基于X-ray CT图像的沥青混合料车辙过程空隙分布评估

X射线计算机断层扫描(X-ray computed tomography,X-ray CT)技术作为一种无损测试方法,已被广泛用于评估沥青混合料中的空隙结构和与空隙有关的病害。基于X-ray CT和图像处理技术,从细观结构层面探讨了车辙变形过程中沥青混合料的空隙结构特征。提出了体积等效球棍模型来表征空隙连通性的变化,用改进的环扇分割变异系数、位置偏心率和球度分别描述了空隙的分布和形状特征。结果表明,车辙对沥青混合料空隙结构的影响机制因混合料类型而异。与密级配沥青混凝土(AC-13)相比,沥青玛蹄脂碎石混合料(SMA-13)中的空隙更加不均匀和离散,尤其是那些体积小于0.01 mm^(3)的空隙。此外,SMA-13中的空隙连通性和分布更容易受到外部荷载的影响,其粗集料在变形过程中往往会产生定向移动进而改变初始位置。尽管车辙变形同时增加了2种混合料中空隙的水平不均匀性,但AC-13的竖向不均匀性减少,而SMA-13的竖向不均匀性增加。加载使AC-13混合料的空隙几何形状变得复杂和分散,而SMA-13则相反,预示着与AC混合料相比,SMA混合料在加载1 h后仍保持抵抗车辙破坏的潜力。总体而言,沥青混合料中空隙的拓扑特征及其在车辙变形过程中的动态响应主要取决于混合料的级配形式。

Fast X-ray imaging beamline at SSRF

The fast X-ray imaging beamline(BL16U2)at Shanghai Synchrotron Radiation Facility(SSRF)is a new beamline that provides X-ray micro-imaging capabilities across a wide range of time scales,spanning from 100 ps toμs and ms.This beamline has been specifically designed to facilitate the investigation of a wide range of rapid phenomena,such as the deformation and failure of materials subjected to intense dynamic loads.In addition,it enables the study of high-pressure and high-speed fuel spray processes in automotive engines.The light source of this beamline is a cryogenic permanent magnet undulator(CPMU)that is cooled by liquid nitrogen.This CPMU can generate X-ray photons within an energy range of 8.7-30 keV.The beamline offers two modes of operation:monochromatic beam mode with a liquid nitrogen-cooled double-crystal monochromator(DCM)and pink beam mode with the first crystal of the DCM out of the beam path.Four X-ray imaging methods were implemented in BL16U2:single-pulse ultrafast X-ray imaging,microsecond-resolved X-ray dynamic imaging,millisecond-resolved X-ray dynamic micro-CT,and high-resolution quantitative micro-CT.Furthermore,BL16U2 is equipped with various in situ impact loading systems,such as a split Hopkinson bar system,light gas gun,and fuel spray chamber.Following the completion of the final commissioning in 2021 and subsequent trial operations in 2022,the beamline has been officially available to users from 2023.

Comparison of efficacy of lung ultrasound and chest X-ray in diagnosing pulmonary edema and pleural effusion in ICU patients: A single centre, prospective, observational study

