Impact of relative humidity and temperature on the shrinkage of soft biological tissue during microCT imaging: a static study for 4D-microCT perspectives

Details

Supervisors

Kerckhofs, Greet

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil biomédical, à finalité spécialisée

Abstract

enThe mechanical characterization of biological tissues plays a crucial role in modern biomedical research. It not only improves therapeutic approaches in tissue engineering and surgical simulators but also enhances diagnostic and treatment tools for diseases. A better understanding of the relationship between tissue microstructure and mechanical behavior could lead to significant advancements in the medical field. Currently, an emerging technique that combines 3D-microCT imaging and in situ mechanical testing, known as 4D-microCT, is increasingly used to better understand the complex relationships between microstructural properties and mechanical behavior of materials. However, its application to biological tissues remains limited, mainly due to dehydration of the samples during prolonged imaging sessions. Dehydration has major consequences on the mechanical properties of tissues, potentially altering their stiffness, elasticity, and viscoelastic behavior, which is highly undesirable. Therefore, it is essential to maintain proper hydration during these in vitro experiments in order to faithfully reproduce in vivo physiological conditions. To overcome these dehydration-related limitations, an in-house environmental chamber compatible with the microCT system was developed. This chamber allows control of ambient air humidity and temperature to minimize dehydration during imaging. The primary objective of this study was to demonstrate the importance of environmental control during microCT imaging of biological tissues. To this end, the impact of ambient air temperature and humidity on sample hydration levels was studied. A static time-lapse study was conducted on porcine descending thoracic aorta tissues under twelve different environmental conditions, combining four levels of relative humidity (30%, 50%, 75%, and 95%) and three temperatures (10°C, 20°C, or 30°C). The results suggest that dehydration is strongly influenced by relative humidity and temperature, with a decrease in relative humidity leading to increased volume loss, while an increase in temperature is associated with greater dehydration. Consequently, among the twelve conditions tested, the combination of 10°C and 95% relative humidity showed the greatest potential for preserving tissue hydration. Overall, the average curves show that the dehydration process exhibits a very linear behavior over time. The absence of a noticeable slowdown in the process can be explained by the fact that the samples still retained a significant amount of water at the end of the experiments. An additional experiment was conducted to assess the effectiveness of the 10°C and 95% RH condition in a long-duration, high-resolution imaging context. Although this environmental setting considerably improved hydration maintenance compared to uncontrolled conditions, a volume loss of 18.01% (compared to a maximum of 3.3% in previous experiments) was still observed. Therefore, the effectiveness of a given environmental condition in maintaining sample hydration depends on the specific imaging context and applications.