Pore structure of ore granular media by computerized tomography image processing

The pore structure images of ore particles located at different heights of leaching column were scanned with X-ray computerized tomography (CT) scanner, the porosity and pore size distribution were calculated and the geometrical shape and connectivity of pores were analyzed based on image process method, and the three dimensional reconstruction of pore structure images was realized. The results show that the porosity of ore particles bed in leaching column is 42.92%, 41.72%, 39.34% at top, middle and bottom zone, respectively. Obviously it has spatial variability and decreases appreciably along the height of the column. The overall average porosity obtained by image processing is 41.33% while the porosity gotten from general measurement method in laboratory is 42.77% showing the results of both methods are consistent well. The pore structure of ore granular media is characterized as a dynamical space network composed of interconnected pore bodies and pore throats. The ratio of throats with equivalent diameter less than 1.91 mm to the total pores is 29.31%, and that of the large pores with equivalent diameter more than 5.73 mm is 2.90%.

Three-dimensional finite element simulation and reconstruction of jointed rock models using CT scanning and photogrammetry

The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.

PC-BASED SURFACE RECONSTRUCTION OF MEDICAL CT IMAGES

It is an active research area to reconstruct 3-D object and display its visible surfacesfrom cross-sectional images. In this paper, the methods of reconstructing 3-D object from medicalCT images and displaying the visible surfaces are discussed. A polygon approximation methodthat forms polygon with the same number of segment points and a fast interpolation method forcross-sectional contours are presented at first. Then the voxel set of a human liver is reconstructed.And then the liver voxel set is displayed using depth and gradient shading methods. The softwareis written in C programming language at a microcomputer image processing system with a PC/ATcomputer as the host and a PC-VISION board as the image processing unit. The result of theprocessing is satisfying.

Investigation of noise properties in grating-based x-ray phase tomography with reverse projection method

The relationship between noise variance and spatial resolution in grating-based x-ray phase computed tomography（PCT） imaging is investigated with reverse projection extraction method, and the noise variances of the reconstructed absorption coefficient and refractive index decrement are compared. For the differential phase contrast method, the noise variance in the differential projection images follows the same inverse-square law with spatial resolution as in conventional absorption-based x-ray imaging projections. However, both theoretical analysis and simulations demonstrate that in PCT the noise variance of the reconstructed refractive index decrement scales with spatial resolution follows an inverse linear relationship at fixed slice thickness, while the noise variance of the reconstructed absorption coefficient conforms with the inverse cubic law. The results indicate that, for the same noise variance level, PCT imaging may enable higher spatial resolution than conventional absorption computed tomography（ACT）, while ACT benefits more from degraded spatial resolution. This could be a useful guidance in imaging the inner structure of the sample in higher spatial resolution.

The diagnostic value of 3D spiral CT imaging of cholangiopancreatic ducts on obstructive jaundice

Objective: Computerized tomography (CT) plays an important role in the diagnosis of diseases of biliary tract. Recently, three dimensions (3D) spiral CT imaging has been used in surgical diseases gradually. This study was designed to evaluate the diagnostic value of 3D spiral CT imaging of cholangiopancreatic ducts on obstructive jaundice. Methods: Thirty patients with obstructive jaundice had received B-mode ultrasonography, CT, percutaneous transhepatic cholangiography (PTC) or endoscopic retrograde cholangiopancreatography (ERCP), and 3D spiral CT imaging of cholangiopancreatic ducts preoperatively. Then the diagnose accordance rate of these examinational methods were compared after operations. Results: The diagnose accordance rate of 3D spiral CT imaging of cholangiopancreatic ducts was higher than those of B-mode ultrasonography, CT, or single PTC or ERCP, which showed clear images of bile duct tree and pathological changes. As to malignant obstructive jaundice, this examinational technique could clearly display the adjacent relationship between tumor and liver tissue, biliary ducts, blood vessels, and intrahepatic metastases. Conclusion: 3D spiral CT imaging of cholangiopancreatic ducts has significant value for obstructive diseases of biliary ducts, which provides effective evidence for the feasibility of tumor-resection and surgical options.

基于CT技术的混凝土三维有限元模型构建

提出了一种基于CT数字图像技术的混凝土材料三维有限元模型构建的新方法。首先,采用医用CT扫描系统,对混凝土试样进行逐层扫描,生成材料的内部细观结构图像,利用CT图像的三维重构技术,将得到的剖面细观图像逐层叠加,形成三维细观结构图像;然后,将该图像映射到有限元程序中进行三维网格剖分,建立真实状态下的混凝土细观数值分析模型;在此基础上,对钢纤维混凝土进行了劈裂试验。结果表明,这种基于CT技术的数字图像三维有限元模型构建方法可真实地反应混凝土材料的内部结构与材料的固有力学特性,其数值分析结果与物理试验结果吻合,是数值分析领域中的一种新的尝试与创新。

