共查询到20条相似文献,搜索用时 109 毫秒
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反散射成像法是数字辐射成像的主要方法之一,介绍了获得反散射数字图像的实验装置,并着重分析了针对此装置获得的反散性图像的处理方法。 相似文献
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在大型物体辐射成像系统中,成像质量是衡量成像系统的决定性指标。提出采用品质因子Q做为指标来描述成像系统,并结合蒙特卡罗模拟方法研究了在常见的X射线成像系统中发生的散射干扰对成像质量的影响. 相似文献
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在X射线CT(Computed Tomography)成像尤其是锥束成像过程中,散射是不可忽略的影响因素。探测信号中散射信号的存在导致CT图像中的伪影。依据散射信号的特征属性,提出了一种散射的估计方法。该方法利用简单的解析公式估计散射,简单易操作。实际的实验数据验证了方法的有效性。 相似文献
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本文验证了基于Micromegas探测器的宇宙线缪子散射成像系统进行快速核材料检测的可行性,并对实验室宇宙线缪子成像系统原型进行参数估算。基于Geant4程序开发了用于模拟宇宙线缪子物理过程、传输径迹及Micromegas探测器响应的模拟程序。在模拟数据的基础上,实现并改进了两种主要的宇宙线缪子散射成像算法。根据模拟和成像结果,1 m×1 m成像系统可在10 min内检测到被重元素屏蔽的核材料。10 cm×10 cm成像系统的缪子事例触发率为0.16 s-1,要获得较为清晰的成像结果,要求探测器位置分辨率达到300 μm,探测器增益为1 000时实际测量事例至少需要20 h。 相似文献
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450keV锥束CT系统的散射校正研究 总被引:2,自引:0,他引:2
在450keV锥束工业CT成像系统中,对投影数据进行适当的散射校正是一步重要的数据校正.结合国内外散射校正方法研究的现状,对一种用散射校正板来进行散射校正方法的原理和实现进行了深入的研究.实验结果表明,这种校正方法能够对450KeV锥束CT成像系统进行有效地散射校正. 相似文献
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X射线横向移动成像是一种新的散射成像方法,直接利用大面积探测器分开探测单次和多次散射光子强度来识别被覆盖物体的组成类型、尺寸和浅表面缺陷等,法已被用于地雷探测.利用蒙特卡罗模拟软件MCNP5分别模拟了覆盖于土壤中的不同横向面积的铁、TNT以及含空气缺陷的TNT中X光子的散射过程.根据模拟结果分析了两类探测器上散射光子的... 相似文献
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本介绍北京同步辐射装置(BSRF)小角X射线散射实验站实验数据的初步处理方法,即由成像板探测器检测到的散射信号转换成角度及其对应的强度数据的方法,并对数据转换过程中可能遇到的问题进行了详细的讨论. 相似文献
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为进一步深入开展宇宙线μ子散射成像技术研究,发挥其在国土安全、防范核走私、核不扩散等方面的重要作用。论文综述了国内外在宇宙线μ子散射成像技术上的研究进展情况,提出了一些存在的问题以及未来的研究方向。 相似文献
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利用640层容积CT对颈动脉、脑动脉及冠状动脉扫描一次成像,初步探讨心脑血管联合成像后的图像质量和患者所受的辐射剂量,并研究临床进一步应用的价值。其中心脑联合成像20例(1组),冠状动脉CTA 20例(2组),常规颈-脑血管CTA20例(3组),所有患者采用前瞻性心电门控,分别测量每组患者升主动脉根部、两侧颈总动脉、颈内动脉及大脑中动脉M1图像CT值及图像噪声。采用4分法评估冠状动脉图像,3分法评价颈-脑血管图像,分别记录各组扫描后患者所受辐射剂量。最终得出640层容积CT低剂量“一站式”大螺距心脑血管联合成像能同时提供满足临床诊断需要的冠状动脉及颈-脑血管图像。本研究得到了满足诊断的冠状动脉图像97.5%,未出现不能诊断的颈-脑血管图像,心脑血管联合成像的有效辐射暴露剂量仅(3.99±0.37)mSv,辐射暴露剂量完全在患者所能接受的合理范围之内,避免患者重复多次进行CTA 检查,能一次为临床治疗提供更多信息,是一种简便、快捷、无创、对比剂使用少、辐射剂量低、客观和重复性强的检查。 相似文献
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为解决cm级尺寸射线源的空间分布诊断,本文提出大孔径厚针孔成像方法。采用Geant4软件编写蒙特卡罗程序模拟5、10和15 mm大孔径厚针孔的成像过程,采用Matlab软件实现逆滤波、Wiener滤波和Lucy-Richardson复原算法,以均方根误差σ作为复原效果评判标准,优化了Wiener滤波信噪比参数和Lucy-Richardson算法迭代次数参数。将复原算法应用于不同孔径厚针孔的图像复原,发现理想逆滤波算法会引起噪声放大;Wiener滤波算法图像复原解存在较严重的伪影;Lucy-Richardson算法可获得清晰的复原图像。结合Lucy-Richardson算法的5、10、15 mm大孔径厚针孔成像获取的图像的σ是0.5 mm孔径传统针孔成像结果的1.15、1.21、1.26倍。结果表明,结合图像复原算法的大孔径厚针孔成像技术能获得与传统针孔成像接近的源图像测量结果,初步验证了该方法具有可行性。 相似文献
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Yuasa T. Akiba M. Takeda T. Kazama M. Hoshino A. Watanabe Y. Hyodo K. Dilmanian F.A. Akatsuka T. Itai Y. 《IEEE transactions on nuclear science》1997,44(1):54-62
We describe a new attenuation correction method for fluorescent X-ray computed tomography (FXCT) applied to image nonradioactive contrast materials in vivo. The principle of the FXCT imaging is that of computed tomography of the first generation. Using monochromatized synchrotron radiation from the BLNE-5A bending-magnet beam line of Tristan Accumulation Ring in KEK, Japan, we studied phantoms with the FXCT method, and we succeeded in delineating a 4-mm-diameter channel filled with a 500 μg I/ml iodine solution in a 20-mm-diameter acrylic cylindrical phantom. However, to detect smaller iodine concentrations, attenuation correction is needed. We present a correction method based on the equation representing the measurement process. The discretized equation system is solved by the least-squares method using the singular value decomposition. The attenuation correction method is applied to the projections by the Monte Carlo simulation and the experiment to confirm its effectiveness 相似文献
