Ex-vivo Identification of Tumor from Parenchyma in Human Liver using Electrochemical Impedance Spectroscopy on a Needle

Percutaneous ethanol injection for hepatocellular carcinoma and biopsy for pathological examination of lesions in the liver are widely performed using a fine needle under ultrasonography guidance. However, it is often difficult to distinguish a malignant tumor from a parenchyma via ultrasonography. This study proposes a method for identifying a malignant tumor in the liver using coplanar bipolar electrodes fabricated on a fine needle, called electrochemical impedance spectroscopy on a needle (EoN). The electrical impedances of the malignant tumor and parenchyma were measured in two pathological statuses, more specifically in human ex-vivo normal liver and in human ex-vivo cirrhotic liver. Statistically significant differences in the electrical impedance between the malignant tumor and parenchyma in each pathological status were observed in a frequency range of 0.46MHz to 1MHz (p < 0.05). Given a real-time measurement in clinical trials, the optimal frequency suggested was indicated by the largest value in the discrimination index between the malignant tumor and the parenchyma. The electrical properties (conductivity and permittivity) of the tissues were estimated to generalize the sensor output without regard to the dimension and shape of the electrodes. The values of the electrical properties of cancer in the cirrhotic liver and normal liver were significantly higher than those of each parenchyma. These experimental results imply that EoN can be used as a potential tool for identification of malignant tumors in the liver during percutaneous ethanol injection and fine needle aspiration procedures.