Feasibility of Sectional Bioelectrical Impedance Spectrum Evaluating Joint Effusion in Rat

Abstract

Background: Joint effusion is a significant cause of disability worldwide. Practical assessment and diagnosis can avoid the secondary damage caused by the effusion. Nowadays, bioimpedance spectroscopy (BIS) is an emerging tool to differentiate biological tissue characteristics between normal and illness conditions. Objective: This paper aims to verify the feasibility of the five-section BIS method in evaluating joint effusion in rats. Methods: The joint effusion usually locates near the articular cavity in the form of ion solution. The joint effusion will significantly change the low-frequency bioimpedance of limbs, which reflected in the change of extracellular water (ECW) impedance. The five-section impedance model is designed depending on the body structure of the rat, and the trunk and limbs are equivalent to five impedance area. According to the Cole model, the impedance values at direct current and infinite frequency are calculated by using curve fitting, and the impedance of extracellular and intracellular water (ICW) can be obtained. The impedance of limbs and soma can be calculated by solving the impedance model equations. The measurement results of healthy limbs are used to assess the sick degree of the effusion joint. In the experiment, the saline solution has been injected into the left lower limb joint as the joint effusion. Results: The low-frequency impedance has a significant increase after the knee injection. By comparing the impedance of healthy limbs and the effusion limb, the impedance change of the effusion limb is more significant than the healthy limb. The impedance relative change parameter K is used to evaluate the degree of effusion. Conclusion: The experiment results show that the sectional bioimpedance spectroscopy could evaluate joint effusion. The rat five-section model can provide a reference for the diagnose, and this method reduces the difficulty in the equipment popularization.