VISUALIZATION OF PENETRATING TRANSMURAL ARTERIES IN-SITU BY MONOCHROMATIC SYNCHROTRON-RADIATION

Background Penetrating transmural arteries with a diameter of <500 mu m are considered to be a critical vascular component that causes a tra nsmural variation of myocardial blood flow under various pathophysiolo gical conditions. However, the conventional coronary angiographic syst em is not oriented to the visualization of such small arteries as thes e. Methods and Results We magnified and monochromatized the inherently narrow beam (3 mm along the vertical direction) of synchrotron radiat ion by using an asymmetrically cut silicon crystal with 311 reflecting planes to obtain a monochromatic x-ray with relatively large beam siz e (60x25 mm) and with an energy of just above (+130 eV) the K-absorpti on edge of the contrast materials (33.17 and 37.41 keV for iodine and barium, respectively). We irradiated dogs or excised hearts with the m onochromatic x-ray and obtained coronary angiograms using an image int ensifier and video system with a spatial resolution of 170 mu m. In th e anesthetized dog experiments, we visualized the transmural penetrati ng arteries (5 to 15 mm in length) arising every 4 to 7 mm from the ep icardial branch. Visualization of these arteries filled with heavy ele ment-loaded microspheres (15 mu m in diameter) in the excised-heart ex periments, in which the monochromatic x-ray was irradiated to the hear ts through a 10- to 20-cm acrylic plate, indicated that this system co uld be used for human patients, in whom body absorption of x-ray is su bstantial. Conclusions Coronary angiogram by means of monochromatic x- ray is useful for a precise evaluation of coronary circulation, both i n clinical settings and in physiological animal experiments.