Acousto-electric And Acoustic-vibration Modulation Mechanism And Modeling

Electrical and elastic properties of biological tissue contain pathological and physiological information.Effectively obtaining the electrical parameters and elastic parameters of biological tissue and performing non-destructive functional evaluation have important guiding significance for the diagnosis of diseases and the evaluation of health conditions.When low-intensity focused ultrasound acts on biological tissues,it can cause changes in the electrical parameters and the mechanical response of biological tissue.This thesis focuses on modeling the interaction between low-intensity focused ultrasound and electrical characteristic and mechanical characteristic of biological tissue,which will provide the theoretical and experimental basis for the measurement and imaging of electrical and elastic properties of tissues.The main work of this thesis includes:(1)Acousto-electric modeling and parameter analysis.The acoustic and electrical coupling simulation modeling is carried out,and the problem of the coupling of the acoustic field and the electric field is solved.Besides,the influencing factors of acousto-electric modulation are discussed according to the modulation effect of focused ultrasound on electrical parameters.The simulation results show that the pressure of ultrasound,the excitation current and the initial electrical parameters of the tissue can affect the acousto-electric modulation.Increasing the amplitude of the pressure and the excitation current can both enhance the modulating effect of focused ultrasound on the conductivity of the tissue.(2)Acoustic-vibration modeling and parameter analysis.According to the mechanism of the acoustic-vibration process,the energy conversion process is divided into two physical fields: high-frequency source sound field(MHz)and low-frequency vibration field(k Hz),and the finite element method is combined to solve the problem of solving the coupling simulation model of acoustics and mechanics.By discussing the amount of tissue displacement,the influencing factors of mechanical response caused by dynamic acoustic radiation force are analyzed.The simulation results show that both the excitation ultrasound parameters and the tissue hardness can affect the mechanical response.Using softer tissue and increasing the pulse width and pulse repetition frequency of the focused ultrasound can increase the mechanical response of the tissue in the focal area.(3)Realization of acousto-electric and acoustic-vibration experimental system and verification for the simulation results.The experimental system platforms are built respectively.The timing for the ultrasound and electrical excitation is also designed and optimized.For the verification of multiphysics coupling simulation model,the homogeneous phantom experiment is used to discuss the influencing factors of acousto-electric and acousto-vibration modulation.This work is prepared for the measurement and imaging of tissue electrical and elastic characteristics.