Sensing Radius of an Open-Ended Coaxial Probe for Dielectric Measurement of Tissues: Calculation with Relative Permittivity versus Conductivity

The dielectric properties of biological tissues are important parameters used in the design and optimisation of electromagnetic-based medical technologies. Typically, these parameters are measured ex-vivo using the open-ended coaxial probe technique. However, the accuracy of such reported dielectric data can be impacted by confounders in the measurement process. Strategies are needed to control and compensate for these confounders, which could contribute to uncertainty or error in dielectric measurements, especially for complex heterogeneous tissues. Therefore, this work examines a key source of error in the interpretation of dielectric properties. Specifically, this work investigates the sensing radius of a coaxial probe in the context of heterogeneous tissue measurements. The sensing radius is calculated for different simulated heterogeneous breast tissue samples, and the impact of using relative permittivity in the calculation of the sensing radius versus using conductivity is examined.