| Electrical Impedance Tomography(EIT)is an emerging medical application technology for imaging the electrical impedance/conductivity distribution of internal tissues and organs.The internal organs of the human body have different impedance changes under different physiological and pathological conditions.A small safe excitation current is applied to the human body through the electrodes,an electric field is generated inside the human body,and the voltage signal of the body surface is measured,according to a certain image reconstruction algorithm.Image reconstruction of the internal electrical impedance distribution of the human body.Compared with traditional medical imaging technologies such as X-ray and CT,EIT technology has obvious advantages such as non-invasive,fast imaging,low cost and continuous detection.It can provide technical support for clinical medical diagnostic monitoring and has good future application.prospect.In this paper,a 16-electrode EIT system with independent intellectual property rights has been developed for the problems of complex circuits,less voltage information,and large amount of inversion imaging calculations in the existing systems,combined with the high-precision and real-time requirements of EIT systems.The functional analysis of the modules of the EIT system was carried out.The EIT requirements analysis of the human organ was carried out for the data acquisition module,control module and image reconstruction module of the EIT system,and the design scheme of the hardware system was determined,including the selection of the power supply and measuring instruments,and the sensor.The design of the model,the design and manufacture of the switch gating circuit,and the 16-electrode EIT hardware system test device were built.The control circuit board of data acquisition system based on single chip microcomputer was developed,and the data acquisition module control software was developed.The control software mainly includes the switch gating program of current excitation and voltage measurement and the voltage measurement program of high performance digital multimeter 34410 A,which realizes switch selection.The highspeed switching of the circuit and the automatic reading and storage of the electrode voltage ensure the data acquisition speed of the EIT system.The theoretical problem of EIT is deduced in detail,and the finite element simulation model of EIT positive problem is established.The model meshing and coefficient matrix solving are studied.Finally,the initial conductivity of the model is given in the finite element simulation software.Solve the potential distribution in the field to obtain the boundary voltage data.An EIT image reconstruction program was established,and the image reconstruction of the internal conductivity distribution of the simulation model was completed by using the voltage data obtained from the positive problem.Mathematical analysis and imaging comparison of image reconstruction algorithms such as linear back projection algorithm(LBP)and Gaussian Newton error method(GN)are carried out.The GN method with good imaging effect and only one iteration is needed as the EIT system designed in this paper.Rebuild algorithm.The voltage measurement program is combined with MATLAB to realize the mixed programming of MATLAB and LABVIEW,which integrates the data acquisition and imaging of the whole system and improves the working speed of the system.A 16-electrode EIT system test platform was built to test the channel consistency of the sensor device.The nylon test pieces of different shapes were designed and processed to carry out basic research experiments and image reconstruction.The basic functions of the EIT system designed in this paper were verified.Research lays the foundation. |
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