Background and Aims While chest X-ray (CXR) has been a conventional tool in intensive care units (ICUs) to identify lung pathologies, computed tomography (CT) scan remains the gold standard. Use of lung ultrasound (LUS) in resource-rich ICUs is still under investigation. The present study compares the utility of LUS to that of CXR in identifying pulmonary edema and pleural effusion in ICU patients. In addition, consolidation and pneumothorax were analyzed as secondary outcome measures. Material and Methods This is a prospective, single centric, observational study. Patients admitted in ICU were examined for lung pathologies, using LUS by a trained intensivist;and CXR done within 4 hours of each other. The final diagnosis was ascertained by an independent senior radiologist, based on the complete medical chart including clinical findings and the results of thoracic CT, if available. The results were compared and analyzed. Results Sensitivity, specificity and diagnostic accuracy of LUS was 95%, 94.4%, 94.67% for pleural effusion;and 98.33%, 97.78%, 98.00% for pulmonary edema respectively. Corresponding values with CXR were 48.33%, 76.67%, 65.33% for pleural effusion;and 36.67%, 82.22% and 64.00% for pulmonary edema respectively. Sensitivity, specificity and diagnostic accuracy of LUS was 91.30%, 96.85%, 96.00% for consolidation;and 100.00%, 79.02%, 80.00% for pneumothorax respectively. Corresponding values with CXR were 60.87%, 81.10%, 78.00% for consolidation;and 71.3%, 97.20%, 96.00% for pneumothorax respectively. Conclusion LUS has better diagnostic accuracy in diagnosis of pleural effusion and pulmonary edema when compared with CXR and is thus recommended as an effective alternative for diagnosis of these conditions in acute care settings. Our study recommends that a thoracic CT scan can be avoided in most of such cases.

Microstructure Evolution of Sandstone Cemented by Microbe Cement Using X-ray Computed Tomography

The bio-sandstone, which was cemented by microbe cement, was firstly prepared, and then the microstructure evolution process was studied by X-ray computed tomography （X-CT） technique. The experimental results indicate that the microstructure of bio-sandstone becomes dense with the development of age. The evolution of inner structure at different positions is different due to the different contents of microbial induced precipitation calcite. Besides, the increase rate of microbial induced precipitation calcite gradually decreases because of the reduction of microbe absorption content with the decreasing pore size in bio-sandstone.

Use of high-resolution X-ray computed tomography and 3D image analysis to quantify mineral dissemination and pore space in oxide copper ore particles

Mineral dissemination and pore space distribution in ore particles are important features that influence heap leaching performance. To quantify the mineral dissemination and pore space distribution of an ore particle, a cylindrical copper oxide ore sample (I center dot 4.6 mm x 5.6 mm) was scanned using high-resolution X-ray computed tomography (HRXCT), a nondestructive imaging technology, at a spatial resolution of 4.85 mu m. Combined with three-dimensional (3D) image analysis techniques, the main mineral phases and pore space were segmented and the volume fraction of each phase was calculated. In addition, the mass fraction of each mineral phase was estimated and the result was validated with that obtained using traditional techniques. Furthermore, the pore phase features, including the pore size distribution, pore surface area, pore fractal dimension, pore centerline, and the pore connectivity, were investigated quantitatively. The pore space analysis results indicate that the pore size distribution closely fits a log-normal distribution and that the pore space morphology is complicated, with a large surface area and low connectivity. This study demonstrates that the combination of HRXCT and 3D image analysis is an effective tool for acquiring 3D mineralogical and pore structural data.

X-ray Computed Tomography Characterization of 3D Tufted Twill Textile Composite for Aerostructures

Damage assessments in three dimensional (3D) textile composites subjected to mechanical loading can be performed by non-destructive and destructive techniques.This paper applies the two techniques to investigate the fracture behavior of 3D tufted textile composites.X-ray computed tomography as a non-destructive evaluation method is appropriate to detect damage locations and identify their progression in 3D textile composites.Destructive methods such as sectioning toward observing damage provide valuable information about damage patterns.The results of this research could be utilized to evaluate the initial cause of rupture in 3D tufted composites used in aerospace structures and analyze fracture modes and damage progression.

In situ compression and X-ray computed tomography of flow battery electrodes

Redox flow batteries offer a potential solution to an increase in renewable energy generation on the grid by offering long-term, large-scale storage and regulation of power. However, they are currently un- derutilised due to cost and performance issues, many of which are linked to the microstructure of the porous carbon electrodes used. Here, for the first time, we offer a detailed study of the in situ effects of compression on a commercially available carbon felt electrode. Visualisation of electrode structure us- ing X-ray computed tomography shows the non-linear way that these materials compress and various metrics are used to elucidate the changes in porosity, pore size distribution and tortuosity factor under compressions from 0%-90%.

