CORONARY ANGIOGRAPHY USING SYNCHROTRON RADIATION - STUDIES IN HUMAN-SUBJECTS WITH THE SYSTEM NIKOS-II

Worldwide at many synchrotron radiation laboratories different systems have been developed for digital subtraction angiography (DSA) in energy subtraction mode (dichromography). Aim of the work is to visualize coronary arteries down to 1 mm diameter with an iodine mass density of 1 mg/cm2, thus allowing non-invasive investigations by intravenous application of the contrast agent. The two images for subtraction are simultaneously taken with photon energies just below and above the iodine K-edge (33.17 keV) in a line scan mode. In the Hamburger Synchrotronstrahlungslabor HASYLAB at DESY the system NIKOS II (NIKOS = Nicht-invasive Koronarangiographie mit Synchrotronstrahlung) consists of six main parts: the 20 pole wiggler HARWI, a two beam monochromator, a safety system, a fast scanning device, a fast low-noise two-line detector, and a computer system. In 1990 the first patients were investigated with the system NIKOS II. 30 ml of contrast medium were injected within 2 s into the vena cava superior. The scan velocity was 9 cm/s corresponding to 5.6 ms per line. The resulting images have a size of 10.0 cm (horizontal) X 12.3 cm (vertical). The pixel size in the images is 0.5 X 0.5 mm2. The radiation dose per scan (two energy images) was 25 mGy on the average. There are two main problems with the intravenous investigations using DSA in energy subtraction mode for visualization of coronary arteries: - The correct time T from the injection of the contrast material up to the beginning of the scan depends on the individual circulation time of the patient. - In intravenous investigations the small structures of interest (coronary arteries) can bc superimposed by large structures (aorta, left atrium and ventricle). The images from the investigations are compared to angiograms, conventionally obtained. They have not yet the quality necessary for clinical routine but show the potential of the method if the system is optimized.