Microwave reflectometry circuits integration with coaxial probe for initial breast tumor detection

A six-port reflectometry (SPR) system was developed to predict the dielectric properties of both tumor and normal breast tissue, intended for medical diagnostic applications. Ensuring precise measurements, the SPR underwent calibration using a well-established four-step procedure, which will be briefly outlined. Afterward, the investigated coaxial probe was connected to the SPR through the calibrated measurement port. Subsequently, the exposed end of the probe aperture was immersed into synthetic samples representing both healthy and cancerous breast tissue to assess the dielectric constant, εrʹ and loss factor, εrʺ across frequencies ranging from 1.5 GHz to 3.3 GHz. The dielectric constant, εrʹ and loss factor, εrʺ were derived from the measured reflection coefficient using a closed-form equation associated with the coaxial probe. An examination was undertaken to compare the performance of a commercially available vector network analyzer (VNA) outfitted with a Keysight 85070E dielectric probe against an SPR-probe system. The comparison was based on analyzing the reflection coefficient magnitude, phase shift, dielectric constant, and loss factor of synthetic breast tissue samples. The study revealed maximum absolute errors of 0.01, 1.07°, 1.12, and 0.75 for the measured reflection coefficient magnitude, phase shift, dielectric constant, and loss factor, respectively. The calibrated reflection coefficient and predicted relative permittivity, εr can be effectively utilized to distinguish between normal (εrʹ < 50) and tumor (εrʹ > 50) breast tissue.