Research On Image Monitoring Method Of Pulmonary Respiratory Bioimpedance

Electrical Impedance Tomography(EIT)is an imaging technology that detects variation in boundary voltage or current by applying a certain amount of excitation current or voltage to the surface of the object to be tested,thereby reconstructing the internal conductivity distribution of the object and its variation image.EIT has the advantages of non-invasiveness,non-radiation,portability and functional,which make it widely used in imaging fields such as medicine and geological prospecting.At present,the field of medical imaging has developed to a stage very close to clinical applications.In this dissertation,around the dynamic physiological process of lung breathing,three dimensional lung breathing dynamic variation simulation research and the construction of a hardware imaging system for lung breathing dynamic monitoring are carried out.This thesis mainly completed the following work:Firstly,in order to obtain the quantitative relationship between lung respiration,body surface potential and chest cavity impedance,this thesis establishes a three-dimensional chest cavity model including the lungs,and proposes to introduce lung tissue air filling parameters into the three-dimensional chest cavity model to describe the amount of air in the lungs.The conductivity variation parameter is set according to the relationship between air volume and conductivity.And the dynamic variation process of the lungs from the end of inhalation to the end of expiration is simulated.At the same time,the finite element method is used to calculate the relationship between lung tissue air volume and chest surface potential and chest impedance,and the lung breathing and physiological electrical signals are calculated further quantitative analysis.Secondly,in order to obtain the dynamic variations of lung breathing intuitively,this thesis built a 16-electrode EIT imaging system to image the variations of lung respiratory impedance.Several modules required by the system,including signal excitation module,electrode gating multiple switch module,and voltage acquisition module,have been optimized and designed.At the same time,STM32 single-chip microcomputer is used to achieve precise control of each circuit of the system,which enhances system stability.It can accurately perform lung and respiratory imaging at the same time.Finally,in order to verify the accuracy of the lung breathing monitoring method proposed in this article,two sets of related experiments were conducted on volunteers according to the simulation method.The relationship between the amount of air in the lungs,body surface potential and chest impedance during deep breathing of volunteers was calculated.The experimental results are highly consistent with the simulation results,which proves the accuracy of the method.At the same time,the performance of the lung breathing imaging system built is analyzed.The results show that the system has high channel consistency and good signal-to-noise ratio.And using the system to perform dynamic imaging of the lung deep breathing process,the dynamic variations of lung breathing can be observed intuitively,which further proves the feasibility of the system.