Dielectric Properties of Healthy Ex-Vivo Ovine Lung Tissue at Microwave Frequencies (original) (raw)

IEEE Transactions on Dielectrics and Electrical Insulation

Knowledge of dielectric properties of lung tissue is fundamental for the improvement of lung disease diagnostics and therapeutic solutions (e.g. microwave imaging and microwave thermal ablation 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, 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 lung tissue of different density is 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. Index Terms-Cole-Cole model fitting, dielectric spectroscopy, lung tissue air content, lung tissue dielectric properties, open-ended coaxial probe I. INTRODUCTION NOWLEDGE of tissue dielectric properties is paramount in various electromagnetic-based medical applications such as diagnostics, therapy, dosimetry, and monitoring. A diagnostic and monitoring technique relying on dielectric properties knowledge is Microwave Imaging (MWI) [1]. MWI determines the position of healthy and malignant tissue based on contrast in dielectric properties. Examples of its use from the literature are in the liver [2], and lately, in lung tissue [3]. A therapeutic technique that benefits from an accurate knowledge of the dielectric properties is microwave thermal ablation (MWA) [2], [4], [5]. While tissues such as liver [5]-[7], heart [6], muscle [5], [6], [8], and breast tissue [9] are well characterized, lung tissue remains insufficiently studied in the microwave range due to handling difficulties and tissue heterogeneity [6]. Nevertheless, the number of lung diseases diagnosed yearly is continuously rising, the incidence of lung cancer is second This research was funded by Government of Ireland, Disruptive Technology Innovation Fund (DTIF), grant number DT2020189. K. Vidjak and M. Cavagnaro are with the