Medical Diagnostics Using Re∞ection Method and Waveguide Probes | Feasibility Study

Paper deals with the complex permittivity measurement of biological tissues. Ap- plication of a waveguide probe for this measurement is shown. A non-destructive and non-invasive method based on re∞ection coe-cient measurement attaching the material under test is used. New types of the probes are under investigation | the section of waveguide with H cross-section, the section of waveguide with the rectangular cross-section and with shorted walls, the section of waveguide with inserted dielectric wedge and flnally the section of waveguide fllled with the liquid dielectric. Properties of these prototypes are studied in the frequency range from 300kHz to 3GHz. The method of flnite difierence in time domain is utilized for the numerical modeling and simulation of the re∞ection coe-cient. The condition for the input re∞ection coe-cient of the waveguide probe is the range from (0.7{0.3) in the broad frequency band. Although the waveg- uide is a narrowband microwave component, its modiflcations could have broadband frequency behavior of the re∞ection coe-cient. Results indicate that the most interesting and suitable is the solution with removable dielectric. This liquid dielectric with the low value of permittivity has signiflcant in∞uence on the cut-ofi frequency of waveguide with dominant mode propagation. The knowledge of dielectric parameters of materials is essential for microwave or radio engineers in analysis and synthesis of devices. Relative permittivity, loss factor and conductivity are input parameters for electromagnetic fleld modeling and simulations. Although for many materials these parameters could be found in the tables, very often their experimental determination is necessary. Dielectric properties of biological tissues are determining factors for the dissipation of elec- tromagnetic energy in the human body and therefore they are basic parameters in hyperthermia cancer treatment. Measurement of the dielectric parameters of biological tissues is also a promis- ing method in the medical diagnostics and imaging. Knowledge of the complex permittivity in an area under treatment, i.e., knowledge of the complex permittivity of healthy and tumor tissue, is very important for example in the diagnosing of tumor cell-nests in the human body or in the design of thermo-therapeutic applicators which transform electromagnetic energy into thermal in the pathological tissue (1).