Sensitivity and Sensing Depth Analysis of Open-ended Contact Probes for Cancer Diagnosis

Open-ended contact probes have been widely utilized in laboratory environment to quantify the dielectric properties of high permittivity and lossy materials such as biological tissues and other lossy liquids. At microwave frequencies, the dielectric properties of biological tissues have been quantified with open-ended contact probes method with the motivation of building microwave diagnostic and therapeutic technologies. The method is preferred to other microwave dielectric property measurement techniques due to broadband measurement capabilities and minimal sample preparation requirements. However, the measurement procedure is cumbersome and the measurements tend to be error-prone. The commercial probes can have error rates as high as 5% and it can increase with the cable movements, calibration degradation, and probe wear-off. Although the technique is powerful and able to measure the inherent dielectric property discrepancy between different tissues the applications are confined to laboratory use. To explore the true potential of this technique and enable the transition of this technique to a diagnostic technology, there is a need to improve the technique and analyze the performance in a layered heterogeneous medium. In this work, we performed simulations and measurements with open-ended contact probes having different aperture diameters. The probes are built with copper and Teflon sandwiched between inner and outer conductors. Measurements with open-ended coaxial probes are performed on layered medium emulating the dielectric properties of the biological tissues to analyze the sensing depth and sensitivity of four in-house fabricated open-ended coaxial probes. An in-house algorithm is utilized to retrieve the dielectric properties of the mediums utilized during this study.