Research On Wireless MEIT System And Image Improvement

Electrical impedance tomography (EIT) is an attractive imaging technique which aims to estimate the interior conductivity or resistivity distribution of an unknown object. In EIT, an array of electrodes are attached to the boundary of an object, safe alternating currents are injected through electrodes, and the resulting voltages are measured to reconstruct the distributions using specific algorithms. Compared to the conventional medical imaging techniques, such as X-ray computerized tomography (CT) or magnetic resonance imaging (MRI), EIT has the advantages of low cost, no radiation and easy portability and suitable for clinical monitoring applications.Threshold strategy is a kind of post processing method with merits of easy, direct and efficient. In this paper, the threshold strategy is described corresponding to three different conditions by Gauss-Newton algorithm and filter back-projection algorithms separately. The threshold value is varied with algorithms and conditions. The simulation results indicate the image’s quality improved evidently. In order to evaluate the improvement, two performance targets, image reconstruction error and correlation coefficient, are calculated. The image and data show that threshold strategy is verified effective and achievable.A set of MEIT system based on wireless transmission technology is designed to measure the boundary voltages, which is carried out through an integrated chip AD5933 and a microcontroller with peripheral circuits. The system is composed with data acquisition module, analog switch array module, and wireless communication module. The characteristic is tested by over hundreds of measurements, and the signal-to-noise ratio is attained up to 69dB. The images are reconstructed and improved through the approach developed in this thesis, and the imaging effect is well.This paper has the following three innovation points:first, a simple but effective method is put forward to improve image quality; second, a compact and integrated MEIT system is completed with satisfied targets; thirdly, wireless communication technology is adopted to avoid the transferring noises. The achievements in this paper play a pushing role to make EIT more suitable for clinical application.