Abstract
Background: Conventional coronary angiography can visualize vessels of 300 μm in diameter, but not those of smaller diameter, such as the proliferating collateral arteries of ischemic heart disease and the new blood vessels formed in regenerative medicine. We have developed a system of synchrotron radiation coronary microangiography (SRCA) in the in vivo rat. The purpose of this study was to define the minimum detectable caliber change in the coronary arteries of the in vivo rat by inducing vasoconstriction with endothelin during SRCA. Method: SRCA was performed at the Photon Factory of the High Energy Accelerator Research Organization (Tsukuba, Japan). The advantages of synchrotron radiation derived X-rays are high spatial resolution (5 μm/pixel) due to increased photon density and straightness of beam. High density resolution is obtained with a high-gain avalanche rushing amorphous photoconductor camera using a fiber-optic plate. Rats were anesthetized. The polyethylene tube for angiography was inserted into the carotid artery. SRCA was performed before and after endothelin administration. Results: The electrocardiography showed ST elevation after endothelin administration. High spatial and density resolution images were obtained. Figures A and B show the changes in the caliber of the coronary arteries: Figure A shows the arteries before endothelin administration, and Figure B shows them after endothelin administration. The minimum identified coronary artery diameter in the in vivo rat was 65 μm, and the minimum detectable caliber change was 20 μm. Conclusion: The SRCA system could confirm the microvascular constriction of the coronary arteries in the in vivo rat after endothelin administration. We plan next to use SRCA to evaluate endothelial dysfunction in diabetic rats. SRCA may aid investigation of collateral artery proliferation in ischemic heart disease and new blood vessel formation in regenerative medicine in the near future.
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