Magnetic Induction Tomography System With Multi-excitation Frequency Mode

Magnetic Induction Tomography(MIT)is a new type of tomography based on electromagnetic induction principle and eddy current detection principle.It has the characteristics of non-contact,noninvasive,low cost,strong penetration and high center sensitivity,it has a good application prospect in biomedical examination and diagnosis.Based on the research of MIT detection system at home and abroad,aiming at the long-term monitoring imaging problem of human brain hematoma,according to the standard of biological tissue imaging frequency and human safety magnetic field,design a set of operating frequency is from 10 kHz-4 MHz,multi-excitation frequency mode 8-channel MIT detection system,the main work of this paper can be included as follow:Firstly,based on the designing of Human brain hematoma simulation model and image reconstruction,the system excitation frequency range is determined according to the simulation model.And based on the international human body magnetic field safety standard,the range of system excitation magnetic field is determined,it ensure that the system is harmless to the human body in the long-term monitoring.Secondly,according to the characteristics of human blood conductivity and the range of excitation frequency obtained by simulation model,design the three model excitation source of single frequency,sweep frequency and mixed frequency used in MIT detection system,and optimizing the design of coil sensor array.Thirdly,based on the industrial bus CPCI standard interface,design a highly integrated MIT detection system hardware circuit,including multi-coil sensor channel selection module,analog filter module,digital to analog conversion module and data communication interface module and so on;and programming to achieve the logic function of each module.Finally,on the basis of the system design,testing the signal to noise ratio of the system excitation source and the sensor each channel's test data.The test results show that the excitation source and each channel's test data have good consistency,single frequency mode excitation source's signal to noise ratio is 48 dB,the channel test data's signal to noise ratio is 46 dB.And using the multi-frequency MIT system to obtain the experimental data under high conductivity medium distribution condition by using the physical model simulation experiment.The data that acquired at different excitation frequencies uses Tikhonov image reconstruction algorithm,to realize the image reconstruction under different media distribution condition,verify the availability of the designed system.