Research On Data Acquisition Technique For Induced Current Electrical Impedance Tomography

Induced current electrical impedance tomography (ICEIT) is a new branch of electrical impedance tomography (HIT). It applies several excitation coils on the boundary of the object. When one of the coils is stimulated by constant alternating current, the magnetic field is established. The current in the object is induced by the magnetic field. The difference of the potential between any electrodes can be measured on the periphery of the object and the data can be used to reconstruct the images.We design and set up a high accuracy ICEIT hardware system with 32 electrodes based on physical phantom. The system consists of phantom, signal source block, power amplifier block, measuring mode setting block, high accuracy amplifier and high speed demodulator. The programs of the acquisition was developed with Visual C++ and NI-DAQ.We bring forward a new method to reduce the additive electromotive force(EMF) in circuit of the electrode leads. By using the twisted pair wire, the additive EMF in the circuit of the electrode leads is reduced to 10% of that of before and the accuracy of the system is improved. It's performance is better than that of other ICEIT systems which had been reported.The accuracy of the final results is better than 0.5% after 1000 measurement data averaged.Applying the variable metric method,we got preliminary images based on physical phantom.Finally, we analyzed the performance and problems of the system anddiscussed the possible methods to improve its accuracy in the further research.