Minimally Invasive Lung Tissue Differentiation Using Electrical Impedance Spectroscopy: A Comparison of the 3- and 4-Electrode Methods

Multiple imaging techniques are used for the diagnosis of lung diseases. The choice of a technique depends on the suspected diagnosis. Computed tomography (CT) of the thorax and positron emission tomography (PET) are imaging techniques used for the detection, characterization, staging and follow-up of lung cancer, and these techniques use ionizing radiation and are radiologist-dependent. Electrical impedance spectroscopy (EIS) performed through a bronchoscopic process could serve as a minimally invasive non-ionizing method complementary to CT and PET to characterize lung tissue. The aim of this study was to analyse the feasibility and ability of minimally invasive EIS bioimpedance measures to differentiate among healthy lung, bronchial and neoplastic lung tissues through bronchoscopy using the 3- and 4-electrode methods. Tissue differentiation was performed in 13 patients using the 4-electrode method (13 healthy lung, 12 bronchial and 3 neoplastic lung tissues) and the 3-electrode method (9 healthy lung, 10 bronchial and 2 neoplastic lung tissues). One-way analysis of variance (ANOVA) showed a statistically significant difference (P < 0.001) between bronchial and healthy lung tissues for both the 3- and 4-electrode methods. The 3-electrode method seemed to differentiate cancer types through changes in the cellular structures of the tissues by both the reactance (Xc) and the resistance (R). Minimally invasive measurements obtained using the 3-electrode method seem to be most suitable for differentiating between healthy and bronchial lung tissues. In the future, EIS using the 3-electrode method could be a method complementary to PET/CT and biopsy in lung pathology diagnosis.