Adaptive Mesh Generation Method Based On Boundaries Of 2D Arbitrary Polygon In EIT

Electrical impedance tomography is a novelty imaging technique. It reconstructs the internal impedance distribution by the electrical parameter measurements made on the electrodes placed on the surface of the organism. Since the organism has different impedance distribution under the different condition,the reconstructed image can reflect the state of the organism and provides useful information for medical diagnosis. The advantages such as the functional imaging,non-invasive modality and the relative low cost make EIT become a research hot in medical imaging.Image reconstruction in EIT is a difficult problem because of the ill-posedness and non-linearity. But it is reported that the result of EIT image is not good, because most reconstruction models are based on round boundary and the inner boundary is not considered. Otherwise, well-proportioned grids are meshed in the model. These lead to reconstruction errors. Then EIT is not applied to clinic. Fourth Military Medical University EIT group put forward and made a breakthrough in EIT real-time dynamic image guardianship. Pathological changes of brain and abdomen could be location and displayed by our research. But there are problems in the research: the image border is not clear enough and range is too vast.So an adaptive mesh refinement method based on boundaries of arbitrary polygon in EIT reconstruction is proposed. Then the realistic body boundaries are considered, and grids at boundary are densely meshed while other grids are sparsely meshed. EIT image is promoted based on the FEM model.This dissertation mainly studies the adaptive mesh refinement method with the aim of increasing precision and spatial resolution of EIT .The construction of realistic finite element method (FEM) model and EIT image applying in clinic is researched in this paper. Works are done as follows:1) The method for adaptive mesh refinement model based on boundaries of arbitrary polygon in EIT is carried out. This method is based on the mesh arithmetic and data structure. It is convenient for the realistic FEM model building when the boundaries of human body are got. The quality of adaptive mesh is better compared with general mesh. Distinct impedances variety is cared with fewness mesh in the adaptive model, so EIT image quality can be promoted.2) The software of Adaptive Mesh Refinement is developed. It is programmed with Visual C++.NET and software functions are introduced in detail. We can control the mesh size from changing the mesh dimension and density.3) Adaptive mesh software is embedded in EIT system. Firstly, forward problem is calculated compared with COMSOL and veracity is close to COMSOL. Secondly EIT reconstruction is carried out. The AMR model and round model are compared from different aspects, and the AMR model shows that precision and spatial resolution of EIT are increased. Last, software is applied to animal experiments and clinical imaging monitor. The result shows that AMR is good at location of Perturbation target, and provide a possibility for EIT-CT amalgamation.The research of adaptive mesh refinement method based on boundaries can promote EIT image quality. It is applied to animal experiments and clinical imaging monitor and the result is good. It establishes the foundation for further works.