Effect of Open-Ended Coaxial Probe-to-Tissue Contact Pressure on Dielectric Measurements

Sensors

Bart Nauwelaers¹  Gertjan Maenhout¹  Tomislav Markovic¹  Ilja Ocket² 

[1] Division Telemic, Department of Electrical Engineering (ESAT), KU Leuven, Kasteelpark Arenberg 10, Box 2444, 3001 Leuven, Belgium;imec, Kapeldreef 75, 3001 Heverlee, Belgium;

关键词: dielectric measurement;    contact pressure;    biological tissues;    measurement metadata;    open-ended coaxial probe;   

DOI  :  10.3390/s20072060

来源: DOAJ

【 摘 要 】

Open-ended coaxial probes are widely used to gather dielectric properties of biological tissues. Due to the lack of an agreed data acquisition protocol, several environmental conditions can cause inaccuracies when comparing dielectric data. In this work, the effect of a different measurement probe-to-tissue contact pressure was monitored in the frequency range from 0.5 to 20 GHz. Therefore, we constructed a controlled lifting platform with an integrated pressure sensor to exert a constant pressure on the tissue sample during the dielectric measurement. In the pressure range from 7.74 kPa to 77.4 kPa, we observed a linear correlation of $-0.31\pm 0.09$ % and $-0.32\pm 0.14$ % per kPa for, respectively, the relative real and imaginary complex permittivity. These values are statistically significant compared with the reported measurement uncertainty. Following the literature in different biology-related disciplines regarding pressure-induced variability in measurements, we hypothesize that these changes originate from squeezing out the interstitial and extracellular fluid. This process locally increases the concentration of membranes, cellular organelles, and proteins in the sensed volume. Finally, we suggest moving towards a standardized probe-to-tissue contact pressure, since the literature has already demonstrated that reprobing at the same pressure can produce repeatable data within a 1% uncertainty interval.

【 授权许可】

Unknown