透镜傅里叶变换Ｘ射线全息从记录到数字重现的全过程，给出了实验结果，并对光学重现和数字重现结果作了比较，分析了该记录方式存在的一些问题，指出实际Ｘ射线全息记录中可直接使用波带板＋１级衍射而不必在物面加一滤波小孔。分析了利用数字重现消除记录过程中非线性效应的可行性。并着重指出波带板的多级衍射的互干涉对重现象的干扰，应设法消除。     

Synchrotron microanalysis techniques applied to potential photovoltaic materials

X‐ray synchrotron radiation techniques are used to characterize photovoltaic‐related semiconductors. Micro‐X‐ray‐fluorescence and X‐ray beam induced current mapping of multicrystalline silicon photovoltaic cells show metallic impurities accumulating at the interface of crystallographic defects, and current variations over the cell that are attributed to bulk defects and structural variation of the silicon. Similarly, studies on a single‐crystal GaAs using X‐ray fluorescence and X‐ray excited optical luminescence show an inhomogeneous As distribution correlated with the photoluminescence signal, with higher As concentration regions having stronger photoluminescence signal. Both examples show how the combination of synchrotron microanalysis techniques can contribute to a better understanding of the optical properties of photovoltaic materials.     

X光探伤电视的微机图像处理系统的研究

Ｘ光探伤电视系统虽然具备节省Ｘ光软片和可在线探伤等优点以外，还存在着图像分辨率不很高的问题。其图像分辨率不很高的主要原因是由于Ｘ光所激发的二次射线造成的，这是一种随机的噪声干扰。利用在计算机图像处理中的叠加平均法可有效的去除这种噪声干扰，从而提高Ｘ光探伤电视的图像分辨率。电视图像的数字化需要高速的信号采集系统。用硬件构成的图像存贮体可实现高速的图像信号采集，并结合开窗口技术使得Ｘ光探伤电视的成本降低，为高分辨率Ｘ光探伤电视的广泛应用创造了有利的条件。这些对保证产品质量具有十分重要的意义。     

低强度X射线影像仪的新发展

扼要介绍国内外Ｌｉｘｉｓｃｏｐｅ的概况。提出在国产系统中在Ｘ射线源前加置Ｘ射线准直器,Ｘ射线影像增强采用纤维光学输出窗和小孔径大面积微反,可以必普像质、扩大视场。     

双狭缝透射光栅软X光时空分辨谱仪

 利用双狭缝、透射光栅配亚仟X光条纹相机做了具有一维空间、时间和能谱分辨的三维软X光测量仪器(双狭缝透射光栅软X光时空分辨谱仪), 并成功地获得了金盘靶的N带X光(中心波长1.7nm)时空分辨图象 。该仪器空间分辨可达23μm, 时间分辨可达003ns, 能谱分辨(当源大小为100～300μm时对波长1.7nm的X光)可达0.4～ 0.7nm, 只需稍加改动, 即可用于其它波段的X光测量。     

12MeV LIA X射线斑点测试及其调制传递函数

 介绍了测试12MeV LIA X光斑点的测试系统,利用刀口法和大孔成像法测出所成像的黑密度分布, 获得X光斑点大小结果; 根据该光源的近乎轴对称特点和大孔所成像的密度分布,经数值处理拟合出斑点强度的空间分布;利用该系统,获得了判断12MeV LIA X光成像空间分辨能力的调制传递函数。     

Confocal full‐field X‐ray microscope for novel three‐dimensional X‐ray imaging

A confocal full‐field X‐ray microscope has been developed for use as a novel three‐dimensional X‐ray imaging method. The system consists of an X‐ray illuminating `sheet‐beam' whose beam shape is micrified only in one dimension, and an X‐ray full‐field microscope whose optical axis is normal to the illuminating sheet beam. An arbitral cross‐sectional region of the object is irradiated by the sheet‐beam, and secondary X‐ray emission such as fluorescent X‐rays from this region is imaged simultaneously using the full‐field microscope. This system enables a virtual sliced image of a specimen to be obtained as a two‐dimensional magnified image, and three‐dimensional observation is available only by a linear translation of the object along the optical axis of the full‐field microscope. A feasibility test has been carried out at beamline 37XU of SPring‐8. Observation of the three‐dimensional distribution of metallic inclusions in an artificial diamond was performed.