One-dimensional Information Extraction And Analysis For Electrical Impedance Tomography

Electrical Impedance Tomography(EIT),a new type of functional imaging technology, is becoming a matter of concern for more and more people. Because it is a noninvasively, convenient, harmless and inexpensive technology, and it can do monitoring bedside ,which is long-term and real time dynamics. EIT group of FMMU made breakthroughs in early preliminary research work and developed a EIT system by themselves, especially do some clinical experiments on particular patients.In clinical applications, EIT imaging can monitor physiological and pathological change and locate the position.Primary research has showed that the dynamic EIT imaging system is able to subtly reflect electrical impedance changes within human body caused by pathological changes. However, with the depth of clinical research and the aim of better application of clinical care, the existing dynamic EIT imaging system requires improvements as follows: 1. information extraction based on dynamic EIT images; 2. simple, intuitionistic and real-time monitoring of the overall trend of electrical impedance change using the extracted information; 3. combination of the extracted information and dynamic EIT images so that they can complement each other. Data analysis of dynamic EIT imaging shows that one-dimension monitoring of electrical impedance is relatively simple, intuitionistic and convenient. It is able to subtly reflect the overall electrical impedance change of the object to be monitored. Also, it can provide real-time trend of the overall electrical impedance change and hold the possibility of a quantitative assessment towards the change. If the one-dimension information of electrical impedance can be extracted and analyzed based on the dynamic EIT imaging system and the two approaches can be used in combination, both real-time monitoring of the change of dynamic EIT images and intuitionistic observation of the trend of the overall electrical impedance change can be achieved. Thus EIT can be better applied to clinical research.In order to address these issues and improve clinical applications, we will find a 1-D index of EIT from the process of EIT imaging, which has high sensitive for the whole internal resistivity change. And do some experiments test and verify the sensibility of this index. The research were done as follows:(1) Find a index of EIT base on EIT imagingImage reconstruction in EIT has two parts: one is forward solver and the other is inverse solvers. Through the process of two parts, we find voltage measurements made on the surface has high sensitive for the whole internal resistivity change. From this relationship we find a 1-D index of EIT, which is obtained by the result of the sum of voltage measurements made on the surface devided by injected current. This index is called one dimension impedance (ODI) of EIT and is shown in the form of curve with the EIT images. The new system has complementary advantages.(2) Test and verify ODIIn order to test and verify the sensibility of ODI, We do some experiments which contain simulation experiments based on FEM model and physical model, human subjects experiment, clinical experiments.In the experiments based on FEM, we change the position and area of impedance target. The results indicated that ODI curve is sensitive to these changing. At the same time EIT images can give some information about the position of impedance target.In the experiments based on physical model, we design a hemispherical tank which is filled with NaCl solution and simulate cranium brain. A agar block is used as impedance target. The result is consistent with the FEM model.In the human subjects experiment, we monitor ODI and EIT image on the cranium brain when people change their body posture. In this process the whole internal brain resistivity is changing,. ODI curve has obvious trend but EIT images changing is not obvious, because EIT imaging has less sensitive for the whole internal resistivity change.According to the characteristic that one dimension impedance (ODI) is sensitive to the overall electrical impedance change, cases of mannitol-induced hydration treatment and burr hole craniostony with closed-system drainage are selected to be monitored in clinical trials. By analyzing the data from mannitol-induced hydration treatment, it is found that ODI is able to provide a simple, intuitionistic and real-time reflection on the trend of the overall electrical impedance change in the brain in the process. In addition, the fluctuation of the ODI curve coincides with the effect period of mannitol, which provides evidence to the effect of mannitol-induced hydration. In the process of burr hole craniostony with closed-system drainage, the dynamic EIT images provide a real-time reflection on the electrical impedance change caused by cerebral hematoma drainage, while ODI curve correspondingly displays a real-time trend of the overall electrical impedance change. Thus the advantages of the two approaches can be complementary to each other.From a series of experiments , we have tested and verified the sensibility of ODI, The new system which contain ODI curve and EIT image has complementary advantages and broad clinical prospects.