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High precision Multifrequency Electrical Impedance Tomography System and Preliminary imaging results on saline tank

To establish a high precision data acquisition system for multi-frequency electrical impedance tomography (EIT), a series of methods were introduced. Those methods include building a driving signal with up to four frequency components to diminish the effect of the dynamic change of tissues resistivity, extracting the impedance information by a digital demodulator that can improve the SNR by 8 times. The system that established can work at a wide range from 1.6 kHz to 380 kHz. Its CMRR is 74 dB at 100 kHz. The output impedance of current source is 2 MOmega at that frequency. And measurement precision on a 100 ohm resistor is better than -80 dB in full bandwidth. Both the quasi-static and the dynamic imaging results based on a saline tank can reflect the resistivity changes inside the phantom clearly. Therefore, the system was competent in multifrequency EIT research work