Radiation-induced alterations in the dielectric features of irradiated tissues

In this study, we investigated the dielectric characteristics of the brain, lung heart, liver, spleen and kidney that were either directly irradiated or were abscopal to the irradiated region, in an attempt to utilize the physical tool of dielectric spectroscopy to identify the biological effects of ionizing radiation. The dielectric analyses were performed for 1-2 mm thick freeze-dried samples, of the different organs, sandwiched between two brass electrodes at room temperature in the frequency range 0.1-10⁷ Hz. The results show notable modifications in the dielectric properties of the liver of the whole body irradiated group (WB) and the kidney of lower-limb (LL) and cranially (CR) irradiated groups. The data show increase in the imaginary electric modulus M^'' and decrease in the permittivity and AC conductivity in the heart and brain of all of the irradiated groups. The data show a general trend of increase in the conductivity of the liver of WB and the kidney of CR and LL groups. The Cole-Cole plot (M^'' vs. M^'), as a good depiction of the dielectric behavior of the tissues, show differential response of the different organs. The expansion of loss tangent peaks indicates relaxation dispersion with a steady relaxation time distribution for the liver, kidney and lung. The extended relaxation periods and frequency shifts to lower values results indicate variation in the rigidity of biological macromolecules in the liver, lung and kidney only. The experimental data suggest induction of abscopal effect occur in the liver, kidney, lung than heart, brain and spleen.