# An Improved Cole–Cole Model for Characterizing In Vivo Dielectric Properties of Lung Tissue at Different Tide Volumes: An Animal Study

## TL;DR

This study improves a model to better understand how lung tissue's electrical properties change with different air volumes in live rabbits.

## Contribution

An optimized Cole–Cole model is proposed to more accurately characterize in vivo lung tissue dielectric properties.

## Key findings

- Conductivity and permittivity of rabbit lung tissue decrease with increasing tidal volume.
- The improved model reduced the average error between measured data and model fitting to under 5%.

## Abstract

Objective: The air content within the lungs directly influences the dielectric properties of lung tissue; however, previous studies were conducted under ex vivo conditions and without quantitatively controlling air volume. This study aims to develop an improved model using in vivo measurements to accurately characterize the dielectric properties of rabbit lung tissue across various tidal volumes. Methods: In this study, six sets of different tidal volumes (30, 40, 50, 60, 70, 80 mL) were set in the frequency band of 100 MHz~1 GHz to analyze the trend of the dielectric properties, and the dielectric parameters were systematically constructed under the conditions of different tidal volumes. Results: It was found that the conductivity and permittivity of rabbit lung tissue showed a decreasing trend with increasing tidal volume in the measuring frequency band. The traditional Cole–Cole model has limitations in simulating the dielectric properties of in vivo lung tissues. Therefore, by refining and optimizing the model, this study successfully reduced the average error between the measured data and the model fitting to less than 5%. Conclusions: This study lays the groundwork for investigating the relationship between total air volume within the lungs and their dielectric properties in vivo.