The Effect of Pressure of the Open-ended Coaxial Probe on the Measurement of Ex Vivo Biological Tissues Dielectric Properties

The impact of increasing evenly spaced pressures, between 2.58 and 25.8 kPa, on dielectric data ranging from 0.5 to 8.5 GHz was studied using 1 × 1 × 1 cm
³
and 2 × 2 × 2 cm
³
of bovine liver and chicken muscle samples. Results show a reduction exceeding 15% in tissue dielectric properties as pressure increased, until a breaking point is reached, and the trend reversed. The initial decline of dielectric properties aligns with existing literature, which suggests intracellular and interstitial fluid displacement due to probe pressure. We propose that the subsequent increase of dielectric properties may result from cellular membrane rupture, driving water towards the sample surface. Hence, maintaining consistent probe-tissue pressure during measurements is imperative to minimise data inaccuracies. We recommend conducting preliminary pressure tests prior to measuring biological tissue dielectric data. Moreover, we endorse the inclusion of applied pressure details in measurements metadata.