The Age-Dependence of Microwave Dielectric Parameters of Biological Tissues (original) (raw)

Study of Dielectric Properties of Biological Tissues in the Microwave Frequency Range

2009

The complex dielectric constants at room temperature of various goat tissues (liver, muscle, kidney, heart and brain) and corn syrup were measured in the frequency range 1 to 10 GHz with the help of a HP Network Analyzer N5230A. Open ended coaxial cable method was employed for the measurement. The system imperfections are completely avoided by calibrating the system with four known materials and their reflection coefficients were used in the calculation along with the reflection coefficient of the sample. The relaxation frequency in the δ region, spread of relaxation, volume fraction of protein present in tissues are calculated from the measured dielectric data. The dielectric constant of corn syrup samples suggests the feasibility of using corn syrup as a tissue equivalent for microwave imaging applications. Introduction and Scope Electrical properties of biological materials and their interaction with electromagnetic waves have attracted the attention of researchers working in the...

Microwave Estimation of Dielectric Properties of Biological Tissue Under Thermal Modification

Archiv Euromedica

The aim of this study was to estimate changes of tissue dielectric parameters under the action of high temperature. We fixed the shifts of dielectric properties of biological tissue samples, associated with short-time influence of high temperature (600C, 5 min.) in vitro. The dielectric properties of tissues (permittivity - ε and conductivity - σ) were determined using original software and hardware complex for near-field resonant microwave sensing developed at the Institute of Applied Physics of the RAS. The study of these parameters was performed at a depth of 5 mm. It was found that short processing of a biological sample in moderate hyperthermia (600C) leads to significant change of dielectric characteristics of the tissue. This is manifested in a significant decrease in the dielectric permittivity (in 2.48 times for an intact specimen) and conductivity (on 25.3%) of the studied biological sample, due to its dehydration. It was shown that used regimen of heating decreases the pe...

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

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