Abnormal coronary development causes various health problems. However, coronary development remains one of the highly neglected areas in developmental cardiology due to limited technology. Currently, there is not a robust method available to map the microvasculature throughout the entire embryonic heart in 3D. This is a challenging task because it requires both micron level resolution over a large field of view and sufficient imaging depth. Speckle-variance optical coherence tomography (OCT) has reasonable resolution for coronary vessel mapping, but limited penetration depth and sensitivity to bulk motion made it impossible to apply this method to late-stage beating hearts. Some success has been achieved with coronary dye perfusion, but smaller vessels are not efficiently stained and penetration depth is still an issue. To address this problem, we present an OCT imaging procedure using optical clearing and a contrast agent (titanium dioxide) that enables 3D mapping of the coronary microvasculature in developing embryonic hearts. In brief, the hearts of stage 36 quail embryos were perfused with a low viscosity mixture of polyvinyl acetate (PVA) and titanium dioxide through the aorta using micropipette injection. After perfusion, the viscosity of the solution was increased by crosslinking the PVA polymer chains with borate ions. The tissue was then optically cleared. The titanium dioxide particles remaining in the coronaries provided a strong OCT signal, while the rest of the cardiac structures became relatively transparent. Using this technique, we are able to investigate coronary morphologies in different disease models.
Yehe Liu, Shi Gu, Michiko Watanabe, Andrew M. Rollins, and Michael W. Jenkins, "SLIME: scattering labeled imaging of microvasculature in excised tissues using OCT (Conference Presentation)," Proc. SPIE 10053, Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XXI, 100530P (Presented at SPIE BiOS: January 31, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2254915.5371723139001.
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