An improved data acquisition method for electrical impedance tomography

Isaacson, Cheney and Seager have demonstrated that simultaneously applying trigonometric patterns of current to a circular electrode array optimizes t he sensitivity of EIT to inner structure. We have found that it is less des irable to measure voltage at an electrode that also applies a current due t o variable contact impedance. In order to preserve the optimum sensitivity while minimizing the effect of electrode artefacts, we have devised an appr oach where we sequentially apply a current between each individual electrod e and a separate, fixed ground while measuring voltages at all other electr odes for each consecutive current impulse. By adding weighted sums of both the applied currents and corresponding measured voltages from individual pa sses, we can synthesize trigonometric patterns of any spatial frequency. Si nce only one of the electrodes in any given acquired data set is used as a source, this approach significantly dilutes the effect of contact impedance on the resulting voltage measurements. We present simulated data showing t he equivalency between the synthesized and actual trigonometric excitation patterns. In addition, we report experimental data, both in vitro and in vi vo, that show improved results using this data acquisition technique.