A gradient method used to identify object boundary in EIT image

With the development of electronic technology and image reconstruction algorithm, the quality of EIT image is improved significantly. EIT technology has the potential to be of great value in medical and industrial applications. However, there is very little research about the estimation of anomaly´s boundary from EIT image. The gradient method is proposed in this paper to identify object boundary from EIT image reconstructed by sensitivity conjugate gradient (SCG) algorithm. The performance of gradient method in terms of position error and size error is compared with traditional threshold method at two threshold levels through computer simulation and phantom experiments. The results show that the result of gradient method can cover the anomaly region in investigated situations and rely on very little priori-knowledge, while threshold method can estimate more accurately if the threshold value is set properly based on priori-knowledge. Improper threshold definition may lead to significant error in boundary identification. The pilot study to estimate the location and size of the anomaly from EIT image further completes EIT research and promotes its practical application.