Electrical biopsy of irradiated intestinal tissue with a simple electrical impedance spectroscopy system for radiation enteropathy in rats-–a pilot study

Changes of electrical impedance characteristics with the radiation induced damage on biological tissue constituents

This study analyzes the response of increasing radiation dose to the pork tenderloin tissue. Considering its significant cell structure, pork tenderloin tissue samples are selected for the experimental objects to measure their electrical impedance characteristics. This study proposes and investigates an effective approach to characterize the variation of the internal change of the components of pork tenderloin tissues caused by radiation. Changes in the pork tenderloin tissues are that the gap of the myotome is more far apart with increase of radiation dose because of the destroyed Myofibrils under the damage. With the increase of radiation dose, the impedance value of the pork tenderloin tissue decreases. Each of mean differences in the impedance values before and after irradiation dose under 1 Gy, 2 Gy and 4 Gy show 0.55±0.03, 1.09±0.14 and 1.97±0.14, respectively. However, the mean difference substantially increases to 13.08±0.16 at irradiation dose of 10 Gy. Thus, the cell membrane shows the most severe rupture at a radiation dose of 10 Gy. Changes in the microstructure of the irradiated pork tenderloin tissue samples are also checked and validated by a transmission electron microscope.

Electrical impedance spectroscopy as electrical biopsy for monitoring radiation sequelae of intestine in rats

Electrical impedance is one of the most frequently used parameters for characterizing material properties. The resistive and capacitive characteristics of tissue may be revealed by electrical impedance spectroscopy (EIS) as electrical biopsy. This technique could be used to monitor the sequelae after irradiation. In this study, rat intestinal tissues after irradiation were assessed by EIS system based on commercially available integrated circuits. The EIS results were fitted to a resistor-capacitor circuit model to determine the electrical properties of the tissue. The variations in the electrical characteristics of the tissue were compared to radiation injury score (RIS) by morphological and histological findings. The electrical properties, based on receiver operation curve (ROC) analysis, strongly reflected the histological changes with excellent diagnosis performance. The results of this study suggest that electrical biopsy reflects histological changes after irradiation. This approach may significantly augment the evaluation of tissue after irradiation. It could provide rapid results for decision making in monitoring radiation sequelae prospectively.

The correlation between extracellular resistance by electrical biopsy and the ratio of optical low staining area in irradiated intestinal tissues of rats

BACKGROUND

Electrical biopsy illustrates a tissue's electrical properties by electrical impedance spectroscopy. However, electrical biopsy parameters are different from conventional morphological-based examinations. The correlation between electrical biopsy and the morphological observation has not been checked. Considering the tissue responses to injury, extracellular resistance should be most sensitive with the accumulation of fluid in tissue, and it is expected to increase the ratio of optical low staining area on histological images. In this study, we calculated the ratio of optical low staining area of sampled histological images and compared with the results of electrical biopsy to verify the hypothesis of that the extracellular resistance of electrical biopsy most highly correlates with the ratio of optical low staining area on histological images.

METHODS

The irradiated intestinal tissues of rats after different latent period were used for study. The sampled tissues were measured by electrical impedance spectroscopy for electrical biopsy and the microscopic images were acquired. The sampled histological images were transformed into the Hue-Saturation-Density (HSD) colour model to decouple the stain density. The ratio of optical low staining area on histological images was computed to quantify the morphological changes. The results were related to the parameters from electrical biopsy according to three element circuit model by Spearman's rank correlation test.

RESULTS

The ratio of optical low staining area varied as well as the tissue's electrical parameters. The extracellular resistance (Re) and intracellular resistance (Ri) by electrical biopsy tended to increase with the ratio of low staining area decreasing. The membrane capacitance (Cm) by electrical biopsy tended to increase with the ratio of optical low staining area increasing. The extracellular resistance (Re) of electrical biopsy was the parameter most highly correlated with the ratio of optical low staining area with a correlation coefficient of -0.757 (p < 0.001).

CONCLUSIONS

The results of this report confirm the hypothesis and support the idea that electrical biopsy results reflect the changes in tissues seen in conventional histological findings in a sense of conventional histological knowledge, and this approach may have a great potential for augmenting the pathological diagnosis of tissues.