X-Ray Computed Tomography for Root Quantification

Soil cores from a field growing barley and barley mutants without root hairs under conventional and minimum tillage were sampled. They were X-ray scanned to produce a 3D image and then the roots were washed out and weight and length were determined by conventional means. Root volume and surface area were then calculated from the 3D images using state of the art software and methodology, and the measured and calculated measures were correlated. The only strong and significant correlation was between measured weight and calculated volume for mutants without root hairs. It is concluded that the software cannot segment out very small roots, but segmentation accuracy also depends on root structure in some unknown way. Any study using X-ray computed tomography to quantify roots as they grow in situ should start with a calibration for the conditions in question.

Usefulness of Chest Computed Tomography for Diagnosis of Idiopathic Pneumomediastinum with Negative Findings on Plain X-Ray

Idiopathic pneumomediastinum is rare in children. Few cases of patients with pneumomediastinum show negative findings on X-ray examination. Chest computed tomography (CT) was very useful for the diagnosis and evaluation of the extent of pneumomediastinum. We report here a case of idiopathic pneumomediastinum in a 15-year-old boy who exhibited no significant chest X-ray finding. The patient was referred to our institute for the further evaluation of pre-cordial pain and breathing difficulty. Precordial pain suddenly developed, when he was carrying a portable shrine on his shoulder (day of onset). He was admitted to another institute 3 days after onset because of worsening precordial pain. On admission, he presented with 98% saturation of hemoglobin in the peripheral blood under room air. Plain chest X-ray also revealed no abnormal findings. A half-dissolved gastrographin swallow showed no leakage of gastrographin from the pharynx and esophagus to the mediastinum, and no diverticulum within the esophagus. Plain chest CT revealed extensive emphysema around the trachea from the neck to the portion inferior to the carina of trachea. The patient was diagnosed with idiopathic pneumomediastinum because the cause was unclear. We decided to admit him to our institute under fasting conditions and rest. His symptoms improved 3 days after onset. The lesion had disap-peared 8 days after onset on chest CT. When young people experience precordial pain which increases on inspiration, we must consider pneumomediastinum in a differential diagnosis, and it is important to perform chest CT.

基于X-CT成像的泡沫混凝土细观损伤模拟方法

为探究常用于隧道减震设计的泡沫混凝土材料在受压荷载下的细观裂纹损伤发展过程以及细观损伤对宏观力学行为的影响,提出基于X-CT成像从细观尺度分析泡沫混凝土损伤过程的模拟方法。首先,借助X-CT扫描技术获取可表征泡沫混凝土细观多孔结构的X-CT图像,并对该图像进行二值化处理以获取用于建立泡沫混凝土细观模型的二值图;然后,采用自主编译的Python脚本插入内聚力单元模拟泡沫混凝土模型的损伤开裂过程,并分析不同孔隙率下泡沫混凝土的细观损伤变化规律。研究表明:1)泡沫混凝土应力-应变曲线上升阶段、塑性平台阶段的细观模拟结果与试验结果吻合较好,该方法为研究泡沫混凝土材料的细观损伤机制和宏观力学参数标定提供了新手段;2)在单轴受压过程中,连接多孔材料相邻孔隙的水泥基充当了“支柱”作用,接触法向压力随着应变积累而连通发展,泡沫混凝土模型受压时主要表现为剪切破坏;3)当泡沫混凝土孔隙率较低时,其峰值抗压强度会显著增加,但材料可能会在局部产生大规模开裂,孔隙的作用不能得到充分发挥。

