Study on Dual-Frequency Imaging of Capacitively Coupled Electrical Impedance Tomography: Frequency Optimization

In this work, a new dual-frequency imaging framework of capacitively coupled electrical impedance tomography (CCEIT) is presented. Unlike conventional single-frequency imaging and recently emerged multifrequency imaging, the dual-frequency imaging adopts two different working frequencies to obtain the real part and the imaginary part of the impedance, respectively. With the real part image and the imaginary part image reconstructed at the two frequencies, the framework further introduces image fusion to obtain the fused image. To achieve the optimal selection of the two frequencies, data collection in a wide frequency range is carried out with a 12-electrode CCEIT sensor, an impedance analyzer, and a computer to obtain the real part and the imaginary part measurements. The multifrequency data are then analyzed in depth, and other two aspects, including the sensitivity distribution and the imaging quality at different frequencies, are also investigated. Research results show that a low working frequency is recommended for the real part, while a relatively high working frequency is recommended for the imaginary part. Within the investigated frequency range of 200 kHz–20 MHz, the working frequencies for the real part and the imaginary part are optimized under the investigated distribution setups. Results of verification experiment show that the proposed framework is effective. Compared with single-frequency CCEIT, dual-frequency CCEIT with the two optimized frequencies has much better imaging performance.