The Research On Measurement Method And Parametric Model Of Biological Tissue Dielectric Properties In The Radio Frequency

The biological tissue dielectric properties are inherent factors of tissue absorbing and coupling the electromagnetic energy.Therefor,the measurement of biological tissue dielectric properties is of great significance to the studies on bio-electromagnetic effect,diagnoses,life sciences and so on.Although a considerable amount of achievements have been accumulated for the half of century in the measurement of biological tissue dielectric properties,there is still a continuing need for further studies to fill in the blanks of application in fact.This thesis studied the methods of probe measurement and the parameter model fitting of biological tissue dielectric properties which is used to analyze the frequency-dependent behavior of biological tissue dielectric properties in the radio frequency band according to the structure character of biological tissue.The main work includes:The conventional measurement and caculation method of the open-ended coaxial probe for measurement of the dielectric properties of biological tissues was improved in this thesis.The conventional equivalent circuit analysis model was improved according to the results of simulation.As well as,the evolutionary optimization methods was introduced for calculation of the improved model.The simulation and experiment were achieved to validate the improved equivalent circuit analysis model,which solved the problem of conventional model and improved the stability of measurement.The measurement on the dielectric properties of heterogeneous biological tissue with the inclusion was studied and analyzed.The feasibility that the open-ended coaxial probe could be used to measure the dielectric properties of heterogeneous biological tissue was validated by the simulations.The influence of the inclusion in tissues on the dielectric measurement of heterogeneous biological tissues was studied.As well as,the mixing rule was also validated that could be used in the measurement of dielectric properties of heterogeneous biological tissue.The measurement of dielectric properties of anisotropic tissue was studied.A new sensor was introduced for avoiding the errors of measurement which could achieve the anisotropy measurement in two directions only by single measurement.Simulations were performed to give the expatiation of several techniques of sensor.As well as the probe was also producted in fact.The experiments were performed to validate the application value of the sensor.The multi-pole Debye model of dielectric spectrum of biological tissue was investigated.The simulated annealing algorithm(SA)was introduced to fit the measured data of dielectric spectrum.The experiments were performed which validated that the multi-pole Debye model could be used in the analysis of dielectric spectrum of biological tissue.In this thesis,the problems of conventional measurement of the dielectric properties of biological tissues in the radio frequency band were solved.The research approaches of measurement of the dielectric properties of biological tissues were also increased which could lay the root for the future research.