Optical clearing of articular cartilage: a comparison of clearing agents

Alexander Bykov; Tapio Hautala; Matti Kinnunen; Alexey Popov; Sakari Karhula; Simo Saarakkala; Miika T. Nieminen; Valery Tuchin

doi:10.1117/12.2183882

17 July 2015 Optical clearing of articular cartilage: a comparison of clearing agents

Alexander Bykov, Tapio Hautala, Matti Kinnunen, Alexey Popov, Sakari Karhula, Simo Saarakkala, Miika T. Nieminen, Valery Tuchin

Author Affiliations +

Proceedings Volume 9540, Novel Biophotonics Techniques and Applications III; 95400A (2015) https://doi.org/10.1117/12.2183882
Event: European Conferences on Biomedical Optics, 2015, Munich, Germany

Abstract

Optical clearing technique was applied to the problem of OCT imaging of articular cartilage and subchondral bone. We show that optical clearing significantly enhances visualization of articular cartilage and cartilage-bone interface. The effect of different clearing agents was analyzed. For the clearing, iohexol solution and propylene glycol (PG) were used. Clearing was performed in vitro at room temperature by immersion method. Cylindrical osteochondral samples (d=4.8mm) were drilled from bovine lateral femur and stored in phosphate-buffered saline at -20°C until clearing. Monitoring of clearing process was performed using high-speed spectral-domain OCT system providing axial resolution of 5.8μm at 930nm. Total duration of experiment was 90-100min to ensure saturation of clearing. We have shown that iohexol solution and PG are capable to optically clear articular cartilage enabling reliable characterization of cartilagebone interface with OCT. Being a low osmolarity agent, iohexol provides minimal changes to the thickness of cartilage sample. Clearing saturation time for the cartilage sample with the thickness of 0.9 mm measured with OCT is of 50 min. However, less than 15 min is enough to reliably detect the rear cartilage boundary. Alternatively, PG significantly (60%) reduces the cartilage thickness enabling better visualization of subchondral bone. It was observed that PG has higher clearing rate. The clearing saturation time is of 30 min, however less than 5 min is enough to detect cartilage-bone interface. We conclude that iohexol solution is superior for OCT imaging of cartilage and cartilage-bone interface, while PG suits better for subhondral bone visualization.

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Alexander Bykov, Tapio Hautala, Matti Kinnunen, Alexey Popov, Sakari Karhula, Simo Saarakkala, Miika T. Nieminen, and Valery Tuchin "Optical clearing of articular cartilage: a comparison of clearing agents", Proc. SPIE 9540, Novel Biophotonics Techniques and Applications III, 95400A (17 July 2015); https://doi.org/10.1117/12.2183882

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