Dielectric Properties of Healthy Ex Vivo Ovine Lung Tissue at Microwave Frequencies

Knowledge of dielectric properties of lung tissue is fundamental for the improvement of lung disease diagnostics and therapeutic solutions [e.g., microwave imaging (MWI) and microwave thermal ablation (MWA) treatment]. Although lung disease rates are increasing, lung tissue remains one of the least characterized tissues due to its heterogeneity, variability in air content, and handling difficulties. In this work, the dielectric properties of ex vivo ovine lung tissue samples were measured in the frequency range 500 MHz-8 GHz, together with measurements of sample density (air content). Different Cole-Cole models were applied to the measured dielectric properties values. The best fitting model was chosen, and results were compared with available literature. Furthermore, the dielectric property measurements were correlated with the air content of the samples. Updated Cole-Cole models for the lung tissue of different densities are provided in the 500 MHz-8 GHz range. The existence of air content threshold in lung is shown. Below this limit, the properties begin to change drastically with the change in density.