First results with a novel X-ray source for dual energy angiography

In angiographic practice an iodate contrast medium is injected in patient vessels with a catheter. The iodine is used because its linear absorption coefficient shows a K-edge at 33.169 keV. In digital subtraction angiography (DSA), some images are acquired before and during the injection of the contrast medium. The vessels' morphology is obtained by subtracting the live images from the first (mask) image. A new approach is presented where two quasimonochromatic beams, having mean energies lower and higher than the iodine K-edge, are produced simultaneously-starting from an X-ray tube-by means of a pyrolytic graphite crystal monochromator. These two thin parallel beams impinge on the phantom simulating patient vessels and are detected with solid-state array detectors. The image results as the difference between the remaining intensities of the two beams. Performance-in terms of spatial resolution, contrast and reduction of iodine concentration in an invasive perfusion medium-are presented and compared with the full spectra subtraction method in use.