In recent years, the regenerative treatment of osteoarthritis (OA) by transplantation of autologous cultured cartilage has been developed, but biomechanical diagnostic evaluation of cartilage has not yet been performed in the follow-up after transplantation as well as typical OA diagnostic treatment. In this study, we constructed an Optical Coherence Doppler Velocigraphy (OCDV) system based on low coherence interferometer (OCT) and a compression tester as loading device, which can provide micro-tomographic visualization of tissue deformation and joint fluid flow inside cartilage tissue. The constructed system was applied to not only the normal sample of porcine knee cartilage but also the simulated degenerative one by collagenase enzyme treatment for 2 hours. As experimental results, during compression period, the both cartilage samples in the middle layer were observed to move toward surface, generating the compressive strain further in superficial layer. Doppler velocity of the degenerated cartilage was detected to be about 50µm/sec in the middle layer, which was twice as high as that of normal cartilage. Just after stress relaxation, Doppler velocity decreased immediately to be less than 5µm/sec in the normal cartilage, whereas are keeping about 10µm/sec in the degenerated one. These are considered to be due to the decrease in biomechanical properties, i. e. visco-elasticity, of degenerated cartilage. In conclusions, the proposed method can discriminate quantitatively between normal and OA cartilage from the spatiotemporal change of the detected Doppler velocity, in the virtue of revealing microscopic tissue deformation and joint fluid flow with high spatio-temporal resolution, therefore OCDV has an effective potential as a real-time diagnostic imaging system.
