Neural Network for Data Preprocessing in Computed Tomography

Automation and Remote Control - We propose a lightweight noise-canceling filtering neural network that implements the filtering stage in the algorithm for tomographic reconstruction of convolution...     

计算机断层扫描图像的剖切研究

工业CT扫描通常只能得到某一断面上的二维信息，不能得到被检测物的整体描述，技术人员只能根据获得的系列二维图像在人脑中综合复原为三维结构。因而人们希望能得到直观地、精确地展示被检测物体三维空间结构的ICT直观图像，能得到比二维图像更加丰富的信息。因此断层图像的三维重建在工业无损探伤、天体结构的观察及其它更广泛的领域有着极其重要的实用价值和研究意义。本文提出了一种剖切显示的3D图像处理方法，借助Matlab工具，用软件的方法得到直观的3D图像。     

High-Quality Volumetric Reconstruction on Optimal Lattices for Computed Tomography

Within the context of emission tomography, we study volumetric reconstruction methods based on the Expectation Maximization (EM) algorithm. We show, for the first time, the equivalence of the standard implementation of the EM-based reconstruction with an implementation based on hardware-accelerated volume rendering for nearest-neighbor (NN) interpolation. This equivalence suggests that higher-order kernels should be used with caution and do not necessarily lead to better performance. We also show that the EM algorithm can easily be adapted for different lattices, the body-centered cubic (BCC) one in particular. For validation purposes, we use the 3D version of the Shepp-Logan synthetic phantom, for which we derive closed-form analytical expressions of the projection data. The experimental results show the theoretically-predicted optimality of NN interpolation in combination with the EM algorithm, for both the noiseless and the noisy case. Moreover, reconstruction on the BCC lattice leads to superior accuracy, more compact data representation, and better noise reduction compared to the Cartesian one. Finally, we show the usefulness of the proposed method for optical projection tomography of a mouse embryo.     

基于连续X射线谱的CT重建算法仿真

关于提高CT图像精度的问题,传统的CT重建算法都是基于X射线源是单色源的假设,忽略了X射线的多色性.直接用多色投影数据进行图像重建易产生金属、硬化等伪影,降低图像质量,影响CT值标定,从而影响医学或工业诊断.考虑到X射线能谱的连续性,采用仿真手段实现连续X射线谱的统计重建.首先将连续X射线谱离散成若干单能谱,再根据待检工件的材质信息以及射线能量所对应的质量衰减系数,构建基于连续X射线谱的工件材质模型;最后利用多能统计重建算法对多能投影数据进行迭代重建.仿真结果表明,算法充分地利用了X射线的多能性,在一定程度上可以有效地降低图像伪影,提高CT重建图像质量.     

工业CT数据采集系统的控制逻辑研究

数据采集系统的控制逻辑是工业CT(Industrial Computed Tomography)的重要组成部分,如何保证数据采集系统的控制逻辑工作的稳定、可靠、一致性,对于研制工业CT,提高工业CT的整体性能有重要的意义.文中介绍了工业CT数据采集系统控制逻辑的设计方法,论述了数据采集系统控制逻辑的总体设计和详细设计,给出了系统的设计与实现方案.     

Quick and Dirty GOMS: A Case Study of Computed Tomography Interpretation

GOMS (goals, operators, methods, and selection rules) has the potential for a high degree of theoretical accuracy. However, this accuracy is time-consuming to realize under field conditions, and, consequently, GOMS generally is not used by software engineers. Nevertheless, in our experience, GOMS models can be practical if the effort required to produce and use the model is commensurate with its limited practical accuracy. To speed and simplify the development of GOMS models, we developed "quick and dirty" GOMS—or QGOMS. In this work, we detail an 8-year case study in which QGOMS models were used by a software engineering team to develop and evolve an interface for the electronic display of computed tomography (CT) medical images. Experimentally generated timing results were compared to model estimates to provide an indication of expected accuracy for QGOMS models under field conditions. We have also implemented a direct-manipulation graphical tree editor that allows rapid development and analysis of QGOMS models. In addition to rapid model construction, QGOMS provides "probability selection rules" allowing a more refined GOMS analysis.     

工业CT数据采集系统的控制逻辑研究

数据采集系统的控制逻辑是工业CT(Industrial Computed Tomography)的重要组成部分，如何保证数据采集系统的控制逻辑工作的稳定、可靠、一致性，对于研制工业CT，提高工业CT的整体性能有重要的意义。文中介绍了工业CT数据采集系统控制逻辑的设计方法，论述了数据采集系统控制逻辑的总体设计和详细设计，给出了系统的设计与实现方案。     

一种锥束CT中平板探测器输出图像校正方法

为了消除平板探测器缺陷在锥束CT重建切片中引起的伪影,提出一种投影图像校正方法.通过对投影图像进行暗场和增益不一致校正,推导了像元增益系数公式;对增益系数以及像元输出的期望和方差进行直方图分析以识别坏像素,根据坏像素分布特征设计相应的插补方案;通过局部屏蔽区域数据统计暗场波动幅度并逐行修正.实验结果表明,该方法使投影图像灰度分布均匀,像元输出波动和切片伪影得到有效抑制.     

