IODINE K-EDGE DUAL-ENERGY IMAGING FOR SUBTRACTION ANGIOGRAPHY USING SYNCHROTRON RADIATION AND A 2-DIMENSIONAL DETECTOR

A 2-dimensional energy-subtraction imaging system using synchrotron radiation has been improved in a number of ways; especially the energy-switching mechanism in which a monochromator crystal is oscillated trapezoidally has been improved. These improvements have led to real-time imaging of the right coronary artery in a rabbit after an intravenous injection of a contrast agent. This artery has a diameter of about 0.5 mm. However, this system has limitations concerning the energy difference between two component exposures and the total time of acquiring two images. We have tested a new method. Since the crystal was too heavy to oscillate quickly, the next step was to make the energy switching faster than in the previous method by the use of lighter moving parts. An iodine filter is used in the new method. Filter-chopping of the X-ray beam switches the dual-energy imaging energies, because the iodine filter selectively absorbs high-energy X-rays rather than K-edge energy X-ray. Moreover, by the use of the iodine filter, the energy difference between two exposures can be decreased to less than half of that in the previous method. Preliminary studies on the new method were performed in rats.