呼吸过程三维电阻抗系统研究

发布时间：2018-05-12 10:19

本文选题：电阻抗成像 + 肺呼吸成像　；参考：《天津科技大学》2016年硕士论文

【摘要】：电阻抗断层成像(Electrical Impedance Tomography,EIT)技术是根据生物体内不同组织或同一组织在不同生理、病理状态下具有不同电导率的特征,来得到机体内部图像的无损伤成像技术。通过在生物体表面施加安全电流(电压),并测量表面其他测量点电压,由计算机根据电学断层图像重建算法重构出被测生物体内部电阻抗分布图像。它是将人体组织或器官的生物阻抗的分布和变化以2D/3D图像的形式直观的展现出来,为被测组织或器官进行诊断和评价提供依据。EIT技术以其非侵入、安全无辐射、成本低廉、成像速度快、可连续测量且实时可视化等优点在医学成像技术领域备受关注。本文从EIT技术的物理模型出发,深入研究了三维EIT系统的测量机理,设计并构建了包括信号源模块、数据采集模块、FPGA控制模块等的2D/3D电阻抗成像系统,采用VHDL语言编写了整套系统的应用程序,在物理模型-试验水槽上实现了二维及三维静态和动态电阻抗成像,验证了系统可靠性及稳定性,最后对人体肺呼吸过程进行了电阻抗成像,取得较好效果。主要的研究工作如下:1.设计了一套两层共32电极的三维高精度电阻抗成像系统硬件。该系统以PC机作为主控制器利用LabVIEW编写的上位机软件进行发送指令和将上传的数据处理并调用Matlab进行成像。FPGA作为从控制器负责激励信号的产生、电极通道的切换、程控放大器增益的选择及数据的采集与处理,采集到的数据通过串口与上位机进行通信。实验结果表明该系统测量精度达0.082%,信噪比为60.3dB,空间分辨率达到0.29%。2.针对正交序列数字解调算法中参考信号与测量信号频率不一致而引起的解调结果不准确影响成像质量的问题,提出无需数字解调直接提取幅值进行电阻抗成像的方法:通过多次采样比较和算术平均滤波法获取幅值进行EIT成像。经理论和实验结果证明,验证了直接提取阻抗幅值方法的可行性,提高了数据采集精度和系统的稳定性,改善了图像成像质量。3.对构建的EIT系统进行二维成像的模拟试验。利用COMSOL软件对二维系统进行建模,基于共轭梯度算法,采用MATLAB对采集的数据进行处理,实现了二维静态及动态成像。成像结果较清晰的显示了目标物体在试验水槽中的个数、形状、大小、位置、运动状态等信息。4.在人体上实现肺呼吸过程的电阻抗二维动态成像。利用COMSOL构造了带有先验信息的二维肺部物理仿真模型,结合MATLAB编程,计算灵敏度矩阵。在志愿者胸腔进行了数据采集,通过共轭梯度算法,获得了肺呼吸过程的二维电阻抗图像,成像质量良好。5.在水槽模型上进行了三维电阻抗成像实验。利用COMSOL软件构建三维水槽的物理仿真模型,采用准对角激励和同层相邻测量的工作模式,结合MATLAB编程,计算得到新的灵敏度矩阵。在试验水槽上下两层电极上进行了三维数据采集及静动态成像。成像结果准确地反映了目标物体在试验水槽中的个数、形状、大小、位置、运动状态、高度等信息。6.人体呼吸过程三维电阻抗数据采集实验。在志愿者胸腔外围均匀粘贴两层共32个心电电极,在准对角激励和同层相邻测量的工作模式下,采集呼吸过程边界电压并对采集数据进行了分析。该系统为EIT系统的完善与系统性能的提升以及深入开展肺功能评价研究及呼吸过程的床旁监护和帮助医生做出正确的疾病诊断提供了一种有效的解决方案。本文最后在总结研究工作的基础上还提出了一些改进性的建议。
[Abstract]:Electrical Impedance Tomography (EIT) technology is based on the characteristics of different electrical conductivity of different tissues or the same tissue in different physiological and pathological conditions. The non damage imaging technology of the internal image of the organism is applied to the surface of the organism by applying the safe current (voltage) on the surface of the organism and measuring the other surface. The measuring point voltage is reconstructed by the computer based on the electrical fault image reconstruction algorithm. It shows the distribution and change of the biological impedance of human tissues or organs in the form of 2D/3D image, and provides the basis of.EIT technology for the diagnosis and evaluation of the tissues or organs. The advantages of non-invasive, safe and non radiation, low cost, fast imaging speed, continuous measurement and real-time visualization have attracted much attention in the field of medical imaging technology. This paper, starting from the physical model of EIT technology, deeply studies the measurement mechanism of 3D EIT system, and designs and constructs the module of signal source, data acquisition module and FPGA control module. The 2D/3D electrical impedance imaging system, using the VHDL language to write the application program of the whole system, realized the two-dimensional and three-dimensional static and dynamic electrical impedance imaging on the physical model test sink, verified the reliability and stability of the system. Finally, the electrical impedance imaging of the human lung respiration process was carried out. The main research results were achieved. The work is as follows: 1. a set of three dimensional high precision electrical impedance imaging system hardware with a total of two layers of 32 electrodes is designed. The system uses PC as the main controller to send instructions by the host computer software written in LabVIEW and processing the uploaded data and invoking Matlab for imaging.FPGA as an incentive signal from the