点火位置对X型转子发动机燃烧过程的影响

为探究X型转子发动机独特燃烧室内复杂湍流场与点火位置的耦合作用对混合气燃烧过程的影响,建立了X型转子发动机的三维计算流体动力学模型,并与试验结果进行对比验证,数值研究了不同点火位置下X型转子发动机缸内燃烧过程,揭示了点火位置对火焰传播、燃烧特性及污染物形成的影响规律。结果表明,在压缩末期,X型转子发动机燃烧室内形成了包括涡流和单向流的复杂湍流场,这与点火位置的耦合作用显著影响火焰传播过程。为了获得较高火焰传播速度,点火位置不宜布置在漩涡区处。点火位置位于凹坑中部时,可以充分利用四周空间和涡团与单向流场过渡处形成的较高速度场加速火焰传播,从而提前燃烧重心,增加放热速率,而且峰值压力提高了25%,指示热效率超过30%;同时其也具有较低的HC和CO排放量;但是由于其缸内峰值温度较大,导致NO排放量增加。

Computed tomography versus transthoracic echocardiography in the detection of complex congenial heart diseases in china:a meta-analysis

Objective:To perform a meta-analysis to evaluate the diagnostic performance of computed tomography(CT) and transthoracic echocardiography(TTE) in complex congenital heart diseases(CHD) in China.Methods:MEDLINE,Cochrane library and China National Knowledge Infrastructure(CNKI) database from January 1966 to October 2010,were searched for initial studies in China.All the studies,published in English or Chinese,used TTE,CT,or both as diagnostic tests for CHD and reported the rate of true-positive,true-negative,false-positive and false-negative diagnoses of CHD from TTE and CT findings with the surgical results as the 'gold-standard'(15 studies,XX patients) were collected.The statistic software package,'Meta-Disc 1.4',was used to conduct data analysis.A covariate analysis was used to evaluate the influence of patient or study-related factors on sensitivity.Results:Pooled sensitivity for diagnosis of CHD were 95% [95% confidence interval(CI):94%~96%] for CT studies and 87%(95% CI:85%~88%) for TTE studies.The difference between the pooled sensitivity of CT and that of TTE was statistically significant(P<0.001).TTE had higher sensitivity [0.96(95% CI:0.94~0.97)] for cardiac malformation but lower sensitivity [0.78(95% CI:0.76~0.81)] for extracardiac malformation than CT.Conclusion:CT can provide added diagnostic information compared with TTE in patients with CHD in China,especially for patients suspected of extracardiac malformation.

基于下肢全长X线片及CT平扫探讨鹅足肌腱对胫骨高位截骨术后胫骨远端轴位旋转的影响

目的:基于下肢全长X线片及CT平扫探讨内侧开放楔形胫骨高位截骨术(MOWHTO)后鹅足肌腱的有无对胫骨远端相对于胫骨近端轴位旋转的影响。方法:回顾性收集行MOWHTO的患者63例,根据术中对鹅足肌腱的处理情况,分为未松解组(对照组)、部分松解组(观察组1)和完全松解组(观察组2)各21例(21膝);同时收集自体腘绳肌腱行前交叉韧带重建的患者(观察组3)21例(21膝)。患者术前及术后1周内均行下肢全长正侧位X线检查及髋膝踝CT平扫,测量解剖股骨胫骨角(aFTA)、胫骨近端内侧角(MPTA)和胫骨扭转角(TTA),并进行比较。结果:观察组1、观察组2、观察组3及对照组aFTA分别由术前(180.85±2.51)°、(180.30±2.18)°、(181.01±2.06)°和(181.34±1.98)°,矫正为术后(173.85±1.83)°、(174.11±1.34)°、(173.33±1.56)°和(174.26±1.77)°;MPTA由术前(80.23±1.83)°、(79.37±1.62)°、(81.01±1.52)°和(80.90±1.37)°,矫正为术后(89.54±2.33)°、(88.26±1.89)°、(87.58±1.01)°和(88.42±1.25)°。4组间术前aFTA、术后aFTA、术前MPTA、术后MPTA的差异均无统计学意义(均P>0.05);4组术后与术前TTA差值分别为(-0.52±0.99)°、(-0.07±2.06)°、(-0.13±1.37)°和(-0.89±1.21)°,观察组2、观察组3与对照组相比,差异均有统计学意义(均P<0.05)。结论:完整的鹅足肌腱可导致MOWHTO后胫骨远端相对于胫骨近端内旋,对其进行松解会削弱此作用,在MOWHTO中需合理处理鹅足肌腱,以尽量避免非计划的胫骨扭转。

