| Electrical Impedance Tomography (EIT) is a novel technique of functional imaging, coming forth in recent two decades after the appearance of morphological and structural imaging. In light of the physical principle that different tissues have different bio-electrical impedance, images of biological impedance distribution could be reconstructed by injecting safe currents into body and measuring electrical potentials on the body surface. With the feature of low-cost, non-invasiveness, non-radioactivity, and relatively high temporal resolution and sensitivity, it is possible to apply the bedside monitoring for patients in clinical.Our EIT group developed EIT monitoring system for cerebral injury (CI). In previous research, we used EIT system to have carried out many clinical monitoring for patients and found it is possible to monitor the change of brain tissue. But we also found some problems needing to solve.1) Electrode system is likely to be affected by the electromagnetic disturb. 2) The electrode structure is so complicated that it is different to place. 3) The amount of clinical data is so large that it is difficult to record and manage. 4)Different type of Ag/AgCl electrodes used for EIT have different performance in practice,it is necessary to compare them and find the best. 5)In clinical patients with serious conditions are difficult to monitor with traditional monitoring method.The concrete work of the research is as follows:1. Improvement of electrode lead system. When used in practice, the electrode system can be affected by complicated magnetic environment. Therefore, we improved the electrode through wrapping shield net. Besides, we changed the electrode as an electrode belt to make the application convenient in clinical.2. Selection of electrode. In order to choose the good performance electrode applied in clinical, six types of Ag/AgCl electrode were compared in term of four indicators, contact impedance, uniformity, SNR and stability.3. Design of database management system. Develop the system to record and analysis clinical experimental data, making experimental record more convenient.4. Monitoring research for patients of CI. In clinical, we applied the EIT system to monitor the patients of CI to detect the change of impedance for brain tissue. Through judging the change impedance, we can find the change of patients? condition timely and get more time for patients? therapy. Because EIT techique is sensitive for the funtional change of tissue. Therefore, we attempted to do some research with EIT system for patients with serious conditions and made the following studies. 1) Clinical experiment. In clinical, we applied EIT system to monitor the patient with CI to confirm the feasibility of EIT used in clinical and analysis the specificitied change . 2) Animal experiment. We injected collagenase to the intracalvarium of New Zealand rabbit to set the model of patients in critical stage and we used EIT system to monitor the process.The results show that1. The performance of anti-noise for electrode system improved a lot after mending, SNR improved from 70dB to 90dB, and the adherence of electrode became more convenient, saving about 7 minutes.2. The application of database software made the management of experiment data easier.3. Through analysising the experiment data of 3 patients with CI, we found the specificitied change and carried out animal experiment to conform it .4. To prove the correctness of results for clinical experiment, we applied EIT system to monitor the rabbits modeled with CI. As a result, the change of brain tissue in animal experiment is in accord with the change in clinical experiment.In this research, the property of electrode system was improved after comparison and mending with the performance of small contact impedance, high SNR and good uniformity and stability. Finally, the data collected by EIT system were more precise.It was proved that our bedside EIT monitoring system has the feature of practicability sensitivity and accuracy through the animal and clinical experiment.And it can detect the change of patients? condition through monitoring the change of brain tissue impedance. Meanwhile, it also showed the application of our EIT system for clinical is feasible. |
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