Lung Function Detection System Based On Electrical Impedance Tomography

Electrical impedance tomography(EIT)is a new technology in the field of medical imaging.The principle of EIT is to apply a certain frequency of safe current to the organism by electrodes and then measure the boundary voltage of the target area.The impedance distribution of the organism can be obtained through the corresponding image reconstruction algorithm.EIT takes the impedance distribution of organism tissues or organs as the imaging target,and extracts biomedical information related to physiology and pathology.EIT has the advantages of non-invasion,non-radiation and low cost.At present,EIT technology is mainly used in the diagnosis and research of diseases of brain,heart and respiratory system in medicine.As a preliminary research topic,this paper mainly focuses on the changes of pulmonary impedance by electrical impedance tomography(EIT).The main research work and results are as follows:(1)The theory of biomedical electrical impedance tomography(EIT)is studied,including the establishment of electrical properties and physical models of biological tissues,the composition of EIT data acquisition syste,m,the forward and inverse problems in image reconstruction.(2)The design of EIT data acquisition system for pulmonary function imaging was completed,including circuit design and simulation,hardware circuit construction and testing,experimental model of 16-electrode circular saline tank,analysis and solution of forward and inverse problems based on MATLAB.(3)Aiming at the problems existing in EIT system design,a high-precision signal generator based on ARM and DDS(Direct Digital Frequency Synthesizer)technology is designed.Voltage-controlled current source is designed with the second generation current feedback amplifier,which improves the accuracy and stability of the excitation signal,and the impedance-related information is extracted by orthogonal sequence demodulation(4)Tikhonov regularization and prior Laplace algorithm are used to reconstruct the image,and the impedance distribution image is obtained,which verifies the feasibility of the system scheme.