Study On Electrical Impedance Tomography System Based On PXI Bus Technology

As an emerging functional imaging technology,electrical impedance tomography(EIT)is a new imaging technology other than morphological and structure imaging.Compared with traditional CT imaging technology,EIT is non-invasive,radiation-free,functional imaging,portable,easy to operate,fast imaging,repeatable,reusable,enabling its utility as a bedside monitoring technology for intensive care,surgical and emergency patients.Traditional EIT system is designed and implemented according to the APT working mode of the earliest proposed by the University of Sheffield in the UK.But there is a defect of the phase difference between the measurement data in the same excitation condition.The focus of this research is to study and design a synchronous EIT system.This paper mainly focuses on the following three aspects.The design of asynchronous EIT system based on PXI+FPGA:1.On the basis of the original EIT system based on FPGA,the data acquisition card based on PXI bus is used as the data acquisition part.The asynchronous EIT system based on PXI+FPGA is constituted with three parts:target,data acquisition system and imaging computer,and then complete the commissioning.2.The software program of the system is developed by LabVIEW and MATLAB.3.Static imaging experiments of different target objects are carried out on the vessel,and the image reconstruction is realized by using the image reconstruction algorithm.The design of synchronous EIT system based on PXI bus:1.The synchronous EIT system based on PXI bus is developed with a target,a signal source module,a switch module,a data acquisition module,a controller module and a PC,and then completes the commissioning.2.Using LabVIEW and LabVIEW FPGA software platform developed and perfected the synchronous EIT system software.3.Test the performance of the system.Experimental results show that the performance of the system reaches the imaging requirements.4.Static experiments and dynamic experiments of different target objects are carried out on the vessel,and the images are reconstructed by the image reconstruction algorithm.The imaging results are evaluated by the evaluation index,the result is ideal.5.Imaging results of asynchronous system and synchronous system are compared.Image reconstruction of pulmonary respiration in synchronous EIT system based on PXI bus:1.The EIT system is used in the imaging of human respiratory process,the most important is to transform the electrode.Aiming at the market common Ag/Agcl ECG electrode complete comparison and selection.Impedance characteristics of the selected electrodes are tested by using the impedance analyzer.The results show that the characteristics meet the requirements of EIT measurement.2.The human pulmonary respiration conductivity distribution image is reconstructed,and the imaging results can directly reflect the changes of the impedance of human pulmonary respiration.The innovation of this paper is a new kind of synchronous EIT system is realized,which can overcome the measurement error caused by the phase difference of the asynchronous measurement,and obtains satisfactory imaging results.