Correlation between the dielectric properties and biological activities of humanex vivohepatic tissue

Abstract

Dielectric properties are vital biophysical features of biological tissues, and biological activity is an index to ascertain the active state of tissues. This study investigated the potential correlation between the dielectric properties and biological activities of human hepatic tissue with prolonged ex vivo time through correlation and regression analyses. The dielectric properties of 26 cases of normal human hepatic tissue at 10 Hz to 100 MHz were measured from 15 min after isolation to 24 h at 37 °C with 90% humidity. Cell morphologies, including nucleus area (NA) and alteration rate of intercellular area (ICAR), were analyzed as indicators of biological activities. Conductivity, complex resistivity, and NA exhibited opposing changes 1 h after isolation. Relative permittivity and ex vivo time were not closely correlated (p> 0.05). The dielectric properties measured at low frequencies (i.e. <1 MHz) were more sensitive than those measured at high frequencies in reflecting the biological activity of ex vivo tissue. Highly significant correlations were found between conductivity, resistivity and the ex vivo time (p < 0.05) as well as conductivity and the cell morphology (p < 0.05). The findings indicated that establishing the correlation between the dielectric properties and biological activities of human hepatic tissue is of great significance for promoting the role of dielectric properties in biological science, particularly in human biology.

Ex-Vivo Characterization of Bioimpedance Spectroscopy of Normal, Ischemic and Hemorrhagic Rabbit Brain Tissue at Frequencies from 10 Hz to 1 MHz

“…If tissue impedance is equivalent to a parallel capacitance and conductance circuit [29], tissue impedance is given by: $Z=Z_{real}+j{Z}_{imag}=\frac{G}{G^2+{\omega }^2{C}^2}-j \frac{\omega C}{G^2+{\omega }^2{C}^2}$ $G=\sigma \frac{S}{l}$ $C=\epsilon \frac{S}{l}$ where $Z_{real}$ is the real part of Z ; $Z_{imag}$ is the imaginary part of Z ; j is the unit imaginary number, $j^2=-1$; C is the equivalent capacitance; G is the equivalent conductance; ω is the angular frequency, $\omega =2\pi \cdot f$; $\sigma$ is the conductivity; ε is the dielectric permittivity.…”

“…However, these studies carried out these measurements only in normal brain tissue and not in stroke lesions. Surowiec et al and Stoy et al did not measure impedance below 20 kHz (whereas a frequency range of 1 MHz is often used to improve the efficiency of MFEIT in stroke detection [20,28]), and the long ex vivo time may have affected the measurement by Gabriel et al [25,29]. …”

In Vivo Bioimpedance Spectroscopy Characterization of Healthy, Hemorrhagic and Ischemic Rabbit Brain within 10 Hz–1 MHz

“…Nevertheless, in these studies, the measurements of impedance spectra of hemorrhagic brain were not taken. Moreover, in the study by Wu et al, the two-electrode technique might affect the measurement results because of electrode contact impedance [16,22]. As for the hemorrhagic brain, several research groups monitored changes in the brain impedance before and after hemorrhagic stroke at a single frequency [20,23,24].…”

Accuracy and precision of electrical permittivity mapping at 3T: the impact of three mapping techniques

“…All these values, nevertheless, were far from the precision required to achieve = 5 units (≈ 0.05%; Figure ), which we deem a considerable improvement for permittivity precision, in relation to the range of tissue permittivity (i.e., 20 ≤ ε r ≤ 85 rel. units for the majority of tissues at 128 MHz, except fat (see, e.g., due studies)). Such a low std in would be reached only for image SNR 1 ≥2500, 1500, and 500 rel.…”

“…Moreover, a great body of literature has shown differences between the electrical properties of healthy and malignant human tissues; such differences could potentially be exploited for diagnostic purposes. Therefore, measuring electrical tissue properties, being permittivity (ε r ) and conductivity (σ), has since long been an important research question …”