Dielectric tissue measurements using a co-axial probe with a quarter-wave choke

As part of a programme to develop combined microwave and thermal computational modelling of body tissue regions, it is necessary to compare thermal conductivity and dieiectric permittivity measurements made on the same tissue samples. This paper is primarily concerned with the design and calibration of a suitable co-axial probe, and the dielectric measurements made with this probe. These permittivity measurements are made at 3 GHz, the frequency corresponding to the minimum loss tangent in water, which is the substance whose properties have the greatest influence on the overall thermal and dielectric properties of body tissue. Permittivities of a variety of animal tissues were measured. Porcine tissues form the greatest category as pork most closely resembles human tissue in constitution. A table listing selected average results where the standard deviation is simply that of the scattering is given. This data is comparable with that reported in Brady et al. (1981) and Burdette et al. (1980). Although the reported data was taken at 37 degrees C rather than 21-25 degrees C, tests have shown that the difference incurred is less than the calibration error reported.