Frequency-Difference Electrical Impedance Imaging of Cervical Specimens

Screening for cervical abnormalities is crucial to reduce the risk of developing abnormal cells in the cervix. Several pathological methods have been proposed to date, however, they require exhaustive histological examination and time. In this paper, we proposed a method to localize the abnormality by using reconstruction images. The weighted frequency-difference Electrical Impedance Tomography (WfdEIT) method was implemented on three cervical specimens: one normal, one with Cervical intraepithelial neoplasia (CIN) grade 2, and one cancer specimen. A 16-electrode probe was developed to work with an EIT system operated at 2-125 kHz excitation frequencies. Experimental results have shown that the abnormalities in the specimens could be identified in most cases, represented by the positive conductivity changes. The localization of the CIN2 specimen was more accurate than that of the cancer specimen. The conductivities of the transformation zone (TZ) part and the cancer region of the specimens were significantly higher than those of the ectocervical part by 1.5-2.2 times. Interestingly, the tissue in the TZ part had a similar frequency spectrum of conductivity to the tissue with cancer and this caused difficulty to distinguish between them. The TZ region of the specimens in the reconstruction images was always positive in conductivity change in a similar manner to cancer. The abnormality imaging for identifying cancer in the TZ region is then still challenging.