基于X射线成像原理的电缆缓冲层缺陷的可视化检测技术对比研究

近年来,高压电缆缓冲层烧蚀缺陷导致电缆故障问题频发,如何有效地对缓冲层缺陷进行检测引起了行业内的广泛关注。基于缓冲层缺陷与其相邻层间的密度差异,分别对X射线数字成像技术和计算机断层成像技术开展了检测参数研究,对比分析了两种方法对不同类型缺陷的检出有效性及在不同干扰下的检测效果。结果表明,计算机断层成像技术在检测准确度和抗干扰性优于X射线数字成像技术,但在检测的现场适用性方面有局限。研究给出两种检测技术的最佳检测参数及各自的优缺点,为后续高压电缆的缓冲层缺陷可视化检测提供了有益的参考。

基于X-ray CT原位三轴剪切试验的砂土颗粒材料微观动力学

将X射线断层扫描技术(CT)与原位三轴剪切试验相结合,分析渥太华砂在剪切过程中的微观动力学演化规律.在试验过程中共完成15次X射线扫描,使用图像分割算法进行颗粒分割并使用球谐函数重构颗粒的表面形貌,根据颗粒的多尺度形态指标序列实现整个加载过程中颗粒的准确匹配与追踪,并分析颗粒位移、转动、局部非仿射运动和局部孔隙率等微观动力学和微观结构指标的演化规律.在剪切过程中颗粒体系的竖向位移分布呈现2个锥形区域,颗粒的转动分布出现明显的X型剪切带.用于度量局部塑性变形程度的局部非仿射运动和局部体积分数呈现出较为明显的相关关系,表明颗粒微观动力学与其微观结构之间存在因果关系,局部自由体积较大的地方更易发生塑性变形.

仿真滤线栅及图像增强后处理算法用于改善儿童低剂量X线片图像质量

目的 观察以仿真滤线栅(SG)和图像增强(SE)改善儿童低剂量X线片图像质量的价值。方法 回顾性分析344例接受410次床旁X线检查的重症监护病房患儿资料,包括290幅胸部平片、51幅腹部平片及69幅胸腹联合平片;分别以SG和SE对图像进行后处理,评估后处理图像质量。结果 410幅SG后处理图像中,2分250幅、1分147幅、0分13幅;SG可显著改善年龄≥1岁和体质量≥10 kg患儿图像质量(P均<0.05),且显示骨骼、气管、外周血管、异物、腰大肌和肠道气体效果较好(P均<0.05)。410幅SE后处理图像中,2分250幅、1分58幅、0分102幅;SE可显著改善年龄≥0.5岁和体质量>4 kg患儿图像质量(P均<0.05),且显示骨骼、气管、大血管、外周血管、心脏后血管和异物效果较好(P均<0.05)。结论 SG可显著改善低剂量X线片显示年龄≥1岁和体质量≥10 kg儿童骨骼、气管、外周血管、异物、腰大肌和肠道气体的质量,而SE则可改善显示年龄≥0.5岁和体质量>4 kg儿童骨骼、气管、大血管、外周血管、心脏后血管和异物的质量。

基于斜孔散射校正板的锥束X射线CT散射校正方法

锥束X射线CT和二维扇束、平行束CT系统相比具有扫描速度快、射线利用率高、重建图像轴向分辨率和水平分辨率一致等优点,是当前工业CT技术发展的重点。然而,由于散射线的存在,其成像质量受到影响。为了减小散射线对图像质量的影响,提出一种新的基于斜孔散射校正板的散射校正方法,对该方法的原理和实现进行了深入的研究,通过获取原始扫描数据以及斜孔散射校正板后的扫描数据,利用插值和平滑处理的方法获得散射场数据。然后,通过将原始数据减去散射场数据后进行重建,即可得到无散射的CT图像。通过与光栅式散射校正板校正方法进行对比,结果表明,该方法应用于涡轮叶片的锥束CT扫描结果校正,典型区域(叶片内冷却通道及叶片内壁)对比度噪声比分别提升了14.2%和56.8%,而光栅式散射校正板校正后,同一位置对比度噪声比分别仅提升了5.6%和27.6%,验证了基于斜孔散射校正板散射校正方法的优越性。

