Research On The Influence Of Electromagnetic Wave Propagation Delay On Magnetic Induction Tomography Technology

Magnetic Induction Tomography(MIT)technology is a new type of electromagnetic imaging technology.MIT has become a research hotspot in the field of biomedicine,due to its non-invasive and non-contact characteristics.The MIT technology uses the phase detection technology to obtain the internal eddy current signal of the object to be measured,and reconstructs the conductivity distribution of the measured object through the image reconstruction algorithm.The influence of phase lag caused by electromagnetic wave propagation delay on the phase detection accuracy of eddy current signal is neglected in classical MIT technology.A series of studies on the influence of electromagnetic wave propagation delay in MIT technology are carried out based on this theory.The main work is as follows:1.The development status of MIT technology is reviewed.The basic principle of eddy current signal measurement is analyzed.The coil model of sensor array in MIT system is analyzed.The calculation formula of phase lag caused by electromagnetic wave propagation delay in MIT is deduced quantitatively through the basic theory of electromagnetic field and wave.2.The model of MIT measurement system is established based on COMSOL multi-physical field coupling simulation software,and the induced voltage of detection coil is extracted and analyzed.The method of solving sensitivity matrix of MIT measurement system is summarized.The sensitivity matrix of four typical excitation-detection combinations in free field and disturbance field is solved and imaged based on the 8-channel MIT measurement model.3.The hardware circuit of MIT measurement system is designed and implemented.The air field and disturbance field were tested and the measured data were recorded.The original measurement data and the modified data considering the influence of propagation delay of electromagnetic wave are reconstructed respectively based on the linear back projection algorithm.The result of image reconstruction:the phase lag caused by electromagnetic wave propagation delay has an important influence on the phase detection accuracy of MIT eddy current signal.4.Based on the propagation characteristics of electromagnetic waves in biological tissues,a bioimpedance measurement system based on open oscillating circuit is designed and built.The starting frequency,stability,repeatability and conductivity sensitivity of the open oscillating circuit of the system are tested and discussed.The relationship between electrical parameters of biological tissues and measured data was deeply explored.