【作者】 陈晓艳；

【导师】 王化祥；

【作者基本信息】 天津大学 ， 检测技术与自动化装置， 2009， 博士

【摘要】 生物电阻抗是指生物体或生物组织、生物器官、生物细胞在低于兴奋阈值的安全电流作用下所表现出的阻抗变化。生物电阻抗断层层析成像技术(Biomedical Electrical Impedance Tomography,MEIT)是通过配置体表电极阵列、施加一定频率的低幅交变安全电流,并通过扫描电极测量电压数据,从而提取与人体生理、病理状态相关的组织或器官的电特性信息,并经数据采集和处理后,重构被测组织或器官的断层分布图像。与CT及MRI技术相比,EIT具有安全、无毒、无害、便携等优点,而且能对人体组织与器官进行无损伤的功能成像,可实现长期、动态、连续图像观察。本课题围绕人体呼吸过程的功能性成像技术开展研究,主要的研究工作包括:1.基于FPGA的数字化肺功能成像系统研究;2.图像重建算法研究:提出肺部电阻抗成像技术的双模型图像重建算法,利用MATLAB仿真重建肺部物理模型的静态图像及肺部呼吸过程的二维动态图像;研究了自适应多重网格算法,参考后验误差求解正问题,采用正则化与自适应多重网格剖分相结合的算法重建场域内部电阻率分布;最后研究了最小二乘共轭梯度图像重建算法,并进行成像仿真,给出了相应技术指标。3.研究了正常肺、心脏、脂肪和肌肉四种离体生物组织的电阻抗特性;并对人体健康肺组织及浸润性肺癌组织的电阻抗频率特性进行了测量及研究。4.融合灵敏场几何分布与电导率分布等先验信息的肺功能成像技术研究:从肺部CT图像获取人体胸部生理结构信息并结合电导率信息,求解灵敏度矩阵,利用MATLAB进行图像重构,提高了重建图像的分辨率;利用Visual C++与Matlab C++数学库以及MathTools混合编程,开发了融入先验信息的肺部电阻抗成像实时软件包,实现了动态监护过程临床需求。5.EIT_TJU_II系统的空间分辨率和阻抗分辨率的系统性能参数研究,并给出了相应结果。6.利用生物电阻抗断层成像技术实现了人体呼吸过程的电阻抗实时成像,并提出利用特征单元数据挖掘更丰富的生物阻抗信息,为临床研究提供了新的监测方法,通过分析特征单元数据,进一步挖掘与呼吸过程相关的心动信息。最后,在总结本课题研究工作基础上,提出今后研究工作改进建议。更多还原

【Abstract】 Bioelectrical impedance is one of the electrical characteristics of biological tissue, organs and cells when injected a safety current under threshold value. Electrical impedance tomography (EIT) is an imaging technique which aims at estimating the interior conductivity or resistivity distribution within a region of interest (ROI). In EIT, a sensing electrode array is attached on the boundary of an object, safe alternating currents are injected through these electrodes, and the resulting voltages are measured which reflecting the electrical characteristics of the biological tissue and organs. After data collection and processing, the conductivity or resistivity distribution is imaged by reconstructed algorithms.Compared to the conventional medical imaging techniques, such as X-ray computerized tomography (CT) or Magnetic resonance imaging (MRI), EIT has the advantages of reasonable cost, harmlessness, and portability, etc. Furthermore,it is of advantage, such as non-invasion functional imaging technique through mining a wealth of physiological and pathological information by means of bioelectrical impedance. EIT makes bedside continuous monitoring achievable. The research work of lung ventilation functional imaging by EIT is illustrated briefly as following:1. EIT_TJU_III system is researched based on Field Programmable Array (FPGA);2. Reconstruction algorithms are researched. Firstly, a dual-model reconstruction algorithm is put forward, which reconstructs two dimension images based on a sensitivity matrix calculated from three dimension model. The dynamic ventilation is imaged by Matlab. Secondly, adaptive multigrid (AMG) reconstruction algorithm considering posterior estimate and adaptive refinement in the forward problem is researched, and the imaging results using regularized gauss-Newton algorithm are achieved. Finally, the conjugate gradient least squares (CGLS) algorithm is also researched and the some performance indexes are given out.3. The impedance frequency characters of pig’s lung, heart, muscle and fat are measured with small current injecting under different frequencies, the human health lung tissue and the soakage lung cancer tissues are also measured and analyzed by frequency dispersion theory. The Cole-Cole parameters are calculated.4. An approach to producing an accurate reconstruction image of the object regarding the physical geometry and prior conductivities information within thorax is proposed and simulated. The sensitivity distributions of traditional circular platform and the proposed physical platform are compared. The lung ventilation experiments are undertaken. A software kit is developed using Visual C++ and the math library of Matlab C++, it can realize the real-time dynamic imaging with prior information.5. The experiments for testing the spatial resolution and the resistivity resolution of EIT_TJU_II are undertaken. The thesis gives out some performance indexes.6. An idea of characteristic pixels is put forward in medical electrical impedance tomography, which can mine more useful biological information for clinic application.At the end of the thesis, the research work is summarized briefly and further research work is suggested.更多还原