controller. The switching of the channel, the selection of the gain of the program control amplifier and the acquisition and processing of the data, the data collected are communicated with the host computer through the serial port. The experimental results show that the measurement accuracy of the system is 0.082%, the signal to noise ratio is 60.3dB, the spatial resolution reaches 0.29%.2., and the frequency of the reference signal and the measured signal is not frequency in the orthogonal sequence digital demodulation algorithm. The unaccurate result of unaccurate demodulation results in the image quality is inaccurate, and the method of electrical impedance imaging is proposed without digital demodulation. The amplitude of EIT is obtained by multiple sampling comparison and arithmetic average filtering. The feasibility of direct extraction of impedance amplitude method is proved by theoretical and experimental results. The accuracy of data acquisition and the stability of the system are improved, and the image imaging quality.3. is improved to simulate the two-dimensional imaging of the constructed EIT system. The two-dimensional system is modeled by the COMSOL software. Based on the conjugate gradient algorithm, the acquired data is processed with MATLAB, and the two-dimensional static and dynamic imaging results are realized. It clearly shows the two-dimensional dynamic electrical impedance imaging of the number, shape, size, position and motion state of the object in the test sink, such as the number, shape, size, position and motion state of the object. Using COMSOL, a two-dimensional lung physical simulation model with prior information is constructed, and the sensitivity matrix is calculated with MATLAB programming. In the volunteers' chest, the.4. is used to calculate the sensitivity matrix. The cavity carries on the data collection, obtains the two-dimensional electrical impedance image of the lung breathing process through the conjugate gradient algorithm. The imaging quality is good.5. is carried out on the 3D electrical impedance imaging experiment on the tank model. The physical simulation model of the three dimensional tank is constructed by using the COMSOL software, and the working mode of the quasi angle excitation and the same layer adjacent measurement is adopted, and the MA is combined with the model. A new sensitivity matrix is obtained by TLAB programming. Three-dimensional data acquisition and static and dynamic imaging are carried out on two layers of electrodes on the test sink. The imaging results accurately reflect the number, shape, size, position, motion state, height, etc. of the target object in the test sink for 3D electrical impedance data acquisition of the.6. body respiration process. The two layers of 32 electrocardio electrodes were pasted evenly on the periphery of the volunteers' chest, and the boundary voltage of the respiratory process was collected under the working mode of quasi diagonal excitation and the adjacent measurement of the same layer. The system is the improvement of the EIT system and the performance of the system, the evaluation of lung function and the breathing process. The bedside monitoring and the help of the doctor to make the correct diagnosis of the disease provide an effective solution. Finally, on the basis of the summary of the research work, some suggestions for improvement are also put forward.

【学位授予单位】：天津科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TP391.41

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