CT9800机器操作使用经验介绍

本文重点介绍了在进行CT断层X-线摄影时,如何灵活应用标准、软组织和骨结构等三种重建图像的软件,既能显著缩短图像重建的时间,又不会遗漏病变的影像。     

颅脑CT扫描技术方法的改进

本文阐述了在颅脑计算机断层射线摄影的扫描过程中,改变扫描层平面距离的情况,即把该距离由10mm增加为11mm,从而形成一个宽1mm的未扫描空间。作者认为,由于一般的CT设备空间解像力低,形成的像素尺寸为1.0×1.0mm,因此,这些未扫描区不会影响诊断。     

CT增强扫描在肺结节病诊断中的价值

目的:探讨肺结节病的多层螺旋CT影像学表现,特别是增强扫描后的特征,以提高本病的诊断水平。方法:回顾性分析经病理及临床证实的32例肺结节病患者的临床资料和CT表现。结果:32例结节病中,肺门、纵隔淋巴结肿大31例,特征为对称性肺门淋巴结肿大伴纵隔淋巴结肿大,不融合,增强后呈中等度较均匀强化;肺内病变25例,多表现为沿支气管血管束分布网状结节。结论:肺结节病的CT表现具有一定特征性,增强CT扫描有助于提高诊断正确率。     

CT、MR技术进展与核医学影像

医学功能影像领域各种新技术层出不穷,已成为多学科交叉的研究热点。特别是CT、MR功能成像技术发展迅速,在中枢神经系统疾病、心血管系统疾病、以及肿瘤诊断中已有较多基础和临床初步应用结果,且部分技术发展前景广阔,这对核医学影像所具有的传统优势在一定程度上带来了冲击或挑战。作为核医学工作者,应主动适应新世纪相关影像设备、技术发展带来的机遇和挑战,不断丰富和拓展核素显像在医学实践中所具有的特色和重要作用,使核素显像能够与其它影像诊断技术形成优势互补之势,才能立于不败之地。     

薄层螺旋CT诊断眼眶内侧壁骨折的应用价值

目的:探讨薄层螺旋CT诊断眶内侧壁骨折的应用价值。方法:对53例患者或志愿者行常规轴位及薄层轴位、冠位扫描。分别将常规轴位扫描图像与薄层轴位扫描图像及薄层冠位扫描图像与轴位薄层扫描MPR冠状位重建图像进行比较。结果:前组图像对病变显示率二者有明显差异(P<0．001),后组无明显差异。结论:仅薄层CT扫描即可精确诊断眶内侧壁骨折,尤以轴位图像显示为佳。     

薄层螺旋CT诊断眼眶内侧壁骨折的应用价值

目的:探讨薄层螺旋CT诊断眶内侧壁骨折的应用价值.方法:对53例患者或志愿者行常规轴位及薄层轴位、冠位扫描.分别将常规轴位扫描图像与薄层轴位扫描图像及薄层冠位扫描图像与轴位薄层扫描MPR冠状位重建图像进行比较.结果:前组图像对病变显示率二者有明显差异(P＜0.001),后组无明显差异.结论:仅薄层CT扫描即可精确诊断眶内侧壁骨折,尤以轴位图像显示为佳.     

浅谈医用CT机计量检定中性能模体的定位

在JJG961-2001《医用诊断计算机断层摄影装置(CT)X射线辐射源》国家计量检定规程中,关于性能模体的定位不很具体。但是性能模体的定位准确与否,将直接影响医用CT机的计量检定结果。性能模体的定位,实际上就是实现性能模体的任意一个横断面与CT机的扫描面平行,而且所得到的横断面图像的对称中心与扫描野的中心重合的过程。为了叙述方便,我们把沿扫描床移动的方向定为Z方向,把水平方向定为X方向,把竖直方向定为Y方向。我们使用的性能模体是VIC鄄TOREEN-AAPM检测模体。这里暂以该性能模体为例,谈一下模体的定位。为工作方便,我们建…     

