Permittivity measurement of biological tissues using interdigital capacitor based resonator

Abstract

A CPW resonator etched on the central conductor is presented to measure the complex permittivity of biological tissues. In the unloaded condition, the proposed structure works as a resonator with a resonant frequency of 5.625 GHz. The proposed sensor is able to cover a wide range of permittivity measurement from approximately 5 (fat tissue) to 70 (malignant tissue) with sensitivity of 4.01 % and FDR( Frequency Detection Resolution) of 270 MHz . Breast phantoms with high fidelity need to be fabricated to imitate the various layers of the breast like skin, fat, glandular tissue, and tumor tissue regarding permittivity with different chemicals in different proportions. The major challenge in fabricating such phantoms is in creating an appropriate combination of substances to get the required characteristics for these biological tissues. A sample of various tissue types was fabricated using Gelatin and safflower-based recipes. The complex permittivity tissue phantoms are measured using a fabricated resonator. The measured dielectric characteristics of biological tissues are in good agreement with the theoretical values from the database.