岩土CT图像中裂纹的形态学测量

利用计算机层析成像(CT)技术提供的岩土体损伤破裂演化图像,定义每一点的CT数变化量为该像素点CT数与其后紧邻的同行像素点、其下紧邻的同列像素点的CT数差的绝对值中的较大值。根据CT数在扫描断面上的分布规律,设定了提取疑似裂纹区的像素点CT数变化量标准值ξ=20,进行了疑似裂纹区的检出操作。并对其上的几何信息和CT数信息进行了统计,接着定义了裂纹长度和宽度,利用该参数对裂纹尺寸进行了计算。该工作对于推动岩土工程CT图像定量化描述具有一定意义。

基于CT图像处理技术的岩土材料有限元模型

提出了一种利用数字图像技术对岩土材料CT图像进行处理的有限元模型方法。该方法建立的有限元模型能充分考虑岩土材料的非均匀性,特别是可以考虑空隙分布对岩土材料力学性质的影响。应用该方法对沥青胶结颗粒材料的劈裂试验进行了数值模拟,结果表明:不同方向拉应力分布不均匀,最大拉应力出现在空隙与颗粒的交界处。

甲烷水合物形成过程的CT识别原理和成像特征

采用计算机断层扫描技术(CT系统)开展了甲烷-纯水体系的气水合物生成和分解实验研究,结果表明,利用CT系统可以直观地获得甲烷水合物生成和分解的动态变化过程。指出:甲烷水合物的生成基本上从气液分界面开始,且形成初期存在突变性;生成的气水合物起初非常疏松、呈絮状,然后逐步变得密实;气水合物分解则是一个不断释放气体,由密实变得疏松的过程。

图像测量技术在岩土工程CT图像定量分析中的应用

首先对计算机层析成像技术(CT 技术)原理进行了简单的介绍,基于图形图像处理技术,引入了数学形态学中图像平移、反射、腐蚀、膨胀等运算方法,基于定义的兴趣域边界提取算法和形状因子实现了其几何测量和空间描述,定量分析了 CT 图像兴趣域的空间物理特性。该方法异于以往数学建模的思路,而是借用数学形态学中空间几何描述的思想,以实现对岩土体中的天然缺陷及其演化过程进行合理刻画。该项工作对于推动岩土工程 CT 图像定量化描述具有一定意义。

基于模型的CT三维医学图像重建仿真

2DShepp-Logan头部模型是CT二维医学图像重建领域普遍采用的经典模型。提出一种思路—以3DShepp-Logan头部模型作为CT三维医学图像重建进行仿真实验和算法性能评价的基本参考模型。首先介绍3DShepp-Logan头部模型的设计以及仿真投影数据的计算,进而描述所设计的CT三维医学图像重建仿真计算过程。数值实验部分给出了基于3DShepp-Logan头部模型的CT三维医学图像重建仿真实例。实验结果表明了该思路的可行性和模型计算的准确性。

胸部CT图像肺区域边界凹陷自动修补

提出用边界曲线局部极小值点连线法修补阈值分割后的CT横断面图像肺区域边界处血管和胸膜结节型凹陷。设置不同的匹配模板,实现在不同坐标系下寻找边界曲线的局部极小值点,从而确定需要修补的位置。将肺区域边界线上的点分为局部极小值点和非局部极小值点两类,连接凹陷缺口处两边的两个邻近局部极小值点,修补肺边界凹陷部分。实验表明,与通过计算边界点的曲率找边界凸点方法相比,该方法不仅有效地降低了肺实质分割的计算量,而且减少了由于过度分割造成的分割错误。

正常胰腺320排动态容积CT灌注成像分析

目的：应用东芝320排动态容积CT灌注成像技术，探讨正常胰腺CT灌注特点，并研究正常胰腺组织动脉血流量（AF）与年龄、性别、身高、体质量及体质指数（BMI）的关系。方法：对26例研究对象（非胰腺疾病患者20例，志愿者6例）进行胰腺CT灌注扫描，利用最大斜率法进行灌注分析。结果：①正常胰腺组织的TDC均呈缓升缓降型，并可见明显灌注峰；②胰头部、胰体部、胰尾部AF值分别为（152．54±35．34）、（155．67±29．54）、（159．79±33．04）ml／（min·100m1），三者之间无统计学意义；③〈40岁组AF值为（158．75±35．30）ml／（min·100m1），40～60岁组（156．67±40．61）ml／（min·100m1），〉60岁组（154．09±27．82）ml／（min·100m1），三者之间无统计学意义（P〉0．05），但随着年龄增大，AF值有下降趋势；④相关性分析：AF值与年龄、性别、身高、体质量及BMI值均无相关性（P〉0.05）。结论：正常胰腺各部位灌注无差异性；正常胰腺的AF值随年龄增长有下降趋势，但无统计学意义；正常胰腺AF值不受个体化因素的影响。

基于CT扫描的计算机模拟薄木刨切

基于CT扫描和计算机模拟技术,本文介绍了一种制定原木截断和木方锯剖方案的方法。通过扫描获得原木内部结构的相关信息、图象处理和三维重建,在计算机上进行原木模拟刨切加工,并在屏幕上显示虚拟刨切薄木的图象。可对同一木段进行多方案的重复加工,通过对显示图象的比较分析,制定出优化加工方案。

