Research And Implementation Of Electromagnetic Induction Tomography System

Electromagnetic induction tomography is a kind of non contact biological impedance imaging technology.It is characterized by no damage,low cost and easy operation,and stands out in a lot of medical imaging technology.Further research on some key theoretical and technical problems in this technology is helpful to promote the development of medical imaging equipment,which has important social significance and application value to the diagnosis of clinical diseases.However,at present,the technology is still in the stage of laboratory research,mainly because its resolution is not up to the standard of medical imaging.The key point to solve the problem lies in the improvement of electromagnetic tomography system.Based on the research significance and key problems of electromagnetic induction tomography technology,this thesis expounds the basic principle and mathematical model of eddy current signal measurement by the basic theory of electromagnetism,also designed and completed a measuring system for the electromagnetic tomography.The main contents are as follows:According to the overall structure of the system hardware,this thesis completed the circuit modular design,schematic drawing,PCB board drawing,chip selection and components welding.The system mainly includes excitation source circuit,sensor coil and resonant circuit,phase detection circuit,data acquisition circuit.The system uses 4 channel synchronous output DDS to provide the excitation signal and the reference signal,enhanced the frequency stability of the signal;In the phase detection circuit,the capacitor compensation is adopted to solve the problem of the additional phase shift with the minimum cost,and the performance of the amplifier is stabilized;The PCB coil replaces the manual winding solenoid coil,and optimizes the structure of the sensor coil.The rationality of the circuit design is verified by the simulation before the circuit is produced by Multisim 12,which provides the basis for the comparison of the measured circuit;According to the performance and logic of the excitation source circuit and data acquisition circuit,the related work flow chart is drawn,and the software design of MCU is completed.In this thesis,the main module circuit and sensor coil were measured,and all the modules can meet the system design requirements.Through the comparison with the theoretical calculation,the error analysis is made;Software design of the system is tested,and the analysis of the relationship between the programming data of excitation source circuit and data acquisition circuit measured results are defined,the relevant error analysis is made.At last,the measurement accuracy and sensitivity of the system are defined by the comprehensive performance test.The multiple set measurement data are collected through the multiple translation and rotation of the cylinder to be measured,and the results of preliminary imaging are obtained by simulation.