Quantitative assessment of hyaline cartilage elasticity during optical clearing using optical coherence elastography

Abstract

Tissue optical clearing is an emerging technique for dynamically modifying tissue optical properties to increase imaging depth, which is useful in applications such as imaging and functional diagnostics of many diseases. For example, optical clearing of cartilage allowed imaging of subchondral bone that is used to assess orthopedic diseases. However, the effect of the clearing processes on tissue elastic properties has not been investigated yet. In this study we report the first use of phase-stabilized swept source optical coherence elastography (PhS-SSOCE) to quantitatively monitor the change in elasticity of hyaline cartilage during the optical clearing process noninvasively. The results showed that PhS-SSOCE was able to assess the increase in cartilage stiffness during the clearing process over time and with different concentrations of glucose. In addition, the results demonstrated that the elasticity of the cartilage was reversed once the clearing agent was replaced with saline. To verify the results obtained from the PhS-SSOCE measurements, benchmark mechanical testing was performed using a uniaxial mechanical compression frame. Both methods demonstrated the same trend of the elasticity change of the cartilage immersed in glucose solution. The data show that during the transition from phosphate buffered saline to the clearing agent, the cartilage stiffness decreases significantly, which indicates that the clearing agent diffused into the cartilage extracellular matrix and decreased the tissue elasticity due to dehydration. Therefore, the proposed optical coherence elastography can dynamically assess the effects of optical clearing and associated changes in tissue biomechanical properties noninvasively and nondestructively. This technique may be potentially useful in orthopedic studies such as early detection and monitoring of osteoarthritic diseases.