Development of a new dual-contrast microangiographic system by using monochromatic synchrotron radiation

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Monochromatic synchrotron radiation with an energy level of just above or below the k-edge of I, Ba, or Ce where a 2 x 2 cm area was scanned by a high-definition TV camera. This camera is an image pick-up tube with an amorphous selenium photoconductive target and is characterized by its internal amplification process, which uses the avalanche phenomenon in a photoconductive layer. The images were stored as a digital image (1024 x 1024 pixels, 4096 grades/pixel in a frame memory). The spatial resolution limit of this system was 25 μm. The detection limit of the vessel sizes are 30 μm in canine, rabbits, and rats. In the animal, the portal vein and bile duct in the liver were filled up with Ba-, Ce-, or I-labeled contrast materials. The pulmonary artery and the respiratory tract in the lung were also filled up with the contrast materials. The samples were exposed to monochromatic synchrotron radiation with just upper and lower energy levels of each K-edge in these elements. By subtraction processing on a computer, the image of these ducts up to 30 μm in diameter were taken separately. The use of a mechanical shutter to improve temporal resolution allowed 2 msec of one frame, which allowed us to obtain a fine image of the coronary artery in beating heart. We also showed that microsphere injection into the coronary artery created microvascular myocardial ischemia in dogs and rabbits.