Initial Characterization of Healthy and Malignant in vivo and ex vivo Human Colon Tissues under Surgery Procedures

TL;DR

The paper addresses the problem of distinguishing malignant from healthy colon tissue via dielectric properties measured during surgery. It employs an open-ended coaxial probe with a vector network analyzer to measure complex relative permittivity $\fr(f)$ in the range $0.5$–$26.5$ GHz, fitting a two-pole Cole-Cole model $\varepsilon_r(f)=\varepsilon_{\infty}+\sum_{m=1}^{2}\frac{\Delta\varepsilon_m}{1+(j\omega\tau_m)^{1-\alpha_m}}+\frac{\sigma_s}{j\omega\varepsilon_0}$ and analyzing differences $\Delta\varepsilon_r'(f)$ and $\Delta\varepsilon_r''(f)$ between tumor and healthy tissues. While aggregated results show little difference between healthy and tumor tissues, stage-stratified analysis reveals substantial disparities for advanced stages (notably T4b), with real-part differences up to ~7.38 at 18 GHz ex vivo and imaginary-part differences up to ~2.66 at 18 GHz in vivo, reflecting greater exposure of tumor tissue to external measurements. This demonstrates the feasibility of intraoperative dielectric sensing and suggests potential for non-invasive diagnostics, though depth-penetration limits emphasize the need for extended campaigns comparing external and internal colon measurements and validating early-stage detectability.

Abstract

The dielectric characterization of human tissues can play a crucial role in the development of new medical diagnostic tools. In particular, the characterization of healthy and pathological tissues can provide vital information for diagnosis. In this paper, preliminary results from a small-scale measurement campaign conducted in 0.5-26.5GHz during real surgeries on healthy and malignant human colon tissues are presented. Those measurements were carried out externally to the colon, without direct contact to the tumor growing inside the colon. Furthermore, different tumor stages are taken into account. Initial findings reveal that advanced tumor stages are related with increased higher values of dielectric properties in malignant tumor tissues compared to the healthy ones.

Figures (8)

• Figure 1: Open-ended coaxial proble system: VNA (left),open-ended coaxial probe (center) and laptop (right).
• Figure 2: Recreation of measurement carried out in the external wall of the colon.
• Figure 3: Image of the measurement system in an in vivo situation in a surgery. It shows how the cable is protected with a sterile bag to protect the patient (center) and how the probe is inserted through an incision made for the surgery (right).
• Figure 4: Image of the measurement system in an ex vivo situation in a surgery. It shows how the tissue is moved close to the calibrated probe with the help of an small elevator and by hands to make sure good contact between the tissue and the probe.
• Figure 5: Means of the dielectric constant and loss factor of healthy and tumor tissues in ex vivo and in vivo measurements.