Flexible, Segmented Tubular Design With Embedded Complementary Split-Ring Resonators for Tissue Identification

Abstract

Due to the worldwide increasing incidence of colorectal cancer, more and more focus is shifting towards methods for the early detection of polyps in the colon. In this work, we present a technique and a design to use dielectric spectroscopy with microwaves to assist in the early detection of colorectal cancer. A flexible, tubular design with six different segments was manufactured on a thin polyimide substrate. This design can be slid over an endoscope and used as a cap-assisted endoscopic attachment. Three different complementary split ring resonators were implemented into this design. When the design is deployed, the segments expand such that the sensors directly contact the colon tissue, even for varying colon diameters. The sensor behavior proved to be stable at different dilation levels and a sensitivity of up to 20.6 MHz per a.u. of permittivity was achieved over a broad permittivity range. Additionally, frequency multiplexing of different sensors was implemented to increase the sensor count while restricting the number of interconnections. Furthermore, several biological tissue samples, with a close resemblance to colorectal tissue, were measured with this design and were correctly identified. At last, a low-cost measurement implementation, that tracks the insertion loss of the sensors, was proposed to replace the expensive microwave lab equipment and a strong correlation was achieved between both measurement setups.