Two-dimensional real-time imaging system for subtraction angiography using an iodine filter

A new type of subtraction imaging system was developed using an iodine filter and a single‐energy broad bandwidth monochromatized x ray. The x‐ray images of coronary arteries made after intravenous injection of a contrast agent are enhanced by an energy‐subtraction technique. Filter chopping of the x‐ray beam switches energies rapidly, so that a nearly simultaneous pair of filtered and nonfiltered images can be made. By using a high‐speed video camera, a pair of two 512 × 512 pixel images can be obtained within 9 ms. Three hundred eighty‐four images (raw data) are stored in a 144‐Mbyte frame memory. After phantom studies, in vivo subtracted images of coronary arteries in dogs were obtained at a rate of 15 images/s.