三维 CT 在锥角增大时对重建图像质量的影响

通过分析圆柱状物体在不同锥角时对重建图像质量的影响 ,从而得出传统三维 CT适宜于小锥角(大约 6°)情况时的重建的结论     

CT机扫描条件对CT值和辐射剂量指数的影响

随着使用的日益广泛．X射线计算机断层摄影装置（Xray Computerized Tomography Scanner，简称CT）已经成为医用诊断中最重要的装置之一，其成像质量对患者病情的诊断有直接的影响；同时，由它带来的辐射剂量控制的问题也越来越受到各国的重视。德国放射防护联邦局1994年的调查结果显示，CT扫描仅仅为所有放射检查的4％，但却是医疗放射人群剂量的1／3；而放射剂量的增加将直接危及人体健康，如增加致癌几率等。我国于2001年制定了JJG961—200l《医用诊断计算机断层摄影装置（CT）X射线辐射源》检定规程，对CT成像质量及剂量指数作出了明确的要求和规定．为CT成像质量及辐射剂量的控制提供了明确的参考。CT成像质量及辐射剂量会受到各方面因素的影响，如管球、探测器、机器类型及使用年限、扫描方式和扫描条件等。在临床单层轴向扫描中，管电压、管电流、曝光时间、层厚、照射野等扫描条件对于CT成像质量及辐射剂量有直接的影响。在本文中，我们根据实际检定工作中得到的临床数据．在其他条件相同的情况下，分析了管电压、管电流和曝光时间对CT值和辐射剂量指数的影响，这将有利于在CT的临床使用中更好地选择扫描条件，保障患者的辐射安全．同时对根据CT值进行临床诊断提供参考依据。     

医用CT机检定操作中的问题与解决方案

<正>0引言医用诊断螺旋计算机断层摄影装置(Computed Tomography简称CT)是现代医学诊断不可或缺的影像设备,其影像质量与疾病的准确诊断密切相关;同时作为X射线辐射源,CT检查时辐射剂量的控制也不容忽视。为此,我国制定了医用CT机X射线辐射源检定规程并于2007年颁布实施,对于保障CT质量性能的可靠、诊断结果的准确和患者的辐射     

The construction and use of convex hulls in limited-angle computerized tomography

A method is developed to construct the convex hull of an object and make use of it in limited-angle x-ray computerized tomography (CT). The convex hull of an object is the smallest convex region containing the object, and therefore it can serve as boundary information in the reconstruction of the object from limited-angle data. Two methods, the intersection version and the superimposition version, of constructing the convex hull of an object from x-ray data are presented. It is shown that the intersection version is very efficient when the noise is very low, whereas the superimposition version is more stable with respect to noise. The usefulness and the construction of the convex hulls of embedded flaws in industrial x-ray CT are also studied. It is demonstrated with simulated data that the use of convex hulls makes it possible to reconstruct high-quality images from limited-angle data.     

Study on beam geometry and image reconstruction algorithm in fast neutron computerized tomography at NECTAR facility

Investigations on the fast neutron beam geometry for the NECTAR facility are presented. The results of MCNP simulations and experimental measurements of the beam distributions at NECTAR are compared. Boltzmann functions are used to describe the beam profile in the detection plane assuming the area source to be set up of large number of single neutron point sources. An iterative algebraic reconstruction algorithm is developed, realized and verified by both simulated and measured projection data. The feasibility for improved reconstruction in fast neutron computerized tomography at the NECTAR facility is demonstrated.     

Vascular blood flow reconstruction with contrast-enhanced computerized tomography

In this work, we study the measurement of blood velocity with contrast-enhanced computed tomography. The transport equation is used as a constraint to obtain stable solutions. The inverse problem is formulated as an optimal control problem. The density of the contrast agent is reconstructed together with the flow field. The existence of a minimizer of the regularization functional and a local unicity are demonstrated. The inversion scheme is tested on a simple numerical phantom.     

基于ARM的嵌入式电脑横机控制器设计

电脑针织横机是羊毛衫生产行业的主要机种,其核心部分是整机控制系统。随着电脑针织的普及,具有高性价比和高集成度的电脑针织横机越来越受到人们的青睐,此类产品的市场需求也越来越大。但目前市场上的横机控制器大多数使用单片机作为主处理器或者以工控机为基础开发而来的,前者集成度不高,稳定性也不好,而后者成本较高。通过对电脑横机系统的结构和功能分析,选用基于ARM内核的EPU芯片,配合目前高集成度的CPLD芯片设计了一款新型的嵌入式横机控制器,解决了上述问题,并给出了软硬件设计。该控制器具备完善的织机控制功能、良好的图形用户界面、海量数据存储接口以及优质的网络支持,能够满足绝大多数织机控制需要和用户需求。基于此设计思路的横机控制器性价比和集成度都较高,具有较好的实用价值。     

Computational methods for materials characterization by electron tomography

Electron tomography (ET) is a powerful imaging technique that enables thorough three-dimensional (3D) analysis of materials at the nanometre and even atomic level. The recent technical advances have established ET as an invaluable tool to carry out detailed 3D morphological studies and derive quantitative structural information. Originally from life sciences, ET was rapidly adapted to this field and has already provided new and unique insights into a variety of materials. The principles of ET are based on the acquisition of a series of images from the sample at different views, which are subsequently processed and combined to yield the 3D volume or tomogram. Thereafter, the tomogram is subjected to 3D visualization and post-processing for proper interpretation. Computation is of utmost importance throughout the process and the development of advanced specific methods is proving to be essential to fully take advantage of ET in materials science. This article aims to comprehensively review the computational methods involved in these ET studies, from image acquisition to tomogram interpretation, with special focus on the emerging methods.     