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阵列康普顿背散射成像研究 总被引:1,自引:0,他引:1
分析了阵列康普顿背散射成像的技术难题及解决方案,利用MCNP程序对准直器及散射函数进行了蒙特卡罗模拟计算,采用反卷积方法实现图像的复原,得到了很好的成像效果。 相似文献
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D. Lübbert T. Baumbach J. Hrtwig E. Boller E. Pernot 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2000,160(4):521-527
We present a method and an equipment for performing μm-resolved X-ray diffraction area maps, and apply it to wafer defect analysis and industrial wafer quality inspection. The method determines simultaneously the macroscopic warpage, the mesoscopic curvature and the microscopic defect structure of semiconductor wagers. It is based on X-ray diffraction rocking curve imaging of the whole wafer with down to 1 μm2 resolution. The new wafer testing equipment determines the maximal and integral peak intensities, the peak position and the half width of the rocking curves with a microscopic resolution, thus imaging simultaneously the macroscopic quality parameters and the microscopic defect structure. This permits to establish a direct one-to-one correlation between the microscopic defects and the resulting macroscopic effects. As an example, wafers of different materials, fabrication technology and resulting perfection are studied. When investigating layered samples, the technique allows furthermore to determine the influence of the wafer quality on the layer properties. The method can be applied generally to characterize non-destructively the quality of all kinds of crystalline structures, like, e.g. microelectronic and optoelectronic devices. 相似文献
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A multichannel X-ray imaging sensor using a CdTe compound semiconductor radiation detector was developed. Both the digital X-ray imaging and energy-information-generating analyzing method were studied. The X-ray imaging sensor consisted of 512-channel CdTe detector elements at a pitch of 0.2 mm. X-ray photons were directly detected using a photon-counting method and high- and low-energy images were obtained simultaneously. The specific resolution was obtained over 2.5 line pairs/mm in the channel direction and 1.6 line pairs/mm in the scanning direction with a scanning pitch of 0.2 mm. The energy subtraction method was found to be effective in distinguishing an object's component materials 相似文献
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Junxiao WANG 《等离子体科学和技术》2022,24(3):35005
We proposed a theoretical spatio-temporal imaging method, which was based on the thermal model of laser ablation and the two-dimensional axisymmetric multi-species hydrodynamics model. By using the intensity formula, the integral intensity of spectral lines could be calculated and the corresponding images of intensity distribution could be drawn. Through further image processing such as normalization, determination of minimum intensity, combination and color filtering, a relatively clear species distribution image in the plasma could be obtained. Using the above method, we simulated the plasma ablated from Al–Mg alloy by different laser energies under 1 atm argon, and obtained the theoretical spatio-temporal distributions of Mg I, Mg II, Al I, Al II and Ar I species, which are almost consistent with the experimental results by differential imaging. Compared with the experimental decay time constants, the consistency is higher at low laser energy, indicating that our theoretical model is more suitable for the plasma dominated by laser-supported combustion wave. 相似文献