CT与MRI诊断前列腺癌的临床价值分析

目的研究CT和MRI对前列腺癌的临床诊断价值,为提高临床诊断率提供理论依据。方法选择对比研究的方式对2013年12月-2014年12月70例前列腺癌患者展开研究,所有患者均行CT检查(对照组)和MRI检查(研究组),并以病理组织诊断结果为标准对两种检查方式进行优劣的比较。结果以病理活检为标准,在前列腺癌A期和B期患者的诊断中,两组患者在诊断相符率、误诊率及漏诊率的比较上χ2=40.17、17.69、12.99,P<0.05,具有明显统计学差异;在前列腺癌C期和D期患者的诊断中,两组患者无明显差异。结论MRI对前列腺癌的诊断准确率高,可作为对患者进行分期评估的临床辅助检查方式进行推广;CT对前列腺癌患者的A期和B期诊断率低,仅在C期和D期的诊断中具有较高的准确率,因此不建议在早期前列腺癌的诊断中使用。

基于CT图像的沥青混合料分形特征的研究

采用分形理论对沥青混合料内部结构的复杂程度进行了量化研究.对沥青混合料内部断面的CT图像,用差分盒维数法得到其断面形貌的分形维数,再通过分形维数的大小描述沥青混合料内部结构的复杂程度.对沥青混合料试件和沥青路面芯样分形维数的比较表明,混合料试件内部结构复杂程度更高;采用相同的试件加工方法在试验室获得三种不同类型的沥青混合料(SM A,AC-20G,AC-25G),得到的分形维数相差不大,但该分形维数与路面芯样相比却有较大差异,说明试件加工方法对沥青混合料内部结构形貌特征有较大影响.分形理论结合CT图像对研究定量描述沥青混合料内部结构特征是一种十分有效的方法.

外伤后脑萎缩的CT早期诊断及其与MRI对比的研究

目的:探讨CT线性测量技术在脑外伤后脑萎缩的早期诊断意义,以及CT与MR I两种成像技术在诊断价值的对比分析。方法:应用CT检查对30例急性脑外伤血肿的患者脑室体部横径指数、Huchm an指数、尾状核指数以及脑沟宽度等进行线性测量;对所有数据与正常对比组进行比较及统计学分析,了解各参考值在脑萎缩早期诊断中的意义。并通过其中5例与MR I测量值的对比,分析诊断的特异性。结果:侧脑室体部横径指数、Huckm an指数、尾状核指数以及脑沟宽度是脑萎缩早期诊断中的敏感指标,与脑萎缩的发生呈线性相关。结论:CT线性测量技术在脑外伤后脑萎缩的早期诊断及监测中具有较大的应用价值,是脑外伤后遗症的临床防治不可或缺的重要辅助手段;MR I线性测量较CT更具特异性。

低仰角射线对电离层CT成像的影响分析

电离层层析成像(Computerized Tomography,CT)是一个有限视角问题,水平射线的缺失造成CT结果垂直分辨率的严重下降.很多人直观地认为低仰角射线可以弥补水平射线的缺失,然而本文的理论分析和数值模拟研究结果表明,低仰角射线对CT结果的影响十分微小,其无法弥补水平射线缺失所带来的垂直分辨率的下降.模拟结果显示,增加低仰角射线前后CT反演结果几乎没有变化;而去掉680条低仰角射线和高仰角射线后,CT反演结果差别巨大;去掉680条低仰角射线的CT结果与模型吻合很好;去掉680条高仰角射线的CT反演结果失真严重,几乎无法恢复模型的扰动特征.

严重急性呼吸综合征患者骨梗死CT和MRI影像分析

目的分析严重急性呼吸综合征(SARS)患者骨梗死的CT、MRI表现,评价这两种影像技术在骨梗死诊断中的作用。方法对12例骨梗死患者的影像学资料进行回顾性分析。结果12例患者CT表现为骨内高密度圈状或斑片状影,呈地图状,MRI示病灶中心T1WI呈等骨髓脂肪信号,T2WI呈等、高混杂信号,病灶边缘T1WI呈纡曲的低信号带,T2WI上该带可分为2层,整个病灶呈地图样改变。结论骨梗死有多种表现形式,其诊断需结合临床病史及流行病史,并除外其他疾病。地图样改变为其显著性表现。

CT机器、图像后处理技术的新进展

１)ＣＴ机的进展:ＣＴ机器自问世以来,随着计算机技术、探测器技术、Ｘ线技术的不断发展以及新的微电子和显微技术不断的应用于ＣＴ机,从而提高了ＣＴ机的性能,标志着ＣＴ扫描从层面扫描到螺旋扫描的换代。２)图象后处理技术:螺旋ＣＴ的出现及计算机软件的开发,利用导航技术做出具有３Ｄ仿真内窥镜的图象,既(ＶＥ),这种新的影像学方法,引起了广泛的关注。