In-vivo dielectric properties of the human oral cavity at microwave frequencies

Abstract

The aim of this investigation was to study the interaction between low-power electromagnetic fields and different tissues within the oral cavity, given by the complex permittivity. In recent years, there have been many research efforts to use electromagnetic fields for medical applications and up-to date different diagnostic and therapeutic modalities in dentistry use ionising radiation, mostly X-rays. This project addresses gaps in knowledge required to develop novel microwave medical devices for diagnosis for imaging and treatment of mouth lesions such as tumours by conducting measurements of the complex permittivity. In particular, this study reports on the in-vivo dielectric measurements of six different areas in the oral cavity, mainly the dorsal (upper-surface of the tongue), ventral (lower surface of the tongue), left and right sides, the tip of the tongue and lips. A rigorous measurement procedure was implemented and in-vivo measurements were conducted on 25 patients from different age groups. It has been observed that even though in dentistry different areas are used to distinguish between different parts of the tongue, there exist no difference in the dielectric data of these different areas. In fact, no dielectric difference was established when comparing ventral and dorsal tissues, left and right sides, and tip and thus the dielectric properties of the tongue can be referenced by one value, calculated by considering a grouped average of the different areas. Additionally, the incidence of different clinical conditions in the oral cavity depends mostly on age of patients, smoking/non-smoking and gender. In this study, the dielectric data was analysed for different patient ages and it was observed that there exists a difference between the dielectric data measured for 40-50 years age group and the 60+ years age group. The latter have higher complex permittivity for tongue, but lower values for lips. The complex permittivity for lips of 20-30 years age group was lower when compared to other age groups. This can be attributed to the extremely low values of two patients having different ethnicity in the group. A study with a larger is planned to better understand the correlation of dielectric data with the various confounders.