| We studied reconstruction and measurement methods for electrical impedance tomography (EIT). EIT is a noninvasive imaging method where currents or voltages are applied to a conductive medium, and the resulting voltages or currents are measured. Based on these measurements, EIT reconstructs the conductivity distribution within.; We divided our work into four chapters and one appendix. In chapter one we extensively reviewed six reconstruction techniques for EIT: backprojection between current streamlines and voltage paths, Newton's method, perturbation, reconstruction based on the lead sensitivity theorem, and a double constraint method. We discussed some practical considerations in an EIT implementation: the number of unique measurements, resolution limits, hidden objects, and measurement techniques.; In chapter two we proposed an improved method of backprojection based on the perturbation technique for EIT. This improvement, which was based on simultaneous rather than sequential corrections, reduced the reconstruction error from 2.1 to 0.4.; In chapter three we discussed how we designed and built an impedance camera for EIT using the two-electrode measurement technique and a physical impedance-phantom. The electrode contact impedance prevented satisfactory image reconstruction, but a voltage-clamp system reduced the contact impedance from 2400 (OMEGA) to 10 (OMEGA).; In chapter four we derived an optimal EIT reconstruction algorithm. We based our algorithm on a modified Newton-Raphson algorithm and finite element method. We derived two methods for calculating the Jacobian matrix: the standard method, and a compensation theorem method. We compared results from two-dimensional reconstruction simulations with four other reconstruction methods. In the absence of noise, the modified Newton-Raphson method converged to virtually zero error. The four other methods and their error were: perturbation (0.25), equipotential (0.78), iterative equipotential (0.2), and double constraint (0.58).; In an appendix we presented a tutorial on the reconstruction methods for EIT. |
