A large-scale study of the ultrawideband microwave dielectric properties of normal breast tissue obtained from reduction surgeries

TLDR

The effectiveness of emerging microwave breast cancer detection and treatment techniques depends on the dielectric properties of normal breast tissue, yet knowledge at microwave frequencies has been limited by gaps and discrepancies in prior small‑scale studies. The study aimed to experimentally characterize the wideband microwave‑frequency dielectric properties of a large cohort of normal breast tissue samples obtained from reduction surgeries at the University of Wisconsin and University of Calgary. The authors performed dielectric spectroscopy from 0.5 to 20 GHz with a precision open‑ended coaxial probe, quantified tissue composition, and fitted a one‑pole Cole‑Cole model to derive median parameters for three adipose‑content groups. Analysis of 354 samples revealed substantial variation in dielectric properties driven by tissue heterogeneity, with no statistically significant difference between within‑patient and between‑patient variability.

Abstract

The efficacy of emerging microwave breast cancer detection and treatment techniques will depend, in part, on the dielectric properties of normal breast tissue. However, knowledge of these properties at microwave frequencies has been limited due to gaps and discrepancies in previously reported small-scale studies. To address these issues, we experimentally characterized the wideband microwave-frequency dielectric properties of a large number of normal breast tissue samples obtained from breast reduction surgeries at the University of Wisconsin and University of Calgary hospitals. The dielectric spectroscopy measurements were conducted from 0.5 to 20 GHz using a precision open-ended coaxial probe. The tissue composition within the probe's sensing region was quantified in terms of percentages of adipose, fibroconnective and glandular tissues. We fit a one-pole Cole-Cole model to the complex permittivity data set obtained for each sample and determined median Cole-Cole parameters for three groups of normal breast tissues, categorized by adipose tissue content (0-30%, 31-84% and 85-100%). Our analysis of the dielectric properties data for 354 tissue samples reveals that there is a large variation in the dielectric properties of normal breast tissue due to substantial tissue heterogeneity. We observed no statistically significant difference between the within-patient and between-patient variability in the dielectric properties.