Low-Dose X-Ray-Induced Changes in Rat Skin Dielectric Properties and Microstructure: A Cole-Cole and SEM Study

Abstract

In soft tissues, low-dose ionizing radiation produces subtle, subclinical radiochemical and structural changes that frequently go undetected by conventional histopathological methods. The low-frequency (20 Hz–20 kHz) dielectric shifts and microstructural abnormalities in healthy versus X-irradiated (0–5.25 mGy) albino rat skin are measured and modelled in this study. A bespoke parallel-plate sample cell was used to analyze ex vivo skin tissue at 37 °C. Cole-Cole parameters were retrieved and associated with 3D axisymmetric COMSOL Multiphysics X-ray beam propagation simulations and surface topographies from scanning electron microscopy (SEM). Core capacitive parameters underwent a monotonic collapse as a result of X-ray irradiation. A significant decrease in static permittivity (εs from 22.84 to 7.29) and a similar decrease in dielectric strength (∆ε) were noted at 5.25 mGy, indicating reduced polarization as a result of structural protein denaturation. At the same time, typical relaxation periods (τ) decreased from 41 to 14 µs, suggesting that macromolecules were breaking up into smaller, quickly reorienting dipolar units. A change from a loose, healthy fibre web to a compacted, fragmented matrix was verified by SEM. Peak energy deposition (~8 J/kg) was localized by COMSOL simulations close to a 3 mm focal depth. By jeopardizing membrane integrity, low-dose radiation significantly impairs skin macroscopic bioelectrical properties, facilitating the creation of non-invasive bioimpedance sensors.