Progettazione di un device di imaging tomografico, basato su principio impedenziometrico, per la valutazione di cicli cardio-respiratori in atleti

Electrical impedance tomography (EIT) is an imaging modality wherein the spatial map of conductivity and permittivity inside a medium is obtained from a set of surface electrical measurements. Electrodes are brought into contact with the surface of the object being imaged and a set of currents are applied and the corresponding voltages are measured. These voltages and currents are then used to estimate the electrical properties of the object using an image reconstruction algorithm which relies on an accurate model of the electrical interaction. The process of property estimation, called inverse problem, is highly nonlinear, ill-conditioned, and ill-posed. Reconstruction of the electrical properties distribution is an under-determined problem requiring a regularization method. The objective of this thesis was to develop a device for EIT imaging, which could be convenient, portable, inexpensive, noninvasive and easily programmable. A simple EIT system and its hardware parts has been developed. A belt with 32 electrodes in circular and planar geometry was built for two dimensional samples. The developed device provides current less than 1mA with frequencies higher than 60KHz. This are safe value for human body. The data processing was accomplished by utilizing a web site for the solution of EIT inverse-problem reconstruction. A series of images has been produced to evaluate the performance of the hardware developed. The difficulties in EIT image reconstruction, mainly due to the fact that the illposedness of the EIT reconstruction problem renders the solution sensitive to measurement errors and noise. Experiments have indicated that the EIT system can reconstruct resistive images of good contrast, with adequate robustness towards experimental fluctuations.