New iterative reconstruction methods for fan-beam tomography

In this paper, we present a novel class of iterative reconstruction methods for severely angular undersampled or/and limited-view tomographic problems with fan-beam scanning geometry. The proposed algorithms are based on a new analytical transform which generalizes Fourier-slice theorem to divergent-beam scanning geometries. Using a non-rigid coordinate transform, divergent rays can be reorganized into parallel ones. Therefore, one can employ a simpler parallel-beam projection model instead of more complicated divergent-beam geometries. Various existing iterative reconstruction techniques for divergent-beam geometries can be easily adapted to the proposed framework. The significant advantage of this formulation is the possibility of exploiting efficient Fourier-based recovery methods without rebinning of the projections. In case of highly sparse measurements (few-view data), rebinning methods are not suitable due to error-prone angular interpolation involved. In this work, three new methods based on the novel analytical framework for fan-beam geometry are presented: the Gerchberg-Papoulis algorithm, the Neumann decomposition method and its total variation regularized version. Presented numerical experiments demonstrate that the methods can be competitive in reconstructing from few-view noisy tomographic measurements.     

Meso-structures evolution rules of coal fracture with the computerized tomography scanning method

In order to observe the meso-structure and fracture process of coal interior, the computerized tomography (CT) scanning experimental system was developed. This system includes the nonmetal cylinder shell, loading head, strain test equipment, hydraulic pump and vacuum pump, which can scan coal or rock samples with or without gas under uniaxial and triaxial load. The uniaxial compression experiments of coal were done and CT images were obtained at different stress level. The results show that the raw coal is a kind of heterogeneous material and the internal distribution of density is inhomogeneous. The cracks are uneven and their directions are random. During the loading process the inner structures of coal changed. The density of the coal increases at the beginning of load and decreases with the increment of stress. The fractures of coal occur mainly between the skeleton and matrix and on the weak region of the skeleton. Moreover, CT images from the experiments were used to reconstruct 3D images of coal under different stress states. The deformation and fracture process can be observed obviously. These investigations can provide theoretical foundations for understanding of fracture mechanism of coal.     

Both pelvic radiography and lateral abdominal radiography correlate well with coronary artery calcification measured by computed tomography in hemodialysis patients: A cross‐sectional study

Introduction Lateral abdominal radiograph is suggested as an alternative to coronary artery computed tomography (CT) in evaluating vascular calcification. Simple scoring systems including pelvic radiograph scoring and abdominal scoring system were utilized to study their correlation with coronary artery calcification. Methods In 106 MHD patients, coronary artery CT, lateral abdominal, and pelvic radiograph were taken. The Agatston scoring system was applied to evaluate the degree of coronary artery calcification which was categorized according to Agatston coronary artery calcification score (CACS) ≥ 30, ≥100, ≥400, and ≥1000. Abdominal aortic calcification was scored by 4‐scored and 24‐scored systems. Pelvic artery calcification was scored by a 4‐scored system. Sensitivities and specificities of abdominal aortic calcification scores and pelvic artery calcification scores to predict different categories of coronary artery calcification were analyzed. We studied the diagnostic capability of abdominal aorta calcification and pelvic artery calcification to predict different CACS categories by calculating likelihood ratios. Receiver operator characteristic curves were used to determine the area under the curve for each of these testing procedures. Findings The prevalence was 48(45.3%), 15 (14.2%), 11 (10.4%), 11 (10.4%), and 11 (10.4%) for CACs > 0, ≥30, ≥100, ≥400, and ≥1000, respectively. The degree of CACs was positively correlated with patient age, prevalence of diabetes, abdominal aorta scores, and pelvic calcification scores. The areas under the curves for different CACS by all X‐ray scoring systems were above 0.70 except pelvic 4‐scored system for diagnosing CACS ≥30, without significant difference (P > 0.05). Discussion Both lateral abdominal and pelvic plain radiographs were demonstrated as acceptable alternatives to CT in evaluating vascular calcification.