CT投影采样策略对重建质量影响综述

针对计算机断层成像（Computed Tomography,CT）中投影数据与图像重建关系,综述了CT在投影策略方面对重建质量的影响.对不同采样策略获取的不完全投影数据,应用迭代类算法对投影数据进行重建,研究了均匀采样和非均匀采样情况下不同数据结构对重建图像质量的影响.对仿真数据和实际数据重建结果进行分析,同时对不同策略下的投影数据结合其数据分布特点探讨了重建质量优劣的原因.论文可以为CT重建领域的研究工作者提供全面的采样方法梳理和总结,为当前不完全投影数据获取方式对应的算法改进提供思路,最后对当前研究重点和未来发展进行了展望.     

Automated Planning and Optimization of Lumber Production Using Machine Vision and Computed Tomography

An automated system for planning and optimization of lumber production using Machine Vision and Computed Tomography (CT) is proposed. Cross-sectional CT images of hardwood logs are analyzed using machine vision algorithms. Internal defects in the hardwood logs pockets are identified and localized. A virtual in silico 3-D reconstruction of the hardwood log and its internal defects is generated using Kalman filter-based tracking algorithms. Various sawing operations are simulated on the virtual 3-D reconstruction of the log and the resulting virtual lumber products automatically graded using rules stipulated by the National Hardwood Lumber Association (NHLA). Knowledge of the internal log defects is suitably exploited to formulate sawing strategies that optimize the value yield recovery of the resulting lumber products. A prototype implementation shows significant gains in value yield recovery when compared with lumber processing strategies that use only the information derived from the external log structure.     

肺部CT图像病变区域检测方法

肺部CT图像病变区域检测是肺病辅助诊断技术的重要研究内容,其通过自动分析CT图像并输出病变区域的位置和尺寸等信息,帮助放射科医生做出决策,有利于肺病的早期发现与治疗.本文回顾了肺部CT图像中病变区域自动检测方法所取得的进步,并引入一个通用框架表示和描述现有方法,对2012年以来肺部病变区域辅助检测算法进行了系统性分析和性能汇总.最后讨论了目前存在的问题和有待克服的困难,探讨了未来可能的发展方向.     

基于锥束CT的两类三维表面重构方法比较研究

目前锥束CT的三维重构主要采用面绘制,其方法有两类,即体素级重构和切片级重构。在对比两类方法的基础上,提出了一种新的二维切片轮廓重构与三维表面重构相结合的切片级重构方法,然后以标准MC算法和该算法分别对两个实例进行重构并比较。结果表明,该算法更适合工业产品的三维表面重构。     

基于框架和组件技术的锥束CT应用平台设计与实现*

为使锥束CT应用于航空发动机的研制,采用面向对象的框架和组件技术设计并实现了锥束CT应用平台软件。通过锥束CT应用的领域分析,提出其框架模型;从功能上分割框架模型,得到各组件模块,并阐述了关键组件的技术实现方法。使用Microsoft Visual C++ 6.0/MFC和VTK（Visualization ToolKit）完成锥束CT应用平台的框架和组件开发,突破了限制检测系统的一些瓶颈问题,为锥束CT在企业的实际应用打下基础。     

Tomography from collective measurements

We discuss the tomography of N-qubit states using collective measurements. The method is exact for symmetric states, whereas for not completely symmetric states the information accessible can be arranged as a mixture of irreducible SU(2) blocks. For the fully symmetric sector, the reconstruction protocol can be reduced to projections onto a canonically chosen set of pure states.     

功率超声加工中超声波发生器的研究

介绍了一种在脆性材料钻孔中使用的功率超声波发生器的设计方法,分析和研究了频率自动跟踪电路、驱动电路、功放电路及其完善的保护功能。     

电阻抗成象技术

电阻抗成象技术是国外近十几年来发展起来的一门崭新的医学成象技术，它根据人体内部组织器官具有不同阻抗的特性，借助分布于体表的电极阵列，施加一定模式的注入电流，然后通过测量电极上的电压得到人体内部的阻抗数据，再将这些阻抗数据，依据重建算法，构造出体内组织器官的图象，供临床医生作出判断。本文介绍了电阻抗成象技术的原理，国外发展概况，研究重点和系统实现，以期引起国内医学电子同行的关注，并促进这一新技术在我国的发展。     

Estimating Uncertainties for Geophysical Tomography

We present statistical and interval techniques for evaluating the uncertainties associated with geophysical tomographic inversion problems, including estimation of data errors, model errors, and total solution uncertainties. These techniques are applied to the inversion of traveltime data collected in a cross well seismic experiment. The inversion method uses the conjugate gradient technique, incorporating expert knowledge of data and model uncertainty to stabilize the solution. The technique produced smaller uncertainty than previous tomographic inversion of the data.