Infective severe acute pancreatitis:A comparison of ^(99m)Tc-ciprofloxacin scintigraphy and computed tomography

AIM:To evaluate 99mTc-ciprofloxacin scintigraphy compared with computed tomography(CT)for detecting secondary infections associated with severe acute pancreatitis(SAP)in swine.METHODS:Six healthy swine were assigned to a normal control group(group A,n = 6).SAP was induced in group B(n = 9)and C(n = 18),followed by inoculation of the resulting pancreatic necroses with inactive Escherichia coli(E.coli)(group B)and active E.coli(group C),respectively.At 7 d after inoculation,a CT scan and a series of analyses using infecton imaging(at 0.5,1,2,3,4 and 6 h after the administration of 370 MBq of intravenous infecton)were performed.The scintigrams were visually evaluated and semi-quantitatively analyzed using region of interest assignments.The differences in infecton uptake and changes in the lesion-background radioactive count ratios(L/B)in the 3 groups were recorded and compared.After imaging detection,histopathology and bacterial examinations were performed,and infected SAP was regarded as positive.The imaging findings were compared with histopathological and bacteriological results.RESULTS:In group A,6 animals survived without infection in the pancreas.In group B,7/9 swine survived and one suffered from infection.In group C,15/18 animals survived with infection.Hence,the number of normal,non-infected and infected SAP swine was 6,6 and 16,respectively.The sensitivity,specificity,accuracy,positive predictive value and negative predictive value of the infecton method were 93.8%(15/16),91.7%(11/12),92.9%(26/28),93.8%(15/16)and 91.7%(11/12),whereas these values for CT were 12.5%(2/16),100.0%(12/12),50.0%(14/28),100.0%(2/2)and 46.2%(12/26),respectively.The changes in L/B for the infected SAP were significantly different from those of the non-infected and normal swine(P < 0.001).The mean L/B of the infectious foci at 0.5,1,2,3,4 and 6 h was 1.17 ± 0.10,1.71 ± 0.30,2.46 ± 0.45,3.36 ± 0.33,2.04 ± 0.37 and 1.1988 ± 0.09,respectively.At 3 h,the radioactive counts(2350.25 ± 602.35 k)and the mean L/B of the infectious foci were significantly higher than that at 0.5 h(P = 0.000),1 h(P = 0.000),2 h(P = 0.04),4 h(P = 0.000)and 6 h(P = 0.000).CONCLUSION:99m Tc-ciprofloxacin scintigraphy may be an effective procedure for detecting SAP secondary infections with higher sensitivity and accuracy than CT.

X线诱导声学计算机断层扫描在放射检测及疾病诊断中的研究进展

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基于X-CT扫描技术的泡沫轻质土孔结构分析

为研究泡沫轻质土内部孔隙三维空间分布状态和形态特征,采用X射线计算断层扫描技术(X-ray computed tomography,X-CT)获取了3种湿密度等级泡沫轻质土孔结构,并进行定量分析。基于混合高斯模型,通过解卷积确定孔相和固相灰度阈值,根据阈值将灰度图像划分为孔和固体两相材料,定量表征孔隙率、孔径、球度和孔隙形态等孔结构特征参数。将孔结构特征参数与强度进行关联分析,结果表明:随着泡沫轻质土的湿密度增大,孔径分布更加均匀,平均孔径降低,球状孔隙增多,导致泡沫轻质土应力分布更加均匀,抵抗外部荷载能力更强,整体强度更高。