Design Of Electrical Impedance Tomography System Applied In Pulmonary Ventilation Function Imaging And Experiment Research

Electrical impedance tomography, following the morphological and structural imaging, as a new medical imaging technique emerges in the recent years. Electrical impedance tomography technique visually exhibits the distributing and change of body's tissue and apparatus'bioelectrical impedance in the form of 2D/3D image, which is used to diagnose and evaluate tissue and apparatus in function.This thesis is about the application research of Electrical impedance tomography technique in measuring lung respiration function. The main works and results are as follows:Aiming at the request of high precision and reliability in EIT system, a digital system based on FPGA was designed. Main works are as follow:1. The author designed the system framework adapting to EIT and the function of very module in digital system2. The author utilized VHDL to digitally implement the function of DDS, phase sensitive demodulator (PSD) and UART interface with PC and design periphery circuit to constitute the whole data acquisition system.3. The MCU is developed to be as the embedded control module in the FPGA basing on the implementing flow of EIT system. The MCU controls other module, and harmonizes digital modules with periphery circuit to implement the data acquisition function together.In the aspect of experiment, lots of static object imaging and dynamic real-time pulmonary ventilation image reconstruction experiments were performed. Main works are as follow:1. In the static experiment, a cylindrical flume with the diameter near to body circumference was used as the measuring field. Many objects with different diameter and number were be imaged in order to test the resolving power of the EIT system and the feasibility of application in lung respiration function imaging.2. The lung transverse section model was completed and imaged to test the reconstructed imaging quality of the large diameter object such as body's lung. And the experiment further validates the feasibility of application in lung impedance image reconstruction. 3. The image reconstruction experiment related to pulmonary ventilation was performed. The reconstruction image or data related to pulmonary impedance were analyzed and the result truly reflects the corresponding relation between the reconstruction image or data and the impedance changes in lung with different breathing patterns. That proves the feasibility that EIT can be used to reconstruct the functional image of pulmonary ventilation and establishes the foundation for the further research of application in clinic.At the end of the thesis, some improvement suggestions are presented and discussed.